HomeMy WebLinkAboutowts-manualONSITE WASTEWATER TREATMENT
SYSTEMS MANUAL
June 2018
Alameda County Department of
Environmental Health
1131 Harbor Bay Parkway Alameda, CA 94502
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
MANUAL INTRODUCTION
OVERVIEW
This Onsite Wastewater Treatment Systems Manual (Manual) provides the procedural and technical details
for implementation of the provisions of the Alameda County Onsite Wastewater Treatment Systems
Ordinance (the Ordinance), codified in Chapter 15.18 of the Alameda County General Ordinance Code. The
provisions within this Manual are designed to protect public health, groundwater and surface water bodies
from contamination, and provide safely operating Onsite Wastewater Systems through proper design, siting,
installation, maintenance and monitoring. Onsite Wastewater Systems (or Systems) as referenced herein
include Onsite Wastewater Treatment Systems (OWTS) as defined by the Water Quality Control Policy for
Siting, Design, Operation and Maintenance of Onsite Wastewater Treatment Systems (State OWTS Policy),
adopted by the State Water Resources Control Board, and which took effect on May 13, 2013 and Onsite
Wastewater Containment Units (OWCU) as defined by Alameda County General Ordinance Code Chapter
15.18.
The Alameda County Department of Environmental Health (the Department) is the agency responsible
for the enforcement of the Ordinance and provisions in this Manual. The California Regional Water Quality
Control Boards for the San Francisco Bay Region and Central Valley Region (Regional Water Boards) are
the state agencies responsible for the protection of groundwater and surface water quality in Alameda
County (the County). While the Department administers the local program, the Regional Water Boards
retain the authority to issue Waste Discharge Requirements for any discharge of wastewater that may
affect water quality.
The requirements in this Manual shall apply to all OWCU as defined by the Ordinance and to OWTS with
flows less than ten thousand (10,000) gallons per day (gpd) that accept and treat (1) domestic-strength
wastewater or (2) high-strength wastewater from commercial food service buildings with a biochemical
oxygen demand (BOD) less than or equal to nine hundred (900) milligrams per liter (mg/L). Owners of
OWTS that receive high-strength or high-flow wastewater from non-residential facilities other than
commercial food service facilities or OWTS that do not comply with the requirements of the Ordinance and
this Manual shall notify the Regional Water Board and may be jointly regulated by the Regional Water Board
through issuance of waste discharge requirements (WDRs) and the Department through approval of
design/construction documents and issuance of installation permits.
AMENDMENTS TO THE MANUAL
The regular review and update of this Manual is necessary to keep pace with new issues, policies, procedures
and technologies affecting the use and management of Onsite Wastewater Systems. Any substantive changes
in requirements will require review and approval by the San Francisco Bay Regional Water Board and
adoption by Resolution of the Alameda County Board of Supervisors (Board of Supervisors).
The amendments may include recommended changes originating from the Department, Regional Water
Boards, Zone 7 Water Agency (Zone 7), other departments or agencies, contractors and consultants working
in the Onsite Wastewater System industry or other affected groups or individuals. As changes are made to
this Manual cross references throughout this Manual are also subject to change. Failure of a cross-reference
to indicate the appropriate location of the requirements due to these changes does not void the applicability
of the requirements.
The general process before substantive changes are made to this Manual will be as follows:
1. The Department will announce and provide copies of its proposed changes.
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MANUAL INTRODUCTION
2. The Department will present the changes and allow opportunity for public comments at a
meeting of the Onsite Wastewater Treatment System Commission or other public meeting.
3. After further review and consideration of public comments by the Department the final
changes will be presented to the Board of Supervisors and then will be forwarded to the San
Francisco Bay Regional Water Board for review and approval.
MANUAL ORGANIZATION
This Manual is intended to provide technical guidance for Department staff, property owners, real estate
professionals, consultants and other practitioners that may be involved with the design, installation, repair,
modification, operation and maintenance of new and existing Onsite Wastewater Systems.
This Manual is divided into the following parts:
Part No. Title
REFERENCE GUIDELINES AND STANDARDS
In addition to the requirements set forth in this Manual Onsite Wastewater System practitioners should utilize
applicable guidelines and reference standards including but not limited to the following:
"Onsite Wastewater Treatment Systems Manual", U.S. Environmental Protection Agency, February
2002 and as amended.
“Design Manual – Onsite Wastewater Treatment and Disposal Systems”, U.S. Environmental Protection
Agency, October 1980.
“Field Book for Describing and Sampling Soils”, United States Department of Agriculture, Natural
Resources Conservation Service, September 2002.
“Soil Survey Manual”, United States Department of Agriculture, Natural Resources Conservation
Service, 1993 and as amended.
“Small Decentralized Wastewater Management Systems”, Crites, R., Tchobanoglous, G., 1998.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)III
MANUAL INTRODUCTION
California Plumbing Code, California Code of Regulations Title 24, Part 5, California Building
Standards Commission.
International Association of Plumbing and Mechanical Officials (IAPMO) Industry Standards (Guide
Criteria, Installation Standards, and Material and Property Standards).
American Society for Testing and Materials (ASTM) Standards.
When this Manual does not specifically cover any subject related to the design and installation of Onsite
Wastewater Systems accepted engineering practices shall be employed. When the requirements in this
Manual conflict with the requirements of Onsite Wastewater System guidance documents and reference
standards the requirements of the Manual shall prevail unless otherwise approved by the Department.
ALTERNATIVE MATERIALS, DESIGN AND METHODS OF CONSTRUCTION AND
EQUIPMENT
The provisions of this Manual are not intended to prevent the installation of any material or prohibit any
design or method of construction not specifically prescribed by this Manual provided that any such
alternative has been approved by the Department. An alternative material, design or method of construction
shall be approved where the Department finds that the proposed design is satisfactory and complies with
the intent of the provisions of this code and that the material, method or work offered is, for the purpose
intended, at least the equivalent of that prescribed in this Manual in quality, strength, effectiveness,
durability and safety.
TABLES & FIGURES
Tables referenced in this Manual are located within individual chapters. A list of tables is provided in
Appendix A.
Figures referenced in this Manual are located within individual chapters. A list of figures is provided in
Appendix B.
ACRONYMS & ABBREVIATIONS & DEFINITIONS
The acronyms and abbreviations used in this Manual are defined in Appendix C. The acronyms OWTS
and OWCU refer to both the singular and plural forms of the terms.
A glossary of the terms used in this Manual is provided in Appendix D.
APPROVALS & EFFECTIVE DATES
Regional Water Quality Control Board Approval Date: May 21, 2018
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
PART 1
ALAMEDA COUNTY
ONSITE WASTEWATER SYSTEM
PROGRAM OVERVIEW
CHAPTER TITLE
CHAPTER 1 ONSITE WASTEWATER SYSTEM OVERVIEW
CHAPTER 2 PERMITTING PROCESS OVERVIEW
CHAPTER 3 PRACTITIONER QUALIFICATIONS & COUNTY
REGISTRATION PROGRAMS
CHAPTER 4 COMPLAINTS & INVESTIGATIONS
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CHAPTER 1
ONSITE WASTEWATER SYSTEM OVERVIEW
1.0 CHAPTER OVERVIEW
This chapter provides an overview of the Onsite Wastewater System types that may be approved for use in the
County and is organized as follows:
Section 1.1: Onsite Wastewater System Types
Section 1.2 Onsite Wastewater System Treatment Train Components
1.1 ONSITE WASTEWATER SYSTEM TYPES
A. OVERVIEW
1. Onsite Wastewater Systems treat and/or dispose of wastewater from buildings and
structures with plumbing when public sewer is not available.
2. Onsite Wastewater Systems, for the purposes of this Manual, include OWTS and OWCUs.
3. Graywater systems are a type of onsite wastewater system, and while referenced in this
Manual are not governed by the Ordinance and do not replace the requirement for an OWTS
or OWCU. Graywater systems are referenced in this Manual as they may be used to reduce
the wastewater loading to existing OWTS on constrained sites where maximum extent
practicable measures are required.
B. ONSITE WASTEWATER TREATMENT SYSTEMS (OWTS)
1. An OWTS is an Onsite Wastewater System that may include tanks, piping, treatment
devices, dispersal systems or other components that convey, store, treat and dispose of
wastewater and is located on the property where the wastewater originates or an adjacent
or nearby property under the control of the user. OWTS types include standard OWTS and
advanced OWTS as well as individual OWTS and community OWTS.
a.Standard OWTS. A standard OWTS consists of a septic tank for primary
treatment of wastewater followed by a system of gravity fed trenches for
subsurface dispersal of wastewater into the soil (gravity trench dispersal system).
A standard OWTS utilizes gravity flow to convey wastewater from the septic
tank to the gravity trench dispersal system. A pump tank may be utilized to enable
the installation of a gravity trench dispersal system located up-slope of the structure
or building to be served. Standard OWTS can only be used for domestic-strength
wastewater and require installation of dual dispersal systems.
b.Advanced OWTS: An advanced OWTS utilizes primary treatment (septic tank)
and supplemental treatment and/or a method of wastewater dispersal other than a
gravity trench dispersal system. Advanced OWTS are designed to allow siting of
an OWTS where a standard OWTS is not suitable due to site constraints or for high-
strength or high-flow wastewater streams.
c.Individual OWTS. An individual OWTS serves buildings or structures under the
same ownership on one parcel.
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d.Community OWTS: A community OWTS accepts wastewater from buildings or
structures on two or more parcels or from buildings or structures under separate
ownership whether or not they are on the same parcel. A community OWTS may
be either privately or publicly owned or operated.
C. ONSITE WASTEWATER CONTAINMENT UNITS (OWCU)
1. An OWCU is a self-contained, non-discharging Onsite Wastewater System used to collect
and store wastewater for removal, hauling and disposal at an approved septage receiving
facility by a septage pumper registered with the Department (Septage Pumper).
2. OWCU are allowed under limited conditions where site constraints prohibit the use of an
OWTS.
3. An OWCU is located on the property where the wastewater originates and includes holding
tanks, vault toilets, portable toilets and waterless toilets.
a.Holding Tanks. A holding tank is a self-contained, watertight receptacle designed
to collect and store wastewater prior to it being pumped and removed from the
property by a Septage Pumper. Holding tanks are only allowed in limited
circumstances as set forth in Part 5 or otherwise in this Manual.
b.Non-Discharging Toilets Units. A non-discharging toilet unit is a toilet with a self-
contained, watertight container used to collect and store human waste prior to it
being pumped and removed from the property by a Septage Pumper. Non-
discharging toilet units are only allowed in limited circumstances as set forth in
Part 9 or otherwise in this Manual. Non-discharging toilet units include vault
toilets, portable toilets and waterless toilets.
(1) Vault Toilets. A vault toilet consists of a shelter built above a subsurface
vault that collects human waste and drainage from hand washing facilities.
(2) Portable Toilets. A portable toilet is a chemical toilet facility that is housed
within a portable toilet shelter that collects human waste and drainage from
handwashing sinks.
(3) Waterless Toilets. A waterless toilet includes a composting toilet,
incinerator toilet or similar device for the holding and processing of human
waste.
D. GRAYWATER SYSTEMS
1. A graywater system is designed to collect graywater and transport it out of the building or
structure for distribution in an irrigation field or a subsurface disposal area.
2. A graywater system may include tanks, valves, filter, pumps, and/or other appurtenances
along with piping and receiving landscape for dispersal of graywater and is governed by the
California Code of Regulations, Title 24, Part 5 (California Plumbing Code).
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ONSITE WASTEWATER SYSTEM OVERVIEW
1.2 ONSITE WASTEWATER SYSTEM TREATMENT TRAIN COMPONENTS
A. MAJOR SYSTEM COMPONENTS
1. The major components commonly utilized in Onsite Wastewater System treatment trains
include tanks, supplemental treatment systems and/or dispersal systems.
2.Tanks. The types of tanks approved for use in the County include:
a.Septic tanks;
b.Pump tanks;
c.Flow equalization tanks;
d.Grease interceptor tanks;
e.Holding tanks;
f.Vaults and chambers (non-discharging toilet units); and
g.Other tanks approved by the Department and the Regional Water Board
3.Supplemental Treatment. The types of supplemental treatment systems approved for use
in the County include:
a.Proprietary treatment units (manufactured or “package” units);
b.Intermittent sand filter systems;
c.Recirculating sand filter systems; and
d.Other supplemental treatment systems approved by the Department and the
Regional Water Board.
4.Subsurface Dispersal Systems. The types of subsurface dispersal systems approved for use
in the County include:
a.Gravity trench dispersal systems;
b.Pressure-dosed trench dispersal systems;
c.Subsurface drip dispersal systems;
d.At-grade dispersal systems;
e.Mound dispersal systems;
f.Raised sand filter bed dispersal systems (repair or replacement systems only); and
g.Other dispersal systems approved by the Department and Regional Water Board.
B. OTHER SYSTEM COMPONENTS
1. Other components commonly utilized in Onsite Wastewater Systems include but are not
limited to pumps, filters, valves, regulators, meters, control panels and alarms.
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CHAPTER 2
PERMITTING PROCESS OVERVIEW
2.0 CHAPTER OVERVIEW
This chapter provides an overview of the permitting process for Onsite Wastewater Systems. Detailed
information on each of the topics listed below is presented in subsequent chapters of this Manual.
This chapter is organized in the following sections:
Section 2.1: System Approval and Permitting Process Overview
Section 2.2: System Permits & Permit Exemptions
Section 2.3: Land Use, Site Development and Building Projects Requiring Department Review
2.1 SYSTEM APPROVAL & PERMITTING PROCESS OVERVIEW
A. OVERVIEW
1. The steps in the Department approval and permitting process for an Onsite Wastewater
System will differ depending on the type and complexity of the System and where the System
is located and may include one or more of the following:
a.File review;
b.Office or site consultation meeting;
c.Review/approval of existing Onsite Wastewater System performance evaluations,
as-built plans, repair/modification plans and/or corrective action plans;
d.Review/approval of new Onsite Wastewater System design plans and design reports;
e.Review/approval of potable water supply source testing (flow and quality of well or
spring water) for new development and/or other special circumstances;
f.Review/clearance of building, site development and/or land use permits;
g.Issuance of Onsite Wastewater System installation, repair/modification,
abandonment and/or operating permits;
h.Interagency coordination; and/or
i. Granting of a variance.
B. FILE REVIEW
1. To initiate a file review, an appointment to review the Department files for parcels with
Onsite Wastewater Systems may be made by calling the Department via telephone or online
on the Departments website at: http://www.acgov.org/aceh/landuse/index.htm.
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PERMITTING PROCESS OVERVIEW
C. SERVICE REQUEST APPLICATIONS AND FEES
1. To initiate approval and permitting for an Onsite Wastewater System, a completed Service
Request application (SRA) must be submitted to the Department by the property owner or
the property owner’s authorized representative (Applicant) along with requisite fees and
supporting documents in accordance with the provisions of the Ordinance and this Manual.
2. The SRA and supporting documents must be legible and otherwise adequate for proper
review.
3. The Department will determine whether the SRA is complete in accordance with the
provisions of this Manual. An incomplete SRA (missing key information and/or supporting
documents) will be rejected by the Department and may be assessed a resubmittal
processing fee.
4. Upon submittal of a complete SRA, supporting documents and fees, the project will be
placed in the Department's review queue based on the date payment is received and the
type of service requested.
5. Where warranted, due to the complexity of the project, the Department may require third
party review of SRA supporting documents, the costs which are the responsibility of the
Applicant.
6. The Department will issue a written response to all SRAs. If the application is deemed
incomplete or denied, the Department will state the specific reasons in the response.
D. INTERAGENCY COORDINATION
1. Depending on the type of Onsite Wastewater System or project, the Department may receive
referrals from or need to coordinate with other local, regional, state and federal regulatory
agencies in order to issue approvals and/or permits for a System.
2. Types of projects that may require interagency coordination include but are not limited to:
a.Building, grading and demolition permits issued by the local building department;
b.Site development approvals and permits issued by the local planning department
including but not limited to new lot creation, subdivisions, lot line adjustments,
conditional use permits or other site development reviews;
c.Commercial kitchen permits issued by the Department’s commercial food unit;
d.Complaint investigations conducted in conjunction with local code enforcement
agencies;
e.Onsite Wastewater Systems that require a permit from a regulatory agency with
jurisdiction over safeguarding natural resources;
f.Projects located in the Upper Alameda Creek Watershed above Niles for non-
residential facilities or other projects served by Systems which require project
approval by Zone 7;
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g.Onsite Wastewater Systems permitted by a Regional Water Board through WDRs
requiring design/construction document approval and issuance of installation
permits by the Department; and/or
h.Onsite Wastewater Systems located within requisite setbacks to public water wells
or public water system surface water intakes requiring notification to the public
water system owner(s) and a fifteen (15) day comment period on the proposed
System design and installation.
3. A meeting(s) with the Department, Applicant and other public agencies may be required
after review of the SRA and during the approval/permitting process in order to clarify
aspects of the project, determine additional information that may be required and discuss
other relevant issues. Reimbursement of the Department costs for interagency meetings are
the responsibility of the Applicant.
E. VARIANCES
1. A variance is required if any requirements in the Ordinance or this Manual are not met,
notwithstanding a reference to approving a System or corrective actions that meet
requirements “to the maximum extent practicable.”
2. A variance to any requirement of this Manual may only be granted if the Applicant
demonstrates all of the following criteria:
a.Special circumstances and conditions exist on the property which deprive the
owner of privileges enjoyed by other property subject to the Ordinance;
b. The granting of the variance will not constitute a grant of special privileges
inconsistent with any limitation on other property subject to the Ordinance; and
c.The granting of the variance will not be detrimental to other persons or property
(including but not limited to watercourses or wetlands or the water quality of
subsurface water) or to the public health, safety or welfare.
3. The Department will review any request for a variance and may deny it. If the Department
does not deny a variance request, a recommendation to grant the variance will be sent to
the Board of Supervisors for final review and approval.
4. Reimbursement of the Department costs for variance processing are the responsibility of
the Applicant.
2.2 SYSTEM PERMITS & PERMIT EXEMPTIONS
A. ONSITE WASTEWATER SYSTEM PERMIT TYPES
1.Department Permits. Permits are required from the Department for installation of new
and replacement Systems, repair and modification of existing Systems, decommissioning
of abandoned Systems and System operation.
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PERMITTING PROCESS OVERVIEW
a.Installation Permits. In order to construct a new or replacement Onsite
Wastewater System the owner or Applicant shall obtain an installation permit from
the Department. Unless otherwise expressly stated in writing on the permit, an
installation permit shall automatically expire three (3) years after the date of
issuance. The expiration date on an installation permit may be extended provided
the approved System design documents referenced in the permit comply with all
the requirements in effect at the time of the request for an extension. Requests for
extension of an installation permit shall include submittal of a SRA and payment
of fees required to process the extension based on an actual hourly basis.
b.Repair/Modification Permits. In order to perform repairs or modifications to any
existing Onsite Wastewater System the property owner or Applicant shall obtain a
permit from the Department unless the work is exempt in accordance with the
criteria in Section 2.2.B below. Unless otherwise expressly stated in writing on the
repair/modification permit, a repair/modification permit shall automatically expire
twelve (12) months after the date of issuance. The expiration date on a
repair/modification permit may be extended, provided the approved System design
documents referenced in the permit comply with all the requirements in effect at
the time of the request for an extension. Requests for extension of a
repair/modification permit shall include submittal of a SRA and payment of fees
required to process the extension based on an actual hourly basis.
c.Abandonment Permits. In order to decommission an abandoned Onsite
Wastewater System the owner or Applicant must obtain an abandonment permit
from the Department. Unless otherwise expressly stated in writing on the
abandonment permit an abandonment permit shall automatically expire three (3)
months after the date of issuance. The expiration date on an abandonment permit
may be extended provided the decommissioning procedures referenced in the
permit comply with all the requirements in effect at the time of the request for an
extension. Requests for extension of an abandonment permit shall include
submittal of a SRA and payment of fees required to process the extension based
on an actual hourly basis.
d.Operating Permits. In order to operate an Onsite Wastewater System an annual
operating permit may be required. Advanced OWTS and holding tanks require an
annual operating permit. Other Onsite Wastewater Systems may require an annual
operating permit if requirements or conditions contained in this Manual cannot be
met. The owner is responsible for obtaining the operating permit and complying
with permit conditions and renewal requirements. The operating permit renewal
frequency for advanced OWTS may be extended to a period of three (3) years
contingent upon compliance with all of the following conditions:
(1) The System has been functioning properly for two (2) consecutive years
in compliance with the approved design plans and the operation,
monitoring and maintenance (OM&M) manual; and
(2) The owner is in compliance with the terms of the operating permit
including but not limited to the annual reporting requirements to the
Department.
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The owner of any parcel with an operating permit must notify the Department in
writing of any change in property ownership. When the property changes
ownership, the new owner must apply to the Department for a new operating
permit on or before the anniversary of the operating permit issuance date. The new
owner will not be required to pay either an application or permit fee for the transfer
of ownership, however, a nominal administrative fee may be charged for
transferring the operating permit. The new owner will be responsible for any
annual operating permit renewal fees.
e.Special Permits. Special permits may be required for the use of portable toilets or
waterless toilets. Special permits are not required for portable toilets on
construction sites with a valid building permit.
f.Qualifying Public Agency Permits. In place of the permits listed above, a public
agency with local full-time sanitation and water quality staff may obtain a
qualifying public agency permit. The qualifying public agency permit will cover
the Onsite Wastewater Systems identified in the permit and identify the
installation, operating, repair, modification and abandonment requirements as
applicable.
2.Regional Water Board Permits. In addition to permits issued by the Department, WDRs
may also be required by the Regional Water Board authorizing discharges from an OWTS.
3.Zone 7 Permits. Applicants and owners of Onsite Wastewater Systems located within
Zone 7 jurisdictional boundaries must comply with all Zone 7 requirements for System
approvals. Although the Department and/or the Regional Water Board issue permits for
Onsite Wastewater Systems in the County, the Applicant must additionally apply for Zone
7 permits/approvals in accordance with the requirements of the 1982 Zone 7 Wastewater
Management Plan for the Unsewered, Unincorporated Area of Alameda Creek Watershed
above Niles and the 1985 Zone 7 Resolution 1165. Zone 7 approval is required for the
following OWTS:
a.New Onsite Wastewater Systems constructed, partially or fully, for a non-
residential use;
b. Conversion of an existing residential OWTS to a non-residential use; or
c.Systems requiring a variance from the requirements of the Ordinance and this
Manual and/or Zone 7 policies.
B. PERMIT EXEMPTIONS
1. Permits are not required by the Department for the following work:
a.Septage Pumping: Pump out and servicing of tanks by a Septage Pumper having
a valid Septage Pumper registration with the Department;
b.Routine Onsite Wastewater System Operation, Monitoring and Maintenance:
Any work to monitor and maintain an Onsite Wastewater System in proper
working order in compliance with the approved design plans, the terms of an
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PERMITTING PROCESS OVERVIEW
operating permit and/or other elements of the OM&M manual for the System, as
applicable.
c.Performance Evaluations: Any work to expose, document and/or test portions of
an Onsite Wastewater System in connection with a performance evaluation
provided the work is done in compliance with the requirements of this Manual;
and
d.Limited Repair Work. Repair work conducted on previously permitted Onsite
Wastewater Systems provided the conditions listed below are met:
(1) Repairs are reported to the Department;
(2) A licensed Contractor conducts the work;
(3) There is no evidence of a dispersal system or tank failure;
(4) Work is conducted in accordance with the approved design and the
material and installation requirements of this Manual; and
(5) Work is conducted in compliance with the requirements of other agencies.
2. Limited repair work allowed under this exemption includes:
a.Pipes: Clearing obstructions that are within a pipe and replacing solid pipe
between tanks and the dispersal system;
b.Tanks: Installing, repairing and replacing risers and/or lids, effluent filters,
sanitary tees and other similar components;
c.Other Components: Installing, repairing and replacing distribution boxes, valves
and valve boxes, trench inspection ports, cleanouts and other similar components;
d.Gravity Dispersal Trenches: Repairing or replacing the first twenty feet of piping
(measured from the edge of the trench). This does not include work to correct a
soil absorption problem;
e.Drainage and Erosion Control: Installing, repairing or replacing drainage and
erosion control measures in the tank or dispersal system areas; and/or
f.Electrical and Mechanical Components: Repairing or replacing float switches,
pumps and wiring.
3. Repair work exemptions do not include replacement of tanks or dispersal systems, or
repair/modification of advanced dispersal systems.
4. Exemptions from Department review or permits shall not be deemed to grant authorization
for any work to be done in any manner that causes an impact to an existing Onsite
Wastewater System or is in violation of the provisions of the Ordinance or this Manual.
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C. EMERGENCY REPAIR WORK
1. Nothing in this Manual shall preclude the property owner from performing any emergency
repair work necessary to protect against an imminent threat to human health and safety or
the environment, however the owner must immediately thereafter apply for a permit, if
applicable.
D. OTHER AGENCY PERMITS
1. No permit or approval from the Department for an Onsite Wastewater System shall relieve
the permittee of responsibility for securing other permits or approvals required for work
which is regulated by any other department or agency of the County, or other public
agency, or for obtaining any easements or authorization for the location of Onsite
Wastewater System components on property not owned by the permittee.
2.3 LAND USE, SITE DEVELOPMENT AND BUILDING PROJECTS REQUIRING
DEPARTMENT REVIEW
A. LOT CREATION, SUBDIVISION AND LOT LINE ADJUSTMENTS
1. Proposed lot creation, subdivision and lot line adjustments on parcels not connected to a
public sewer system must adhere to the following requirements:
a.No lot shall be created, and no parcel, subdivision map or lot line adjustment
recorded unless it is demonstrated that all proposed parcels which rely, or will rely
on an OWTS have an approved site evaluation and preliminary design that
demonstrates that each parcel can support a new OWTS that meets the minimum
requirements contained in this Manual, the Ordinance, and in any local zoning and
planning documents and Zone 7 requirements where applicable. If any parcel
contains an existing OWTS that will remain in service, a performance evaluation
of the OWTS shall be completed to verify suitable performance and sufficient
reserve area for a future dispersal system.
b. For any subdivision of land proposed to be served by an OWTS any parcel that
will be served by an OWTS must be at least forty thousand (40,000) square feet if
served by a public water supply or at least sixty thousand (60,000) square feet if
served by an onsite private water supply, unless the property is located in an area
where more restrictive requirements must be met.
c.For any subdivision creating five (5) or more parcels, the subdivision proposal
must be provided to the respective Regional Water Board for review.
d. No parcel shall be created, no parcel or subdivision map shall be recorded, nor
shall a lot line adjustment be approved where the lot or parcel is dependent on the
use of an OWCU for wastewater disposal.
e.No new parcel shall be created if the parcel relies on an OWTS that cannot be sited
within the boundaries of the proposed parcel unless an easement on any parcel
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designated for the OWTS has been recorded including provisions for access for
installation and ongoing OM&M.
2.Agricultural Exemption.
a.In the event that one or more of the parcels in a proposed subdivision are intended
for agricultural purposes only and not for residential or other use which may
generate wastewater, the owner or owner’s authorized designee may seek an
exemption from the requirements of this section by submitting to the Department
a written request for an exemption under this section stating, for each such parcel,
that the parcel for which an exemption is sought is intended for agricultural
purposes only and not for residential or other use which may generate wastewater.
b. Written requests must be accompanied by a tentative map with express written
conditions containing all of the following information:
(1) The parcel or tract number or other legal identifying information
specifically identifying the property area for which exemption is
requested;
(2) The intended use of the identified property area for which an exemption is
sought;
(3) A statement that said area will be restricted in development such that it
will not have a residence on it nor any other structure that would generate
wastewater and that the area is intended for agricultural purposes only;
(4) A statement that the restrictions cannot be altered or modified without the
prior written approval of the Department; and
(5) A statement that the restrictions are binding on all successors, heirs and
future property owners or occupants of the parcel in accordance with
California law.
c.The exemption shall not become effective until owner or designee obtains final
governmental approval of the final map for the proposed subdivision and delivers
to the Department a complete copy of the final map with the conditions specified
above that has been endorsed and filed with the County Recorder.
B. SITE DEVELOPMENT AND BUILDING PROJECTS
1. Proposed site development and building projects on parcels not connected to a public sewer
system shall be referred to the Department by the local building and/or planning department
to evaluate the compatibility of the project for two main purposes:
a.The capacity of new and existing Onsite Wastewater Systems to handle the
wastewater loading associated with the project; and/or
b.Potential physical impacts to existing Onsite Wastewater Systems including areas
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)2-9
CHAPTER 2
PERMITTING PROCESS OVERVIEW
reserved for dispersal system replacement (reserve areas) and compliance with
requisite setbacks from proposed site development and building projects to Onsite
Wastewater System components.
2. Upon review and approval of the requisite documentation, the Department will issue:
a.Installation or Repair/Modification Permit – a permit to install a new Onsite
Wastewater System or repair/modify an existing System; and/or
b. Project Clearance Letter – a letter issued to the local building or planning
department clearing the proposed project.
3.Work Exempt from Department Review. Work done on existing structures that are
exempt from Department review include:
a.Repairs, modifications, remodeling, improvements and replacement to the shell of
an existing building structure including the foundation, roofing, siding, walls,
windows, doors, flooring, etc. provided the:
(1) Footprint of the structure is not expanded; and
(2) Wastewater flow is not increased due to addition of bedrooms or plumbing
fixtures.
b. Work exempt from building, grading, electrical, plumbing and mechanical permits
by the local building department in accordance with the California Building Code
(California Code of Regulations, Title 24, Part 2) and County or city ordinances.
Although exempt from local building department permits, it is recommended that
projects that have the potential to impact existing Onsite Wastewater Systems are
reviewed by the Department. Projects in this category may include but are not
limited to construction and installation of:
(1) One-story detached accessory structures with a footprint less than one
hundred and twenty (120) square feet;
(2) Fences less than six (6) feet high;
(3) Retaining walls less than four (4) feet high;
(4) Water tanks;
(5) Raised decks, platforms and ramps less than thirty (30) inches above the
adjacent ground surface elevation;
(6) Prefabricated swimming pools installed above ground;
(7) Trellis, lath houses, arbors and similar shade structures;
(8) Swings and other playground equipment; and/or
(9) Flag poles and pole-type radio and television antennas.
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PERMITTING PROCESS OVERVIEW
c.Exemptions from Department review or permits shall not be deemed to grant authorization
for any work to be done in any manner that causes an impact to existing Onsite Wastewater
Systems or is in violation of the provisions of the Ordinance or this Manual.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)3-1
CHAPTER 3
PRACTITIONER QUALIFICATIONS & COUNTY REGISTRATION PROGRAMS
3.0 CHAPTER OVERVIEW
This chapter provides an overview of practitioners that are qualified to conduct work and prepare documents
for site evaluations and Onsite Wastewater System design, installation, repair, abandonment, and
operations, maintenance and monitoring. This chapter also present an overview of County registration
programs for specific classifications of practitioners including Service Providers and Septage Pumpers.
This chapter is organized in the following sections:
Section 3.1: Onsite Wastewater System Practitioner Qualifications
Section 3.2: Service Provider Registration Program
Section 3.3: Septage Pumper Registration Program
3.1 ONSITE WASTEWATER SYSTEM PRACTITIONER QUALIFICATIONS
A. PROFESSIONALS, CONTRACTORS, SERVICE PROVIDERS & SEPTAGE PUMPERS
1.Practitioners that may be involved with the design, evaluation, installation, operation,
maintenance and monitoring of an Onsite Wastewater System include Qualified
Professionals, Contractors, Service Providers and Septage Pumpers.
a.Qualified Professionals. A “Qualified Professional” as referenced in this Manual
includes:
(1)System Designers. A “System Designer” is an individual licensed,
registered or certified by a California state agency to conduct site
evaluations and prepare Onsite Wastewater System designs. This includes
an individual who is a California professional civil engineer, professional
geologist or a registered environmental health specialist.
(2) Other Professionals. Other Qualified Professionals include individuals
licensed, registered or certified by a California state agency to practice as
a professional to conduct work and prepare documents to support site
evaluations and Onsite Wastewater System designs including but not
limited to hydrogeological and geotechnical evaluations, topographic and
property line surveys and drainage structure design as allowed under their
license, registration or certification. Depending on the work to be
performed and various licensing, registration and certification
requirements, this may include but is not limited to an individual who is a
professional geotechnical engineer, a professional land surveyor, a
professional structural engineer, a certified engineering geologist, a
certified hydrogeologist or a certified professional soil scientist.
b.Contractors. A “Contractor” is individual licensed as a general engineering
contractor, a general building contractor, a plumbing contractor or a sanitation
system contractor in accordance with the provisions of the California Business and
Professions Code. Contractors engaged in the evaluation, modification, repair or
installation of Onsite Wastewater Systems shall possess basic knowledge and skills
regarding applicable codes, siting, construction and operation of Systems.
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PRACTITIONER QUALIFICATIONS & COUNTY REGISTRATION PROGRAMS
c.Service Providers. A “Service Provider” is an individual registered with the
Department and capable of operating, monitoring and maintaining an Onsite
Wastewater System in accordance with the provisions of this Manual and under the
terms of an operating permit and other elements of the OM&M manual for the
System. The Department has a registration program for Service Providers as
outlined in Section 3.2 of this chapter. System Designers may also provide OM&M
services as allowed under their license and registration and are exempt from
registration as a Service Provider with the Department.
d.Septage Pumpers. A “Septage Pumper” is a person registered with the Department
who is qualified to pump and haul waste from portable/vault toilets, wastewater
holding tanks, tanks in an OWTS treatment train, cesspools, seepage pits,
wastewater ponds, grease traps, or other wastewater source or wastewater
containment unit under the California Health and Safety Code, Division 104, Part
13, Sections 117400 – 117450 and Chapter 15.18 of the Alameda County General
Ordinance. The Department has a registration program for Septage Pumper
businesses as outlined in Section 3.3 of this chapter.
2. Additional information on the qualifications, licenses, registrations and certifications of
Qualified Professionals, Contractors, Service Providers and Septage Pumpers and the
scope of work allowed by their registration, certification or license is provided in
Table 3-1 and Table 3-2 (included at the end of this chapter).
3. A list of Service Providers and Septage Pumpers registered in the County may be found
on the Departments website at:
http://www.acgov.org/aceh/landuse/owts_service_providers.htm.
B. DESIGNER, CONTRACTOR & SERVICE PROVIDER SYSTEM KNOWLEDGE
1. System Designers, Contractors and Service Providers should have specific training in the
design, installation and operational concepts of the type of System they are providing
services for.
2.Manufacturers’ recommendations for system components vary between products. Design,
installation and operations and maintenance knowledge and skill may be product-specific.
3.2 SERVICE PROVIDER REGISTRATION PROGRAM
A. REGISTRATION REQUIREMENTS
1. Service Providers must register with the Department every two (2) years.
2. The requirements for Service Provider registration include submittal of the following to the
Department:
a.A complete Service Provider registration application and fee;
b. Possession of appropriate knowledge and skills regarding OM&M of Onsite
Wastewater Systems;
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PRACTITIONER QUALIFICATIONS & COUNTY REGISTRATION PROGRAMS
c.Documentation of completion of an Onsite Wastewater System OM&M training
course provided by a third-party organization or entity such as California Onsite
Wastewater Association (COWA), National Association of Waste Transporters
(NAWT) or others approved by the Department every two years; and
d. Verification of manufacturer approved training or certification where
manufacturers of a proprietary treatment unit have certification or training
requirements.
3.3 SEPTAGE PUMPER REGISTRATION PROGRAM
A. REGISTRATION REQUIREMENTS
1. Annual registration with the Department is required for all Septage Pumper businesses and
vehicles as defined below unless exempted by California Health and Safety Code, Division
104, Part 13, Sections 117400 – 117450.
a.Businesses. A business that performs the service of pumping or cleaning OWCU,
tanks in an OWTS treatment train, cesspools, seepage pits, wastewater ponds,
grease traps, or other wastewater source or wastewater containment unit.
b.Vehicles. A vehicle that pumps wastewater from OWCU, tanks in an OWTS
treatment train, cesspools, seepage pits, wastewater ponds, grease traps, or other
wastewater source or wastewater containment unit and disposes of wastewater from
these activities in the County. Each Septage Pumper truck that is used for this
purpose in the County must be separately registered with the Department and will
receive a Septage Pumper registration decal. Vehicles must display the valid
registration decal to operate in the County.
B. APPLICATION
1.A Septage Pumper registration application must include the name and address of the
business, the names and addresses of all owners, (if a partnership, then all names and
addresses of all partners shall be disclosed), vehicle license number(s), vehicle
identification number(s) and the location(s) where wastes will be disposed.
2.The application shall be submitted to the Department with the required fee.
C. SEPTAGE PUMPER TRUCK OPERATOR KNOWLEDGE
1. The Septage Pumper truck owner, operator and all employees shall have knowledge of
sanitary principles and of the requirements and restrictions of Septage Pumper truck
business operation and waste disposal.
2. The Department may require demonstration of employee training and knowledge of,
pumping procedures, spill procedures, etc.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)3-4
CHAPTER 3
PRACTITIONER QUALIFICATIONS & COUNTY REGISTRATION PROGRAMS
D. SEPTAGE PUMPER TRUCK BUSINESS COMPLIANCE
1. The Septage Pumper truck business shall observe sanitary laws, ordinances and other
legal requirements.
2. Failure of the registered business to operate in compliance may result in Septage Pumper
registration revocation.
E. SEPTAGE PUMPER TRUCK INSPECTION PROCEDURES
1. The Septage Pumper registration applicant and operator(s) of the Septage Pumper truck(s)
shall schedule an annual inspection of each vehicle with the Department. During the
inspection the applicant and operator(s) shall be required to demonstrate compliance with
the following requirements for each vehicle being registered:
a.Vehicle Identification. The business name and phone number shall be
permanently affixed on both sides of the vehicle. The certified capacity of the tank
in gallons shall be permanently affixed on both sides of the tank. The capacity as
shown shall be that approved and certified by the sealer of weights and measures of
the County or other approved sealer of weights and measures. All lettering and
numerals shall be plain and legible and at least four inches high and shall be visible
at all times.
b.Vehicle in Good Working Condition. Vehicle and all hoses shall be leak proof and
not show signs of deterioration that could lead to leaking.
c.Vehicle Equipment. A minimum of fifty (50) feet of pumping hose and a bucket
and detergent shall be carried on each pumping vehicle. All pumping hoses must be
cleaned out into the truck tank or into the septic tank, OWCU or other receptacle
being pumped and not onto the surface of the ground.
d.Vehicle Spill Kit. A spill kit shall be carried on each vehicle at all times which
shall include but not be limited to a sufficient quantity of chloride of lime or other
chlorine product for disinfection purposes, absorbent material such as kitty litter,
garbage bags, impervious gloves, a shovel and a spill containment barrier.
F. REPORTING REQUIREMENTS
1.On a quarterly basis, the owner of each registered Septage Pumper truck shall report
the following to Department.
a.The name and address of the owner and/or tenant of each and every location where
an OWCU, tanks in an OWTS treatment train, cesspools, seepage pits, wastewater
ponds, grease traps or other wastewater source or wastewater containment unit have
been pumped or cleaned out;
b. The date of service;
c.The amount of gallons pumped;
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PRACTITIONER QUALIFICATIONS & COUNTY REGISTRATION PROGRAMS
d. Incidents where there is or was wastewater surfacing or there are other signs of
Onsite Wastewater System failure; and
e.The locations where the pumped contents were disposed.
2. Immediate notification must be made to the Department if any of the following are
observed at the time of pumping:
a.Surfacing wastewater that poses a clear threat to public health or the environment;
b. Existence of a cesspool; or
c.Other safety hazard associated with an Onsite Wastewater System.
3. The Department recommends that the pumper document for the property owner the
condition of the Onsite Wastewater System and provide recommendations for repairs, if
any.
Table 3-1
Professional, Contractor, Service Provider & Septage Pumper Licensing/Registration/Certification Requirements
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1-1
Notes:
1Refer to the following guides for more information:
“Consumer Guide to Professional Engineering and Professional Land Surveying” http://www.bpelsg.ca.gov/pubs/consumer_guide.pdf)
“Guide to Engineering & Land Surveying for City and County Officials” (http://www.bpelsg.ca.gov/pubs/local_officials_guide.pdf)
Designation Practitioner Licensing/Registration/Certification Entity
1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1-1
Table 3-2
Professional, Contractor, Service Provider and Septage Pumper Qualifications &
Scope of Work Allowed by Registration, Certification or License
Activity Required Work Minimum Qualifications
Site Evaluation Conduct field studies and evaluate geology, soil and
groundwater for System siting and design.
PE, PG, REHS, CPSS, or CHG as allowed by their registration,
certification, or registration and provisions in this Manual.
Topographic Surveying Perform site surveys, property line determinations, and
generate topographic maps for System siting and design. PE or LLS as allowed by their license
Cumulative Impact
Assessment
Assess nitrate loading, groundwater mounding or other
cumulative impacts of Systems for flows as required by this
Manual.
PE, PG, REHS or CHG
as allowed by their license and provisions in this Manual.
Geotechnical Assessment
Assess slope stability, drainage and other geotechnical
issues for Systems located on slopes over thirty (30) percent
and in areas of geologic instability as required by this Manual.
PE, GE, CEG
Performance Evaluation
Conduct performance evaluations of existing Systems in
connection with building permits, land use projects and failure
investigation.
PE, PG, REHS, or
Licensed Contractor (Class A, B, C-36, or C-42)
depending on the scope of work and provisions in the Manual.
Drainage Structures
Prepare plans and supporting design analysis required for
permitting and installation of groundwater or surface water
drainage structures.
PE
System Design Prepare plans and supporting design analysis required for
permitting and installation of Systems.
PE, PG, or REHS
as allowed by their registration or license and provisions in this
Manual
System Installation,
Repair/Modification or
Abandonment
Install, repair/modify or abandon Systems in accordance with
approved plans and permit conditions issued by the
Department.
Licensed Contractor
(Class A, B, C-36, or C-42)
Inspection, Monitoring,
Maintenance & Reporting
of Systems with an
Operating Permit
Perform inspection, monitoring, routine maintenance of
System and annual reporting in accordance with conditions of
operating permit issued by the Department.
PE, PG, REHS, or Service Provider
Inspection, Monitoring,
Maintenance & Reporting
of Standard Systems
Perform inspection, monitoring, routine maintenance and
reporting to the Department confirming proper System
functioning.
Property owner, PE, REHS, PG, Service Provider
or Licensed Contractor (Class A, B, C-36, or C-42)
Well Installation or
Abandonment
Install or abandon a well under permit by the well permitting
agency.
Licensed Contractor
(Class C-57)
Septage Pumping
Pumping or cleaning of OWCU, Tanks in an OWTS Treatment
train, cesspools, seepage pits, or other wastewater source or
containment units.
Registered Septage Pumper
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)4-1
CHAPTER 4
COMPLAINTS & INVESTIGATIONS
4.0 CHAPTER OVERVIEW
This chapter provides an overview of the complaint and investigation process and is organized in the
following sections:
Section 4.1: Onsite Wastewater System Complaints
Section 4.2: Department Investigations
Section 4.3: Illegal Work
4.1 ONSITE WASTEWATER SYSTEM COMPLAINTS
A. FILING A COMPLAINT
1. A complaint regarding an Onsite Wastewater System may be filed with the Department by
calling the Department via telephone or online on the Department’s website at:
http://www.acgov.org/aceh/landuse/index.htm.
4.2 DEPARTMENT INVESTIGATIONS
A. PROCEDURE
1. Upon receipt of a complaint, the Department will conduct a complaint assessment
and/or investigation. The actions that the Department may take include the following:
a.The Department will contact the complainant to collect information about the
alleged violation.
b. The Department will contact the local code enforcement agency and request
assistance in contacting the owner or tenant to notify them of the complaint and
request an appointment to conduct a joint site visit.
c.If the Department is unable to contact the owner or tenant, the Department in
conjunction with the code enforcement agency will attempt to ascertain whether
there is a violation from observations obtained from a neighboring property or
public vantage point.
d. If the Department and the code enforcement agency are unable to contact the owner
and/or tenant, the Department and code enforcement agency will send the owner
and/or tenant a certified letter with details of the complaint and a request for an
appointment to conduct a site visit.
e .If the Department and code enforcement agency are unable to access the property
to conduct a complaint investigation the Department will request that the code
enforcement agency seek an inspection warrant from a judge.
2.If the Department determines that public health and/or the environment may be at risk, or
that an Onsite Wastewater System has been installed or repaired illegally, the property
owner is responsible for Department costs associated with the complaint.
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CHAPTER 4
COMPLAINTS & INVESTIGATIONS
3.No Person(s) shall obstruct, impede or interfere with the investigation performed by the
Department in response to a complaint.
4. The Department may take photographs and videos to document conditions on the site.
4.3 ILLEGAL WORK
A. ILLEGAL SYSTEM INSTALLATION OR REPAIR WORK
1.If the Department determines that an Onsite Wastewater System has been illegally installed
or work is being conducted without necessary permits, or outside of issued permit
conditions, the Department may issue a “Stop Work Order”. Once the order is issued, no
further work shall be conducted until the Stop Work Order is released by the Department.
2.If a licensed Contractor is found performing work without necessary permits, they may be
reported to the State Contractors License Board. Any Person conducting work without
necessary permits is in violation of the Alameda County Ordinance and, in addition to any
other fine and penalty that may be imposed, subject to a fine of double the permit fee. The
fine is separate from required fees for permits and services to bring the Onsite Wastewater
System or condition into compliance.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
PART 2
SITE EVALUATION REQUIREMENTS
CHAPTER TITLE
CHAPTER 5 SITE EVALUATION OVERVIEW
CHAPTER 6 SITE PLAN REQUIREMENTS
CHAPTER 7 SOIL PROFILE STUDY REQUIREMENTS
CHAPTER 8 SOIL PERCOLATION TESTING
REQUIREMENTS
CHAPTER 9 GROUNDWATER LEVEL DETERMINATION
REQUIREMENTS
CHAPTER 10 CUMULATIVE IMPACT ASSESSMENT
REQUIREMENTS
CHAPTER 11 GEOTECHNICAL EVALUATION
REQUIREMENTS
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)5-1
CHAPTER 5
SITE EVALUATION OVERVIEW
5.0 CHAPTER OVERVIEW
This chapter provides an overview of the site evaluation process associated with the design and permitting
of Onsite Wastewater Systems and is organized as follows:
Section 5.1: Site Evaluation Overview
Section 5.2: Site Plan Overview
Section 5.3: Soil Profile Study Overview
Section 5.4: Soil Percolation Testing Overview
Section 5.5: Groundwater Level Determination Overview
Section 5.6: Cumulative Impact Assessment Overview
Section 5.7: Geotechnical Evaluation Overview
Detailed requirements for each of the above listed elements of a site evaluation are provided in subsequent
chapters in Part 2 of this Manual.
5.1 SITE EVALUATION OVERVIEW
A. GENERAL
1.A site evaluation is the first step in the design process for an Onsite Wastewater System
and must be conducted by a Qualified Professional as allowed by their license or
registration and in accordance the requirements of this Manual.
2.A site evaluation is an assessment of the characteristics of a parcel sufficient to determine
its suitability for the installation, use and sustainability of an Onsite Wastewater System
meeting the requirements of this Manual and the Ordinance.
3.A site evaluation takes into consideration soil texture, soil percolation rate, depth to
groundwater and horizontal setback distances from natural land features and structures to
the proposed Onsite Wastewater System and site topography.
4.The information presented in Chapter 6 through Chapter 11 of this Manual is primarily
for new and replacement Systems and includes detailed procedures and requirements for
the range of potential studies and work that might have to be done to support the System
design.
5. Some level of site evaluation will be required for repairs or modifications of existing Onsite
Wastewater Systems needing corrective action, but the detail and level of work will vary
depending on the specific project and site conditions.
6. Site evaluations shall be performed in coordination with the Department so that
Department personnel may be present for any facet of the process.
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SITE EVALUATION OVERVIEW
B. SYSTEM CONFIGURATION CONSIDERATIONS
1. When conducting the site evaluation the System Designer should take into consideration
the System configurations and siting criteria presented in the following tables (included at
the end of this chapter):
a.Table 5-1 (Gravity Trench Dispersal Systems)
b.Table 5-2 (Pressure-Dosed Trench Dispersal Systems)
c.Table 5-3 (Subsurface Drip Dispersal Systems)
d.Table 5-4 (At-Grade Dispersal Systems)
e.Table 5-5 (Mound Dispersal Systems)
f.Table 5-6 (Raised Sand Filter Bed Dispersal Systems)
2. The System Designer should also be familiar with the detailed requirements presented in
Part 7 of this Manual for each of the dispersal system types listed above.
C. HORIZONTAL SETBACK DISTANCE CONSIDERATIONS
1. When conducting the site evaluation the System Designer should take into consideration the
minimum setback distances from Onsite Wastewater System components to natural land
features, structures and utilities in accordance with the following criteria:
a.County Requirements. The Onsite Wastewater System design and installation
shall meet the minimum horizontal setback distances provided in Table 5-7
(included at the end of this chapter), as applicable.
b.California Plumbing Code: The Onsite Wastewater System design and
installation shall also meet the minimum setback distances for building sewer and
sanitary drainage provided in the California Plumbing Code, as applicable.
c.Incorporated Cities Requirements. Incorporated cities may also have their
own requirements for setbacks that are not included in the Ordinance and this
Manual. The System Designer and Applicant are encouraged to check with the
local jurisdiction planning and building departments.
5.2 SITE PLAN OVERVIEW
A. GENERAL
1. An important step in the site evaluation process is preparation of a site plan to identify
physical features of the parcel and adjacent parcels that may impact or limit:
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SITE EVALUATION OVERVIEW
a.Siting and performance requirements of a new Onsite Wastewater System;
b. Siting and performance requirements of an existing Onsite Wastewater System;
c.Proposed work associated with a local building agency permit for grading,
demolition or new site construction with respect to potential impact to existing
Onsite Wastewater Systems and OWTS reserve areas; and/or
d. Proposed land use projects including lot creation, lot line adjustments, subdivisions,
site development review and conditional use permits with respect to new Onsite
Wastewater System design or potential impact to existing Onsite Wastewater
Systems and OWTS reserve areas.
2. The site plan is used as the base map for Onsite Wastewater System evaluation and design.
3. Site plan requirements are contained in Chapter 6 of this Manual.
5.3 SOIL PROFILE STUDY OVERVIEW
A. GENERAL
1. The purpose of the soil profile study is to determine the suitability of the soil for absorption
of wastewater in the area of a dispersal system to:
a.Ensure that proper soil conditions and effective soil depth exist to allow appropriate
effluent retention, treatment and filtration;
b. Prevent wastewater from discharging to the ground surface or contaminating
groundwater or surface water resources;
c.Inform the design of the Onsite Wastewater System; and
d. Verify that there is adequate vertical separation between the bottom of the dispersal
system and bedrock, groundwater or impermeable soil strata.
2. Soil profile study requirements are contained in Chapter 7 of this Manual.
5.4 SOIL PERCOLATION TESTING OVERVIEW
A. GENERAL
1. Subsurface dispersal systems are sized based on wastewater application rates that are
representative of the soil classification and percolation rates for the soil zone corresponding
to the sidewall and/or bottom of the dispersal system and the type of OWTS proposed.
2. Percolation testing is performed to provide information required to determine the potential
wastewater absorption rate of soil in the dispersal system areas including the reserve areas.
3. Percolation testing does not replace the need or requirement for a soil profile study, soil
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)5-4
CHAPTER 5
SITE EVALUATION OVERVIEW
textural determination and determination of high seasonal groundwater levels.
4. Soil percolation testing requirements are contained in Chapter 8 of this Manual.
5.5 GROUNDWATER LEVEL DETERMINATION OVERVIEW
A. GENERAL
1. Some locations in Alameda County are subject to high groundwater levels (high seasonal
groundwater) which can have an adverse impact on the performance of an OWTS by
eliminating or minimizing the zone of aeration in soil that is critical for wastewater
treatment.
2. Installing an OWTS on a site that appears to have adequate separation to groundwater in
the dry season but experiences shallow groundwater during the rainy season may result in
an OWTS which functions properly only part of the year.
3. Failure to provide the required separation to high seasonal groundwater may potentially
result in OWTS failure leading to:
a.Introducing untreated wastewater to groundwater which could affect area water
wells, water quality and public health;
b. Wastewater surfacing on the ground; and/or
c.Wastewater backing up into building or structure plumbing fixtures.
4. Groundwater level determination requirements are contained in Chapter 9 of this
Manual.
5.6 CUMULATIVE IMPACT ASSESSMENT OVERVIEW
A. GENERAL
1.Certain projects require the completion of a “cumulative impact assessment” in situations
where cumulative impacts to groundwater and/or surface water from OWTS are of
potential concern.
2. Cumulative impacts are defined as the persistent and/or increasing effect resulting from
the density of OWTS discharges in relation to the assimilative capacity of the local
environment. Examples include, but are not limited to:
a.Nitrate and salt additions to groundwater or surface water;
b. Rise in groundwater levels that interferes with the performance of the OWTS or
results in other adverse hydrological or soil conditions affecting public health,
water quality or public safety; and/or
c.Bacteriological contamination from animal and human waste in surface water,
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)5-5
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SITE EVALUATION OVERVIEW
groundwater and drinking water wells.
3. Cumulative impact issues from OWTS may occur due to the following factors:
a.Constituent levels in wastewater (e.g., nitrogen content);
b. Volume of wastewater flow;
c.Density of OWTS discharges in a given area; and/or
d. Sensitivity and beneficial uses of water resources in a particular location.
4. These issues are not necessarily addressed by conformance with standard siting and design
criteria for OWTS.
5. Cumulative impact assessment requirements are contained in Chapter 10 of this Manual.
5.7 GEOTECHNICAL EVALUATION OVERVIEW
A. GENERAL
1. Certain projects require the completion of a slope stability analysis where warranted by site
topography such as steep slopes or if the System is located within an earthquake fault zone
or a seismic hazard zone.
2. These issues are not necessarily addressed by conformance with standard siting and design
criteria for OWTS.
3. Geotechnical evaluation requirements are contained in Chapter 11 of this Manual.
Table 5-1
Gravity Trench Dispersal Systems
Configurations & Siting Criteria
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 of 2
No.
Primary
and/or
Supplemental
Treatment
Gravity
Fed or
Pressure
Dosed
Dispersal
System
Type
Depth to
Bottom
Infiltrative
Surface
(bgs)1
Percolation
Rate
Maximum
Ground
Slope2
Minimum
Effective
Soil
Depth
(feet)3
Minimum
Separation to
High Seasonal
Groundwater
(feet)3
Wastewater
Application Rate
Table
1 Primary
Treatment
Gravity
Fed
Trench
(Drain Rock
or Gravelless
Distribution
Product)
2.5 to 5
feet
> 60 MPI N/A N/A N/A N/A
6 to 60 MPI 30% 5 feet 5 feet Table 25-1
(Standard)
1 to 5 MPI 30% 5 feet 20 feet Table 25-1
(Standard)
< 1 MPI N/A N/A N/A N/A
2
Primary &
Supplemental
Treatment
Gravity
Fed
Trench
(Drain Rock
or Gravelless
Distribution
Product)
2.5 to 5
feet
> 60 MPI N/A N/A N/A N/A
6 to 60 MPI 30%3 3 Table 25-1
(Standard)
1 to 5 MPI 30% 3 5 Table 25-1
(Standard)
< 1 MPI N/A N/A N/A N/A
Notes:
1Depth measured from native ground surface
2Increases of up to five (5) percent may be allowed if supported by a geotechnical evaluation
3Depth measured from bottom of dispersal system infiltrative surface
MPI = Minutes per inch
N/A = Not allowed
Table 5-1
Gravity Trench Dispersal Systems
Configurations & Siting Criteria
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 2 of 2
Notes:
1Depth measured from native ground surface
2Depth measured from bottom of dispersal system infiltrative surface
MPI = Minutes per inch
N/A = Not allowed
No.
Primary
and/or
Supplemental
Treatment
Gravity
Fed or
Pressure
Dosed
Dispersal
System
Type
Depth to
Bottom
Infiltrative
Surface1
Percolation
Rate
Maximum
Ground
Slope
Minimum
Effective
Soil
Depth2
Minimum
Separation to
High Seasonal
Groundwater2
Wastewater
Application Rate
Table
Table 5-2
Pressure-Dosed Trench Dispersal Systems
Configurations & Siting Criteria
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 of 4
Notes:
1Depth measured from native ground surface
2Increases of up to five (5) percent allowed with geotechnical evaluation
3Depth measured from bottom of dispersal system infiltrative surface
MPI = Minutes per inch
N/A = Not allowed
No.
Primary
and/or
Supplemental
Treatment
Gravity
Fed or
Pressure
Dosed
Dispersal
System
Type
Depth to
Bottom
Infiltrative
Surface1
Percolation
Rate
Maximum
Ground
Slope2
Minimum
Effective
Soil
Depth3
Minimum
Separation to
High Seasonal
Groundwater3
Standard
Application Rate
Table 5-2
Pressure-Dosed Trench Dispersal Systems
Configurations & Siting Criteria
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 2 of 4
Notes:
1Depth measured from native ground surface
2Increases of up to five (5) percent allowed with geotechnical evaluation
3Depth measured from bottom of dispersal system infiltrative surface
MPI = Minutes per inch
No.
Primary
and/or
Supplemental
Treatment
Gravity
Fed or
Pressure
Dosed
Dispersal
System
Type
Depth to
Bottom
Infiltrative
Surface1
Percolation
Rate
Maximum
Ground
Slope2
Minimum
Effective
Soil
Depth3
Minimum
Separation to
High Seasonal
Groundwater3
Standard
Application Rate
Table 5-2
Pressure-Dosed Trench Dispersal Systems
Configurations & Siting Criteria
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 3 of 4
Notes:
1Depth measure from native ground surface
2Increases of up to five (5) percent allowed with geotechnical evaluation MPI = Minutes per inch
3Depth measured from bottom of dispersal system infiltrative surface N/A = Not allowed
4Trench sand thickness of twelve (12) inches
5Trench sand thickness of twenty-four (24) inches
6Trench sand thickness of six (6) inches
No.
Primary
and/or
Supplemental
Treatment
Gravity
Fed or
Pressure
Dosed
Dispersal
System
Type
Depth of
Bottom
Infiltrative
Surface1
Percolation
Rate
Maximum
Ground
Slope2
Minimum
Effective
Soil
Depth3
Minimum
Vertical
Separation to
High Seasonal
Groundwater3
Wastewater
Application Rate
Table
4
5
6
4
Table 5-2
Pressure-Dosed Trench Dispersal Systems
Configurations & Siting Criteria
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 4 of 4
Notes:
1Depth measure from native ground surface
2Increases of up to five (5) percent allowed with geotechnical evaluation MPI = Minutes per inch
3Depth measured from bottom of dispersal system infiltrative surface N/A = Not allowed
4Trench sand thickness of twelve (12) inches
5Trench sand thickness of twenty-four (24) inches
6Trench sand thickness of six (6) inches
No.
Primary
and/or
Supplemental
Treatment
Gravity
Fed or
Pressure
Dosed
Dispersal
System
Type
Depth of
Bottom
Infiltrative
Surface1
Percolation
Rate
Maximum
Ground
Slope2
Minimum
Effective
Soil
Depth3
Minimum
Separation to
High Seasonal
Groundwater3
Standard
Application Rate
4
5
6
4
Table 5-3
Subsurface Drip Dispersal Systems
Configurations & Siting Criteria
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
No.
Primary
and/or
Supplemental
Treatment
Gravity
Fed or
Pressure
Dosed
Dispersal
System
Type
Depth of
Bottom
Infiltrative
Surface1
Percolation
Rate
Maximum
Ground
Slope2
Minimum
Effective
Soil
Depth3
Minimum
Separation to
High Seasonal
Groundwater3
Wastewater
Application Rate
Table
1
Primary and
Supplemental
Treatment
Pressure
Dosed
Subsurface
Drip 0.67 to 1
> 120 MPI N/A N/A N/A N/A
6 to 120 MPI 50%2 feet 2 feet Table 25-3 (Drip)
1 to 5 MPI 50% 2 feet 3 feet Table 25-3 (Drip)
< 1 MPI N/A N/A N/A N/A
2
Primary and
Supplemental
Treatment
Primary and
Supplemental
Treatment
Pressure
Dosed
Pressure
Dosed
Subsurface
Drip
Subsurface
Drip with
Cover Soil
0.16 to <1
> 120 MPI N/A N/A N/A N/A
6 to 120 MPI 20%2 feet 2 feet Table 25-3 (Drip)
1 to 5 MPI 20% 2 feet 3 feet Table 25-3 (Drip)
< 1 MPI N/A N/A N/A N/A
Notes:
1Depth measured from native ground surface
2Increases of up to five (5) percent allowed with geotechnical evaluation
3Depth measured from bottom of dispersal system infiltrative surface
MPI = Minutes per inch
N/A = Not allowed
Table 5-4
At-Grade Dispersal Systems
Configurations & Siting Criteria
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
No.
Primary
and/or
Supplemental
Treatment
Gravity
Fed or
Pressure
Dosed
Dispersal
System
Type
Bottom
Infiltrative
Surface
Depth1
Percolation
Rate
Maximum
Ground
Slope2
Minimum
Effective
Soil
Depth3
Minimum
Separation to
High Seasonal
Groundwater3
Wastewater
Application Rate
Table
1 Primary
Treatment
Pressure
Dosed At-Grade 0 feet
> 60 MPI N/A N/A N/A N/A
6 to 60 MPI 20 %3 feet 3 feet Table 25-1
(Standard)
1 to 5 MPI 20 % 3 feet 5 feet Table 25-1
(Standard)
< 1 MPI N/A N/A N/A N/A
2
Primary and
Supplemental
Treatment
Pressure
Dosed At-Grade 0 feet
> 120 MPI N/A N/A N/A N/A
91 to 120
MPI 15 %2 feet 2 feet Table 25-1
(Standard)
61 to 90 MPI 15 %
2 feet 2 feet Table 25-1
(Standard)
2 feet 3 feet Table 25-2
(Enhanced)
6 to 60 MPI 20 %
2 feet 2 feet Table 25-1
(Standard)
2 feet 3 feet Table 25-2
(Enhanced)
1 to 5 MPI 20 %
2 feet 3 feet Table 25-1
(Standard)
2 feet 5 feet Table 25-2
(Enhanced)
Notes:
1Depth measured from native ground surface MPI = Minutes per inch
2Increases of up to five (5) percent allowed with geotechnical evaluation N/A = Not allowed
3Depth measured from bottom of dispersal system infiltrative surface
Table 5-5
Mound Dispersal Systems
Configurations and Siting Criteria
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
No.
Primary
and/or
Supplemental
Treatment
Gravity
Fed or
Pressure
Dosed
Dispersal
System
Type
Bottom
Infiltrative
Surface
Depth1
Percolation
Rate
Maximum
Ground
Slope2
Minimum
Effective
Soil
Depth3
Minimum
Separation to
High Seasonal
Groundwater3
Wastewater
Application Rate
Table
1 Primary
Treatment
Pressure
Dosed Mound 0 feet
> 120 MPI N/A N/A N/A N/A
61 to 120 MPI 15% 2 feet 2 feet Table 25-2
(Enhanced)
6 to 60 MPI 20%2 feet 2 feet Table 25-2
(Enhanced)
1 to 5 MPI 20% 2 feet 3 feet Table 25-2
(Enhanced)
< 1 MPI N/A N/A N/A N/A
2
Primary
Treatment and
Supplemental
Pressure
Dosed Mound 0 feet
> 120 MPI N/A N/A N/A N/A
61 to 120 MPI 15%2 feet 2 feet Table 25-2
(Enhanced)
6 to 60 MPI 20% 2 feet 2 feet Table 25-2
(Enhanced)
1 to 5 MPI 20% 2 feet 2 feet Table 25-2
(Enhanced)
< 1 MPI N/A N/A N/A N/A
Notes:
1Depth measured from native ground surface MPI = Minutes per inch
2Increases of up to five (5) percent allowed with geotechnical evaluation N/A = Not allowed
3Depth measured from bottom of dispersal system infiltrative surface
Table 5-6
Raised Sand Filter Bed Dispersal Systems
Configurations & Siting Criteria
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
No.
Primary
and/or
Supplemental
Treatment
Gravity
Fed or
Pressure
Dosed
Dispersal
System
Type
Bottom
Infiltrative
Surface
Depth1
Percolation
Rate
Ground
Slope2
Minimum
Effective
Soil Depth3
Minimum
Separation to
High Seasonal
Groundwater3
Wastewater
Application Rate
Table
1 Primary
Treatment4
Pressure
Dosed
Raised
Sand Filter
Bed
0 feet
> 60 MPI N/A N/A N/A N/A
6 to 60 MPI 30%2 feet 2 feet Table 25-2
(Enhanced)
1 to 5 MPI 30% 2 feet 3 feet Table 25-2
(Enhanced)
< 1 MPI N/A N/A N/A N/A
2
Primary and
Supplemental
Treatment5
Pressure
Dosed
Raised
Sand Filter
Bed
0 feet
>60 MPI N/A N/A N/A N/A
6 to 60 MPI 30%2 feet 2 feet Table 25-2
(Enhanced)
1 to 5 MPI 30% 2 feet 2 feet Table 25-2
(Enhanced)
< 1 MPI N/A N/A N/A N/A
Notes:
1Depth measured from native ground surface MPI = Minutes per inch
2Increases of up to five (5) percent allowed with geotechnical evaluation N/A = Not allowed
3Depth measured from bottom of dispersal system infiltrative surface
4Minimum sand fill depth of twenty four (24) inches required
5Minimum sand fill depth of twelve (12) inches required
Table 5-7
Minimum Horizontal Setback Distances
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 3
Site Feature
Minimum Horizontal Setback Distance1
(Feet)
To Dispersal Field
To Tanks,
Supplemental
Treatment Units
Perennial and Intermittent Watercourses (from top of bank):
All Watercourses
Watercourses between 1,200 to 2,500 feet from a state
small water or public water system intake2
Watercourses within 1,200 feet of a state small water or
public water system intake2
100
200
400
50
100
100
Ephemeral Watercourses and Storm Water Drainage
Structures:
Drainage Swales and Drainage Ways (from the high
water mark)3
Manmade Impervious Lined (concrete, asphalt or
equal) Drainage Ditch or Swale (from the edge of the
ditch/swale)
Closed drain pipe or watertight culverts or conduits
(from the edge of the pipe)
4 X depth
15
10
4 X depth
15
10
Edge of 100-year flood plain 0 0
Private Water Supply Wells4 and Springs 100 50
Public Water Supply Wells 150 150
Drinking Water Reservoir or Lake (from highwater mark):
All Reservoirs/Lakes
Reservoirs/lakes within 1,200 feet of a state small water
or public water system intake2
200
400
200
400
Non-Drinking Water Ponds (unlined), Springs or Lakes 100 50
Storm Water Infiltration Ponds 50 25
Swimming Pools, Lined Ponds or Basins 25 10
Curtain Drains (measured from the centerline of the
nearest dispersal trench to the centerline of the curtain
drain trench)
Uphill of the dispersal field
Lateral to the dispersal field (along slope contour)
Downhill of the dispersal field
5 feet + depth of
trench
25
50
N/A
N/A
N/A
Table 5-7
Minimum Horizontal Setback Distances
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 2 OF 3
Notes:
1Repairs and replacement systems may be allowed to comply with horizontal setback distances to the
maximum extent practicable.
2For areas tributary to and upstream of water supply intake, setback distance measured from high water
mark. Exceptions may be allowed as follows:
a.Replacement Systems, comply to the maximum extent practicable and incorporate supplemental
treatment which may be waived if there is sufficient evidence that there is no impact or
significant threat to water source;
b. New Systems on pre-existing lot of record, comply to maximum extent practicable and
incorporate supplemental treatment for pathogens.
3The required setback distance shall not be less than twenty five (25) feet nor more than fifty (50) feet
from the high water mark.
4Setback also applies to private water supply wells that have been abandoned (i.e., a well whose original
purpose and use has been permanently discontinued or which is in such a state of disrepair that it cannot be
used for its original purpose) unless documentation from the well permitting agency is provided to the Department
that demonstrates the well has been properly destroyed so that it will not produce water nor act as a
conduit for the movement of water.
Notes (continued):
Site Feature
Minimum Horizontal Setback Distance1
(Feet)
To Dispersal Field
To Tanks,
Supplemental
Treatment Units
Energy Dissipaters (measured from edge of nearest
Dispersal Trench to the daylight end of outlet pipe).
Upslope
Downslope
Lateral of the System components
50
25
25
20
10
10
Geological Unstable Land Mass5 (visual scarp, slump or slide) 100 100
Manmade Cut /Fill Banks (from top of cut)5,6 4 X h 4 X h
Natural Steep Slopes (from toe of slope)5,7 10 10
Property Lines 10 10
Structures and Foundations, including Footings8 10 5
Ground Mounted Solar Panels9 10 5
Edge of Road Easements, Right of Ways, Pavement,
Driveways, or Areas Subjected to Vehicular Traffic10 5 5
Edge of Underground Utility Easements (unless
easement is specifically for an OWTS)11 0 0
Table 5-7
Minimum Horizontal Setback Distances
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 3 OF 3
5Setback distance may be reduced in accordance with recommendations provided in a geotechnical report
prepared by a Qualified Professional.
6Cut bank and fill banks are considered to be any altered area of land surface where the height (h) of the
manmade cut or embankment is greater than two (2) feet, with a slope greater than fifty (50) percent, and
any part of which is lower in elevation than the ground surface at the nearest point of the OWTS.
The required setback distance shall not be less than twenty five (25) feet nor more than fifty (50) feet
from the top of the cut or embankment. Cuts supported by retaining walls or similar structures shall be
included in this definition as shall steep natural ground surfaces where a sharp break in the ground slope is
discernible.
7Steep slope is considered to be land with a slope greater than fifty (50) percent and a height of greater
than ten (10) feet, and any part of which is higher in elevation than the ground surface at the nearest
point of the OWTS. The required setback distance is measured from the toe of slope.
8Including porches, steps, breezeways, roof patios, carports, covered walkways, covered driveways,
fences, retaining walls and other similar structures and appurtenances.
9The setback distance to the dispersal field may be reduced to four (4) feet when installed over and
between dispersal trenches and design is stamped by a Registered Civil Engineer.
10Setback distance to tanks may be reduced to zero (0) feet where traffic rated.
11If sewer tight line is properly bedded or sleeved.
N/A = Not applicable
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)6-1
CHAPTER 6
SITE PLAN REQUIREMENTS
6.0 CHAPTER OVERVIEW
This chapter provides the requirements for preparation of site plans to support the design and permitting of
Onsite Wastewater Systems and is organized as follows:
Section 6.1: Site Plan Overview
Section 6.2: Vicinity Sketch
Section 6.3: Contour Lines, Spot Elevations & Slope Designations
Section 6.4: Site Evaluation Field Investigation Locations
Section 6.5: Existing Onsite Wastewater System Locations
Section 6.6: Building and Structure Locations & Footprints
Section 6.7: Pertinent Features Relative to Horizontal Setback Requirements
6.1. SITE PLAN OVERVIEW
A. GENERAL
1. The site plan shall be used as the base map for Onsite Wastewater System evaluation and
design and shall be prepared by a Qualified Professional as allowed by their registration
and license.
2. The site plan shall include data obtained by field inspection and topographic survey,
and information from the Department files, local building and planning department files,
well permitting agency databases, Federal Emergency Management Act (FEMA) flood
maps, United States Geological Survey (USGS) maps and other available databases as
applicable.
6.2. VICINITY SKETCH
A. MINIMUM CRITERIA
1. The site plans shall incorporate a vicinity sketch (not at map scale) indicating the location
of the parcel relative to the principal roadways and showing the lengths and compass
bearings of property boundaries of the entire parcel and adjacent parcels.
2. On large parcels the vicinity sketch must show the general location of the following features
to facilitate determination of compliance with horizontal setback requirements during plan
review:
a.Existing Onsite Wastewater Systems, private and public potable water sources
(wells, springs, reservoirs, etc.) and buildings and structures on the parcel; and/or
b. Public water system wells and surface water intake points on adjacent parcels.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)6-2
CHAPTER 6
SITE PLAN REQUIREMENTS
6.3. CONTOUR LINES, SPOT ELEVATIONS & SLOPE DESIGNATIONS
A. MINIMUM CRITERIA
1. The site plans shall provide spot elevations, slope designations (percent and direction) and
contours of the earth’s surface of existing terrain and proposed grading in the vicinity of
existing and proposed Systems to facilitate evaluation, siting and design.
2. Contour intervals shall be adequate to verify code compliance during plan check.
6.4. SITE EVALUATION FIELD INVESTIGATION LOCATIONS
A. MINIMUM CRITERIA
1. The site plans shall show the locations of soil profile test pits, percolation test holes,
geotechnical evaluation borings and test pits, groundwater monitoring wells and
piezometers and any other areas of the parcel and adjacent parcels investigated during site
evaluation activities.
6.5. EXISTING ONSITE WASTEWATER SYSTEM LOCATIONS
A. MINIMUM CRITERIA
1. The site plans shall show the location of the components of all existing Onsite Wastewater
Systems on the parcel including but not limited to:
a.Cesspools and seepage pits;
b.OWCU (holding tanks, vault toilets, portable toilets);
c.OWTS;
d. Wastewater ponds (including wastewater from water softening processes); and
e.Graywater systems.
6.6. BUILDING AND STRUCTRUE LOCATIONS & FOOTPRINTS
A. MINIMUM CRITERIA
1.The site plans shall show the location and footprint of all existing and proposed buildings
and structures on the parcel and shall identify which buildings and structures have
wastewater plumbing.
6.7. PERTINENT FEATURES RELATIVE TO HORIZONTAL SETBACK REQUIREMENTS
A. GENERAL
1.The site plans shall show pertinent features located within the horizontal setback distances
that may have an impact on the System siting and design.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)6-3
CHAPTER 6
SITE PLAN REQUIREMENTS
B. FEATURES WITHIN 50 FEET OF SYSTEM COMPONENTS
1. The following features (existing and proposed) may be relevant and must be shown on the site
plans if they are within fifty (50) feet of existing and proposed Systems:
a.Parcel lines, lengths and compass bearings (verified through pin location or boundary
surveys, if required).
b. Surface water and groundwater drainage structures (e.g., infiltration trenches,
interceptor drains, roof run-off piping, sumps, swales, v-ditches, canals, culverts,
energy dissipaters, outfalls, etc.);
c.Drainage ways, drainage swales, and other ephemeral watercourses (measured from
top of bank or high water mark if there is no discernible channel);
d. Vehicle traffic and storage areas (paved or unpaved);
e.Subsurface utility lines (existing and proposed electrical, sewer, water, gas, etc.);
f.Landscaped/irrigated areas;
g.Easements, access agreements, and public right-of-ways (e.g., underground utility
easements, above ground utility easements, public roadway right-of-ways,
private potable water supply access agreements and easements, Onsite
Wastewater Systems access agreements and easements, etc.);
h. Graded/fill areas (e.g., building pads, berms, etc.);
i. Retaining walls;
j. French drains or groundwater interceptor drains or cutoff walls;
k.Hazardous materials storage areas including above ground and underground storage
tanks;
l. Trees or vegetation that pose a construction or operational concern for the Onsite
Wastewater Systems; and
m.Other site development related features and appurtenances including but not
limited to patios, decks, gazebos, walkways, children’s play structures, fences,
driveways, bridges, decorative ponds, hot tubs/spas, pools, pool houses, ground
mounted solar installations, animal pens/corrals, animal wash pads, crush pads,
garbage enclosures, etc.).
C. FEATURES WITHIN 100 FEET OF SYSTEM COMPONENTS
1. The following features may be relevant and must be shown on the site plans if they are within
one hundred (100) feet of existing and proposed Onsite Wastewater Systems.
a.Steep slopes (measured from the break of slope);
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)6-4
CHAPTER 6
SITE PLAN REQUIREMENTS
b. Cut or steep embankments (measured from the top of cut);
c.Unstable land masses or any other areas subject to earth slides identified by a seismic
hazard zone map or a professional civil engineer or other professional as allowed
by their license, registration or certification;
d. Private existing, abandoned, and proposed potable water supply sources (springs
or wells) and associated appurtenances including water storage and treatment
facilities (e.g., storage tanks, pump houses, water softener ponds, etc.);
e.Perennial or intermittent watercourses (measured from the natural or levied top of
bank or high water mark if no defined bank);
f.Reservoirs, lakes, ponds or other non-flowing surface water bodies (measured
from the high water mark);
g.Springs;
h. Floodplain boundaries (100-year); and
i. Wetlands.
D. FEATURES WITHIN 200 FEET OF SYSTEM COMPONENTS
1. The following features may be relevant and must be shown on the site plans if they are within
two hundred (200) feet of existing and proposed Onsite Wastewater Systems.
a.Sanitary sewer lines.
E. FEATURES WITHIN 600 FEET OF SYSTEM COMPONENTS
1. The following may be relevant and must be shown on the vicinity sketch if they are within
six hundred (600) feet of existing and proposed dispersal systems:
a.Public water system wells.
F. FEATURES WITHIN 2,500 FEET OF SYSTEM COMPONENTS
1. The following may be relevant and must be shown on the vicinity sketch if they are within
two thousand five hundred (2,500) feet of existing and proposed dispersal systems:
a.Public water system surface water intake points.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)7-1
CHAPTER 7
SOIL PROFILE STUDY REQUIREMENTS
7.0 CHAPTER OVERVIEW
This chapter provides the requirements for conducting soil profile studies used to support the design and
permitting of Onsite Wastewater Systems and is organized as follows:
Section 7.1: Soil Profile Test Pit Requirements
Section 7.2: Laboratory Tests to Verify Soil Classification Requirements
7.1 SOIL PROFILE TEST PIT REQUIREMENTS
A. DEPARTMENT OBSERVATION
1. A Qualified Professional must perform the soil profile in the presence of the Department
representative. The Department may authorize the soil profile to proceed without a
Department representative, however, such authorization must be in writing and, may require
submittal of photo documentation.
2. Written notice must be given to the Department at least forty-eight (48) hours in advance of
conducting the soil profile study. Additional time may be required to schedule the presence
of the Department representative.
3. Notification and the request must include the Applicant’s name and assessor’s parcel
number and street address of the property. Failure to provide sufficient notice may result in
delay or a requirement to repeat the test.
4. All soil profile test pits must be dug prior to the Department field observation appointment.
5. If more than one site visit is required to observe the soil profile a fee may be charged for
each visit.
B. SOIL PROFILE TEST PITS – NUMBER, DEPTH AND DISTRIBUTION
1. Soil profile test pits shall be sufficient in number and adequately spaced to encompass and
represent the soil conditions of the entire area of the dispersal system including reserve
areas.
2. A minimum of two (2) soil profiles are required:
a.Standard OWTS: One (1) profile in each of the dual dispersal system areas.
b.Advanced OWTS: One (1) profile in the dispersal system area and one (1) profile
in the reserve area.
3. Additional soil profiles may be required if the initial soil profiles do not provide sufficient
information for design and/or determination of code compliance.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)7-2
CHAPTER 7
SOIL PROFILE STUDY REQUIREMENTS
C. SOIL PROFILE TEST PIT EXCAVATIONS
1. Soil profile test pits shall be excavated by a backhoe, excavator or by hand unless an
exception is approved by the Department.
2. Soil profile test pits must be excavated to the appropriate depth to verify that there is
adequate vertical separation from groundwater and effective soil beneath the bottom of the
dispersal system.
3. The measurement of effective soil depth is taken from natural ground surface elevation and
must not consider fill material or imported soil.
4. Auger test holes may be an acceptable alternative to backhoe or hand-dug soil profile test
pits and may be allowed under the following conditions:
a.The use of a backhoe or similar excavating machinery is impractical due to site
access constraints or fragile soils;
b. Testing is necessary only to verify conditions based on prior soils investigations;
c.Soil profiles are required to be no greater than three (3) feet deep;
d. Testing is done in connection with geologic investigation;
e.Where verification of groundwater separation requires additional deeper
subsurface exploration; or
f.In connection with corrective actions or documentation of an existing Onsite
Wastewater System.
5. When the auger method is used for new or replacement dispersal systems, at least two (2)
test holes in each dispersal system area and two (2) test holes in the reserve area (for
advanced OWTS) are required.
D. SOIL PROFILE OBSERVATIONS
1. The excavated sidewall of the soil profile test pit shall be picked away with a sharp
instrument to expose the natural soil structure.
2. The Qualified Professional shall identify each soil horizon from ground surface to the
bottom of the soil profile.
3. Soil profile observations shall be recorded on a form provided by the Department and shall
include a description of the following soil features:
a.Soil texture, color, structure, consistency, plasticity, and porosity for each soil
horizon in the excavation utilizing the United States Department of Agriculture
(USDA) soil classification system and soil textural triangle presented in Figure 7-
1 and Figure 7-2 (included at the end of this chapter);
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SOIL PROFILE STUDY REQUIREMENTS
b.Depth and type of limiting layer or condition;
c.Depth of soil mottling, gleying or other evidence of periodic soil saturation;
d.Depth of effective soil; and
e.Other prominent soil features including but not limited to percentage of rock or
coarse fragments, root porosity, dampness, shrinkage cracks, gopher holes or depth
and type of fill or imported soil in the profile.
7.2 LABORATORY TESTS TO VERIFY SOIL CLASSIFICATION REQUIREMENTS
A. MINIMUM CRITERIA
1. If the classification of the soil is in question, the Department may require the Qualified
Professional to provide laboratory test data to verify the actual classification of the soil
including but not limited to the percentage of sand, silt, and clay and the expansive potential.
2. All samples shall be appropriately labeled and analyzed in accordance with an approved
American Society of Testing and Materials (ASTM) method or USDA method by a soil
mechanics laboratory.
Figure 7-1
USDA Soil Textural Traingle
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
Source: United States Department of Agriculture
Figure 7-2
Soil Profile Classification
To classify a soil sample using the USDA Soil Textural Triangle, plot the intersection of the
three lines that correspond to the proportions of clay, sand and silt. The percentages of the
three components must add up to one-hundred (100) percent.
Example: Classify a soil sample that is 30% clay, 15% silt, and 55% sand.
First locate 30% on the clay axis, and draw a line horizontally from left to right. Next, locate
15% on the silt axis, and draw a line going down diagonally to the left. Finally, locate 55% on the
sand axis, and draw a line going up diagonally to the left. The intersection is in a region called
Sandy Clay Loam. See figure below.
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CHAPTER 8
SOIL PERCOLATION TESTING REQUIREMENTS
8.0 CHAPTER OVERVIEW
This chapter provides the soil percolation testing requirements used to support the design and permitting of
Onsite Wastewater Systems and is organized as follows:
Section 8.1: Soil Percolation Testing Requirements
Section 8.2: Design Percolation Rate Requirements
Section 8.3: Interpretation of Percolation Test Results
8.1 SOIL PERCOLATION TESTING REQUIREMENTS
A. DEPARTMENT OBSERVATION
1. Soil percolation testing shall be performed under the responsible charge of a System
Designer or other Qualified Professional as allowed by their license and registration. The
Department may elect to witness the installation of the percolation test holes, verify
presoaking and be present during all or part of the testing.
2. The Department may authorize the percolation tests to proceed without a Department
representative, however, such authorization must be in writing.
3. Written notice must be given to the Department at least forty-eight (48) hours in advance of
conducting soil percolation tests. Additional time may be required to schedule the presence
of a Department representative.
4. Notification and the request must include the Applicant’s name and the assessor’s parcel
number and street address of the property. Failure to provide sufficient notice may result in
delay or a requirement to repeat the test.
5. All soil percolation test holes must be dug prior to the Department field observation
appointment.
6. If more than one site visit is required to observe soil percolation tests, a fee may be charged
for each additional visit.
B. PERCOLATION TESTS – NUMBER, DEPTH AND DISTRIBUTION
1. Percolation tests shall be sufficient in number and adequately spaced to encompass and
represent the soil conditions of the dispersal system areas including the reserve area for
advanced OWTS.
2. A minimum of six (6) percolation tests shall be conducted:
a.Standard OWTS: Three (3) percolation tests in each of the dual dispersal system
areas.
b.Advanced OWTS: Three (3) percolation tests in the dispersal system area and three
(3) in the reserve area.
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SOIL PERCOLATION TESTING REQUIREMENTS
3. The location of the percolation test holes shall be evenly distributed horizontally and
vertically in the dispersal system areas to provide a reasonable representation of conditions
within the dispersal system bottom infiltration zone and the sidewall infiltration zone (if
applicable).
4. Additional percolation tests may be required if the initial tests do not provide sufficient
information for design or to refine an exclusion area represented by failed percolation tests.
C. PERCOLATION TESTING WINDOW
1. Percolation testing shall normally be conducted at the time of or shortly following the soil
profile investigation.
2. If the soil profile observations indicate the presence of expansive soil with high shrink-swell
characteristics, percolation testing during the normal wet weather season will be required.
This is because expansive, high shrink-swell soil may exhibit suitable percolation rates
during the dry season due to shrinkage cracks in the soil; but, when they become wet, the
same soil may swell to the point of providing little or no percolation.
a.Other methods to bring the soil moisture content to a level representative of wet
weather testing period conditions, such as application of irrigation water for an
extended period of time (e.g., several days to a week or more) until appropriate
conditions are achieved, may be approved by the Department in lieu of conducting
wet weather percolation testing.
3. Field judgment of the need for wet weather percolation testing shall be made based on:
a.Visual evidence of soil shrinkage cracks; and/or
b. Soil exhibiting high clay content (e.g., exceeding forty [40] percent) in combination
with massive, columnar or angular blocky soil structure.
D. PERCOLATION TEST HOLE CONSTRUCTION
1. Percolation test holes shall be hand augured or machine augured per the specifications
provided below and as shown in Figure 8-1 (included at the end of this chapter):
a.Test holes shall be six inches (6) inches in diameter;
b. Test hole sides shall be kept as straight as possible;
c.The bottom and sides of the test holes shall be carefully scarified with a blunt
edged instrument to remove smeared soil particles and remove loose soil material;
d. The native soil structure shall be visible on the bottom ten (10) to twelve (12)
inches of the side wall;
e.Two (2) inches of gravel, one-half (½) to three-quarter (¾) inches in diameter, shall
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SOIL PERCOLATION TESTING REQUIREMENTS
be placed in the bottom of the hole to protect the bottom from scouring and
sediment; and
f.The test hole shall be stabilized by placing a four (4) inch perforated pipe and a one
(1) inch sidewall gravel pack in the test hole to prevent silting of the bottom of the
hole and sidewall cave-in.
2. An alternative method of construction as shown on Figure 8-2 (included at the end of this
chapter) may be used for deep percolation test holes.
3. Methods proposed for evaluating soil percolation rates for designing shallow subsurface
drip dispersal systems must be submitted to the Department for evaluation/approval prior
to use.
E. PERCOLATION TEST HOLE PRESOAKING
1. The purpose of the presoaking is to bring the soil moisture to levels representative of wet
season conditions.
2. Presoaking shall consist of filling each percolation test hole with clean water to a
minimum depth of twelve (12) inches above the base of the hole and refilling after drain
down as necessary throughout a four (4) hour period.
a.If more than six (6) inches of water remains above the bottom of the hole after
presoaking and prior to the start of the test, this constitutes a failure without any
further testing.
b.If less than six (6) inches of water remains in the test hole after presoaking
percolation testing of the hole may proceed.
3. Presoaking is required to be conducted on the day before the testing except under the
following conditions:
a.Expansive Clay Soil. In expansive clay soil, presoaking may occur on the same
day if the testing is done during the wet weather testing period.
b.Sandy Soil. In sandy soil with little or no clay content, presoaking may occur on
the same day of testing and may be reduced to a minimum period of two (2) hours if
after initially filling the hole twice with twelve (12) inches of water the water seeps
completely away in less than ten minutes.
F. PERCOLATION TEST PROCEDURE
1. Percolation tests shall be conducted in accordance with the procedures below and results
recorded on a form provided by the Department.
2. Clean water shall be added to bring the depth of water in the test hole to approximately six
(6) inches above the bottom of the hole after the required presoaking period.
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SOIL PERCOLATION TESTING REQUIREMENTS
3. The start time and water level in the pipe shall be measured and recorded. After thirty (30)
minutes have passed the time and the water level in the pipe shall be measured and recorded
again.
4. Each hole shall be refilled to six (6) inches of water above the bottom of the hole. Water
refill and water level drop measurement procedures shall be continued for a period of at
least two (2) hours until:
a.The water level drop stabilizes from a fixed reference point; and
b. Three (3) consecutive water level drop readings do not vary by more than ten (10)
percent or one-eighth (1/8) inch of each other.
5. If after one (1) hour the water level is dropping so rapidly to make thirty (30) minute
readings infeasible, the time interval between readings shall be decreased to ten (10)
minutes. The ten (10) minute tests shall be continued for at least one (1) hour and until the
water level drop stabilizes in accordance with the requirements listed above. If the water
drains so rapidly that ten (10) minute readings are infeasible:
a.The interval shall be further reduced to five (5) minutes; and/or
b. The time it takes for the water to drop exactly one (1) inch shall be measured and
recorded as the resultant rate in minutes per inch (MPI)
E. ALTERNATIVE PERCOLATION TEST PROCEDURES
1. Alternate methods of measuring the percolation rate may be approved by the Department
if the proposed procedures can be shown to produce a stabilized rate as described above.
8.2 DESIGN PERCOLATION RATE REQUIREMENTS
A. METHODOLGY
1. Percolation rates are first calculated for individual test holes (stabilized percolation rates)
and are then adjusted (adjusted percolation rates) and averaged together for a design
percolation rate.
B. INDIVIDUAL TEST HOLE PEROCLATION RATES
1.Stabilized Percolation Rate. A stabilized percolation rate shall be determined in
accordance with the formula in Table 8-1 for each test hole by averaging the last three (3)
successive stabilized readings varying by no more than ten (10) percent or one-eighth (1/8)
inch of each other.
Table 8-1
Stabilized Percolation Rate Formula
Stabilized Percolaton Rate (MPI)=∑(Last 3 Readings)
3
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SOIL PERCOLATION TESTING REQUIREMENTS
C. ADJUSTED PERCOLATION RATES
1.Adjusted Percolation Rate. An adjusted percolation rate shall then be calculated in
accordance with the formula in Table 8-2 for each test hole using a correction factor to
adjust for the displacement of water by the gravel pack. The correction factor for a six (6)
inch diameter hole with a four (4) inch perforated pipe and a one (1) inch thick gravel pack
is 1.6.
D. DESIGN PERCOLATION RATE
1. The percolation rate used to determine the wastewater application rate for dispersal system
design shall be calculated in accordance with the formula in Table 8-3 as the sum of the
adjusted percolation rates for each individual percolation test hole divided by the total
number of percolation test holes completed.
Table 8-3
Design Percolation Rate Formula
Design Percolaton Rate (MPI)=∑(Adjusted Percolation Rates)
# Test Holes
8.3 INTERPRETATION OF PERCOLATION TEST RESULTS
A. FAILING TEST RESULTS
1. If percolation rates are faster that one (1) MPI or slower than one hundred and twenty (120)
MPI then the following guidelines shall be followed:
a.If there are one (1) or two (2) failing test results, the following options are
available:
(1) Include the failing result(s) in the design percolation rate calculation and
design the dispersal system accordingly;
(2) Exclude the area represented by the failing test hole(s) in the design
percolation rate calculations and design the dispersal system using the
results from the other test holes. The lateral extent of the exclusion area
shall be taken from the midpoint of the test hole with failing results and
nearby passing test holes.
Table 8-2
Adjusted Percolation Rate Formula
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SOIL PERCOLATION TESTING REQUIREMENTS
(3) Conduct additional testing in an alternate area or to refine the exclusion
area represented by the failed test result(s).
b. If there are more than two (2) failing test results, additional testing will be required
to define the limits of acceptable soil areas for the dispersal system and reservearea.
B. SOIL TYPE
1. Percolation rates are influenced by soil type as well as other factors such as structure, roots,
gopher holes, coarse fragments and shrink-swell conditions.
2.Table 8-4 provides a general relationship between soil type and expected percolation rate.
Where percolation test results vary significantly from Table 8-4 guidelines the System
Designer shall evaluate and provide an explanation for the deviations.
Table 8-4
Soil Types & Associated Percolation Rate Guidelines
Soil Type Soil Percolation Rate
(MPI)
..
FIGURE 8-1
STANDARD METHOD OF CONSTRUCTION
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
FIGURE 8-2
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CHAPTER 9
GROUNDWATER LEVEL DETERMINATION REQUIREMENTS
9.0 CHAPTER OVERVIEW
This chapter provides the requirements for determining the groundwater level at a site during the site evaluation
process to support design and permitting of an Onsite Wastewater System and is organized as follows:
Section 9.1: Groundwater Level Determination Requirements
Section 9.2: Wet Weather Testing Requirements
9.1 GROUNDWATER LEVEL DETERMINATION REQUIREMENTS
A. GENERAL
1. The anticipated high seasonal groundwater in the vicinity of an OWTS shall be estimated
by:
a.Visual indications observed in the soil profile study including the depth to saturated
soil or free water and/or the highest extent of soil mottling and/or gleying; and/or
b. Direct observation of groundwater levels during the time of year when the highest
groundwater conditions are expected or known to occur (wet weather testing).
2. Where there is a discrepancy between the soil profile indications and direct observation, the
direct observation shall govern.
9.2 WET WEATHER TESTING REQUIREMENTS
A. WHEN REQUIRED
1. Wet weather testing shall be performed by a System Designer or other Qualified
Professional as allowed by their license and registration and may be required to verify the
depth to the high seasonal groundwater under the following conditions:
a.There is a discrepancy between soil profile indications (mottling or gleying) of high
seasonal groundwater, data from nearby soil evaluations or groundwater
observations, and other site characteristics or historical documentation indicating
that a shallow groundwater table is likely to occur during the rainy season;
b. The soil profile indicates sandy soil that lacks the necessary iron compounds
required for mottling or gleying; and/or
c.Field observations indicate high seasonal groundwater issues including but not
limited to:
(1) Landscape position, such as dispersal system location at the base of a hill,
near a creek or otherwise located where water is likely to accumulate;
and/or
(2) Springs or other indications such as swampy/marshy appearance or
presence of riparian or water-loving vegetation (e.g., sedges, rushes,
dockweed, willows, or perennial grasses) indicating prolonged soil
moisture.
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GROUNDWATER LEVEL DETERMINATION REQUIREMENTS
d. An exception to wet weather testing may be allowed for sloping sites greater than
five (5) percent where a curtain drain may feasibly be installed to intercept and
remove lateral groundwater flow in the proposed dispersal system area in
accordance with the design criteria in Chapter 12.
B. WET WEATHER TESTING PERIOD
1. Wet weather testing shall be conducted when sufficient rainfall has occurred in the area to
establish the normal high seasonal groundwater table.
2. The wet weather testing period is from October through April and after at least fifty (50)
percent of the average annual rainfall (as measured from October 1st through September
30th) has fallen and within a ten (10) day period following rainfall of at least one-half (0.5)
inch in a forty-eight (48) hour period.
3. The wet weather testing period may be extended or shortened by the Department depending
on rainfall patterns in a given year.
4. Data from local rainfall monitoring stations shall be used to determine when sufficient
rainfall has occurred (e.g., California Irrigation Management Information System (CIMIS)
at: http://www.cimis.waterca.gov/). The System Designer may propose a different source
of historical data.
C. GROUNDWATER LEVEL MONITORING & PIEZOMETER INSTALLATION WORK
PLAN REQUIREMENTS
1. Prior to conducting wet weather testing a work plan must be submitted to the Department.
The work plan must include the following:
a.Preliminary Site Plan. A preliminary site plan with pertinent topography and
features and the proposed locations of piezometers to monitor the groundwater
levels. A sufficient number of piezometers adequately spaced to encompass and
represent the entire dispersal system area(s) including the reserve area for advanced
OWTS shall be proposed.
b.Piezometer Construction Details. Piezometer construction details including
depth and screen interval.
(1) Piezometer depth shall be equal to or greater than the required depth from
the bottom of the dispersal system to groundwater.
(2) High-flow OWTS may require installation of deeper groundwater
monitoring wells to assess groundwater mounding (see Chapter 10).
c.Proposed Testing Frequency. A proposed schedule for monitoring groundwater
levels.
(1) There must be a minimum of three (3) groundwater level readings spread
equally over a minimum two (2) month period during the wet weather
testing period.
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GROUNDWATER LEVEL DETERMINATION REQUIREMENTS
(2) During the testing period there must also be at least one (1) additional
reading within two (2) days of a significant rainfall event, defined as one
(1) or more inches of rainfall within a twenty-four (24) hour period.
(3) More frequent observations may be necessary during elevated groundwater
periods to identify maximum groundwater levels.
(4) A request may be made to the Department for an alternative testing
frequency.
2. A permit may be required to install piezometers from the well permitting agency (Zone 7
Water Agency, Alameda County Water District, Alameda County Public Works or other
well permitting agency). A copy of all permits must be submitted to the Department.
D. DEPARTMENT OBSERVATION
1.The System Designer or Qualified Professional must perform the wet weather testing in the
presence of a Department representative. The Department may authorize the wet weather
testing to proceed without a Department representative, however, such authorization must
be in writing and may require submittal of photo documentation.
2. Written notice must be given to the Department at least forty-eight (48) hours in advance of
conducting the wet weather testing. Additional time may be required to schedule the
presence of the Department representative.
3. Notification and the request must include the Applicant’s name and assessor’s parcel
number and street address of the property. Failure to provide sufficient notice may result in
delay or a requirement to repeat the test.
4. If more than one site visit is required to observe the wet weather testing, a fee may be
charged for each visit.
5. Piezometers must be staked and flagged so that they can be readily located for periodic
observations.
E. WET WEATHER TESTING ALTERNATIVES
1. During years of low rainfall, such as drought conditions, or when wet weather testing is not
practical for other reasons alternative approaches for the determination of high seasonal
groundwater levels may approved.
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GROUNDWATER LEVEL DETERMINATION REQUIREMENTS
2. Alternatives that may be approved are:
a.Conservative Assumption. Adopt a highly conservative (worst case assumption)
of groundwater vertical separation for the dispersal system design by extrapolating
data from adjacent sites with consistent site conditions; or
b.Hydrogeological Report. A complete groundwater report prepared by Qualified
Professional as allowed by their license and registration may be submitted to the
Department for review and approval.
The report must contain supporting data for groundwater elevation conclusions
and include an analysis of expected maximum groundwater elevations for dispersal
system area. Elements of the report shall include:
(1) Topographical and geographical characteristics of the site including slope
of the land that could affect surface and subsurface drainage
characteristics;
(2) Soil classification and hydraulic conductivity of the soil;
(3) Restrictive layers in the soil profile;
(4) Indicators of high seasonal groundwater (e.g., gleying or soil mottling);
and
(5) Depth of observed groundwater in relationship to minimum soil depth
requirements and depth of dispersal system.
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CHAPTER 10
CUMULATIVE IMPACT ASSESSMENT REQUIREMENTS
10.0 CHAPTER OVERVIEW
This chapter provides the requirements for conducting cumulative impact assessments as part of the site
evaluation process to support design and permitting of an Onsite Wastewater System and is organized as
follows:
Section 10.1: Projects Requiring Cumulative Impact Assessments
Section 10.2: Groundwater Mounding Analysis Requirements
Section 10.3: Groundwater Nitrogen Loading Analysis Requirements
Section 10.4: Zone 7 Groundwater Nitrogen Loading Requirements
Section 10.5: Groundwater Monitoring Well Installation Requirements
10.1 PROJECTS REQUIRING CUMULATIVE IMPACT ASSESSMENTS
A. WHEN REQUIRED
1.An evaluation of groundwater quality conditions and/or potential groundwater mounding
beneath and in the vicinity of a site may be required as part of an Onsite Wastewater
System design and installation approval.
2. Projects where cumulative impact assessments are required are listed in Table 10-1
(included at the end of this chapter).
3. In addition to the projects listed in Table 10-1, the completion of a cumulative impact
assessment may be required in any case where special circumstances related to the size,
type or location of the OWTS warrant such analysis.
4. Criteria for assessing hydrological impacts for groundwater mounding or nitrogen loading
will be considered on a case-by-case basis. The Department may rely upon Regional Water
Board or Zone 7 staff or a third-party consultant to assist in the review. Costs for retaining
a third-party consultant are the responsibility of the Applicant.
B. CUMULATIVE IMPACT ISSUES
1. The primary issues to be addressed in cumulative impact assessments include:
a.Groundwater Mounding: A rise in the groundwater table, referred to as
"groundwater mounding", that may occur beneath or downgradient of OWTS as a
result of concentrated or high volume of hydraulic loading from one or more OWTS
in a limited area.
b.Groundwater Nitrogen Loading: Discharges from OWTS containing high
concentrations of nitrogen that may contribute to rises in the nitrate level of local
and regional aquifers.
2. Analysis of cumulative impact issues, other than those listed above which could pose
potential water quality, public health, or safety risks may also be required.
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CUMULATIVE IMPACT ASSESSMENT REQUIREMENTS
10.2 GROUNDWATER MOUNDING ANALYSIS REQUIREMENTS
A. MINIMUM CRITERIA
1. The following is required for groundwater mounding analysis:
a.Analysis of groundwater mounding effects shall be conducted using accepted
principles of groundwater hydraulics. The cumulative impact assessment submitted
to the Department shall include a description of the specific methodology and shall
be supported with accompanying literature references, as appropriate.
b. Assumptions and data used for the groundwater mounding analysis shall be stated
along with supporting information.
c.A map of the project site showing the location and dimensions of the proposed
OWTS and the location of other nearby Onsite Wastewater Systems, wells and
relevant hydrogeological features (e.g., site topography, watercourses, subsurface
drains, etc.) shall be provided.
d. The wastewater flow used for groundwater mounding analyses shall be the
wastewater design flow, unless supported adequately by other documentation or
rationale.
e.Groundwater mounding analyses shall be used to predict the highest rise of the
groundwater table and shall account for background groundwater conditions during
the wet weather season.
f.All relevant calculations necessary for reviewing the groundwater mounding
analysis shall accompany the submittal.
g.Any measures proposed to mitigate or reduce the groundwater mounding effects
shall be presented and described as to their documented effectiveness elsewhere,
special maintenance or monitoring requirements or other relevant factors.
h. The maximum acceptable rise of the groundwater table for short periods of time
(e.g., one [1] to two [2] weeks) during the wet weather season, as estimated from
groundwater mounding analyses, shall be such that the minimum two (2) feet
separation to the groundwater is maintained for all OWTS.
10.3 GROUNDWATER NITROGEN LOADING ANALYSIS REQUIREMENTS
A. MINIMUM CRITERIA
1.Annual Chemical-Water Mass Balance. Analysis of nitrogen loading effects shall, at a
minimum, be based upon construction of an annual chemical-water mass balance. The
specific methodology shall be described and supported with accompanied literature
references as appropriate.
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CUMULATIVE IMPACT ASSESSMENT REQUIREMENTS
2.Assumptions and Data. Assumptions and data for the mass balance analysis shall be stated,
along with supporting information. Such supporting information should include, at a
minimum:
a.Climatic data (e.g., precipitation, evapotranspiration rates);
b. Groundwater occurrence, depth and flow direction(s);
c.Background groundwater quality data, if available;
d. Soil conditions and runoff factors;
e.Wastewater characteristics (i.e., flow and nitrogen content); and
f.Other significant nitrogen sources in the impact area (e.g., livestock, other waste
discharges, etc.).
3.Calculations. All relevant calculations necessary for reviewing the nitrogen loading
analysis shall accompany the submittal.
4.Map of Project Siting. A map of the project siting showing the location and dimensions of
the proposed OWTS and the location of other nearby Onsite Wastewater Systems, wells and
relevant hydrogeological features (e.g., site topography, watercourses, subsurface drains,
etc.) shall be provided.
5.Wastewater Flow and Nitrogen (N) Concentrations. The minimum values for average
wastewater flow and average wastewater nitrogen concentration of septic tank effluent used
for nitrogen loading analyses shall be in accordance with the criteria in Table 10-2 unless
supported adequately by other documentation or rationale.
Table 10-2
Nitrogen Loading Analysis
Minimum Average Wastewater Flow & Nitrogen Concentration Criteria
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CUMULATIVE IMPACT ASSESSMENT REQUIREMENTS
6.Total Annual Nitrogen Loading Calculations. The total annual nitrogen loading from an
Onsite Wastewater System shall be determined in accordance with the formula provided in
Table 10-3.
N (lb
year)=(Average Wastewater Flow,gpd)∗(3.785L
gal )∗(N Concentration, mg
L )∗(365 day
year )∗(lb
453,592 mg)
Notes:
(1) Dwellings with less than or equal to three (3) bedrooms. The minimum average
wastewater flow for residential dwellings with up to three (3) bedrooms shall be one
hundred and fifty (150) gpd.
(2) Dwellings with more than 3 bedrooms: The minimum average wastewater flow for
residential dwellings with more than three (3) bedrooms shall be one hundred and
fifty (150) gpd for the first three (3) bedrooms plus an additional fifty (50) gpd for
each additional bedroom.
(3) Nitrogen Concentration. The concentration of nitrogen in milligrams per liter of
wastewater shall be in accordance with the criteria in Table 10-2.
7.Cumulative Nitrogen Loading Criteria. The minimum criteria for evaluating the
cumulative nitrogen loading from proposed OWTS (measured in milligrams of nitrate per
liter [mg-N/L]) shall not cause the groundwater nitrate-nitrogen concentration to exceed the
criteria in Table 10-4.
Table 10-4
Minimum Cumulative Nitrogen Loading Criteria from Proposed OWTS
3 –
1
≤ 7.5 2
1
≤ 103
2
Notes:
1Concentration measured at the nearest existing or potential point of groundwater
withdrawal (e.g., well location).
2Average concentration measured over the geographical extent of the subdivision.
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3The United States Environmental Protection Agency (USEPA) maximum
contaminant level (MCL) drinking water standards limit. Elevated nitrate can
interfere with blood-oxygen levels in infants and cause methemoglobinemia or
blue-baby syndrome.
8.Use of More Conservative Values. The Department reserves the right to require in any
individual case the use more conservative values than cited above if the values are not likely
to be representative of the proposed OWTS or where deemed necessary for protection of
public health, or based upon specific requirements or recommendations of the Zone 7 or
San Francisco Bay Regional Water Board.
9.Nitrogen Reducing Treatment Processes. Any measures proposed to mitigate or reduce
the nitrogen loading effects shall be presented and described as to their documented
effectiveness elsewhere, special maintenance or monitoring requirements or other relevant
factors.
10.4 ZONE 7 GROUNDWATER NITROGEN LOADING REQUIREMENTS
A. NEW, REPLACEMENT AND MODIFIED OWTS REQUIREMENTS
1. New, replacement and modified OWTS on parcels located in the Upper Alameda Creek
Watershed above Niles (Watershed) must meet the nitrogen loading requirements
contained in the Zone 7 2015 Nutrient Management Plan for the Livermore Valley
Groundwater Basin (NMP), issued by Zone 7 in February 2015 and adopted by the San
Francisco Bay Regional Water Board in March 2016, and all subsequent changes.
B. EXISTING OWTS REQUIREMENTS
1. The Zone 7 NMP provides an exception to the nitrogen loading requirements for existing
OWTS that are properly-functioning and properly-sized.
C. AREAS OF CONCERN FOR HIGH GROUNDWATER NITRATE CONCENTRATIONS
1. The NMP nitrogen loading requirements are dependent on the total size of the parcel and
whether the parcel is located inside one of five (5) localized areas of concern within the
Watershed with high groundwater nitrate concentrations where the use of OWTS is the
predominant method for wastewater disposal.
2. The areas of concern (AOC) are shown in Figure 10-1 (included at the end of this chapter)
and include:
a.Happy Valley, Pleasanton;
b. Buena Vista, Livermore;
c.Mines Road, Livermore;
d. May School, Livermore; and
e.Greenville, Livermore.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)10-6
CHAPTER 10
CUMULATIVE IMPACT ASSESSMENT REQUIREMENTS
D. NITROGEN LOADING REQUIREMENTS
1. The NMP nitrogen loading requirements are the total maximum allowable nitrogen loading
rates from all OWTS (existing and proposed) on the parcel and are based on the assumption
that the nitrogen loading from one rural residential equivalent (RRE) is thirty-four (34)
pounds of nitrogen per year (i.e., nitrogen loading from a typical single-family dwelling
served by a standard OWTS).
2. The NMP nitrogen loading requirements include minimization of nitrogen loading from all
OWTS (existing and proposed) by applying one (1) RRE provisions based on the location
and size of the parcel as discussed below and in accordance with the criteria presented in
the chart on Figure 10-2 (included at the end of this chapter) and in Table 10-5 below. The
Department may be contacted to assist with determining the requirements that apply to a
parcel.
a.Parcels Located Outside AOC. Application of one (1) RRE per five (5) acre
maximum provisions.
b.Parcels Located Inside AOC. Application of one (1) RRE per ten (10) acre
maximum provisions and requiring advanced OWTS with nitrogen-reducing
treatment.
Table 10-5
Maximum Allowable Annual Nitrogen Loading Per Parcel
for Parcels Located in Zone 7 Jurisdiction
s ≤ 5 Acres
s ≤ 7 Acres
1
Notes:
1Alternative loading rate allowed if a hydrogeological study is performed
that assesses current groundwater nitrate conditions beneath the site and
demonstrates that the proposed project will not cause nitrate concentrations
to rise.
3.Hydrogeological Study Requirements. The provision for increased maximum allowable
annual nitrogen loading rates per parcel is intended to encourage additional hydrogeological
studies that can further define the boundaries and nitrate concentrations of areas of concern.
The study must show that total onsite recharge does not exceed the lower of the following
concentrations:
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)10-7
CHAPTER 10
CUMULATIVE IMPACT ASSESSMENT REQUIREMENTS
a.Thirty-six (36) milligrams per liter (i.e., eighty [80] percent of the MCL
concentration for drinking water). The eighty (80) percent MCL limit is based on
Zone 7 Water Quality Policy and provides a standard buffer for not exceeding the
MCL; or
b.The maximum concentration at the site as determined from groundwater monitoring
data.
4.High-Strength Wastewater and High-Flow OWTS. In addition to the requirements in
Table 10-5, facilities with high-strength wastewater and high-flow OWTS must demonstrate
by analysis that the project will result in an improved nitrate condition beneath the site and
not cause the offsite condition to worsen and must install groundwater monitoring wells to
monitor nutrient loading from OWTS operation.
10.5 GROUNDWATER MONITORING WELL INSTALLATION REQUIREMENTS
A. WHEN REQUIRED
1.Installation of groundwater monitoring wells to assess the current groundwater nitrate
conditions beneath the site, evaluate groundwater mounding and/or monitor nutrient
loading from an OWTS may be required as part of the OWTS design and installation
approval.
2.Monitoring wells are required to be installed on high-strength wastewater and high-flow
OWTS for the purpose of monitoring the groundwater quality in the vicinity of the OWTS.
a.For high-strength wastewater and high-flow OWTS, at least one monitoring well
shall be constructed to a depth that will allow verification that the OWTS is
functioning properly and not contaminating groundwater;
b. Monitoring wells shall extend to one foot below the anticipated lowest seasonal
groundwater level; and
c.Monitoring wells must meet applicable standards for monitoring wells and be
constructed under permit from the administrative authority for well permits.
B. WORK PLAN REQUIREMENTS
1. OWTS design documents for sites requiring an evaluation of groundwater quality conditions
and/or potential groundwater mounding require submittal of a groundwater monitoring well
installation work plan prepared by a Qualified Professional as allowed by their license and
registration for review and approval by the Department, Zone 7 and/or the Regional Water
Board.
2. Installation of groundwater monitoring wells requires a permit. Applications for permits for
groundwater monitoring wells must be submitted for approval to the applicable well
permitting agency (Zone 7 Water Agency, Alameda County Water District, or Alameda
County public Works). A copy of permits must be submitted to the Department.
Table 10-1
Projects Requiring Cumulative Impact Assessment1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
Notes:
1The Department reserves the right to require the completion of a cumulative impact assessment in any case where special circumstances
related to the size, type, or location of the OWTS warrant such analysis.
2This is an average lot size for a subdivision.
3The hydrological and water quality analysis requirements may be modified depending on site specific conditions and the extent to which
the OWTS discharge contributes flow to any catchment area.
Type of Project Geographic
Location
Lot Size
(acres)
Design
Wastewater Flow (gpd)
Groundwater
Mounding Analysis
Nitrogen
Loading Analysis
Individual
Residence
Residence with
Second Unit
Multiunit and Non-
Residential
Subdivisions
2
2
Any System
< 200 feet from a
Wetland or Vernal Pool3
Figure 10-1
Nitrate Impacted Groundwater Areas of Concern
Upper Alameda Creek Watershed Above Niles
Source Zone 7 Water Agency July 2015 Nutrient Managment Plan
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
FIGURE 10-2
Nitrogen Loading Requirements
within Zone 7 Water Agency Jurisdictional Boundaries
0
20
40
60
80
100
120
140
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
To
t
a
l
A
l
l
o
w
b
l
e
N
i
t
r
a
t
e
L
o
a
d
i
n
g
f
r
o
m
A
l
l
S
y
s
t
e
m
s
o
n
P
a
r
c
e
l
(l
b
s
N/
y
r
)
Parcel Size (Acres)
Limit Outside Areas of Concern
Limit Inside Areas of Concern
1 RRE/parcel
0.7 RRE/parcel
RRE = Rural Residential Equivalent
ONSITE WASTEWATE PAGE 1-1
Source: Zone 7 Water Agency July 2015 Nutrient Management Plan
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)11-1
CHAPTER 11
GEOTECHNICAL EVALUATION REQUIREMENTS
11.0 CHAPTER OVERVIEW
This chapter provides the requirements for conducting geotechnical evaluations as part of the site evaluation
process to support design and permitting of an Onsite Wastewater System and is organized as follows:
Section 11.1: Projects Requiring Geotechnical Evaluations
Section 11.2: Geotechnical Report Requirements
11.1 PROJECTS REQUIRING GEOTECHNICAL EVALUATIONS
A. WHEN REQUIRED
1. Geotechnical evaluations shall be required in any of the following circumstances:
a.When dispersal systems are proposed on sites with natural ground slopes greater
than thirty (30) percent;
b. When a specific type of dispersal system is proposed in an area with a slope greater
than the maximum slope requirements provided in Table 5-1 through Table 5-6.
(increases of up to five [5] percent may be allowed);
c.When a proposed Onsite Wastewater System is located within an earthquake fault
zone or a seismic hazard zone, as delineated on the official maps published for that
purpose by the USGS, or when such hazards are otherwise known or suspected in
the location of the Onsite Wastewater System;
d. When benching or fill is proposed in the dispersal system area, with the exception
of fill required for an at-grade or mound dispersal system;
e.For corrective actions or repair of an existing Onsite Wastewater System if warranted
by site topography;
f.For proposed reductions in horizontal setbacks from cuts, embankments, steep
slopes or an unstable land mass; and/or
g.As otherwise required by law.
2. The scope of geotechnical work shall include an evaluation and recommendations to support
the siting of the System.
11.2 GEOTECHNICAL REPORT REQUIREMENTS
A. MINIMUM CRITERIA
1. A geotechnical report, prepared by a Qualified Professional as allowed by their license and
registration, shall be used to communicate soil and geologic site conditions,
interpretations, analysis and recommendations pertinent to the design, installation and
operation of a System where required by this Manual.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)11-2
CHAPTER 11
GEOTECHNICAL EVALUATION REQUIREMENTS
2. The geotechnical report must specially reference the System design plan.
3.If at some future date, the System design plan is appreciably modified, an amended
geotechnical report must be submitted that addresses the modified design plan.
4. The geotechnical report must discuss the following:
a.Geology;
b. Slope stability and seismic hazards;
c.Soil;
d. Groundwater;
e.Drainage;
f.Percolation rate;
g.Topography;
h. Cuts;
i.Vegetation; and
j.Other pertinent site features.
5. The geotechnical report shall include any recommendations deemed appropriate or
necessary to mitigate potential slope stability, drainage or seepage concerns associated
with the System design, installation and operation including as applicable recommended
horizontal setback(s) from any cut banks, embankments, steep slopes or unstable land
masses.
6. The geotechnical report shall state specifically in the conclusion that the proposed System
will not (or other wording such as not likely to, risk is very low, etc.):
a.Permit wastewater effluent to surface;
b. Degrade water quality;
c.Affect soil stability;
d. Present a threat to public health or safety; and
e.Create a public nuisance.
7. The geotechnical report shall be wet-stamped and signed by the Qualified Professional.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
PART 3
SITE MODIFICATION &
STABILIZATION REQUIREMENTS
CHAPTER TITLE
CHAPTER 12 GROUNDWATER CURTAIN DRAIN REQUIREMENTS
CHAPTER 13 SURFACE WATER DRAINAGE DESIGN
REQUIREMENTS
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)12-1
CHAPTER 12
GROUNDWATER CURTAIN DRAIN DESIGN REQUIREMENTS
12.0 CHAPTER OVERVIEW
This chapter provides design criteria for site modification measures that may be used to control shallow perched
groundwater and is organized as follows:
Section 12.1: Curtain Drain Overview
Section 12.2: Curtain Drain Siting Requirements
Section 12.3: Curtain Drain Design & Approval Requirements
12.1 CURTAIN DRAIN OVERVIEW
A. GENERAL
1. Dispersal trenches can act as a collection area for transient subsurface water flow and in
the worst case may be flooded during heavy rain events or throughout the rainy season.
This reduces the dispersal system capacity during the wet season and can also contribute
to a long-term decline in the dispersal system effectiveness and potential surface failures.
2. In areas where rainfall readily percolates through very permeable surface soil and perches
along the contact with the less permeable substrata site drainage measures may be required
to lower the groundwater level in the dispersal system area.
3. One of the most effective drainage measures is a “curtain drain” (also called “subdrain” or
“french drain”) which consists of a subsurface gravel trench installed upslope of a dispersal
system designed to intercept shallow perched groundwater flow and divert it away from or
around the dispersal system area.
4. The installation of a curtain drain may be considered for new OWTS installations as well
as to rehabilitate a failing OWTS affected by high seasonal groundwater.
12.2 CURTAIN DRAIN SITING REQUIREMENTS
A. GROUND SLOPE
1. Curtain drains shall only be allowed on sites with a slope of greater than five (5) percent.
2. The use of curtain drains to dewater a flat site will not be allowed.
B. LOCATION
1. Curtain drains may be positioned upslope or to the side of a dispersal system area to intercept
and drain subsurface water away from the dispersal system in accordance with the horizontal
setback requirements in Table 5-7.
2. Curtain drains are not to be used as underdrains located downslope from the dispersal system
area in an attempt to lower the groundwater table.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)12-2
CHAPTER 12
GROUNDWATER CURTAIN DRAIN DESIGN REQUIREMENTS
C. SITE INVESTIGATION REQUIREMENTS
1. Prior to approval of a curtain drain, a site investigation shall be conducted by a Qualified
Professional as allowed by their license and registration to:
a.Document soil, geologic and groundwater conditions on the site;
b.Assess the subsurface conditions to determine the feasibility and means of
controlling groundwater levels with a curtain drain including whether or not the
groundwater of concern is a perched condition above a clearly definable
restrictive/impermeable soil layer;
c.Determine the appropriate depth and location for the proposed curtain drain and
outlet point based on soil, groundwater and other site conditions; and
d.Prepare a map of the site including slope contours, drainage and other pertinent site
features.
12.3 CURTAIN DRAIN DESIGN & APPROVAL REQUIREMENTS
A. DESIGN REQUIREMENTS
1.Specifications. The curtain drain shall consist of a gravel trench constructed as shown
in Figure 12-1 (included at the end of this chapter) and designed in accordance with the
following minimum specifications:
a.Trench Width. Twelve (12) inches minimum.
b.Trench Depth. Shall extend to a depth of at least six (6) inches into the
underlying impermeable layer.
c.Filter Material. Filter material shall meet the material specifications for drain
rock in Chapter 35 and shall extend from trench bottom to within six (6) to
twelve (12) inches of adjacent ground surface elevation. Caltrans Class 2
permeable filter material may substituted for drain rock.
d.Filter Fabric. A geotextile “filter fabric” meeting the material specifications in
Chapter 36 shall surround the drain rock. The Department may waive the
requirements of a filter fabric where Caltrans Class 2 permeable filter material is
used.
e.Perforated Collection Pipe. Collection pipe shall consist of four (4) inch
diameter perforated drain pipe meeting the material specifications in Chapter 33,
oriented with holes down and installed on top of the drain rock approximately
two (2) to four (4) inches above the trench bottom.
f.Backfill Material. Native soil shall be use to backfill the trenches to match the
elevation of the adjacent finished ground surface subsequent to placement of the
pipe, filter fabric and filter material.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)12-3
CHAPTER 12
GROUNDWATER CURTAIN DRAIN DESIGN REQUIREMENTS
g.Outlet Pipe. The outlet pipe shall consist of minimum four (4) inch diameter solid
(non-perforated) drain pipe meeting the material specifications in Chapter 33.
h.Cleanouts. Cleanouts shall be provided to the finished ground surface elevation:
at a minimum in the following locations:
(1) at the upslope end of the drain;
(2) at bends of forty-five (45) degrees or greater; and
(3) at least every four hundred (400) feet along the length of the drain.
i. Slope. The trench and pipe shall be sloped for gravity flow at a minimum one (1)
percent gradient throughout the trench and extending to the outlet point. The
curtain drain must drain by gravity only.
j. Outlet. The outlet must be on the property being developed and located so the
flow does not adversely affect the drainage or any existing or proposed System on
the subject parcel or neighboring parcels. The downslope outlet shall be protected
against blockage or damage through the use of screening, rock cover, junction box
or other suitable means.
k.Erosion Control. Erosion control protection shall be provided at drain outlet point.
2.Engineering Plan. An engineering plan for the curtain drain shall be prepared by a Qualified
Professional as allowed by their license and registration and shall include at a minimum:
a.Plan, profile, cross section, and details of the curtain drain, supporting data and
calculations and a plan for groundwater monitoring;
b.The site map prepared to support the design and show the location of proposed and
existing Systems on the parcel; and
3. The curtain drain design must be incorporated into the OWTS design plans or corrective
action plans for existing OWTS.
B. FIELD DEMONSTATION REQUIREMENTS
1. Depending on the site conditions and the supporting information supplied with the
engineering plan a field demonstration may be required to evaluate the effectiveness of the
curtain drain prior to approval of the plans by the Department:
a.No Field Demonstration Required. For cases where the site investigation shows
the groundwater condition to be mitigated is perched water above a clearly
definable restrictive/impermeable layer (e.g., stiff, plastic clayey soil), the curtain
drain plan may be approved without the need for field demonstration of its
effectiveness.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)12-4
CHAPTER 12
GROUNDWATER CURTAIN DRAIN DESIGN REQUIREMENTS
b.Pilot Demonstration Required. For cases where the site investigation shows the
groundwater condition to be mitigated is most probably perched water but there is
some level of uncertainty about the extent or degree of impermeability of the
identified restrictive layer, the Department may require a pilot test of a portion of
the proposed curtain drain prior to approval. The pilot test, conducted by a Qualified
Professional, will require the installation of a section of the curtain drain in
accordance with the proposed design, along with installation of piezometers in
appropriate locations (upslope and downslope of the drain) as needed to provide
evidence of the effectiveness in lowering the groundwater table during the wet
season. The Qualified Professional is responsible for presenting the details of the
pilot demonstration, overseeing the installation, monitoring the performance and
reporting the results to the Department.
c.Full-Scale Demonstration Required. For cases where the site investigation shows
limited or questionable evidence that the groundwater condition to be mitigated is
perched water above a defined restrictive layer, the Department may require a full-
scale installation and monitoring of the proposed curtain drain prior to approval of
the OWTS design. The full-scale test, conducted by a Qualified Professional, will
require the installation of the entire curtain drain in accordance with the proposed
design, along with installation of piezometers in appropriate locations (upslope and
downslope of the drain) as needed to provide evidence of the effectiveness in
lowering the groundwater table during an entire wet weather season. The Qualified
Professional is responsible for presenting the details of the monitoring plan,
overseeing the installation, monitoring the performance, and reporting the results to
the Department.
.
GRANULAR SLOPE
PROTECTION; 4"
RIPRAP
NON-PERFORATED
DRAINPIPE
CROSS SECTION OUTLET DETAIL
DRAINFIELD TRENCH
IMPERMEABLE LAYER
CROSS SECTION
NATIVE TOP SOIL BACKFILL;
MOUND 6" TO 8" TO FORM
CONTINUOUS DRAINAGE BERM
SURFACE DIVERSION DITCH
FILTER FABRIC; MIRADRAIN
OR APPROVED EQUAL
34" - 112" DRAIN ROCK
3" OR 4" PERFORATED
PLASTIC DRAINPIPE; LAY
INVERT ON DRAIN ROCK; 2"
ABOVE TRENCH BOTTOM
12"
3'
6" MIN.
12"
15' MIN.
FIGURE 12-1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)13-1
CHAPTER 13
SURFACE WATER DRAINAGE DESIGN REQUIREMENTS
13.0 CHAPTER OVERVIEW
This chapter provides design criteria for site modification measures that may be used to control surface water
drainage and is organized as follows:
Section 13.1: Surface Water Drainage Site Modifications & Stabilization Measures Overview
Section 13.2: Surface Water Drainage Structure Requirements
Section 13.3: Erosion Control Requirements
13.1 SURFACE WATER DRAINAGE SITE MODIFICATION & STABILIZATION
MEASURES OVERVIEW
A. GENERAL
1. Site modifications and stabilization measures used to control surface water and stabilize the
site to protect the integrity and performance of Onsite Wastewater System components may
be required in certain situations.
2. Site modification and stabilization measures that may be used include but are not limited to
surface water drainage structures and erosion control measures.
13.2 SURFACE WATER DRAINAGE STRUCTURE REQUIREMENTS
A. MINIMUM DESIGN CRITERIA
1. Any concentrated flow of surface water drainage that may affect an Onsite Wastewater
System shall be intercepted and diverted from the System.
2. For new Onsite Wastewater Systems, drainage for the site development shall be planned
and dispersed in a way that does not adversely affect the Onsite Wastewater System.
3. Surface water drainage structures proposed as part of the Onsite Wastewater System design
must be designed by a Qualified Professional as allowed by their license and registration
and incorporated into the site drainage and grading plan, as applicable, and OWTS design
plans or corrective action plans.
4. Surface water drainage structures shall not adversely affect the drainage or any existing or
proposed Onsite Wastewater System on the subject parcel or neighboring parcels.
5. Surface water drainage structure designs shall include at a minimum the following:
a.Plan, profile, cross section, and details of the drainage structure and outlet
protection.
b. The site map prepared to support the System design showing the location of
proposed and existing Systems on the parcel, the surface water drainage structures
and watershed;
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)13-2
CHAPTER 13
SURFACE WATER DRAINAGE DESIGN REQUIREMENTS
c.Supporting runoff and hydraulic calculations;
d. Meet horizontal setback requirements in Table 5-7; and
e.Meet all other requirements, including local ordinances.
6. Surface water drainage designs may require approval by the local building authority.
13.3 EROSION CONTROL REQUIREMENTS
A. MINIMUM CRITERIA
1. Design of Onsite Wastewater Systems must consider measures to protect against erosion
during construction and stabilize the site at the conclusion of work.
2. Erosion control measures must be implemented and shown on the site plans in the
following OWTS:
a.Systems that include above ground dispersal systems (e.g., at-grade, mound or
cover fill dispersal systems);
b. Systems on slopes greater than twenty (20) percent;
c.High-flow Systems;
d. Systems located adjacent to a surface water body; and/ or
e.Systems located in environmentally sensitive areas, as determined during the
planning or building department review.
3. Erosion control plans must meet all other requirements, including local ordinances, and be
approved by the local building department, as applicable.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
PART 4
WASTEWATER FLOW & STRENGTH
DESIGN CRITERIA
CHAPTER TITLE
CHAPTER 14 WASTEWATER DESIGN FLOW REQUIREMENTS
CHAPTER 15 WASTEWATER DESIGN STRENGTH
REQUIREMENTS
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)14-1
CHAPTER 14
WASTEWATER DESIGN FLOW REQUIREMENTS
14.0 CHAPTER OVERVIEW
This chapter provides the criteria for wastewater design flows used in Onsite Wastewater System design and is
organized as follows:
Section 14.1: Wastewater Design Flow Requirements Overview
Section 14.2: Design Flow Requirements for Single Family Residences & Secondary Units
Section 14.3: Design Flow Requirements for Multi-Unit Residential and Non-Residential Facilities
14.1 WASTEWATER DESIGN FLOW REQUIREMENTS OVERVIEW
A. GENERAL
1. The System Designer is responsible for ensuring that the wastewater flow rate used for the
design of Onsite Wastewater Systems is developed based on full consideration of projected
activities, occupancy and types of facilities.
2. All system components shall be sized using the peak daily wastewater flow rate (or
wastewater design flow).
3. The dispersal system may be sized using an average wastewater flow rate if a flow
equalization tank is incorporated into the treatment train.
14.2 DESIGN FLOW REQUIREMENTS FOR SINGLE FAMILY RESIDENCES &
SECONDARY UNITS
A. WASTEWATER DESIGN FLOW CRITERIA
1. The wastewater design flow used for design of Onsite Wastewater Systems for single
family residences and secondary units (including manufactured homes) shall be based on
a factor of one hundred and fifty (150) gallons per day (gal/day) per bedroom for the
first three (3) bedrooms, plus seventy-five (75) gal/day for each additional bedroom,
as indicated in the Table 14-1 below.
Table 14-1
Wastewater Design Flow Criteria – Residential Facilities
No. of Bedrooms gal/day
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)14-2
CHAPTER 14
WASTEWATER DESIGN FLOW REQUIREMENTS
2. For residential buildings the Department may grant wastewater design flow reductions of
up to twenty (20) percent where water saving devices such as low flush toilets, urinals,
flow restrictors and aerators for faucets and showerheads that meet low-flow efficiency
standards set by the California Energy Commission are incorporated permanently into the
buildings being used.
3. The wastewater design flows for a primary residence and secondary dwelling unit shall be
determined independently, regardless of whether the flows are treated separately or
combined in a single Onsite Wastewater System.
14.3 DESIGN FLOW REQUIREMENTS FOR MULTI-UNIT RESIDENTIAL AND NON-
RESIDENTIAL FACILITIES
A. WASTEWATER DESIGN FLOW CRITERIA
1. The wastewater design flow used for the design of Systems for multi-unit residences
and non-residential facilities shall be developed based on full consideration of projected
activities, occupancy and types of facilities.
2. Minimum wastewater design flows used for the design of Systems for multi-unit residences
and non-residential facilities are presented in Table 14-2 (included at the end of this
chapter).
3. The Department may consider adjustment to the minimum criteria listed in Table 14-2
for specific facilities based upon documented wastewater flow monitoring data.
4. For facilities not listed in Table 14-2 wastewater design flows are to be estimated based
on either:
a.Appropriate literature references (e.g., USEPA) for the type of facility proposed; or
b. Documented wastewater flow monitoring data for a comparable facility.
5.In all cases, the design plans shall include sufficient technical information to support the
proposed wastewater design flow estimate.
Table 14-2
Wastewater Design Flow Guidelines
Multi-Unit and Non-Residential Facilities
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 2
Type of Business or Facility
Minimum
Wastewater Design
Flow Criteria
(gallons per day)
Camps (per person)
- day use (no meals served)
- overnight use, with flush toilets, no showers
- overnight use, with flush toilet and showers
- summer and seasonal
15
25
35
50
Churches (per seat)
- sanctuary
- with kitchen waste
5
7
Dance Halls (per person) 5
Factories (per employee)
- without showers
- with showers
- with cafeteria, add
25
35
5
Hospitals (per bed)
- kitchen waste only
- laundry waste only
250
25
40
Hotels (per bed – 2 person)
- without kitchen 60
Institutions (per person)
- Resident
- Nursing home
- Rest home
75
125
125
Laundromat, with self-service washing machines
- per wash cycle
- commercial (per manufacturer’s specifications)
50
Mobile Home Parks (per space)
- Picnic parks (toilets only)
250
20
Motels (per bed space)
- without kitchen
- with kitchen
50
60
Offices (per employee) 20
Table 14-2
Wastewater Design Flow Guidelines
Multi-Unit and Non-Residential Facilities
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 2 OF 2
Type of Business or Facility
Minimum
Wastewater Design
Flow Criteria
(gallons per day)
Parks with Picnic Areas (per person)
- with flush toilets (only) 20
Recreational Vehicle Parks (per space)
- without individual water hook-ups (per space)
- with individual water hook-ups (per space) 75
100
Restaurants
- cafeterias (per space)
- toilet (per customer)
- kitchen wastes (per meal served)
- kitchen waste, disposable service (2 per meal)
- add for garbage disposal (per meal served)
- add for cocktail lounge (per customer)
20
7
6
2
1
2
Schools
- staff and office (per person)
- elementary school (per student)
- intermediate and high school (per student)
- with gym and showers, add (per student)
- with cafeteria, add (per student)
- boarding school, total waste (per person)
20
15
20
5
3
100
Service Station, Toilets
- 1st bay
- for each additional bay 1000
500
Stores
- per employee
- public restrooms, add (per 10 square feet of floor space) 20
1
Swimming Pools
- per person 10
Theaters, auditoriums
- per seat 5
Wineries (sanitary waste only)
- tasting room, per visitor
- per employee
- special events
2.5
15
case-by-case
Source: California Plumbing Code, 2016
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)15-1
CHAPTER 15
WASTEWATER DESIGN STRENGTH REQUIREMENTS
15.0 CHAPTER OVERVIEW
This chapter provides the criteria for wastewater strength used in Onsite Wastewater System design and is
organized as follows:
Section 15.1: Wastewater Design Strength Requirements Overview
Section 15.2: Wastewater Types
Section 15.3: Wastewater Quality Parameters
Section 15.4: Wastewater Strength Criteria
15.1 WASTEWATER DESIGN STRENGTH REQUIREMENTS OVERVIEW
A. GENERAL
1. The System Designer is responsible for ensuring that wastewater strength in each project
is properly characterized and is developed based on full consideration of projected
activities, occupancy and types of facilities.
15.2 WASTEWATER TYPES
A. GENERAL
1. For the purposes of this Manual wastewater consists of blackwater, graywater and process
water.
2. The design of Onsite Wastewater Systems must take into account the characteristics and
strength of wastewater which are dependent on the relative composition of blackwater,
graywater and/or process water in the wastewater stream.
B. BLACKWATER
1. Blackwater is defined as wastewater contaminated with human or kitchen wastes,
generally originating from toilets and kitchen sinks.
2. Blackwater includes, but is not limited to, wastewater discharges from kitchen sinks,
garbage grinders, water closets, toilets, urinals or similar fixtures alone or in combination
with other wastewater.
C. GRAYWATER
1. Graywater is defined as untreated wastewater that has not been contaminated by any toilet
discharge, and has not been affected by infectious, contaminated, or unhealthy bodily
wastes, and does not present a threat from contamination by unhealthful processing,
manufacturing or operating wastes (Health and Safety Code section 17922.12).
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)15-2
CHAPTER 15
WASTEWATER DESIGN STRENGTH REQUIREMENTS
2. Graywater includes but is not limited to wastewater from bathtubs, showers, bathroom
washbasins, clothes washing machines and laundry tubs.
3. Graywater does not include wastewater from kitchen sinks or dishwashers.
D. PROCESS WATER
1. Process water is generated from any manufacturing, processing institution, commercial,
or agricultural operation or any operation that discharges other than domestic-strength
wastewater.
2. All wastewater treatment and disposal systems for process wastewater are jointly regulated
by the Regional Water Board and the Department.
15.3 WASTEWATER QUALITY PARAMETERS
A. PRIMARY PARAMETERS USED TO EVALUATE THE QUALITY OF WASTEWATER
IN ONSITE WASTEWATER SYSTEM DESIGN
1. Knowledge of the constituents found in wastewater and the fate of these constituents when
released to the environment are of fundamental importance in the design and operation of
Onsite Wastewater Systems.
2.Residential Facilities. The primary analyses used to quantify the physical, chemical and
biological constituents typically found in wastewater from residential facilities for use in
Onsite Wastewater System design and operation include but are not limited to the following:
a.Biochemical Oxygen Demand (BOD). BOD measures oxygen required for
biochemical degradation of organic and inorganic material. High BOD causes an
increased biochemical demand on downstream system components and may
shorten the life of the System. BOD5 is the five (5) day biochemical oxygen demand
exerted after five (5) days of a BOD test.
b.Total Suspended Solids (TSS). TSS are suspended solids in water and are a
constituent of total solids. TSS can include a wide variety of material, such as
soil particles, decaying plant and animal matter and wastewater. The total amount
of TSS in liquid is determined by a laboratory test that measures the dry weight of
residue retained on a filter after drying the sample and is a measure of the level of
treatment being achieved. In wastewater with high TSS, inorganics are less easily
broken down and can accelerate mechanical clogging of the infiltrative surface
of the dispersal system.
c.Fats, Oil and Grease (FOG). FOG is a measure of biological lipids and mineral
hydrocarbons in wastewater. The analytical test for FOG does not measure an
absolute quantity, but is useful in making comparisons of wastewater. High FOG
results in increased biological demand on downstream system components and may
shorten the life of the System.
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CHAPTER 15
WASTEWATER DESIGN STRENGTH REQUIREMENTS
d.Nitrogen. Nitrogen is a nutrient in wastewater that can pose a potential health risk
to groundwater and surface water. Nitrogen can change form as it moves through a
System and into the receiving environment. Elevated nitrate in groundwater is a
concern for drinking water use because nitrate can interfere with blood-oxygen
levels in infants and cause methemoglobinemia or blue-baby syndrome. Where
groundwater recharges stream flow, nitrate-enriched groundwater can contribute
to eutrophication, a process that leads to high algal population and growth,
especially blue-green algal populations. While not directly toxic to fish life, like
ammonia, nitrate can have indirect effects on fish if it contributes to this
eutrophication.
(1) The principal forms of nitrogen found in wastewater are organic nitrogen
(Organic-N), ammonia nitrogen (NH3-N), ammonium nitrogen (NH4-N),
nitrite-nitrogen (NO2-N) and nitrate-nitrogen (NO3-N).
(2) Nitrogen is usually introduced into the OWTS as organic nitrogen
(Organic-N) and ammonium nitrogen (NH4-N).
(3) Organic-N (including feces, urea, and other animal and vegetable matter)
in wastewater is converted into ammonium (NH4-N) by the process of
ammonification. In ammonification, proteins, amino acids, and other
nitrogen-containing compounds are biochemically degraded by
heterotrophic bacteria. Ammonification typically occurs in primary
treatment (septic tank) and transport lines as well as in the supplemental
treatment process. Because of this, a raw wastewater ammonia
concentration may be significantly lower than the concentration of the
effluent from the primary treatment (septic tank).
(4) Total Kjeldahl Nitrogen (TKN) is the sum of Organic-N and NH3-N and
thus TKN is a better measure of overall nitrogen content and should be
used when determining the wastewater load to OWTS components
downstream of primary treatment (septic tank).
e.Coliform. The biological characteristics of wastewater are of fundamental
importance in the control of diseases caused by pathogenic organisms of human
origin. Coliform bacteria is used as an indicator organism for the number of
pathogenic organisms present in wastewater. The intestinal tract of humans
contains a large population of coliform bacteria. Each person discharges from one
hundred (100) to four hundred (400) billion coliform bacteria per day, in addition
to other kinds of bacteria. The absence of coliform bacteria is groundwater or
surface water is taken as an indication that the water is free from disease-producing
bacteria.
3.Non-Residential Facilities. In addition to the analysis listed above, other analysis used to
quantify physical, chemical and biological constituents found in non-residential
wastewater must also be included in the design and operation of Onsite Wastewater
Systems.
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CHAPTER 15
WASTEWATER DESIGN STRENGTH REQUIREMENTS
15.4 WASTEWATER STRENGTH CRITERIA
A. DOMESTIC-STRENGTH WASTEWATER
1. Domestic-strength wastewater is defined as wastewater with a measured strength less than
high-strength wastewater and is defined as having a thirty (30) day average concentration
in (mg/L of the constituents listed in Table 15-1 prior to a septic tank or other OWTS
treatment component:
Table 15-1
Wastewater Strength Criteria
Constituent
Domestic-Strength
Wastewater
(mg/L)
High-Strength
Wastewater
(mg/L)
≤ 330
5 ≤ 300
≤ 100
2. Domestic-strength wastewater is comprised of blackwater and graywater and is normally
discharged from residential plumbing fixtures, appliances and other household devices
including, but not limited to toilets, bathtubs, showers, laundry facilities, dishwashing
facilities and garbage disposals.
3. Domestic-strength wastewater may include wastewater from multi-unit residences (e.g.,
apartments, condominiums, mobile home parks) and other non-residential facilities
provided the wastewater strength is comprised of blackwater and graywater that meets the
criteria for domestic-strength wastewater.
4. Domestic-strength wastewater may include incidental recreational vehicle (RV) holding
tank dumping but does not include wastewater consisting of a significant portion of RV
holding tank wastewater such as at RV dump stations.
5. Domestic-strength wastewater does not include wastewater from industrial processes.
B. HIGH-STRENGTH WASTEWATER
1. High-strength wastewater is defined as wastewater with a measured strength greater than
domestic-strength wastewater and is defined as having a thirty (30) day average
concentration of the BOD5, TSS, and FOG prior to the septic tank or an OWTS treatment
component as described in Table 15-1 above.
2. High-strength wastewater must receive supplemental treatment to lower the wastewater
strength to domestic-strength wastewater before discharge into the dispersal system.
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CHAPTER 15
WASTEWATER DESIGN STRENGTH REQUIREMENTS
3. Guidelines for high-strength wastewater facilities are provided in Table 15-2 (included at
the end of this chapter) and are based on the type of business or facility, waste streams and
usage characteristics.
4. The System Designer is responsible for ensuring that wastewater in each project is properly
characterized and, whenever possible, wastewater streams should be sampled and actual
values used in the design.
5. The Department may consider adjustment to the guidelines listed in Table 15-2 for specific
facilities based on submittal of technical information to support the proposed wastewater
strength estimate.
6. For facilities not listed in Table 15-2 wastewater strength is to be estimated based on either:
(a) appropriate literature references (e.g., USEPA) for the type of facility proposed; or (b)
documented wastewater strength monitoring data for a comparable facility.
Table 15-2
Wastewater Strength Guidelines – Multi-Unit Residential and Non-Residential Facilities
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
Wastewater
Type Type of Business of Facility Wastewater Types Primary-treated Effluent
Concentrations1
1 Apartments
Condominiums
Mobile Home Parks
Residential Subdivisions
Hotels/Motels/Inns
Work Camps
Domestic Wastewater
(Blend of Black and Gray
Wastewater)
BOD5: 140 to 250 mg/L
TSS: 40 to 140 mg/L
TKN2: 50 to 80 mg/L
2
Airport
Campgrounds
Fire Departments
Golf Courses
Manufacturing Facilities
Offices
Parks
Public Toilets/Rest Areas
RV Parks2
Visitor Centers
Primarily Black
Wastewater
BOD5: 300 to 500 mg/L
TSS: 80 to 250 mg/L
TKN2: 90 to 200 mg/L
3
Churches
Schools Primarily Black Wastewater
with Surge Flows
BOD5: 300 to 500 mg/L
TSS: 80 to 250 mg/L
TKN2: 90 to 150 mg/L
4
Hospitals
Retirement Facilities
Veterinary Clinics
Primarily Black Wastewater
with Pharmaceuticals or
Toxic Inhibitors
BOD5: 300 to 700 mg/L
TSS: 100 to 350 mg/L
TKN2: 70 to 120 mg/L
5
Bars
Casinos
Delis
Gas Stations
Restaurants
Shopping Centers
Strip malls
Black Water
with Restaurant Waste
BOD5: 300 to 1000+ mg/L
TSS: 80 to 300 mg/L
TKN2: 90 to 200+ mg/L
Notes:
1The System Designer is responsible for ensuring that wastewater in each project is properly characterized and, whenever possible, wastewater
streams should be sampled and actual values used in the design.
2Wastewater may include incidental recreational vehicle (RV) holding tank dumping but does not include wastewater consisting of a significant
portion of RV holding tank wastewater such as at RV dump stations.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
PART 5
TANK
REQUIREMENTS
CHAPTER TITLE
CHAPTER 16 GENERAL TANK REQUIREMENTS
CHAPTER 17 SEPTIC TANK REQUIREMENTS
CHAPTER 18 FLOW EQUALIZATION TANK
REQUIREMENTS
CHAPTER 19 GREASE INTERCEPTOR TANK
REQUIREMENTS
CHAPTER 20 PUMP TANK REQUIREMENTS
CHAPTER 21 HOLDING TANK REQUIREMENTS
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)16-1
CHAPTER 16
GENERAL TANK REQUIREMENTS
16.0 CHAPTER OVERVIEW
This chapter provides general design guidelines applicable to all tanks that may be utilized as part of the
treatment train of an Onsite Wastewater System. The requirements in this chapter are applicable to all new
and replacement buried and/or above ground tanks. In addition to the general design requirements in this
chapter, tanks must also meet the design requirements for the specific type of tank as applicable contained
in Chapters 17 through Chapter 21.
This chapter is organized in the following sections:
Section 16.1: Compliance with Standards and Codes
Section 16.2: General Performance Requirements
Section 16.3: Siting Criteria Requirements
Section 16.4: Tank Installation Requirements
16.1 COMPLIANCE WITH STANDARDS AND CODES
A. REQUIREMENTS
2. All tanks in the treatment train are to be watertight and constructed of durable, corrosion
resistant material and shall conform to latest version of the International Association of
Plumbing and Mechanical Officials (IAPMO) and National Sanitation Foundation (NSF) or
American Society for Testing and Materials (ASTM) standards and comply with state and
local building codes, including the California Plumbing Code.
2. All tanks in the treatment train must have a current IAPMO or an American National
Standards Institute (ANSI) accredited testing organization approval listing.
3. An exception to IAPMO or ANSI approval listing may be granted where structural design
calculations for the tank are provided by a professional civil engineer qualified to perform
structural design.
4. Each tank shall be permanently marked with the manufacturer’s name and/or trademark and
the nominal working volume in accordance with IAPMO requirements.
5. Permanent markings shall be adequately protected from corrosion so as to remain permanent
and readable over the life of the tank. The product shall also bear the Uniform Plumbing
Code certification mark (UPC®).
6. Sealants for sealing concrete tanks may be required and must be in accordance with
manufacturer’s specifications and IAPMO requirements.
16.2 GENERAL PERFORMANCE REQUIREMENTS
A. MATERIALS
1. Prefabricated tanks must meet the IAPMO material requirements for concrete, fiberglass-
reinforced plastic or polyethylene tanks used in residential or non-residential Systems.
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CHAPTER 16
GENERAL TANK REQUIREMENTS
2. Use of other alternative materials or methods of construction not specifically prescribed by
IAPMO or the California Plumbing Code may be approved by the Department provided the
proposed design is satisfactory and complies with the intent of the provisions of IAPMO or
the California Plumbing Code and that the material, method or work offered, is for the
purpose intended, at least the equivalent of that prescribed by the codes in quality, strength,
effectiveness, fire resistance, durability and safety.
B. STRUCTURALLY SOUND
1. Tanks shall be designed to be structurally sound to withstand the live and dead loads
experienced at the site to prevent cracking or collapse.
2. The potential impacts due to structurally unsound tanks include safety of people in the
proximity of the tank, the operation of the System and the formation of cracks or other
openings that cause leaks.
3. Tank selection shall be based on all reasonably expected loading conditions, including burial
depth, hydrostatic forces when tank is full or empty and any other reasonable expected
loading conditions.
C. TANK ACCESS
1. Access to tanks shall be designed to allow maintenance and prevent injury or death caused
to a human or animal due to unintended entry into the tank.
2. Access at ground level or above shall be provided for all tanks and/or components contained
therein.
3. Access to each compartment of a tank for maintenance shall be provided by a minimum
twenty (20) inch diameter opening or equivalent.
4. Tanks shall be installed so that manhole covers are within twenty-four (24) inches of the
ground surface.
5. The riser lid must be capable of preventing accidental or unauthorized entry. Access shall
be secured by bolting or locking lids or by virtue of the lids own weight. Covers, risers and
lids shall be capable of bearing the expected live and dead loads. Potential loads could
include people, lawn equipment or vehicles.
6. Access openings shall be located to provide visual inspection, maintenance and/or repair of
sanitary tees, effluent filters, baffles and pump assemblies.
D. TANK RISERS
1. All access openings on tanks shall have risers extended a minimum of two (2) inches above
the finished ground surface elevation except in areas of traffic, where they should be flush
mounted.
2. Except for concrete grade rings, risers shall be installed in one continuous piece without
seams.
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CHAPTER 16
GENERAL TANK REQUIREMENTS
3. All risers shall be securely attached by means of a watertight collar and/or other sealant
material applied according to the manufacturer’s instructions.
4. All risers shall be fitted with gastight, watertight, vermin proof, securely fastened covers
that are removable with standard hand tools.
5. All covers shall be of durable construction, manufactured specifically for their intended use.
E. TANK CONNECTIONS & CLEANOUTS
1.All connections between pipes and tanks shall conform to construction standards as required
by state and local building codes including the California Plumbing Code.
2.A cleanout at the finished ground surface elevation shall be provided between each structure
and/or building directly connected to a tank and at other appropriate locations in the piping
system.
F. WATERTIGHT
1.Prevention of Infiltration and Exfiltration. Tanks shall be watertight to prevent
infiltration (or inflow) of groundwater and surface water and exfiltration (or outflow) of
wastewater.
a.Inflow of Groundwater or Surface Water. Onsite Wastewater Systems are
designed to return a predetermined volume and quality of wastewater to the
environment. A tank allowing inflow of groundwater or surface water into the
Onsite Wastewater System can overwhelm the design capacity of the System and/or
lead to hydraulic overload of the System and/or inadequate wastewater treatment.
Surges of inflow can also displace solids from the tank adversely affecting the
operation of the System and life expectancy of downstream components.
b.Outflow of Wastewater. Leaking tanks can create a public health hazard and
contaminate surface water and groundwater due to bypassing the downstream
components of the treatment train.
16.3 SITING CRITERIA REQUIREMENTS
A. HORIZONTAL SETBACKS
1. All tanks must be installed to meet the horizontal setbacks for tanks provided in Table 5-7.
2. In areas where the site evaluation has determined that the high seasonal groundwater level
is within six (6) feet or less from original ground surface elevation, tanks shall be analyzed
for and properly designed to resist buoyant forces.
16.4 TANK INSTALLATION REQUIREMENTS
A. GENERAL
1. Installation depth for tanks shall be no greater than the manufacturer’s specifications.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)16-4
CHAPTER 16
GENERAL TANK REQUIREMENTS
2. Excavations for tanks shall be made according to the manufacturer’s requirements.
3. Excavations shall provide a level, uniform load-bearing surface free of embedded rock
formations or large boulders.
4. Tanks shall be set on a level and compacted bed according to the manufacturer’s
requirements.
5. Wet and/or unstable soil shall be over-excavated, backfilled and compacted with an
approved material suitable to stabilize and support the tank.
6.Backfilling and compaction shall be performed according to the manufacturer’s
specifications.
7. Backfill material shall be friable and not contain stones larger than three (3) inches in
diameter or debris of any type.
8. The separation between any two tanks shall be a minimum of two (2) feet unless a closer
distance is approved by the tank manufacturer.
.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)17-1
CHAPTER 17
SEPTIC TANK REQUIREMENTS
17.0 CHAPTER OVERVIEW
This chapter provides the design criteria for septic tanks. In addition to the requirements in this chapter,
septic tanks must comply with the general tank design requirements presented in Chapter 16.
This chapter is organized in the following sections.
Section 17.1: Septic Tank Overview
Section 17.2: Septic Tank Sizing Requirements
Section 17.3: Septic Tank Design Requirements
Section 17.4: Effluent Filter Requirements
17.1 SEPTIC TANK OVERVIEW
A. PURPOSE
1. The primary purpose of the septic tank is to clarify the wastewater (i.e., separate
constituents that float and sink from the other wastewater constituents).
2. A second benefit of the septic tank is that decomposition of organic material begins in the
septic tank. Raw waste is reduced to sludge, scum, gases and effluent with the aid of
beneficial microbes that reduce the organic material without outside energy sources.
3. Septic tanks that are properly sized and constructed provide highly efficient treatment
capable of yielding effluent that is relatively free of fats, oils, greases, solids and other
constituents that can clog and foul System components.
17.2 SEPTIC TANK SIZING REQUIREMENTS
A. MINIMUM CAPACITY
1. Adequate septic tankage will anaerobically digest organic material, remove settleable and
floatable solids, help modulate flow, and consistently discharge effluent that meets primary
treatment standards.
2.Residential Facilities. The minimum capacity of septic tanks for OWTS shall be
determined by the number of bedrooms in the dwelling as presented in Table 17-1.
Table 17-1
Minimum Septic Tank Capacity Criteria – Residential Facilities
No. of Bedrooms Gallons
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CHAPTER 17
SEPTIC TANK REQUIREMENTS
3.Multi-Unit Residential and Non-Residential Facilities.
a.The minimum capacity of septic tanks for non-residential facilities shall be one
thousand five hundred (1,500) gallons or three times the wastewater design flow
for the facility served, whichever is greater.
b. Larger tankage is recommended for non-residential facilities with high-strength
wastewater for optimal OWTS performance and may be required for certain
proprietary treatment units.
c.Guidelines for minimum and preferred septic tank sizing for certain facility types
and certain proprietary treatment units are provided in Table 17-2 (included at the
end of this chapter).
17.3 SEPTIC TANK DESIGN REQUIREMENTS
A. MINIMUM CRITERIA
1.A septic tank system consists of the tank, riser(s) and inlet/outlet ports (see Figure 17-1
included at the end of this chapter).
2.Septic tanks shall have a minimum of two (2) compartments.
3.The inlet compartment shall be a minimum of two-thirds (2/3) of the total liquid capacity
of the tank.
4.Single compartment septic tanks may be used in series for high-flow OWTS.
5.Septic tank inlets, outlets, sanitary tees, partitions and baffles must conform to the IAPMO
design requirements for septic tanks.
17.4 EFFLUENT FILTER REQUIREMENTS
A. MINIMUM CRITERIA
1.Effluent discharged from a septic tank directly to a dispersal system area or pump tank
must pass through an effluent filter sized based upon the type of facility (residential or non-
residential) and the wastewater design flow.
2.The outlet of the septic tank shall be fitted with an effluent filter capable of screening
solids in excess of three-sixteenths (3/16) of an inch in diameter and conforming to
NSF/ANSI Standard 46 or as otherwise approved by the Department.
3.All effluent filters shall be located in the outlet compartment of the septic tank, unless
located in a separate tank after the septic tank and shall be easily inspected, cleaned and
maintained.
4.For multiple septic tanks in series, outlet sanitary tees may be used in lieu of an effluent
filter except for the last septic tank where an effluent filter is required.
Table 17-2
Grease Interceptor Tanks and Primary Tanks Sizing Chart Guidelines
Based on Hydraulic Residence Time (HRT)
Grease Tankage1 Primary Tankage2 Grease Tankage1 Primary Tankage2
HRT (days) HRT (days) HRT (days) HRT (days)
a) restrooms only n/a 3 n/a 4
a) restrooms and kitchen 3 4 5 5
Convenience Store/Gas Station
a) restrooms only n/a 3 n/a 4
b) restrooms and kitchen/deli 2 3 4 4
a) restrooms only n/a 3 n/a 4
b) restrooms and restaurant/kitchen 3 3 5 4
a) restrooms only n/a 2.5 + Surge n/a 4 + Surge
b) restrooms and kitchen 2 2.5 + Surge 4 4 + Surge
a) restrooms only n/a 3 + Surge n/a 4 + Surge
b) restrooms and kitchen 3 3 + Surge 5 4 + Surge
a) restrooms only n/a 3 n/a 4
b) restrooms and floor drains n/a 3 + Surge n/a 4 + Surge
a) RV spaces n/a 3 n/a 4
b) dump station n/a 8 n/a 10
a) gaming floor n/a 3 n/a 4
b) hotel/motel n/a 3 n/a 4
c) restaurant/deli 3 4 5 5
a) bunk houses n/a 3 n/a 4
b) main houses n/a 3 n/a 4
c) kitchen 2 3 4 4
School
Dog Kennel/Veterinary Clinic
Restaurant/Deli
Hotel/Motel/Multiple Dwelling Units
Church
Facility Minimum Preferred
Office/Manufacturing/Light Industrial
Notes: 1. Grease tankage HRT is based on a separate kitchen peak flow, which is integrated into the main flow prior to introduction to the primary septic tanks.
2. Primary tankage HRT is based on total peak flow.
Tankages are based on long-term performance satisfaction (with respect to septage removal) and nominal (minimum) to high-quality (preferred) effluent. If effluent strength is higher than the expected level or if a higher level of treatment is required, greater tankage will be necessary.
RV Park
Resort/Camp
Casino
Source: Orenco Systems Inc.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
TYPICAL SEPTIC TANK
FIGURE 17-1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)18-1
CHAPTER 18
FLOW EQUALIZATION TANK REQUIREMENTS
18.0 CHAPTER OVERVIEW
This chapter provides the design criteria for flow equalization tanks. In addition to the requirements in this
chapter, flow equalization tanks must comply with the general tank design requirements presented in
Chapter 16.
This chapter is organized in the following sections.
Section 18.1: Flow Equalization Tank Overview
Section 18.2: Flow Equalization Tank Sizing Requirements
Section 18.3: Requirements for Sizing of Upstream and Downstream System Components
18.1 FLOW EQUALIZATION TANK OVERVIEW
A. GENERAL
1. Flow equalization is the process of controlling the rate of wastewater flow through an
OWTS by providing storage capacity to hold surges of incoming flow with timed-release
of the accumulated wastewater to even-out the flow to downstream treatment and/or
dispersal components.
2. Flow equalization tanks can reduce the size and cost of downstream system components.
3. Flow equalization tanks may be used for non-residential facilities that experience
significant, regular and predictable fluctuations in wastewater flows and allow for flexibility
and efficiency in System design.
4. Examples of applicable facilities include, but are not limited to churches, schools and
special-event venues.
5. Depending on the size and complexity of the System an operating permit may be
required.
18.2 FLOW EQUALIZATION TANK SIZING REQUIREMENTS
A. MINIMUM CRITERIA
1. Flow equalization tanks shall be installed following the septic tank to aid in better System
performance by allowing peak surges in wastewater flow (e.g., from a weekend event) to
be temporarily stored and metered into the supplemental treatment system and/or
dispersal system at a relatively even (“average”) rate over an extended number of days (e.g.,
during the subsequent week).
2. The flow equalization tank must be sized based on a mass balance analysis.
3. Design calculations and specifications must be submitted to substantiate the proposed
design and operation of the flow equalization tank.
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CHAPTER 18
FLOW EQUALIZATION TANK REQUIREMENTS
18.3 REQUIREMENTS FOR SIZING OF UPSTREAM AND DOWNSTREAM SYSTEM
COMPONENTS
A. UPSTREAM SYSTEM COMPONENTS
1. Where flow equalization is incorporated in an OWTS, the septic tank capacity shall be
sized based on the wastewater design flow for the facility.
B. DOWNSTREAM SYSTEM COMPONENTS
1. Where flow equalization is incorporated in an OWTS, the supplemental treatment system
and/or the dispersal system may be designed based on the equalized (“average”) flow rate
rather than the wastewater design flow for the facility.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)19-1
CHAPTER 19
GREASE INTERCEPTOR TANK REQUIREMENTS
19.0 CHAPTER OVERVIEW
This chapter provides the design criteria for grease interceptor tanks. In addition to the requirements in this
chapter, grease interceptor tanks must comply with the general tank design requirements presented in
Chapter 16.
This chapter is organized in the following sections.
Section 19.1: Grease Interceptor Tank Overview
Section 19.2: Plumbing Fixture Connection Requirements
Section 19.3: Grease Interceptor Tank Sizing Requirements
Section 19.4: Grease Interceptor Tank Maintenance Requirements
19.1 GREASE INTERCEPTOR TANK OVERVIEW
A. WHEN REQUIRED
1. Grease interceptor tanks are required at all facilities connected to an OWTS that generate
more than two hundred (200) gallons per day of wastewater and provide foodservice
and/or food preparation producing wastewater containing floatable oil, wax, fats or grease.
B. EXEMPTIONS
1. A food facility or other commercial operation that demonstrates that the daily discharge of
grease, floatable oil, wax or fats is less than one hundred (100) mg/L may be exempt from
the minimum grease interceptor tank sizing, installation or maintenance requirements of this
chapter.
a.Sampling and testing, if required by the Department, shall be performed at the
owner’s expense and by an independent certified testing organization using
accepted testing methods.
2. An under the counter type grease trap may be used in lieu of a grease interceptor if justifiable
based on the food facility menu.
19.2 PLUMBING FIXTURE CONNECTION REQUIREMENTS
A. MINIMUM CRITERIA
1. Wastewater from plumbing fixtures where floatable oil, wax, fats or a grease may be
introduced shall be plumbed separately from other plumbing fixtures into the grease
interceptor tank first and then into the septic tank.
2. The following plumbing fixtures shall be connected to the grease interceptor tank:
a.Dishwashers (kitchen dishwashing appliances should be high-temperature
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GREASE INTERCEPTOR TANK REQUIREMENTS
disinfection models only; low temperature chemical disinfection dishwashers
are not recommended);
b. Three-compartment sinks;
c.Floor sinks;
d. Mop sinks; and
e.Other fixtures as determined by the Department.
3. Garbage disposals are prohibited for commercial establishments that use Onsite Wastewater
Systems for wastewater disposal.
4. Plans and specifications for the plumbing system shall be submitted to the Department with
the OWTS design plans.
19.3 GREASE INTERCEPTOR TANK SIZING REQUIREMENTS
A. MINIMUM CAPACITY
1. Grease interceptors for non-residential facilities shall be sized according to the formula in
Table 19-1:
Table 19-1
Minimum Grease Interceptor Tank Capacity Formula
Where,
P = Peak number of meals per hour
WF = Wastewater design flow rate (from Table 14-2 in gallons per day)
RT = Retention Time:
RT = 1.5 (for single-service/disposable utensils)
RT = 2.5 (for multi-service utensils)
SF = Storage Factor (minimum capacity of 750 gallons):
SF = 1 (for hours of operation ≤ 8 hours)
SF = 2 (for hours of operation between 9 and 16 hours)
SF = 3 (for hours of operation between 17 and 24 hours)
2. The minimum capacity of the grease interceptor tank shall be eight hundred and ten (810)
gallons. Larger tankage is required for optimal OWTS performance. Recommended
guidelines for minimum and preferred grease interceptor tank sizing for certain facility types
is provided in Table 17-2.
3.An interior grease recovery device meeting the requirements of Chapter 15.20 of the
Alameda County General Ordinance may be approved at the discretion of the Department.
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CHAPTER 19
GREASE INTERCEPTOR TANK REQUIREMENTS
19.4 GREASE INTERCEPTOR TANK MAINTENANCE REQUIREMENTS
A. MINIMUM CRITERIA
1. Grease interceptor tanks shall be located, installed and constructed so that the temperature
of wastewater will be reduced to allow separation of grease and to allow easy access for
cleaning.
2. Grease interceptors shall be cleaned regularly by a Septage Pumper.
3. Written receipts of all grease interceptor and grease recovery device pumping and
maintenance events shall be included in annual operating permit reports submitted to the
Department. The receipts shall document the following:
a.Name and address of the company performing the work;
b. Date the work was performed; and
c.Volume of grease removed.
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CHAPTER 20
PUMP TANK REQUIREMENTS
20.0 CHAPTER OVERVIEW
This chapter provides the design criteria for pump tanks. In addition to the requirements in this chapter,
pump tanks must comply with the general tank design requirements presented in Chapter 16.
This chapter is organized in the following sections.
Section 20.1: Pump Tank Overview
Section 20.2: Pump Tank Design Requirements
Section 20.3: Pump Requirements
Section 20.4: Control and Alarm Requirements
Section 20.5: Design Specifications and Calculation Requirements
20.1 PUMP TANK OVERVIEW
A. PURPOSE
1. Wastewater pumping systems may be considered when they offer a better alternative for
the protection of public health and safety or are required for parcel development or due to
site constraints.
2. Wastewater pumping systems may be utilized to enable:
a.Installation of a System or components of a System hydraulically upgradient of the
structure to be served;
b. Pressure dosing of effluent to the dispersal system;
c.Flow equalization;
d. Transporting of wastewater or solids from a sump tank serving non-dwelling units
to a septic tank; and/or
e.Supplemental treatment.
20.2 PUMP TANK DESIGN REQUIREMENTS
A. MINIMUM CAPACITY
1.Separate Pump Tank. All wastewater pumping systems shall be separate from the septic
tank.
2.Connection to the Septic Tank. Any wastewater pumping system transporting wastewater
or solids to a septic tank shall have its own penetration into the septic tank with a three (3)
inch minimum diameter sanitary tee.
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PUMP TANK REQUIREMENTS
a.At least three (3) feet should be provided between the connection and the septic
tank to minimize turbulence in the septic tank. The pumping flow rate, in either
case, should be minimized.
b. An exception to this requirement may be granted where a wye connection is
provided to the gravity line.
3.Minimum Tank Capacity. The minimum pump tank size shall have sufficient capacity to
hold the following volumes:
a.Dosing volume and the displacement volume of the pump required to deliver the
design dose.
b. Emergency wastewater reserve storage volume in case of a power outage equal to
one (1) day’s wastewater design flow between the high level alarm and the invert
of the pump tank inlet.
c.An exception to providing reserve storage capacity equal to one (1) day’s
wastewater design flow may be granted where the following are provided:
(1) Reserve storage capacity equal to fifty (50) percent of the wastewater
design flow;
(2) Duplex pump system; and
(3) Emergency backup power capability.
d. Multiple interconnected tanks may be used to meet these requirements.
20.3 PUMP REQUIREMENTS
A. MINIMUM CRITERIA
1. All wastewater pumps shall meet the following requirements:
a.Pumps shall be rated for wastewater applications;
b. Motors shall be continuous-duty with overload protection;
c.Pumps shall have durable impellers of bronze, cast iron or other materials
approved by the Department;
d. Pumps used to pump wastewater to a septic tank shall be rated as a solids handling
pump and shall be able to pass two (2) inch solids. Grinder pumps are not allowed;
e.Pumps shall be sized to meet the hydraulic design requirements of the System
and shall be able to provide the required gallons per minute (gpm) at the design
head;
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PUMP TANK REQUIREMENTS
f.Pumps shall be automatically controlled with mechanical switches (or floats
that are compatible with the specified pump and control panel;
g.Pumps shall be equipped with a high level alarm float, set to trigger at a liquid level
approximately two (2) inches above the “on” float;
h. Float switches shall be installed such that the float switches or wires do not
become entangled. Clamps shall be of non-corrosive material;
i. Pumps shall be provided with an easy, readily accessible means of electrical and
plumbing disconnect and a noncorrosive lifting device as a means of removal for
servicing;
j. Check valves are required at the pump;
k.Pumps shall be seated on a level and stable platform of poured concrete or cement
block or placed in suspended pump assemblies;
l. Pumps or suspended pump assemblies shall be installed in accordance with
the manufacturer’s requirements;
m.There shall be sufficient distance from the tank bottom to the pump inlet to allow
space for any solids to settle without interfering with the pump operation; and
n. Pump intake ports shall be placed in the clear liquid zone.
20.4 CONTROL AND ALARM REQUIREMENTS
A. MINIMUM CRITERIA
1. All pumps shall be connected to, and operated from, control panel assemblies
manufactured specifically for their intended use.
2. Electrical components used in Systems shall comply with all applicable state and local
building codes. Prior to doing any electrical work a permit must be obtained from the local
building department and all permit and inspection requirements met.
3. Pump controls and alarms shall be contained in an exterior rated, water proof, non-
corrosive, tamper proof control panel box that can be opened with standard hand tools.
Control panels in areas accessible to the public shall be locked to prevent unauthorized
access.
4. Control panels shall be equipped with a visible and audible alarm and located in
accordance with the following provisions:
a. Control panels shall be easily accessible for service and inspection;
b.Control panels shall not be located in an environment that may damage the
components;
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PUMP TANK REQUIREMENTS
c. Control panels shall be mounted no more than fifty (50) feet away from the residence
or the common area of the non-residential building served by the System;
d.In cases where there are multiple buildings, alarms shall be located at the
building that is most often occupied; and
e. If the primary alarm is not located as required above, a remote visible and
audible alarm (or telemetric alarm) that notifies the owner and Service Provider or
System Designer in the event of system malfunction shall be required.
5. Pumps shall have automatically resetting audible and visual high water level alarms with
a manual silence switch. Only the audible alarm may be user cancelable.
6. Pumps shall have a non-resettable dose counter and/or elapsed time meter included in the
control panel.
7. Pump controls and alarm floats shall be connected to separate electrical circuits.
8. There shall be a manual override switch in the electrical box to facilitate dosing control
during inspections.
20.5 DESIGN SPECIFICATIONS AND CALCULATION REQUIREMENTS
A. MINIMUM CRITERIA
1. The following minimum information shall be provided on the design plans and in the
design report submittal:
a. Specification sheets for pump tanks, tank risers and pumps including pump
performance curves;
b.Specification sheets for float switches and the placement of the floats in the tank
indicating the storage capacity between float switches;
c. Dosing volume and emergency storage volume calculations supported by
manufacturer volume-depth tank rating information;.
d.Specification sheets for audio/visual alarms and the location of the control box and
alarm;
e. The elevation of the pump and dispersal system pipe at the highest elevation; and
f. Calculations for total dynamic head including friction losses through the piping and
valves. The System Designer shall provide friction loss tables to support the total
dynamic head calculations.
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CHAPTER 21
HOLDING TANK REQUIREMENTS
21.0 CHAPTER OVERVIEW
This chapter provides specifications for holding tanks. In addition to the requirements in this chapter, holding
tanks must comply with the general tank design requirements presented in Chapter 16.
This chapter is organized in the following sections:
Section 21.1: Holding Tank General Requirements
Section 21.2: Holding Tank Siting and Design Requirements
Section 21.3: Holding Tank Installation and Permitting Requirements
21.1 HOLDING TANK GENERAL REQUIREMENTS
A. MINIMUM CRITERIA
1. A holding tank is a watertight container designed to collect and temporarily store
wastewater from a building or structure, for subsequent removal by a Septage Pumper and
transport to an approved treatment and disposal site.
2.A holding tank must provide safe and adequate temporary storage of wastewater with
scheduled and approved pumping service and must not contaminate groundwater or surface
water, expose the public to untreated wastewater or be a source of nuisance odors.
3. Depending upon the facility served or the particular set of circumstances surrounding the
use of a holding tank, the expense of wastewater pumping, hauling, and disposal at an
approved facility can be very costly, especially on a long-term basis.
4. In addition, the potential for operational/management problems with resulting public
exposure to wastewater is significant and for this reason, the use of a holding tank is limited.
B. RESIDENTIAL DWELLINGS
1. Holding tanks for existing residential dwellings where no public sewer is available are only
allowed as a temporary measure while corrective action on a failed OWTS is being
completed.
2. Holding tanks for existing residential dwellings on a non-temporary basis may be allowed
as a last resort when an OWTS has failed and may be permitted under the following
conditions:
a.The site cannot be approved for the installation of a replacement OWTS due
to severe site constraints;
b.No public sewer system is available; and
c.All permit conditions are met.
3. Holding tanks shall not be used for accommodating home expansions or additions.
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HOLDING TANK REQUIREMENTS
4. Holding tanks shall not be used as a method for wastewater disposal for creating lots and
parcels.
C. NON-RESIDENTIAL FACILITIES
1. Holding tanks may in very limited circumstances be permitted for industrial, commercial,
or recreational facilities where installation of an OWTS for wastewater is not feasible or
allowed.
21.2 HOLDING TANK SITING AND DESIGN REQUIREMENTS
A. SITING REQUIREMENTS
1. Holding tanks must be located in such a way as to facilitate pumping while limiting the
general public exposure to, or nuisance caused by, accidental wastewater spillage during
pumping.
2. Holding tanks must meet the same horizontal set-backs required for tanks in the treatment
train of an OWTS provided in Table 5-7.
B. DESIGN REQUIREMENTS
1. Holding tanks must meet the general performance requirements for tanks contained in
Chapter 16 of this Manual and requirements of applicable building codes for ancillary
structures and equipment (e.g., concrete pads, impervious surfaces around the access ports,
vent pipes, etc.).
2. Holding tanks and piping shall be designed by a Qualified Professional as allowed by their
license and registration.
3. If installed above-ground, adequate support must be provided for all associated piping;
4. If the facility or building is to be permanently served by the holding tank incorporation of
water-saving fixtures and processes where possible within the facility or dwelling is
required.
5. Holding tanks shall have a minimum liquid capacity of fifteen hundred (1,500) gallons and
shall be sized to accommodate a minimum of two hundred (200) percent of the
wastewater design flow between anticipated pumping events in accordance with the
formula in Table 21-1.
Table 21-1
Holding Tank Sizing Formula
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HOLDING TANK REQUIREMENTS
6. The minimum liquid capacity can be met with multiple holding tanks. Where multiple,
interconnected tanks will be installed, they must prevent breakage of connections and
differential settling through use of a common slab, flexible connections or bedding.
7. Tanks shall be located and designed to facilitate visual inspection and removal of
contents by pumping.
8. Holding tanks shall be equipped with both an audible and visual alarm, placed in a
location acceptable to the Department to indicate when the tank is seventy-five (75) percent
full. Only the audible alarm may be user cancelable.
9. Holding tanks shall have no overflow vent at an elevation lower than the overflow level of
the lowest fixture served.
C. VENTING AND ODOR CONTROL
1.Gravity Flow to Holding Tanks. Separate venting directly from the holding tank is not
required since the holding tank will vent through the building sewer. Special care shall be
necessary however to assure that pumping and service access ports lids are leak-proof so
all sewage gases will vent through the facility waste vent pipes.
2.Pressure Flow to Holding Tanks. Direct venting of the holding tank is required since
gases will not adequately vent through the pressurized line from the pump. Vent pipes
should terminate high enough and away from area of human activity to avoid vent stack
odors and related nuisances. To assure that the gases vent through the vent stack, pumping
and service access port lids must be leak proof.
D. WASH DOWN AREA
1. Design and installation of the holding tank must provide a means to “wash down” the area
around the pumping access port(s) and service access(s).
2. The surface adjacent to the access port(s) and service access(s) must be impervious to
wastewater and sloped so any spilled wastewater and/or associated wash down water will
drain back into the holding tank.
3. If the wash down hose could enter the holding tank, a back-flow prevention device must
be installed on the water supply. The back-flow preventer must be accessible for periodic
servicing as needed.
21.3 HOLDING TANK INSTALLATION AND PERMITTING REQUIREMENTS
A. PERMIT CONDITIONS
1. Issuance of an installation permit is conditioned on the acceptance of the conditions that will
be contained in the operating permit. An operating permit is required prior to issuance of
the final installation approval.
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HOLDING TANK REQUIREMENTS
2. The installation and operating permits are conditioned on the owner of the property
connecting to a public sewer system when it becomes available and prior to the renewal
date of the operating permit. An operating permit for a holding tank will not be renewed if
a public sewer system is available.
3. The owner shall provide the Department with the following as a condition of the operating
permit:
a.A copy of a contract with a Septage Pumper that shows the holding tank shall
be pumped at regular intervals or as needed to prevent use of greater than seventy-
five (75) percent of the holding tank's capacity;
b. A record of pumping dates, amounts pumped, and operation records including,
but not limited to alarms, servicing and repairs shall be maintained by the owner,
included in the annual operating report and made available to the Department upon
request; and
c.Financial guarantee for operation, such as a bond or an assignment of funds, in an
amount at least equal to the cost of one year’s service and/or the estimated cost of
cleanup and abatement of sewage spill or prepayment of one years’ service.
4. Failure to properly and regularly pump a holding tank may result in revocation or non-
renewal of the operating permit which will result in red-tag of the property.
.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
PART 6
SUPPLEMENTAL TREATMENT SYSTEM
REQUIREMENTS
CHAPTER TITLE
CHAPTER 22 GENERAL SUPPLEMENTAL TREATMENT
SYSTEMS REQUIREMENTS
CHAPTER 23 PROPRIETARY SUPPLEMENTAL TREATMENT
UNIT REQUIREMENTS
CHAPTER 24 RECIRCULATING AND INTERMITTENT SAND
FILTER SYSTEM REQUIREMENTS
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CHAPTER 22
GENERAL SUPPLEMENTAL TREATMENT SYSTEM REQUIREMENTS
22.0 CHAPTER OVERVIEW
This chapter provides general design guidelines for supplemental treatment systems approved for use in
the County.
This chapter is organized in the following sections:
Section 22.1: Supplemental Treatment Systems Overview
Section 22.2: General Performance Requirements for Supplemental Treatment Systems
22.1 SUPPLEMENTAL TREATMENT SYSTEMS OVERVIEW
A. GENERAL
1. Supplemental treatment systems may be proprietary treatment units and/or engineered
filter systems that provide a specified level of treatment prior to wastewater dispersal
into the dispersal system.
2. Dispersal systems receiving wastewater from a supplemental treatment unit are subject to
the siting criteria for the specific type of dispersal system proposed, including any
allowances for the incorporation of supplemental treatment.
3. Allowances for supplemental treatment may include reduced vertical separation distances,
use of enhanced wastewater application rates or modified slope restrictions.
4. Refer to Part 7 of this Manual for the adopted guidelines for the specific type of dispersal
system for applicable requirements and supplemental treatment allowances.
22.2 GENERAL PERFORMANCE REQUIREMENTS FOR SUPPLEMENTAL TREATMENT
SYSTEMS
A. MINIMUM CRITERIA
1. Supplemental treatment systems must be designed to meet the following BOD and TSS
concentrations:
a.Thirty (30) day average BOD concentration shall not exceed thirty (30) mg/L, or
alternatively, a carbonaceous BOD (CBOD) in excess of twenty-five (25) mg/L.
b. Thirty (30) day average TSS concentration shall not exceed thirty (30) mg/L.
2. Where nitrogen is identified as a water quality concern, nitrogen reducing performance
requirements must also be met in accordance with the specific requirements for the area of
concern (refer to Chapter 10 for Zone 7 Water Agency nitrogen loading requirements for
designated areas of concern).
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GENERAL SUPPLEMENTAL TREATMENT SYSTEM REQUIREMENTS
B. DISINFECTION
1. Disinfection may be required when:
a.New OWTS, installed on parcels of record existing at the time of the effective date
of the Ordinance and this Manual that cannot meet the minimum horizontal setback
distances from public water supply wells or surface water intake points provided
in Table 5-7 and requiring maximum extent practicable technology; or
b. Replacement OWTS or repairs to an existing OWTS located within the minimum
horizontal setback distances from a surface water body or a well and requiring
maximum extent practicable technology.
2. Add-on components performing disinfection must be designed to achieve an effluent total
coliform bacteria concentration, at the 95th percentile, not greater than the following:
a.Ten (10) most probable number (MPN) per one hundred (100) milliliters (ml) prior
to discharge into the dispersal system where the soil exhibits percolation rates of
one (1) to ten (10) MPI or where the soil texture is sand; or
b. One thousand (1,000) MPN per one hundred (100) ml prior to discharge into the
dispersal system where the soil exhibits percolation rates greater than ten (10) MPI
or where the soil texture is other than sand.
C. REMOTE NOTIFICATION
1. Where feasible, supplemental treatment systems shall be equipped with a remote
notification mechanism that notifies the owner and Service Provider or System Designer
in the event of System malfunction.
D. SYSTEM PERFORMANCE
1.All Systems with supplemental treatment require an operating permit.
2.The performance of Systems with supplemental treatment shall be demonstrated through
the operation, maintenance, monitoring and reporting requirements as described in
Chapter 43 of this Manual.
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CHAPTER 23
PROPRIETARY TREAMENT UNIT REQUIREMENTS
23.0 CHAPTER OVERVIEW
This chapter provides general design guidelines for proprietary treatment units approved for use in the
County and is organized in the following sections:
Section 23.1: Proprietary Treatment Unit Overview
Section 23.2: Proprietary Treatment Unit Siting Requirements
Section 23.3: Design, Installation & Maintenance Requirements
23.1 PROPRIETARY TREATMENT UNIT OVERVIEW
A. GENERAL
1. Propriety treatment units cover a category of manufactured or “package” supplemental
treatment systems specifically developed for residential and other small-scale wastewater
treatment applications. Most proprietary treatment units currently available fall into the
following two general categories:
a.Aerobic Treatment Units (ATUs). ATUs utilize forced air to oxidize the
wastewater, promoting aerobic decomposition of the wastewater solids. These
systems provide supplemental treatment of wastewater for improvement in
dispersal system performance; they also provide varying degrees of nitrogen
removal. In general, ATUs can be relied on to produce secondary quality effluent
concentrations of less than 30 mg/L BOD and TSS. ATUs are generally not as
effective in reducing pathogen levels as are supplemental treatment systems that
incorporate media filtration. However, some ATUs provide reduction in nitrogen
levels equal to or greater than that provided by sand filters and other media filters.
b.Media Filters. Media filters include proprietary designs that function similar to
sand filters. In these systems the sand is replaced with an alternate media including
but not limited to peat, gravel or textile. Textile and other media filters have
been found to produce effluent quality reasonably similar to recirculating sand
filters and provide similar capabilities in overcoming various soil and site
constraints.
2. Effluent from proprietary treatment units may be discharged to gravity dispersal systems
and to any type of advanced dispersal system identified in Part 7 of this Manual.
23.2 PROPRIETARY TREATMENT UNIT SITING REQUIREMENTS
A. MINIMUM CRITERIA
1. All siting criteria for tanks, as specified in Chapter 16 of this Manual shall also apply to
proprietary treatment units and associated tanks and pumping units.
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CHAPTER 23
PROPRIETARY TREAMENT UNIT REQUIREMENTS
23.3 DESIGN, INSTALLATION & MAINTENANCE REQUIREMENTS
A. NSF STANDARD 40 COMPLIANCE
1. Proprietary treatment units must be listed by the NSF/ANSI, meeting the NSF/ANSI
Standard 40, Class 1 performance evaluation and have a training/certification program for
installers.
2. Proprietary treatment units must be manufactured and installed in accordance with the
design specifications used to determine compliance to NSF/ANSI Standard 40. The
NSF/ANSI Standard 40 listing is applicable to proprietary treatment units for wastewater
flows of up to one thousand five hundred (1,500) gpd and is based on compliance with
USEPA standards for secondary treatment of municipal wastewater, including thirty (30)-
day average effluent limits of twenty-five (25) mg/L for CBOD5 and thirty (30) mg/L for
TSS.
3. Proprietary treatment units for flows in excess of one thousand five hundred (1,500) gpd
will require certification by a third-party listing agency as complying with NSF/ANSI
Standard 40 performance requirements.
B. DESIGN REQUIREMENTS
1.Wastewater Design Flow. Sizing and design of proprietary treatment units shall be based
on the projected wastewater flow for the structures or facilities being served, determined in
accordance with wastewater flow estimation guidelines in Chapter 14 of this Manual.
2.Tanks. All tanks housing a proprietary treatment unit shall be structurally sound, water-
tight and shall be capable of withstanding one-thousand (1,000) pounds of weight. All tanks
must comply with the general tank design requirements presented in Chapter 16.
3.Controls. Control panels shall be designed and configured in such a manner that, in the
event of a proprietary treatment unit malfunction, an alarm system will be triggered and
discharge from the proprietary treatment unit to the dispersal system will be interrupted
until the proprietary treatment unit malfunction is rectified. At a minimum, the alarm
system shall include an audible and visual alarm located within fifty (50) feet of the
building served by the System.
4.Emergency Storage Provisions. Where a proprietary treatment unit is used in
conjunction with a gravity dispersal system, the system shall provide emergency storage
capacity equal to at least one (1) times the wastewater design flow, consistent with
requirements for pump systems provided in Chapter 20 of this Manual.
5.Compliance with Manufacturer Requirements. The System Designer and installer of the
proprietary treatment unit shall follow the manufacturer’s design, installation, construction,
and operations procedures.
6.System Design Plans. Design plan submittals for proprietary treatment units shall
provide documentation of compliance with manufacturer requirements and sufficient
design analysis to verify the appropriateness of the treatment unit for the proposed
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CHAPTER 23
PROPRIETARY TREAMENT UNIT REQUIREMENTS
application. System design documents shall contain specific step-by step construction
guidelines and notes for use by the installer, including any manufacturer instructions.
C. INSTALLATION AND MAINTENANCE REQUIREMENTS
1.Installer Requirements. Anyone installing a proprietary treatment unit shall be trained and
certified by the system manufacturer. Documentation verifying the training/certification
shall be provided to the Department prior to system installation.
2.Maintenance Contract. The owner must provide proof of a written maintenance
agreement with a Service Provider or System Designer for the proposed proprietary
treatment unit to ensure satisfactory post-construction operation and maintenance. Proof of
a written maintenance agreement is required as a condition of the operating permit.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)24-1
CHAPTER 24
INTERMITTENT & RECIRCULATING SAND FILTER SYSTEM REQUIREMENTS
24.0 CHAPTER OVERVIEW
This chapter provides general design guidelines for intermittent sand filters (ISF) and recirculating sand
filter (RSF) systems and is organized in the following sections:
Section 24.1: ISF and RSF Systems Overview
Section 24.2: Siting Requirements
Section 24.3: Influent Wastewater Strength Requirements
Section 24.4: Pressure Dosing Requirements
Section 24.5: Containment Structure Requirements
Section 24.6: Sand Filter Basal Area Sizing Requirements
Section 24.7: Sand Filter Media Requirements
Section 24.8: Gravel Distribution Bed Requirements
Section 24.9: Underdrain Requirements
Section 24.10: Air Manifold Requirements
Section 24.11: Internal Pump System Requirements (ISF Only)
Section 24.12: Cover Requirements
Section 24.13 Inspection Well Requirements
24.1 ISF AND RSF SYSTEMS OVERVIEW
A. DESCRIPTION
1. ISF and RSF systems are used to provide supplemental treatment of septic tank effluent
prior to discharge to the dispersal system. They are used to improve or restore the
capacity of the dispersal system, reduce pathogenic bacteria loading and can provide
additional nitrogen removal.
2.An ISF consists of a packed-bed filter of medium-grained sand designed for single pass-
through treatment of septic tank effluent; it is sometimes referred to as a “single pass
filter”.
3.An RSF utilizes coarse-grained sand and a recirculation system usually controlled by a
timer that causes the effluent to pass through the sand media several times prior to final
dispersal. RSFs have the ability to produce effluent quality similar to ISFs except that
they are less effective in bacteria removal. However, RSFs typically provide greater
nitrogen removal than ISFs, on the order of fifty (50) percent reduction as compared with
primary treatment (septic tank) effluent.
4. Discharge of effluent from an intermittent sand filter to a dispersal system is required.
Direct discharge of effluent from an intermittent sand filter to surface water or upon the
ground surface is prohibited. Effluent from sand filters may be discharged to any type of
dispersal system identified in this Manual.
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CHAPTER 24
INTERMITTENT & RECIRCULATING SAND FILTER SYSTEM REQUIREMENTS
5. Effluent from an ISF or RSF designed and operated in accordance with these guidelines
will be considered to meet the criteria for supplemental treatment.
6. Schematic and cross-section diagrams of ISF are provided in Figure 24-1 and Figure 24-2
and a cross-section diagram of a RSF is provided in Figure 24-3 (included at the end of this
chapter) to illustrate the key design features of ISF and RSF.
24.2 SITING REQUIREMENTS
A. MINIMUM CRITERIA
1. All siting criteria for tanks, as specified in Chapter 16 shall also apply to ISF and RSF
systems and associated tanks and pumping units.
24.3 INFLUENT WASTEWATER STRENGTH REQUIREMENTS
A. MINIMUM CRITERIA
1. ISF and RSF systems are designed for treating domestic-strength wastewater. The
wastewater applied to the sand filter shall not be higher in strength than domestic-strength
wastewater. Lower wastewater strengths are preferable for assuring long term operation
of sand filter systems.
2. The following treatment requirements shall apply in connection with the use of ISF and RSF
systems:
a.Primary (septic tank) treatment shall be the minimum level of treatment.
b. Supplemental treatment using an approved proprietary treatment unit identified in
this Manual, shall be required for high-strength wastewater in order to reduce
its strength prior to introduction into the ISF or RSF system.
24.4 PRESSURE DOSING REQUIREMENTS
A. MINIMUM CRITERIA
1. Septic tank effluent shall be applied to the ISF or RSF by pressure dosing utilizing either an
automatic dosing siphon (ISF system only) or a pump.
2. The pressure distribution system shall be designed in accordance with accepted industry
practices to achieve at a minimum:
a.Uniform dosing of effluent over the surface application area of the sand filter
distribution bed;
b. Adequate flow rate, screening of effluent, suitable piping network and orifice shields
to preclude solids accumulation in the pipes or clogging of discharge orifices;
c.Suitable access provisions for inspection, testing and adjustment of the pressure
distribution system;
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CHAPTER 24
INTERMITTENT & RECIRCULATING SAND FILTER SYSTEM REQUIREMENTS
d.At least one distribution lateral for every thirty-six (36) inches of bed width; and
e.Dosing volumes as follows:
(1) Intermittent Sand Filters Systems: Dosing may be either on demand or
time dosing. For on demand systems the dosing volume should be designed
to achieve a minimum of three (3) to five (5) doses per day at wastewater
design flow conditions. For time dosed systems the volume should be
sufficient to ensure complete filling of the distribution piping and even
dispersal throughout the sand filter bed with each dose;
(2) Recirculating Sand Filters: Timed dosing to achieve a recirculation
rate of approximately five to one (5:1) at wastewater design flow
conditions.
3. The pump or siphon system must be designed in accordance with the pump system
requirements provided in Chapter 20 of this Manual.
4. Additional requirements for the design and construction of pressure distribution systems
contained in Chapter 26 of this Manual shall also apply.
5. Where a sand filter is used in conjunction with a gravity-fed dispersal system, the dosing
pump system for the ISF or RSF system shall provide emergency storage capacity equal to
at least one (1) times the wastewater design flow consistent with requirements for pump
systems provided in Chapter 20 of this Manual.
24.5 CONTAINMENT STRUCTURE REQUIREMENTS
A. CONTAINMENT LINER
1. The ISF/RSF system shall be provided with an impermeable containment liner along all
sides of the filter bed to prevent lateral leakage out of or into the filter.
2. The liner shall consist of either:
a. Synthetic membrane lined pit (30 mil plastic);
b.Reinforced poured-in-placed concrete; or
c. An equivalent impermeable structure or barrier.
3. Plastic liners shall meet the material specifications provided in Chapter 36.
4. Containment walls over four feet in height measured from the bottom of the footing to the
top of the walls must be designed by a Qualified Professional as allowed by their license
and registration.
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CHAPTER 24
INTERMITTENT & RECIRCULATING SAND FILTER SYSTEM REQUIREMENTS
B. FINISHED GRADE AND STRUCTURAL SUPPORT
1. The finished surface elevation of the sand filter shall be above the surrounding ground
surface elevation and shall be structurally supported with retaining wall(s), as required.
C. SAND FILTER BED DIMENSIONS
1. The sand filter shall not be restricted as to its shape in plan view.
2. The raised sand filter bed dispersal system may be divided into compartments or multiple
units.
24.6 SAND FILTER BASAL AREA SIZING REQUIREMENTS
A. MINIMUM CRITEERIA
1. The basal area of the sand filter shall be sized as follows:
a.Wastewater Flow. The wastewater flow used for sizing the basal area of the sand
filter shall be the wastewater design flow for the System.
b.Wastewater Application Rate. The maximum wastewater application rate used
for sizing the basal area of the sand filter shall be as shown in Table 24-1 below:
Table 24-1
Maximum Wastewater Application Rate for Sand Filter Basal Area Sizing
Sand Filter
Type
Individual
Residential OWTS
Commercial, Industrial,
Institutional and Multi-Unit
Residential OWTS
2 2
2 2
Note: Reduction in the above wastewater loading rates or other provisions to
ensure the long-term integrity and performance of the sand filter may be
required for high-strength wastewater flows.
2.Minimum Sizing. The minimum size (square feet) of the basal area of the sand filter system
shall be determined in accordance with the formula provided in Table 24-2 using the
applicable wastewater application rate listed in Table 24-1 above.
Table 24-2
Sand Filter Basal Area Formula
Sand Filter Basal Area (ft2)=Wastewater Design Flow Rate (gpd)
Wastewater Application Rate (gpd
ft2 )
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)24-5
CHAPTER 24
INTERMITTENT & RECIRCULATING SAND FILTER SYSTEM REQUIREMENTS
24.7 SAND FILTER MEDIA REQUIREMENTS
A. SAND SPECIFICATIONS
1. The sand filter media shall be a medium to coarse sand which meets the gradation
specifications for ISFs or RSFs in Chapter 35.
2. Documentation of laboratory sieve analysis results for the proposed sand filter media
material shall be provided to the Department to verify conformance with the above
specifications prior to final installation approval.
B. SAND DEPTH
1. The minimum depth of sand fill below the gravel distribution bed shall be twenty-four
(24) inches.
24.8 GRAVEL DISTRIBUTION BED REQUIREMENTS
B. GRAVEL SPECIFICATIONS
1. The gravel distribution bed shall consist of clean pea gravel which meets the material
specifications in Chapter 35.
C. GRAVEL DEPTH
1. Pea gravel shall extend a minimum of six (6) inches below the invert and two (2) inches
above the top of the distribution piping.
2.If the distribution piping is installed with gravelless chambers, the pea gravel depth below
the distribution pipe may be reduced from six (6) inches to four (4) inches, and the two (2)
inch pea gravel cover may be eliminated.
D. SILT BARRIER
1.ISF Systems. The gravel distribution bed shall be covered in its entirety with a geotextile
("filter fabric") silt barrier meeting the filter fabric specifications in Chapter 36.
2.RSF Systems. RSFs do not require a silt barrier.
24.9 UNDERDRAIN REQUIREMENTS
A. STORAGE VOLUME
1. The underdrain beneath the sand filter must be designed with sufficient void storage
volume to provide for a single drainfield dose with reserve capacity to maintain unsaturated
filter media above the underdrain system.
2. Collection pipes must be of sufficient size with adequate perforations or slots so that filtrate
can flow from the void storage space into the collection pipe rapidly enough to
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)24-6
CHAPTER 24
INTERMITTENT & RECIRCULATING SAND FILTER SYSTEM REQUIREMENTS
maintain unsaturated filter media above the underdrain system.
B. GRAVEL AND PIPE CRITERIA
1. The underdrain shall have a minimum depth of nine (9) inches and shall consist of a minimum
three (3) inch layer of pea gravel over a six (6) inch medium gravel layer containing the
collection pipe consisting of four (4) inch diameter perforated drain pipe installed with
perforations oriented down.
2. The purpose of the pea gravel is to restrict the migration of sand into the gravel and pipe
in the underdrain. The gravel surrounding the perforated pipe should be sized larger than
the perforations to prevent migration of gravel into the pipe.
3. For the purpose of calculating void storage space in the medium gravel, three (3) gallons
per cubic foot may be used assuming forty (40) percent void space per cubic foot.
4. The pipe and gravel shall meet the material specifications in Chapter 33 and Chapter 35.
C. GRADE
1. The underdrain shall be constructed and the drain pipe set with a minimum gradient of one
(1) percent toward the outlet point.
D. WATERTIGHT OUTLET BOOT
1. The underdrain shall be equipped with a watertight outlet "boot" for connection of piping
to the pump tank.
2.An exception to this is for ISF systems that are equipped with an internal pump system
for direct dosing to the dispersal system (see Section 24.11 below).
E. CLEAN-OUT RISER
1. For cleanout and inspection purposes the upslope end of the perforated drain pipe in the
underdrain shall be equipped with a vertical riser constructed of non-perforated pipe of
equal diameter.
2. The riser shall extend to the finished surface elevation of the sand filter.
24.10 AIR MANIFOLD REQUIREMENTS
A. MINIMUM CRITERIA
1. An air manifold shall be installed within the gravel underdrain above the perforated pipe for
the purpose of introducing forced air into the sand filter media, as needed, for maintenance
or drainage rehabilitation.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)24-7
CHAPTER 24
INTERMITTENT & RECIRCULATING SAND FILTER SYSTEM REQUIREMENTS
2. The air manifold shall consist of small diameter pressure pipe meeting the material
specifications in Chapter 33, with drilled perforations (pointed down), or an equivalent
piping system, for example drip line tubing.
3. The manifold shall be connected to a vertical leader pipe that extends to the surface of the
sand filter, fitted with a threaded pipe cap or plug at the top where a portable air-line can be
connected.
24.11 INTERNAL PUMP SYSTEM REQUIREMENTS (ISF ONLY)
A. MINIMUM CRITERIA
1. In lieu of gravity flow from the sand filter to the dispersal system, an internal pump system
may be installed within the ISF system for dosing directly to the dispersal field.
2. In such applications:
a.The pump chamber shall be seated at or below the bottom of the underdrain;
b. The pump operating depth shall be entirely within the depth of the underdrain; and,
c.A storage volume equal to at least fifty (50) percent of the dispersal field dose volume
shall be provided in the network of perforated drain pipes within the underdrain.
24.12 COVER REQUIREMENTS
A. ISF SYSTEMS
1.Material. A continuous soil cover consisting of a medium, loamy-textured soil shall be
placed over the entire distribution bed.
2.Depth. The soil cover depth shall be a minimum of twelve (12) inches and a maximum of
eighteen (18) inches over the top of the distribution bed. The soil cover shall be crowned
or sloped to promote rainfall runoff.
B. RSF SYSTEMS
1.Material. A granular media cover shall be placed over the distribution bed, consisting of
clean gravel that meets the material specifications in Chapter 35.
2.Depth. The soil cover depth shall be a minimum of twelve (12) inches and a maximum of
eighteen (18) inches over the top of the distribution bed.
24.13 INSPECTION WELL REQUIREMENTS
A. MINIMUM CRITERIA
1.A minimum of one (1) inspection well shall be installed within the gravel distribution bed
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)24-8
CHAPTER 24
INTERMITTENT & RECIRCULATING SAND FILTER SYSTEM REQUIREMENTS
of each sand filter compartment for the purpose of checking wastewater levels and water
quality sampling.
2. Inspection wells shall be constructed of two (2) inch to four (4) inch diameter pipe,
equipped with a wrench-tight cap or pipe plug and a bottom cap.
3. Inspection wells shall extend from the finished surface elevation to the pea gravel-sand
interface of the gravel distribution bed and shall be perforated in the gravel zone only as
shown on Figure 24-2 (ISFs) and Figure 24-3 (RSFs).
4. Perforations shall consist of hacksaw slots at nominal one (1) inch spacing, or equivalent
commercially-slotted pipe.
5. For ISFs, inspection wells shall be sealed to prevent surface infiltration with a bentonite or
concrete annular seal (or equivalent) through the soil backfill zone.
PLAN VIEW
30 MIL PVC LINER,
SECURE TOP EDGE BY
FASTENING TO BOARD
CLEANOUT WITH
THREADED CAP (TYP.)
STANDARD ORIFICE SHIELD OR
CHAMBER OVER EACH LATERAL (TYP.)
UTILITY BOX (TYP.)
4" SCH.40, PVC SLOTTED COLLECTION
PIPECLEAN OUT WITH THREADED CAP (TYP.)
2" PRESSURE LINE FROM PUMP CHAMBER #1
12" TO 18" (TYP.)
INSPECTION RISER
(TYP.) TO GRADE
INSPECTION WELL (TYP.)
2" PVC END
MANIFOLD
PVC GATE VALVE
(TYP.)
24" TO 36" (TYP.)
INTERMITTENT SAND FILTER
SCHEMATIC
FIGURE 24-1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
INSPECTION WELL
INTERNAL
PUMP BASIN,
30" DIA. PVC
(TYP.)
UTILITY BOX
(TYP.)
MANIFOLD
DISCHARGE
HOLES W/
SHIELD, OR
EQUAL (TYP.)*
LATERAL
SHUT-OFF VALVE
DOUBLE WASHED PEA
GRAVEL
SAND BEDDING
(TYP.)
SLOTTED
UNDERDRAIN
TO DISPOSAL FIELDTOPSOIL
PRESSURE
LINE FROM
DOSING PUMP
END RISER & FLUSH
PORT
MEDIUIM SAND 24" MIN. DEPTH
30 MIL PVC
LINER OR
EQUAL
4" UNDERDRAIN
CLEANOUT
6" MIN.
PERIMETER
RETAINING
STRUCTURE
(TYP.)
FILTER FABRIC
SILT BARRIER
PEA GRAVEL DISTRIBUTION
BED; 6" MIN. BELOW PIPE, 2"
MIN. ABOVE PIPE
DISTRIBUTION
LATERAL
12" (TYP.)
PERFORATED PVC
AIR INJECTION
MANIFOLD; W/
CONNECTION
PORT AT SAND
FILTER SURFACE
FOR PORTABLE
BLOWER
*NOTE: DISCHARGE HOLES
MAY BE SHIELDED WITHIN A
CONTINUOUS PLASTIC
CHAMBER, OR THEY MAY BE
ORIENTED DOWN WITHOUT
THE NEED FOR ANY SHIELD.
INTERMITTENT SAND FILTER
WITH INTERNAL PUMP BASIN CROSS-SECTION
SLOPE = .02
FIGURE 24-2
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
UTILITY BOX
(TYP.)
MANIFOLD
DISCHARGE
HOLES W/
SHIELD, OR
EQUAL (TYP.)*
LATERAL SHUT-OFF
VALVE
DOUBLE WASHED PEA GRAVEL
SAND BEDDING
(TYP.)
SLOTTED
UNDERDRAIN
RIVER RUN ROCK
PRESSURE
LINE FROM
DOSING PUMP
END RISER & FLUSH
PORT
COURSE SAND 24" MIN. DEPTH
30 MIL PVC
LINER OR
EQUAL
4" UNDERDRAIN
CLEANOUT
6" MIN.
PERIMETER
RETAINING
STRUCTURE
(TYP.)
* NOTE: DISCHARGE HOLES
MAY BE SHIELDED WITHIN A
CONTINUOUS PLASTIC
CHAMBER, OR THEY MAY BE
ORIENTED DOWN WITHOUT
THE NEED FOR ANY SHIELD.
PEA GRAVEL DISTRIBUTION
BED; 6" MIN. BELOW PIPE, 2"
MIN. ABOVE PIPE
DISTRIBUTION
LATERAL
12" (TYP.)
PERFORATED PVC
AIR INJECTION
MANIFOLD; W/
CONNECTION
PORT AT SAND
FILTER SURFACE
FOR PORTABLE
BLOWER
RETURN LINE TO
RECIRCULATION
TANK
INSPECTION WELL
RECIRCULATING SAND FILTER
CROSS-SECTION
SLOPE = .02
FIGURE 24-3
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
PART 7
SUBSURFACE DISPERSAL SYSTEM
REQUIREMENTS
CHAPTER TITLE
CHAPTER 25 SUBSURFACE DISPERSAL SYSTEMS GENERAL
REQUIREMENTS
CHAPTER 26 PRESSURE DISTRIBUTION DISPERSAL SYSTEM
REQUIREMENTS
CHAPTER 27 GRAVITY TRENCH DISPERSAL SYSTEM
REQUIREMENTS
CHAPTER 28 PRESSURE DOSED TRENCH DISPERSAL SYSTEM
REQUIREMENTS
CHAPTER 29 SUBSURFACE DRIP DISPERSAL SYSTEM
REQUIREMENTS
CHAPTER 30 AT-GRADE & MOUND DISPERSAL SYSTEM
REQUIREMENTS
CHAPTER 31 RAISED SAND FILTER BED DISPERSAL SYSTEM
REQUIREMENTS
CHAPTER 32 COVER FILL REQUIREMENTS
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)25-1
CHAPTER 25
SUBSURFACE DISPERSAL SYSTEM GENERAL REQUIREMENTS
25.0 CHAPTER OVERVIEW
This chapter provides an overview and general design criteria for subsurface dispersal systems approved
for use in the County. The criteria apply to new and replacement OWTSs and modifications or repairs to
existing OWTS.
This chapter is organized in the following sections:
Section 25.1: Dispersal Systems Overview
Section 25.2: Wastewater Application Rate Requirements
Section 25.3: Effective Soil Depth &Vertical Separation to Groundwater Requirements
Section 25.4: Ground Slope Requirements
Section 25.5: Horizontal Setback Requirements
Section 25.6: Dual Dispersal System Requirements
Section 25.7: OWTS Performance Well Requirements
25.1 DISPERSAL SYSTEMS OVERVIEW
A. TYPES OF SYSTEMS
1. A summary of the subsurface dispersal system types and associated treatment train
configurations that may be approved for use in the County are provided in the following
tables:
a.Table 5-1 (Gravity Trench Dispersal System Configurations);
b.Table 5-2 (Pressure-Dosed Trench Dispersal System Configurations);
c.Table 5-3 (Subsurface Drip Dispersal System Configurations);
d.Table 5-4 (At-Grade Dispersal System Configurations);
e.Table 5-5 (Mound Dispersal System Configurations); and
f.Table 5-6 (Raised Sand Filter Bed Dispersal System Configurations).
2. Other dispersal systems and treatment train configurations may be approved for use in the
County under Regional Water Board Waste Discharge Requirements.
25.2 WASTEWATER APPLICATION RATE REQUIREMENTS
A. MINIMUM CRITERIA
1. Subsurface dispersal systems are sized based on wastewater application rates that are
representative of the soil classification and percolation rates for the soil zone corresponding
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SUBSURFACE DISPERSAL SYSTEM GENERAL REQUIREMENTS
to the sidewall and/or bottom of the dispersal system and the type of OWTS proposed.
2. Wastewater application rates shall be determined using the design percolation rate
calculated in accordance with the procedures presented in Chapter 8 of this Manual.
3.Alternative Method. Where there is a substantial variation in the individual adjusted
percolation rates (i.e., an order of magnitude difference between high and low values)
calculated in accordance with the procedures presented in Chapter 8 the wastewater
application rate for dispersal system design may be determined by averaging the individual
wastewater application rates corresponding to each adjusted percolation rate.
B. WASTEWATER APPLICATION RATE TABLES
1. The wastewater application rate for sizing dispersal systems shall be based upon
representative percolation test results for the soil zone corresponding with the depth of the
sidewall and/or bottom of the dispersal system.
2.Standard Wastewater Application Rates. Standard wastewater application rates are
presented in Table 25-1 (included at the end of this chapter) and must be utilized with
gravity trench dispersal systems and other advanced dispersal system types, as applicable.
3.Enhanced Wastewater Application Rates. Enhanced wastewater application rates are
presented in Table 25-2 (included at the end of this chapter). Enhanced wastewater
application rates may be utilized as follows:
a.To size pressure-dosed sand trench dispersal systems, mound dispersal systems and
raised sand filter bed dispersal systems.
b. To allow smaller dispersal system sizing of any dispersal system utilizing pressure
distribution when all of the following conditions are met:
(1) The dispersal system is preceded by supplemental treatment; and
(2) The vertical separation to high seasonal groundwater requirement is met
for the same type of dispersal system preceded by primary (septic tank)
treatment only.
4.Wastewater Application Rates for Subsurface Drip Dispersal Systems. Wastewater
application rates for subsurface drip dispersal systems are provided in Table 25-3
(included at the end of this chapter).
5.Table 5-1 through Table 5-6 provide guidance on the requisite wastewater application rate
table to use when sizing dispersal systems.
25.3 EFFECTIVE SOIL DEPTH & VERTICAL SEPARATION TO GROUNDWATER
REQUIREMENTS
A. MINIMUM CRITERIA
1. Dispersal systems shall be designed to meet the minimum effective soil depth and vertical
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)25-3
CHAPTER 25
SUBSURFACE DISPERSAL SYSTEM GENERAL REQUIREMENTS
separation distances from high seasonal groundwater or other limiting layer.
2. Where advanced OWTS are utilized, the minimum effective soil depth and the vertical
separation to groundwater distance may be reduced from the requirements that apply to
standard OWTS.
3. Minimum vertical separation distances to high seasonal groundwater and minimum
effective soil depth requirements for subsurface dispersal systems that may be approved
for use in the County are provided in Table 5-1 through Table 5-6.
25.4 GROUND SLOPE REQUIREMENTS
A. MAXIMUM CRITERIA
1. Dispersal systems shall be designed to comply with the maximum ground slope
requirements allowable for the specific type of dispersal system.
2. Maximum ground slope for OWTS configurations that may be approved for use in the
County are provided in Table 5-1 through Table 5-6.
3.A geotechnical report is required in accordance with the requirements of Chapter 11 of
this Manual for OWTS on sites with ground slopes greater than thirty (30) percent.
25.5 HORIZONTAL SETBACK REQUIREMENTS
A. MINIMUM CRITERIA
1. Subsurface dispersal systems must meet the horizontal setback requirements provided in
Table 5-7 as well as additional setback criteria for the specific type of dispersal system.
25.6 DUAL DISPERSAL SYSTEM REQUIREMENTS
A. WHEN REQUIRED
1. Standard OWTS must have a dual dispersal system equipped with a manual diversion
device meeting the specifications in Chapter 34 of this Manual to allow alternating use of
the two systems, switching between dispersal fields every six (6) to twelve (12) months.
Each dispersal field shall be designed to accept one hundred (100) percent of the
wastewater design flow.
B. EXCEPTIONS FOR ADVANCED OWTS
1. In lieu of the dual dispersal system requirement, a reserve area shall be identified and
preserved for future use for installation of a replacement dispersal system, if required in
the future. The reserve area must be:
a.A dedicated area of land having suitable site conditions and sufficient area for
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)25-4
CHAPTER 25
SUBSURFACE DISPERSAL SYSTEM GENERAL REQUIREMENTS
installation of a replacement dispersal system (sized for one hundred [100]
percent of the wastewater design flow and able to meet all the design
requirements of the system proposed);
b. Totally separate from the installed dispersal system; and
c.Fully protected to prevent damage to soil and any adverse impact on the immediate
surroundings that may affect the future installation of the replacement system and
its function.
25.7 OWTS PERFORMANCE MONITORING WELL REQUIREMENTS
A. WHEN REQUIRED
1.For OWTS utilizing pressure distribution for the purpose of reduced groundwater
separation or where required due to soil percolation rates, OWTS performance monitoring
wells shall be installed around the dispersal system in accordance with the requirements
in Table 25-4 and as shown on Figure 25-1 (included at the end of this chapter) for the
purpose of checking groundwater levels periodically and water quality sampling, if needed.
2. OWTS performance monitoring wells may also be required by the Department, for example
where recommended by geotechnical report or in connection with a phased corrective action
plan or setback variance or if there have been complaints about OWTS performance.
B. WELL CONSTRUCTION REQUIREMENTS
1. OWTS performance monitoring wells shall be installed in accordance with the criteria in
Table 25-4 and as summarized below:
a. Within the dispersal system, typically near the center of the dispersal field;
b. Upslope of the dispersal field to serve as background or control wells; and
c.Downslope of the dispersal field to provide a representative point for monitoring
the area estimated to be in the probable flow path of percolating wastewater.
2. OWTS performance monitoring wells shall extend from the ground surface to a depth of three
(3) feet below the bottom of the dispersal system or to contact with impermeable materials,
whichever is less.
3.OWTS performance monitoring wells shall be constructed of two (2) inch to four (4) inch
diameter pipe and equipped with a wrench-tight cap or pipe plug and a bottom cap.
4. All wells shall be perforated beginning at a depth of twelve (12) to eighteen (18) inches below
grade and extending to the bottom of the pipe.
5. Perforations shall consist of hacksaw slots at nominal one (1) inch spacing, or equivalent
commercially-slotted pipe.
6. Wells shall be sealed with a bentonite or concrete annular seal (or equivalent) extending from
the ground surface to a minimum depth of twelve (12) inches to prevent surface water
infiltration.
Percolation Rate
(MPI)
Application Rate (gpd/ft2)
Percolation Rate
(MPI)
Application Rate
(gpd/ft2)
1 to 5 1.20 51 0.4161.12 52 0.40
7 1.04 53 0.4080.96 54 0.39
9 0.88 55 0.38100.80 56 0.38110.78 57 0.37
12 0.77 58 0.36130.75 59 0.36
14 0.74 60 0.35150.72 61 0.35160.70 62 0.34
17 0.68 63 0.34180.67 64 0.34
19 0.65 65 0.33200.64 66 0.33210.63 67 0.33
22 0.62 68 0.32230.61 69 0.32
24 0.60 70 0.32250.59 71 0.31260.59 72 0.31
27 0.58 73 0.31280.57 74 0.30
29 0.57 75 0.30300.56 76 0.30310.55 77 0.29320.55 78 0.29330.54 79 0.29
34 0.53 80 0.28350.52 81 0.28360.52 82 0.28
37 0.51 83 0.27380.50 84 0.27
39 0.49 85 0.27
40 0.49 86 0.26
41 0.48 87 0.26
42 0.47 88 0.26
43 0.46 89 0.25
44 0.46 90 0.25450.45 91-120 0.20
46 0.44
47 0.44480.43
49 0.43500.42
Table 25-1
STANDARD WASTEWATER APPLICATION RATES
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
Note: Pressure-Dosing Required for Soil
Percolation Rates Greater than 60 MPI
Percolation Rate
(MPI)
Application Rate
(gpd/ft2)
Percolation Rate
(MPI)
Application Rate
(gpd/ft2)
1-24 1.20 61 0.52
25 1.19 62 0.51
26 1.17 63 0.50
27 1.16 64 0.49
28 1.15 65 0.48
29 1.13 66 0.47
30 1.12 67 0.46
31 1.09 68 0.46
32 1.06 69 0.45
33 1.03 70 0.44
34 1.00 71 0.43
35 0.97 72 0.42
36 0.94 73 0.41
37 0.91 74 0.40
38 0.89 75 0.39
39 0.86 76 0.38
40 0.83 77 0.37
41 0.80 78 0.36
42 0.77 79 0.35
43 0.74 80 0.34
44 0.71 81 0.33
45 0.68 82 0.32
46 0.67 83 0.31
47 0.66 84 0.31
48 0.65 85 0.30
49 0.64 86 0.29
50 0.63 87 0.28
51 0.62 88 0.27
52 0.61 89 0.26
53 0.60 90 0.25
54 0.59 91-120 0.20
55 0.58
56 0.57
57 0.56
58 0.55
59 0.54
60 0.53
Table 25-2 Enhanced Wastewater Application Rates
Note:
High Strength Wastewater. Reduction in the above wastewater loading rates to insure the long-term
integrity and performance of Dispersal Systems may be required for high strength waste flows.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
Table 25-3
Wastewater Application Rates for Subsurface Drip Dispersal Systems
Soil Type1
Soil
Percolation Rate
(mpi)
Wastewater
Application Rate
(gpd/ft2)
Coarse Sand 1 to 4 1.4
Fine Sand 5 to 10 1.2
Sandy Loam 11 to 20 1.0
Loam 21 to 30 0.7
Clay Loam 31 to 45 0.6
Silt-Clay Loam 46 to 60 0.4
Clay, non-swell 61 to 90 0.2
Clay, swell 91 to 120 0.1
Notes:
1Soil types listed for reference information only; design shall be based on site-specific
percolation data.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 2
TABLE 25-4
OWTS PERFORMANCE MONITORING WELL REQUIREMENTS
Dispersal
System Type
Location
Upslope Within Dispersal Field Downslope
Pressure
Dosed
Trenches
One (1) well shall be located upslope
of the dispersal field, typically 10 to 15
away, to serve as a background or
control well, extending from the
ground surface to a depth of three (3)
feet below the bottom of the dispersal
trenches or to contact with
impermeable materials, whichever is
less.
One (1) well shall be located within
the pressure dosed dispersal field,
typically between trenches near the
center of the dispersal field. The
well shall extend from the ground
surface to a depth of three (3) feet
below the bottom of the dispersal
trenches or to contact with
impermeable materials, whichever
is less
One (1) well shall be located down-slope of the
dispersal field, typically ten (10) to twenty-five
(25) feet horizontally from the lowest trench(es),
and positioned to provide a representative point
for monitoring the area estimated to be in the
probable flow path of percolating Wastewater.
The well shall extend from the ground surface to
a depth of three (3) feet below the bottom of the
dispersal trenches or to contact with impermeable
materials, whichever is less.
Drip
One (1) well shall be located ten (10)
to fifteen (15) feet up-gradient of the
dripfield, extending to a depth of a
minimum of three (3) feet or to contact
with impermeable materials,
whichever is less.
One (1) well shall be located within
the dripfield area, extending to a
depth of a minimum of three (3)
feet or to contact with impermeable
materials, whichever is less.
One (1) well shall be located ten (10) to fifteen
(15) feet down-gradient of the dripfield,
extending to a depth of a minimum of three (3)
feet or to contact with impermeable materials,
whichever is less.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 2 OF 2
TABLE 25-4
OWTS PERFORMANCE & DISPERSAL SYSTEM INSPECTION MONITORING WELLS
Dispersal
System Type
Location
Upslope Within Dispersal Field Downslope
At-Grade
One (1) well shall be located five (5) to
ten (10) feet upslope of the dispersal
field, midway along the length of the
dispersal field, extending from the
ground surface to a depth of three (3)
feet or to contact with an impermeable
substratum, whichever is less.
One (1) well shall be located near
the center of the dispersal field,
extending from the fill surface to
the bottom of the gravel distribution
bed.
One (1) well shall be located midway along the
down-slope length of the dispersal field, within
five (5) to ten (10) feet from the toe of the fill
slope, extending from ground surface to a depth
of three (3) feet or to contact with an
impermeable substratum, whichever is less.
Mound
One (1) well shall be located five (5) to
ten (10) feet upslope of the dispersal
field, midway along the length of the
dispersal field, extending from the
ground surface to a depth of three (3)
feet or to contact with an impermeable
substratum, whichever is less.
One (1) well shall be located near
the center of the dispersal field,
extending from the dispersal field
surface to the bottom of the gravel
distribution bed.
One (1) well shall be located within
the effective basal area (outside of
the distribution bed), extending
from the mound dispersal system
surface to six (6) inches into the
native soil.
Four (4) wells shall be located, respectively,
midway along each of the four sides of the mound
dispersal system, near the toe of the slope,
extending from ground surface to a depth of three
(3) feet or to the depth of impermeable materials,
whichever is less.
Raised Sand
Filter Bed
One (1) well shall be located five (5) to
ten (10) feet upslope of the dispersal
system, midway along the length of the
at-grade, extending from the ground
surface to a depth of three (3) feet or to
contact with impermeable materials,
whichever is less.
One (1) well shall be located near
the center of the dispersal system,
extending from the fill surface to the
bottom of the gravel distribution
bed.
One (1) well shall be located near
the center of the raised sand filter
bed dispersal system, extending
from the fill surface to the sand-
soil interface.
One (1) well shall be located midway along the
downslope length of the dispersal system, within
ten (10) to fifteen (15) feet from the edge of the
bed, extending from ground surface to a depth of
three (3) feet or to the depth of impermeable
materials, whichever is less.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
UTILITY BOX FINISHED GRADE
CAP OR PLUG
(WRENCH TIGHT)
12"
CONCRETE, OR EQUAL 12" TO 18"
ANNULAR SEAL
2" TO 4" ABS OR PVC
PIPE (SOLID) DEPTH VARIES
HACKSAW (NICKEL) SLOTS
OR EQUAL, AT 1II NOMINAL
SPACING
PEA GRAVEL OR
COARSE SAND
BOTTOM CAP
OWTS PERFORMANCE MONITORING WELL
(TYPICAL)
FIGURE
25-1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)26-1
CHAPTER 26
PRESSURE DISTRIBUTION DISPERSAL SYSTEM REQUIREMENTS
26.0 CHAPTER OVERVIEW
This chapter provides the design criteria for pressure distribution dispersal systems. The criteria apply to
new and replacement OWTS and modifications or repairs to existing OWTS.
This chapter is organized in the following sections:
Section 26.1: Pressure Distribution Dispersal System Overview
Section 26.2: Pressure Distribution Piping Requirements
Section 26.3: Discharge Orifice Requirements
Section 26.4: Valve Requirements
Section 26.5: Pump System Requirements
Section 26.6: Wastewater Dosing Requirements
Section 26.7: System Head Requirements
Section 26.8: System Cleaning and Hydraulic Testing Requirements
26.1 PRESSURE DISTRIBUTION DISPERSAL SYSTEM OVERVIEW
A. GENERAL DESCRIPTION
1.Pressure distribution dispersal systems apply wastewater effluent to the dispersal field by
pressure dosing, utilizing either an automatic dosing siphon or pump system.
2.A dosing system provides for the periodic discharge of a determined volume of effluent to a
dispersal field.
3.Dosing uses the principle of wetting and resting, which provides multiple daily dosing of
effluent to a subsurface soil absorption system with a period of resting and re-aeration
between doses.
4.This resting period is important in maintaining the aerobic condition of the soil absorption
system in and around the distribution trench or bed, and thus slowing the development of a
clog of soil interfaces and subsequent failure that naturally occurs over time.
5.Because the effluent is discharged in larger doses, the distribution may be more uniform
throughout the dispersal field than that attained by normal gravity flow.
6.The dose-rest cycle is based either on when the dosing tank fills (demand dosing) or on a
time basis (time dosing) at which point the pump or siphon discharges a specific volume to
the dispersal field.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)26-2
CHAPTER 26
PRESSURE DISTRIBUTION DISPERSAL SYSTEM REQUIREMENTS
B. MAJOR COMPONENTS OF A PRESSURE DISTRIBTUION SYSTEM
1. The major components in a pressure distribution dispersal system and associated primary
functions include:
a.Septic Tank: Provides primary treatment of effluent, solids separation and storage;
b.Supplemental Treatment: Provides secondary treatment of effluent if required.;
c.Screens: Protects pumps or siphons and dispersal fields from solids;
d.Pumps or Siphons: Provides storage capacity for dosing volumes and emergency
storage volumes and transport of effluent from the chamber to the distribution
device;
e.Transport Lines: Pipelines that connect the pump to the distribution device;
f.Distribution Devices: Distribution boxes or valves that distribute the flow from the
transport line uniformly to the laterals by gravity or under pressure;
g.Distribution Laterals: Pressure pipe that distributes effluent within the dispersal
field; and
h.Dispersal System: Allows the wastewater effluent from the septic tank or
supplemental treatment to pass into native soil or other receiving media where
various biological and physical processes provide additional treatment.
C. PRESSURE DISTRIBUTION DISPERSAL SYSTEM TYPES
1.Pressure distribution dispersal systems that may be approved for use in the County include:
a.Pressure-Dosed Trench Dispersal Systems (Chapter 28);
b. Subsurface Drip Dispersal Systems (Chapter 29);
c.At-Grade & Mound Dispersal Systems (Chapter 30);
d. Raised Sand Filter Bed Systems (Chapter 31); and
e.Other dispersal systems may be approved for use in the County under Regional
Water Board Waste Discharge Requirements.
2.In addition to the general requirements presented in this chapter, pressure distribution
systems must also comply with the requirements for pump tanks in Chapter 20 and the
design and installation requirements for the specific dispersal system type presented in Part
7 of this Manual.
26.2 PRESSURE DISTRIBUTION PIPING REQUIREMENTS
A. MINIMUM CRITERIA
1.Material Specifications. Pressure distribution piping shall comply with the material
specifications provided in Chapter 33 of this Manual.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)26-3
CHAPTER 26
PRESSURE DISTRIBUTION DISPERSAL SYSTEM REQUIREMENTS
2.Pipe Sizing. All pressure distribution pipes and fittings, including transport lines, manifolds
and laterals must be adequately sized for the wastewater design flow and designed to
minimize frictional losses to the maximum extent practicable.
3.Pipe Support. All pressure distribution piping must be uniformly supported along the
trench bottom and bedded in native soil, except in rocky soil conditions in which case sand
or other material approved by the Department shall be used.
4.Thrust Blocks. Concrete thrust blocks, or equivalent restraint, shall be provided at sharp
changes in piping directions.
26.3 DISCHARGE ORIFICE REQUIREMENTS
A. MINIMUM CRITERIA
1. Orifices shall have a minimum diameter of one-eighth (1/8) inch and shall be evenly
spaced at a distance between two (2) and four (4) feet.
2. Greater hole spacing may be allowed on a case by case basis subject to evaluation of design
and siting factors such as those related to dose volume, effluent quality, dispersal system
size and soil conditions.
26.4 VALVE REQUIREMENTS
A. MINIMUM CRITERIA
1. All valves must be adequately sized for the wastewater design flow and designed to
minimize frictional losses to the maximum extent practicable.
2.Shut-off Valves. Distribution laterals shall be fitted with shut-off valves to adjust or
terminate the flow to portions of the dispersal field. Shut-off valves may be ball or gate
valves.
3.Pump Tank Valves: A gate valve or ball valve must be placed on the pressure
distribution pipe inside or outside of the pump riser of the pump tank.
4.Pump Check Valve: A check valve shall be placed between the pump and the pump tank
gate valve when required.
5.Anti-Siphon Device. An anti-siphon device must be placed on the discharge line within
the pump basin when the dispersal system is located at a lower elevation than the pump.
6.Valve Boxes. All valves must be placed in boxes and accessible for maintenance and repair
from the surface.
26.5 PUMP SYSTEM REQUIREMENTS
A. GENERAL CRITERIA
1. Dosing can be achieved by either a pump or siphon.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)26-4
CHAPTER 26
PRESSURE DISTRIBUTION DISPERSAL SYSTEM REQUIREMENTS
2. Pumps suitable for pumping wastewater must be used.
3. In lieu of pumps, automatic dosing siphons may be used for dosing where a suitable
downhill gradient exists from the elevation of the siphon to the drainfield. Careful
consideration must be given to manufacturer’s specifications during design and installation
of automatic siphons.
26.6 WASTEWATER DOSING REQUIREMENTS
A. MINIMUM CRITERIA
1. Pressure distribution dispersal systems shall be designed in accordance with accepted
engineering practices to achieve uniform dosing of wastewater throughout the dispersal
system.
2. The dose volume shall be sufficient to refill any part of the pressure distribution dispersal
system including supply line and lateral lines plus deliver sufficient additional volume to
disperse the wastewater design flow in an appropriate number of doses per day.
3. The dispersal system performance should be enhanced by dosing the wastewater design
flow in smaller, more frequent doses throughout the day.
.
26.7 SYSTEM HEAD REQUIREMENTS
A. MINIMUM CRITERIA
1.Where the soil absorption area is at a higher elevation than the pump, sufficient dynamic
head shall be provided for both the elevation difference and friction loss.
2.Minimum Head Requirements. The pressure distribution system must be designed to
provide the following minimum head at the orifice farthest from the manifold:
a.Three (3) feet where orifice holes are oriented up; or
b.Two (2) feet where orifice holes are oriented down.
3.Head Variation. The pressure distribution system must be designed with no more than ten
(10) percent head variation between orifices on a distribution lateral.
26.8 SYSTEM CLEANING AND HYDRAULIC TESTING REQUIREMENTS
A. MINIMUM CRITERIA
1.Pressure distribution dispersal systems shall be designed to provide:
a.Adequate flow rate, screening of effluent and suitable piping network to preclude
solids accumulation in the pipes or clogging of discharge orifices; and
b. Access provisions for inspection, testing and adjustment of the pressure
distribution system.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)26-5
CHAPTER 26
PRESSURE DISTRIBUTION DISPERSAL SYSTEM REQUIREMENTS
2.Lateral End Riser. The end of each lateral of a pressure distribution system must be
fitted with a ninety (90) degree long sweep to facilitate line cleaning and hydraulic testing
of pressure distribution system. The end riser pipe shall also be fitted with a ball valve
and/or threaded end cap or plug, housed in a utility/valve box.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)27-1
CHAPTER 27
GRAVITY TRENCH DISPERSAL SYSTEM REQUIREMENTS
27.0 CHAPTER OVERVIEW
This chapter provides design criteria for subsurface gravity trench dispersal systems approved for use in the
County. The criteria apply to new and replacement OWTS and modifications or repairs to existing OWTS.
This chapter is organized in the following sections:
Section 27.1: Gravity Trench Dispersal System Overview
Section 27.2: Onsite Wastewater System Configuration Requirements
Section 27.3: Dispersal System Siting Requirements
Section 27.4: Dispersal System Sizing Requirements
Section 27.5: Dispersal System Piping Requirements
Section 27.6: Dispersal System Inspection Well Requirements
Section 27.7: Dispersal System Installation Requirements
27.1 GRAVITY TRENCH DISPERSAL SYSTEM OVERVIEW
A. GENERAL DESCRIPTION
1. Gravity trench dispersal systems consist of a series of gravity-fed dispersal trenches that use
perforated pipe for subsurface dispersal of effluent into the soil.
2. Gravity trench dispersal systems may be designed with drain rock, plastic chambers or other
approved gravelless alternatives.
3. Schematic and cross-section diagrams illustrating the key design features of gravity trench
dispersal systems constructed with drain rock are provided in Figure 27-1 and Figure 27-
2 (included at the end of this chapter).
27.2 ONSITE WASTEWATER SYSTEM CONFIGURATION REQUIREMENTS
A. GENERAL OVERVIEW
1. Possible System configurations using gravity trench dispersal systems are presented in
Table 5-1 and summarized below.
2.Treatment Train Requirements.
a.Primary Treatment. Primary treatment shall be the minimum level of treatment
preceding a gravity trench dispersal system.
b.Supplemental Treatment.
(1) Supplemental treatment may be used to allow reduced vertical separation.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)27-2
CHAPTER 27
GRAVITY TRENCH DISPERSAL SYSTEM REQUIREMENTS
distance requirements for effective soil and high seasonal groundwater.
(2) Supplemental treatment is required to reduce high-strength wastewater to
domestic strength wastewater prior to discharge to gravity trench dispersal
systems.
3.Effluent Distribution Mechanism.
(1) Gravity. Effluent from the treatment tanks is gravity-fed to the dispersal trenches.
(2) Pressurized. Pump systems may be used in conjunction with gravity trench
dispersal systems to facilitate the siting of the dispersal system at a higher elevation
than the structure(s) being served.
4.Cover Fill Option. Shallow in-ground trench dispersal systems may be constructed with
cover fill in accordance with the requirements in Chapter 32.
5.Dual Dispersal System Requirements.
a.Standard System Configurations. Standard System configurations must have a
dual dispersal system equipped with a manual diversion device meeting the
specifications in Chapter 34 to allow alternating use of the two systems, switching
between systems every six (6) to twelve (12) months. Each dispersal system shall
be designed to accept one hundred (100) percent of the wastewater design flow.
b.Advanced System Configurations. In lieu of the dual dispersal system
requirement, advanced System configurations must have a reserve area identified
and preserved for future use for installation of a replacement dispersal system, if
required in the future. The reserve area must be:
(1) A dedicated area of land having suitable site conditions and sufficient
area for installation of a replacement dispersal system (sized for one
hundred percent of the wastewater design flow and able to meet all the
design requirements of the system proposed);
(2) Totally separate from the installed dispersal system;
(3) Fully protected to prevent damage to soil and any adverse impact on the
immediate surroundings that may affect the future installation of the
replacement system and its function.
27.3 DISPERSAL SYSTEM SITING REQUIREMENTS
A. HORIZONTAL SETBACK CRITERIA
1. Minimum horizontal setback distances from gravity trench dispersal systems to site features
are specified in Table 5-7.
2. Setback distances are measured from the edge of the trenches or the edge of the cover fill
soil, as applicable.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)27-3
CHAPTER 27
GRAVITY TRENCH DISPERSAL SYSTEM REQUIREMENTS
B. VERTICAL SEPARATION CRITERIA
1.Depth to Groundwater. The minimum separation to high seasonal groundwater, as
measured from the bottom of the gravity dispersal trenches shall vary between three (3) and
twenty (20) feet according to soil percolation rate and the level of treatment provided as
specified in Table 5-1.
2.Effective Soil Depth. The minimum depth of effective soil as measured from the bottom of
gravity dispersal trenches shall vary between three (3) and five (5) feet depending on the
level of treatment provided as specified in Table 5-1.
3. Vertical separation depths must be measured from the upslope side of the gravity dispersal
trench bottom.
C. MAXIMUM GROUND SLOPE CRITERIA
1. Maximum ground slope in areas used for gravity trench dispersal systems shall range
between 20 (twenty) and thirty (30) percent depending on whether cover fill is used as
specified in Table 5-1.
a.An increase in slope of up to five (5) percent may be allowed if supported by a
geotechnical evaluation.
27.4 DISPERSAL SYSTEM SIZING REQUIREMENTS
A. MINIMUM INFILTRATIVE AREA CRITERIA
1. The minimum required square footage of trench infiltrative area shall be calculated in
accordance with the formula in Table 27-1.
Where:
Q = Wastewater design flow, in gpd
R = Wastewater application rate, in gallons per square foot per day (gal/ft2-day)
2. A reduction in the minimum infiltrative area requirement of up to thirty (30) percent may be
approved by the Department for IAPMO-certified plastic chambers or other gravelless
alternatives in accordance with the criteria presented in Chapter 37.
Table 27-1
Gravity Trench Infiltrative Area Formula
𝐓𝐫𝐞𝐧𝐜𝐡 𝐈𝐧𝐟𝐢𝐥𝐭𝐫𝐚𝐭𝐢𝐯𝐞 𝐀𝐫𝐞𝐚 (𝐟𝐭𝟐)=𝐐
𝐑
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)27-4
CHAPTER 27
GRAVITY TRENCH DISPERSAL SYSTEM REQUIREMENTS
B. MINIMUM TRENCH LENGTH CRITERIA
1. The trench length required to treat one hundred (100) percent capacity of the wastewater
design flow shall be calculated in accordance with the formula in Table 27-2.
Table 27-2
Gravity Trench Length Formula
𝐓𝐫𝐞𝐧𝐜𝐡 𝐋𝐞𝐧𝐠𝐭𝐡 (𝐟𝐞𝐞𝐭)=𝐐
𝐑∗𝐀
Where:
Q = Wastewater design flow, in gpd
R = Wastewater application rate, in gal/ft2-day
A = Infiltrative area per lineal foot of trench, in square feet per foot (ft2/ft)
C. INFILTRATIVE AREA PER LINEAL FOOT OF TRENCH CRITERIA
1. The maximum infiltrative area for gravity trench dispersal systems shall be four (4) square
feet per lineal foot of trench length.
2. The infiltrative area may include any combination of trench bottom area and trench
sidewall area below the invert of the distribution pipe.
3.Exception: The infiltrative area may be increased up to eight (8) square feet per lineal
foot of trench length under the following circumstances:
a.The ground slope of the dispersal field is less than twenty (20) percent;
b.The soil percolation rate is between five (5) and sixty (60) MPI;
c.The depth to groundwater is greater than or equal to five (5) feet; and
d.All other dispersal system siting requirements are met.
D. WASTEWATER APPLICATION RATE CRITERIA
1.Standard Wastewater Application Rates. Standard wastewater application rates are
presented in Table 25-1 and must be utilized to size gravity trench dispersal systems.
E. TRENCH DIMENSION CRITERIA
1. Gravity trench dispersal systems constructed with drain rock and perforated pipe shall meet
the design specifications provided in Table 27-3 and the material specifications provided
in Part 8 of this Manual, as applicable.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)27-5
CHAPTER 27
GRAVITY TRENCH DISPERSAL SYSTEM REQUIREMENTS
Table 27-3
Gravity Trench Design Criteria (Drain Rock)
Parameter Minimum Maximum
Trenches per dispersal field 1 trench No limit
Trench length 25 feet 100 feet
Trench bottom width1 24 inches 36 inches
Trench depth1,2 30 inches, measured on the
upslope side of the trench 60 inches
Depth of soil cover over rock 12 inches, after settling 18 inches
Depth of drain rock over pipe 2 inches 3 inches
Depth of drain rock under pipe 12 inches 35 inches
Notes:
1Trench minimum width and depth specifications may be reduced for trenches using
gravelless alternatives depending on the gravelless product dimensions.
2Trench depths may be reduced to a minimum of eighteen (18) inches for shallow in-
ground dispersal trenches with cover fill.
F. TRENCH DEPTH CRITERIA
1.In general, gravity dispersal trenches should be kept as shallow as possible to take advantage
of those soil horizons that best provide oxygen and promote microbiological activity; and
within the root zone of plants to take advantage of nitrogen uptake in plants.
2. Trench depths for plastic chambers and other gravelless alternatives will depend on the
dimensions of the product.
3. Shallow in-ground trench dispersal systems may be constructed with cover fill in
accordance with the requirements in Chapter 32. In cover fill systems the trench must be
installed entirely below the original ground surface elevation with a minimum of twelve
(12) inches of soil backfill.
G. TRENCH SPACING CRITERIA
1. Trench spacing shall be in accordance with the requirements in Table 27-4 below.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)27-6
CHAPTER 27
GRAVITY TRENCH DISPERSAL SYSTEM REQUIREMENTS
Table 27-4
Gravity Trench Spacing Criteria
Site Characteristics Minimum Maximum
For level unconstrained sites Five (5) feet
No limit
For slopes greater than
twenty (20) percent
One (1) foot additional spacing for
every five (5) percent increase in
dispersal field ground slope above
twenty (20) percent
For constrained sites
(repair/replacement systems
only)
Two (2) times the depth of rock or
gravelless alternative below the pipe
27.5 DISPERSAL SYSTEM PIPING REQUIREMENTS
A. MINIMUM CRITERIA
1. Gravity trench dispersal system piping shall meet the following requirements and the
material specifications provided in Chapter 33.
a.Dispersal trench drain pipe must be three (3) or four (4) inches in diameter installed
with perforations down.
b.A distribution box shall be used to equally divide the flow amongst the dispersal
trenches.
c.Alternatively, adjacent dispersal trenches on slopes may be connected with a
watertight overflow line (“overflow pipe”) in a manner that allows each trench to
be filled with wastewater to the depth of the drain rock or gravelless alternative
before the wastewater flows to the next lower trench (see Figure 27-2).
27.6 DISPERSAL SYSTEM INSPECTION WELL REQUIREMENTS
A. MINIMUM CRITERIA
1. Inspection wells shall be installed within each trench, preferably at the end of the trench, as
a means of observing the effluent level in the trench.
2. A minimum of one (1) inspection well shall be installed within each and shall extend to the
trench bottom in accordance with the requirements in Table 25-4 and as shown on Figure
27-1 and shall be perforated across the depth of the drain rock, plastic chamber or other
gravelless alternative.
3. Inspection wells shall be constructed of two (2) inch to four (4) inch diameter pipe,
equipped with a wrench-tight cap or pipe plug and a bottom cap. Perforations shall
consist of hacksaw slots at nominal one (1) inch spacing, or equivalent commercially-
slotted pipe. To prevent surface water infiltration, inspection wells shall be sealed with a
bentonite or concrete annular seal (or equivalent) to minimum depth of twelve (12) inches.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)27-7
CHAPTER 27
GRAVITY TRENCH DISPERSAL SYSTEM REQUIREMENTS
27.7 DISPERSAL SYSTEM INSTALLATION REQUIREMENTS
A. MINIMUM CRITERIA
1. Dispersal trenches shall be placed in undisturbed earth in an accessible area and shall not be
covered by paving or other impermeable or compacted surface. Natural topography shall
not be graded to modify the slope in the dispersal field.
2.Dispersal trenches shall not be excavated when the soil is so wet that smearing or compaction
occurs.
3. Dispersal trenches shall be installed on contour (i.e., aligned parallel to the ground surface
contours) to the greatest extent practicable.
4. The bottom of a dispersal trench shall be level, with a variation of no more than two (2)
inches per one hundred (100) lineal feet of trench.
5.In clay soil when glazing occurs on the bottom and sidewall of the trench excavation, the
dispersal trench surfaces shall be scarified to the depth of the glazing and the loose material
removed.
6.Backfill shall be carefully placed to prevent damage to the dispersal system and mounded
over the trench to compensate for expected settlement. Prior to backfilling, drain rock shall
be covered with geotextile filter fabric that meets the material specifications provided in
Chapter 36. Installation of filter fabric in conjunction with gravelless alternative products
shall be done in accordance with manufacturer recommendations.
7. Backfill shall be native soil. Backfill shall be free of large stones, frozen clumps of earth,
masonry, stumps, waste construction materials, or other materials that could damage the
trenches.
8. Erosion control measures must be implemented following installation.
9. Additional requirements for the design and placement of cover fill used in conjunction
with shallow in-ground dispersal trenches shall be in accordance with the criteria provided
in Chapter 32.
FILTER FABRIC
DRAIN PIPE
NATIVE TOPSOIL
BACK FILL
INSPECTION WELL
UTILITY BOXNATIVE TOPSOIL
BACK FILL FINISHED
GRADE
DRAIN PIPE
SANITARY
TEE
RISER CAP
DRAIN ROCK
END VIEW
SIDE VIEW
SANITARY
TEE
ALTERNATE END DETAIL
GRAVITY TRENCH DISPERSAL
SYSTEM (GRAVEL TRENCH) FIGURE
27-1
CROSS-SECTION
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
12” min native backfill over
2” min rock
over pipe
” rock beneath pipe
Overflow pipe at least 4” lower than septic tank outlet
18” – 36”
Varies; 5’ min o.c,
Add 1 foot for each 5% over 20% slope
End View
Septic
Tank
Diversion Valve
Perforated Pipe
Popover
Varies; 5’ min o.c.
FIGURE 27-2
GRAVITY TRENCH DISPERSAL SYSTEM (GRAVEL TRENCH)
OVERFLOW PIPE ON SLOPING SITE
Varies; 5’ min o.c.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)28-1
CHAPTER 28
PRESSURE DOSED TRENCH DISPERSAL SYSTEM REQUIREMENTS
28.0 CHAPTER OVERVIEW
This chapter provides design criteria for subsurface pressure dosed trench dispersal systems approved for
use in the County. In addition to the requirements in this chapter, pressure dosed trench dispersal
systems must also comply with the general requirements for pressure distribution systems presented in
Chapter 26 of this Manual.
This chapter is organized in the following sections:
Section 28.1: Pressure Dosed Trench Dispersal System Overview
Section 28.2: Onsite Wastewater System Configuration Requirements
Section 28.3: Dispersal System Siting Requirements
Section 28.4: Dispersal System Sizing Requirements
Section 28.5: Pressure Distribution System Requirements
Section 28.6: Trench Inspection Well Requirements
Section 28.7: OWTS Performance Monitoring Well Requirements
Section 28.8: Dispersal System Installation Requirements
28.1 PRESSURE DOSED TRENCH DISPERSAL SYSTEM OVERVIEW
A. GENERAL DESCRIPTION
1. Pressure dosed trench dispersal systems are an alternative to gravity trench dispersal
systems and use a pump or dosing siphon and small diameter pressure piping to achieve
broad and uniform distribution of wastewater for improved soil absorption and better
treatment of percolating effluent.
2. Pressure dosed trench dispersal systems may be designed with:
a.Drain rock;
b. Plastic chambers or other approved gravelless alternatives; or
c.Sand and pea gravel to improve treatment of effluent (pressure dosed sand
trenches).
3.Pressure Dosed Sand Trenches (PDST). A PDST is a combined treatment component and
soil dispersal component.
a.Sand lined trenches provide biodegradation or decomposition of wastewater
constituents by bringing the wastewater into close contact with a well-developed
aerobic biological community attached to the surfaces of the filter media.
b. This process requires unsaturated downward flow of the effluent through the filter
media. As a departure from the intermittent or recirculating sand filter, the media is
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PRESSURE DOSED TRENCH DISPERSAL SYSTEM REQUIREMENTS
not contained in a watertight vessel, instead the media is placed in trenches in the native
soil.
4. Schematic and cross-section diagrams illustrating the key design features of pressure-dosed
trench dispersal systems are provided in the following figures (included at the end of this
chapter):
a.All trenches: Figure 28-1
b. Drain rock trenches: Figure 28-2
b. Pressure-dosed sand trenches: Figure 28-3
28.2 ONSITE WASTEWATER SYSTEM CONFIGURATION REQUIREMENTS
A. GENERAL REQUIREMENTS
1. Possible System configurations using pressure dosed trench dispersal systems are
presented in Table 5-2 and summarized below.
2.Treatment Train Requirements.
a.Primary Treatment. Primary treatment shall be the minimum level of treatment
preceding a pressure dosed trench dispersal system.
b.Supplemental Treatment.
(1) Supplemental treatment may be used to allow reduced vertical separation
distance requirements for effective soil and high seasonal groundwater.
(2) Supplemental treatment is required to reduce high-strength wastewater to
domestic strength wastewater prior to discharge to pressure dosed trench
dispersal systems.
3.Effluent Distribution Mechanism. Effluent from the treatment tanks is pressure dosed to
the dispersal trenches.
4.Cover Fill Option. Shallow in-ground trench dispersal systems may be constructed with
cover fill in accordance with the requirements in Chapter 32.
5.Dispersal System Reserve Area Requirements. In lieu of the dual dispersal system
requirement for standard System configurations, pressure dosed trench dispersal systems
must have a reserve area identified and preserved for future use for installation of a
replacement dispersal system, if required in the future. The reserve area must be:
a.A dedicated area of land having suitable site conditions and sufficient area for
installation of a replacement dispersal system (sized for one hundred percent of
the wastewater design flow and able to meet all the design requirements of the
system proposed);
b. Totally separate from the installed dispersal system; and
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PRESSURE DOSED TRENCH DISPERSAL SYSTEM REQUIREMENTS
c.Fully protected to prevent damage to soil and any adverse impact on the immediate
surroundings that may affect the future installation of the replacement system and
its function.
28.3 DISPERSAL SYSTEM SITING REQUIREMENTS
A. HORIZONTAL SETBACK REQUIREMENTS
1. Minimum horizontal setback distances from pressure dosed trench dispersal systems to site
features are specified in Table 5-7.
2. Setback distances are measured from the edge of the trenches or the edge of the cover fill
soil, as applicable.
B. VERTICAL SEPARATION REQUIREMENTS
1.Depth to Groundwater. The minimum separation to high seasonal groundwater, as
measured from the bottom of the trenches, for pressure dosed trenches shall vary between
two (2) and five (5) feet depending on the soil percolation rate and the level of treatment
provided as specified in Table 5-2.
2.Effective Soil Depth. The minimum depth of effective soil, as measured from the trench
bottom for pressure-dosed dispersal systems shall vary between two (2) and three (3) feet
depending on the level of treatment provided as specified in Table 5-2.
3. Vertical separation depths must be measured from the upslope side of the pressure dosed
dispersal trench bottom.
C. MAXIMUM GROUND SLOPE REQUIREMENTS
1. Maximum ground slope in areas used for pressure dosed trench dispersal systems shall
range between 20 (twenty) and forty (40) percent depending on whether cover fill is used
as specified in Table 5-2.
a.An increase in slope of up to five (5) percent may be allowed if supported by a
geotechnical evaluation.
2. Any pressure dosed trench dispersal system located on slopes greater than thirty (30)
percent shall require the completion of a geotechnical report and slope stability analysis as
specified in Chapter 11 of this Manual.
28.4 DISPERSAL SYSTEM SIZING REQUIREMENTS
A. MINIMUM INFILTRATIVE AREA (SQUARE FEET)
1. The minimum required square footage of trench infiltrative area shall be calculated as in
accordance with the formula provided in Table 28-1.
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PRESSURE DOSED TRENCH DISPERSAL SYSTEM REQUIREMENTS
Table 28-1
Pressure Dosed Trench Infiltrative Area Formula
𝐓𝐫𝐞𝐧𝐜𝐡 𝐈𝐧𝐟𝐢𝐥𝐭𝐫𝐚𝐭𝐢𝐯𝐞 𝐀𝐫𝐞𝐚 (𝐟𝐭𝟐)=𝐐
𝐑
Where:
Q = Wastewater design flow, in gpd
R = Wastewater application rate, in gal/ft2-day
2. A reduction in the minimum infiltrative area requirement of up to thirty (30) percent may be
approved by the Department for IAPMO-certified plastic chambers or other gravelless
alternatives in accordance with the criteria presented in Chapter 37.
B. MINIMUM TRENCH LENGTH
1. The trench length required to treat one hundred (100) percent capacity of the wastewater
design flow shall be calculated in accordance with the formula in Table 28-2.
Table 28-2
Pressure Dosed Trench Length Formula
𝐓𝐫𝐞𝐧𝐜𝐡 𝐋𝐞𝐧𝐠𝐭𝐡 (𝐟𝐞𝐞𝐭)=𝐐
𝐑∗𝐀
Where:
Q = Wastewater design flow, in gpd
R = Wastewater application rate, in gal/ft2-day
A = Infiltrative area per lineal foot of trench, in ft2/ft
C. INFILTRATIVE AREA PER LINEAL FOOT OF TRENCH
1.Trenches with Drain Rock or Gravelless Alternatives.
a.The maximum infiltrative area for pressure dosed trench dispersal systems utilizing
drain rock or gravelless trenches shall be four (4) square feet per lineal foot of trench
length.
b. The infiltrative area may include any combination of trench bottom area and trench
sidewall area below the invert of the distribution pipe.
c.Exception: The infiltrative area may be increased up to eight (8) square feet per
lineal foot of trench length, under the following circumstances:
(1) The ground slope of the dispersal field is less than twenty (20) percent;
(2) The soil percolation rate is between five (5) and sixty (60) MPI;
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PRESSURE DOSED TRENCH DISPERSAL SYSTEM REQUIREMENTS
(3) The depth to groundwater is greater than or equal to five (5) feet; and
(4) All other dispersal system siting requirements are met.
2.PDST. The maximum infiltrative area for PDST shall be calculated based on the bottom
area only, up to a maximum of three (3) square feet per lineal foot of trench.
D. WASTEWATER APPLICATION RATE CRITERIA
1.Drain Rock & Gravelless Alternative Trenches
a.Standard Wastewater Application Rates. Standard wastewater application rates
are presented in Table 25-1 and must be utilized to size pressure-dosed dispersal
systems using drain rock or gravelless trenches.
b.Enhanced Wastewater Application Rates. Enhanced wastewater application
rates may be utilized with pressure-dosed trench dispersal systems to allow smaller
dispersal system sizing when all of the following conditions are met:
(1) The dispersal system is preceded by supplemental treatment; and
(2) The vertical separation to high seasonal groundwater requirement is met
for the same type of dispersal system preceded by primary treatment only.
c.Table 5-2 provides guidance on the requisite wastewater application rate table to
use when sizing pressure-dosed trench dispersal systems.
2.PDST. Wastewater application rates used for PDST sizing must include consideration of
both the pea gravel-sand interface and the sand-soil interface using the bottom area of the
trench only. The more restrictive (or conservative) of the criterion shall govern PDST sizing.
a.Pea Gravel-Sand Interface. The wastewater application rate used for sizing the
pea gravel-sand interface shall be determined in accordance with the criteria in
Table 28-3.
Table 28-3
PDST Gravel/Sand Interface
Wastewater Application Rate Criteria
Facility Type Wastewater application Rate
2
2
b.Sand-Soil Interface. The wastewater application rate used for sizing the sand/soil
interface shall be selected in accordance with the criteria provided in Table 5-2.
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PRESSURE DOSED TRENCH DISPERSAL SYSTEM REQUIREMENTS
3. Reduction in the wastewater application rates or other provisions to ensure the long-term
integrity and performance of pressure dosed trench systems may be required for high-strength
wastewater flows.
E. TRENCH DIMENSIONS & SPECIFICATIONS
1.Drain Rock & Gravelless Alternatives. Pressure dosed trench dispersal systems utilizing
drain rock and small diameter pressure pipe shall meet the design specifications provided in
Table 28-4 and the material specifications provided in Part 8 of this Manual, as applicable.
Table 28-4
Pressure Dosed Trench Design Criteria (Drain Rock)
Parameter Minimum Maximum
1,3
2,3
Notes:
1Trench widths may be reduced to twelve (12) inches for Systems with
supplemental treatment.
2Trench depths may be reduced to a minimum of eighteen (18) inches for shallow
in-ground dispersal trenches with cover fill.
3Trench minimum width and depth specifications may be reduced for trenches using
gravelless alternatives depending on the gravelless product dimensions.
2.PDST. Pressure-dosed sand trench dispersal systems shall be constructed with drain rock,
pea gravel, sand filter media and pressure pipe and shall meet the specifications provided in
Table 28-5 below and the material specifications provided in Part 8 of this Manual, as
applicable.
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PRESSURE DOSED TRENCH DISPERSAL SYSTEM REQUIREMENTS
Table 28-5
PDST Trench Design Criteria
Parameter Minimum Maximum
Trenches per dispersal field 1 trench No limit
Trench length 25 feet 100 feet
Trench depth 33 inches, measured on the
upslope side of the trench 60 inches
Depth of soil cover over rock 12 inches, after settling 18 inches
Depth of drain rock over pipe 2 inches 3 inches
Depth of pea gravel under pipe 6 inches 11 inches
a.Minimum Sand Depth. The minimum depth of sand below the pea gravel shall
be dependent on the level of wastewater treatment (primary or supplemental)
and the soil percolation rate as specified in Table 28-6 below.
Table 28-6
PDST - Sand & Gravel Depth Criteria
Thickness of Medium Sand Fill Under Pea Gravel
Trench Width
F. TRENCH DEPTHS (ALL TRENCHES)
1. In general, pressure dosed dispersal trenches should be kept as shallow as possible to take
advantage of those soil horizons that best provide oxygen and promote microbiological
activity; and within the root zone of plants to take advantage of nitrogen uptake in plants.
2. Trench depths for plastic chambers and other gravelless alternatives will depend on the
dimensions of the product,
3. Shallow in-ground trench dispersal systems may be constructed with cover fill in
accordance with the requirements in Chapter 32. In cover fill systems the trench must be
installed entirely below the original ground surface elevation with a minimum of twelve
(12) inches of soil backfill.
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PRESSURE DOSED TRENCH DISPERSAL SYSTEM REQUIREMENTS
G. TRENCH SPACING (ALL TRENCHES)
1. Trench spacing shall be in accordance with the requirements in Table 28-7 below.
Table 28-7
Pressure Dosed Trench Spacing Criteria (All Trenches)
Site Characteristics Minimum Maximum
28.5 PRESSURE DISTRIBUTION SYSTEM REQUIREMENTS
A. MINIMUM CRITERIA
1. The pressure distribution system and pump chamber must be designed in accordance with
the material specifications provided in Chapter 20 and Part 8 of this Manual and the
pressure distribution systems design requirements provided in Chapter 26.
28.6 TRENCH INSPECTION WELL REQUIREMENTS
A. MINIMUM CRITERIA
1. Inspection wells shall be installed within each trench, preferably at the end of the trench, as
a means of observing the effluent level in the trench.
2.Conventional and Gravelless trenches. A minimum of one (1) inspection well shall be
installed within each trench in pressure-dosed trench dispersal systems utilizing drain rock
or gravelless trenches. The inspection well shall extend to the trench bottom in accordance
with the requirements in Table 25-4 and as shown on Figure 28-2 and shall be perforated
across the depth of the drain rock, plastic chamber or other gravelless alternative product.
3.Sand Trenches. A minimum of two (2) inspection wells shall be installed within each
trench in pressure-dosed sand trench dispersal systems in accordance with the requirements
in Table 25-4 as shown on Figure 28-3.
a.One (1) well shall extend to the pea gravel-sand fill interface and shall be perforated
in the pea gravel layer
b. One (1) well shall extend to the trench bottom and shall be perforated in the sand
fill layer.
4.Inspection wells shall be constructed of two (2) inch to four (4) inch diameter pipe,
equipped with a wrench-tight cap or pipe plug and a bottom cap. Perforations shall
consist of hacksaw slots at nominal one (1) inch spacing, or equivalent commercially
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PRESSURE DOSED TRENCH DISPERSAL SYSTEM REQUIREMENTS
slotted pipe. To prevent surface water infiltration, inspection wells shall be sealed with a
bentonite or concrete annular seal (or equivalent) to minimum depth of twelve (12) inches.
28.7 OWTS PERFORMANCE MONITORING WELL REQUIREMENTS
A. MINIMUM CRITERIA
1.OWTS performance monitoring wells shall be installed around the pressure dosed trench
dispersal system in accordance with the requirements in Table 25-4 and as shown on
Figure 25-1 for the purpose of checking groundwater levels periodically and water quality
sampling, if needed.
28.8 DISPERSAL SYSTEM INSTALLATION REQUIREMENTS
A. MINIMUM CRITERIA
1. Dispersal trenches shall be placed in undisturbed earth, in an accessible area, and shall not
be covered by paving or other impermeable or compacted surface. Natural topography shall
not be graded to modify the slope in the dispersal field.
2. Dispersal trenches shall not be excavated when the soil is so wet that smearing or
compaction occurs.
3. Dispersal trenches shall be installed on contour (i.e., aligned parallel to the ground surface
contours) to the greatest extent practicable.
4. The bottom of a dispersal trench shall be level, with a variation of no more than two (2)
inches per one hundred (100) lineal feet of trench.
5.In clay soil when glazing occurs on the bottom and sidewall of the trench excavation, the
dispersal trench surfaces shall be scarified to the depth of the glazing and the loose material
removed.
6. Backfill shall be carefully placed to prevent damage to the dispersal system and mounded
over the trench to compensate for expected settlement. Prior to backfilling, drain rock shall
be covered with geotextile filter fabric that meets the material specifications provided in
Chapter 36. Installation of filter fabric in conjunction with gravelless alternative products
shall be done in accordance with manufacturer recommendations.
7. Backfill shall be native soil. Backfill shall be free of large stones, frozen clumps of earth,
masonry, stumps, waste construction materials, or other materials that could damage the
trenches.
8. Erosion control measures must be implemented following installation.
9. Additional requirements for the design and placement of cover fill used in conjunction
with shallow in-ground dispersal trenches shall be in accordance with the criteria provided
in Chapter 32.
PRESSURE DISTRIBUTION TRENCHES &
LATERALS
LATERAL SHUT-OFF/ADJUSTMENT VALVE
(TYP.)
DISTRIBUTION MANIFOLD (TYP.)
END RISER &
FLUSH PORT (TYP.)
SUPPLEMENTAL
TREATMENT
(OPTION)
PRIMARY DISPERSAL FIELD
P
SEPTIC TANK
PUMP CHAMBER
PVC PRESSURE LINE PRESSURE-DOSED TRENCH
DISPERSAL SYSTEM SCHEMATIC
FIGURE 28-1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
12" MIN. TRENCH BACKFILL
(NATIVE SOILS)
SIDE VIEW
END VIEW
18" TO 36"*
*12" WIDTH OK WITH
SUPPLEMENTAL TREATMENT
2" DRAIN ROCK ABOVE PIPE TRENCH INSPECTION WELL
W/ END CAP
INSPECTION RISER, W/
THREADED END CAP
FILTER FABRIC
SILT BARRIER
PRESSURE
DISTRIBUTION PIPE
3/4" TO 2 1/2" DRAIN ROCK
FINISHED
GRADE
UTILITY BOX
FILTER FABRIC
SILT BARRIER
3/4" TO 2 1/2" DRAIN ROCK
PRESSURE-DOSED TRENCH
DISPERSAL SYSTEM (GRAVEL TRENCH)
CROSS-SECTION
FIGURE 28-2
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
TRENCH BACKFILL
(NATIVE SOIL)
MEDIUM SAND
6" MIN.
6" TO 12", SEE BELOW
6" MIN.
12" TO 24" MIN. FOR SEPTIC TANK EFFLUENT,
6" TO 12" MIN. FOR SUPPLEMENTAL TREATMENT
12" TO 36" (EFFECTIVE APPLICATION AREA)
PRESSURE DOSED SAND TRENCH
EXISTING GRADE
INSPECTION WELL
UTILITY BOX
FILTER FABRIC
SILT BARRIER
DOUBLE WASHED
PEA GRAVEL
MEDIUM SAND FILL
INSPECTION
WELLS
INSPECTION RISER W/
THREADED CAP
FILTER FABRIC
SILT BARRIER
PRESSURE DISTRIBUTION
PIPE
DOUBLE WASHED
PEA GRAVEL
END VIEW
SIDE VIEW
DISPERSAL SYSTEM CROSS-SECTION
FIGURE 28-3
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ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)29-1
CHAPTER 29
SUBSURFACE DRIP DISPERSAL SYSTEM REQUIREMENTS
29.0 CHAPTER OVERVIEW
This chapter provides design criteria for subsurface drip dispersal systems for new and replacement OWTS
and modifications or repairs to existing OWTS. In addition to the requirements in this chapter, subsurface
drip dispersal systems must also comply with the general requirements for pressure distribution systems
presented in Chapter 26 of this Manual.
This chapter is organized in the following sections:
Section 29.1: Subsurface Drip Dispersal System Overview
Section 29.2: Onsite Wastewater System Configuration Requirements
Section 29.3: Dispersal System Siting Requirements
Section 29.4: Dispersal System Sizing Requirements
Section 29.5: Distribution Network Requirements
Section 29.6: Pressure Dosing Requirements
Section 29.7: System Flushing Requirements
Section 29.8: Component Requirements
Section 29.9: Final Grading & Landscaping Requirements
Section 29.10: OWTS Performance Monitoring Well Requirements
Section 29.11: Dispersal System Installation Requirements
29.1 SUBSURFACE DRIP DISPERSAL SYSTEM OVERVIEW
A. GENERAL DESCRIPTION
1.A subsurface drip dispersal system is a method for disposal of treated wastewater that
uses special drip tubing designed for use with wastewater.
2.The dripline is normally placed eight (8) to twelve (12) inches below ground surface and
makes use of the most biologically active soil zone for distribution, nutrient uptake and
evapotranspiration of the wastewater.
3.A subsurface drip dispersal system is comprised of small diameter laterals (“driplines”),
one-half (½) inch to one (1) inch in diameter, usually spaced twenty-four (24) inches apart,
with small-diameter emitters (one-eighth [1/8] inch) located at twelve (12) to twenty-four
(24) inches on-center along the dripline.
4.Effluent is conveyed under pressure to the laterals, normally with timed doses. Prior to
dispersal the effluent requires supplemental treatment.
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SUBSURFACE DRIP DISPERSAL SYSTEM REQUIREMENTS
5.Schematic and detail diagrams are provided in Figure 29-1 and Figure 29-2 (included at the
end of this chapter) to illustrate the key design features of subsurface drip dispersal
systems.
B. ADVANTAGES
1. Drip dispersal has several advantages to other to other dispersal systems, including:
a.Installation of dripline is less site-intrusive and simpler than installation of
conventional gravel trenches. A backhoe is not needed, nor is gravel or geotextile;
b. Dripline can be effective in very shallow soil conditions since it distributes the
wastewater very uniformly to substantially all of the available soil in the dispersal
field;
c.Flexible dripline can be installed in grid or irregular patterns as needed to
accommodate contours on sloped sites, irregularly shaped areas, difficult site
conditions or landscape irrigation applications;
d. Dripline can be installed in multiple small discontinuous “zones” allowing the
hydraulic load to be spread widely rather than concentrated in one main area;
e.Dripline can be installed on steeper slopes since it causes less soil disturbance and
erosion or slope stability hazards;
f. Low flow rates allow for longer lateral runs than can be obtained with
conventional piping;
g. Shallow placement of dripline can enhance treatment by maximizing soil depth
and delivering effluent to a point in the soil profile where there is typically more
oxygen and organic material;
h. A vegetative cover over the dripfield (usually turf) can provide additional
treatment and reuse through plant evapotranspiration;
i. Slow, controlled emitter discharge combined with multiple daily dosing enhances
aerobic conditions in the soil and results in frequent drainfield resting periods;
and
j. Water movement away from the drip emitters is primarily by unsaturated/capillary
flow which maximizes contact with and treatment by the soil.
C. DISADVANTAGES
1. A number of significant design, installation and management issues must be addressed in
order for drip technology to be successful.
2. Some of the challenges involved in drip system design and technical solutions are provided
in Table 29-1 (included at the end of this chapter).
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SUBSURFACE DRIP DISPERSAL SYSTEM REQUIREMENTS
29.2 ONSITE WASTEWATER SYSTEM CONFIGURATION REQUIREMENTS
A. GENERAL REQUIREMENTS
1. Possible System configurations using subsurface drip dispersal systems are presented in
Table 5-3 and summarized below.
2.Treatment Train Requirements. Supplemental treatment shall be the minimum level of
treatment preceding a subsurface drip dispersal system.
3.Effluent Distribution Mechanism. Subsurface drip dispersal systems must be pressure-
dosed.
4.Cover Fill Option. Cover fill may be used in conjunction with subsurface drip dispersal
systems in accordance with the design and construction requirements contained in Chapter
32 of this Manual.
5.Dispersal System Reserve Area Requirements. In lieu of the dual dispersal system
requirement for standard System configurations, pressure dosed trench dispersal systems
must have a reserve area identified and preserved for future use for installation of a
replacement dispersal system, if required in the future. The reserve area must be:
a.A dedicated area of land having suitable site conditions and sufficient area for
installation of a replacement dispersal system (sized for one hundred percent of
the wastewater design flow and able to meet all the design requirements of the
system proposed);
b. Totally separate from the installed dispersal system; and
c. Fully protected to prevent damage to soil and any adverse impact on the
immediate surroundings that may affect the future installation of the replacement
system and its function.
29.3 DISPERSAL SYSTEM SITING REQUIREMENTS
A. HORIZONTAL SETBACK REQUIREMENTS
1. Minimum horizontal setback distances from subsurface drip dispersal systems to site
features are specified in Table 5-7.
2. Setback distances are measured from the edge of the driplines or the edge of the cover fill
soil, as applicable.
B. VERTICAL SEPARATION REQUIREMENTS
1.Depth to Groundwater. The minimum separation to high seasonal groundwater, as
measured from the bottom of the dripline, shall vary between two (2) and three (3) feet
according to soil percolation rate as specified in Table 5-3.
2.Effective Soil Depth. The minimum depth of effective soil as measured from the bottom of
the dripline shall be two (2) feet as specified in Table 5-3.
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SUBSURFACE DRIP DISPERSAL SYSTEM REQUIREMENTS
C. MAXIMUM GROUND SLOPE REQUIREMENTS
1. Maximum ground slope in areas used for subsurface drip dispersal systems shall range
between twenty (20) and fifty (50) percent depending on whether cover fill is used as
specified in Table 5-3.
2. Any subsurface drip dispersal system located on slopes greater than thirty (30) percent
shall require the completion of a geotechnical report and slope stability analysis as specified
in Chapter 11 of this Manual.
29.4 DISPERSAL SYSTEM SIZING REQUIREMENTS
A. WASTEWATER APPLICATION RATES
1.Wastewater application rates used for sizing subsurface drip dispersal systems shall be
based on soil percolation rate in accordance with the criteria in Table 25-3.
2. The wastewater application area refers to the ground surface area encompassed by the
subsurface drip dispersal system.
B. MINIMUM INFILTRATIVE AREA
1. The minimum required square footage of the drip field area shall be calculated in accordance
with the formula in Table 29-1.
Table 29-2
Dripfield Infiltrative Area Formula
𝐓𝐫𝐞𝐧𝐜𝐡 𝐈𝐧𝐟𝐢𝐥𝐭𝐫𝐚𝐭𝐢𝐯𝐞 𝐀𝐫𝐞𝐚 (𝐟𝐭𝟐)=𝐐
𝐑
Where:
Q = Wastewater design flow, in gpd
R = Wastewater application rate, in gal/ft2-day
2. For sizing purposes, the effective infiltrative area used for drip field sizing calculations
shall be limited to no more than four (4) square feet per drip emitter.
a.For example, two hundred (200) lineal feet of dripline with emitters at two (2) foot
spacing would provide a total of one hundred (100) emitters (200/2) and could be
used for dispersal to an effective infiltrative area of up to four hundred (400) square
feet (100 emitters x 4 square feet per emitter).
b. Conversely, if wastewater flow and percolation test design information indicate
the need for an effective infiltrative area of one-thousand (1,000) square feet, the
dripline design and layout would have to be configured to provide a minimum of
two hundred and fifty (250) emitters spaced over the required one-thousand
(1,000) square foot dispersal area.
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SUBSURFACE DRIP DISPERSAL SYSTEM REQUIREMENTS
29.5 DISTRIBUTION NETWORK REQUIREMENTS
A. DRIPLINE CONFIGURATION CRITERIA
1. Driplines must be installed in original, undisturbed soil.
2.Driplines rows must be installed as level as possible and parallel to contours on sloped
sites.
3.Drip lines on sloped sites must be designed and installed to prevent low-level drainage to
lower dripline or other lower level components such as tanks, valve boxes, etc. Low level
drainage can be prevented by:
a.Installing check valves on manifolds between dripline laterals;
b. Feeding dripline from above;
c.Constructing earth dams where dripline is connected to manifolds;
d. Installing dripline at a lower elevation than manifolds; and
e.Connecting driplines to manifolds up gradient to the dripline contour.
4.Drip lines shall be installed at a depth between eight (8) and twelve (12) inches below
original ground surface elevation. Deeper placement of driplines may be considered by the
Department on a case-by-case basis.
5.Line and emitter spacing shall be designed as appropriate for soil conditions, slope and
contour. Typical dripline installations have emitters spaced two (2) feet apart and dripline
installed on two (2) foot centers with increased separation distances on sloped sites.
a.Where soils are compacted or cemented the Department may require a bulk density
test and additional emitters or greater emitter/dripline spacing if warranted.
6.The maximum drip line length shall be designed in accordance with accepted industry
practices and in accordance with the manufacturer’s criteria and recommendations to ensure
equal distribution.
a.Manufacturer recommended maximum dripline runs are generally much longer
than maximum lateral lengths allowed for conventional pressure systems.
b. Dripline runs depend on emitter spacing and applied pressure. Greater lengths are
possible with increasing pressure (within manufacturer’s recommendations).
7.Emitter discharge may be controlled either by use of pressure-compensating emitters or with
a pressure regulator.
a.The maximum allowable flow variance between any two emitters in a distribution
zone is (10) percent.
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SUBSURFACE DRIP DISPERSAL SYSTEM REQUIREMENTS
b. When turbulent flow emitters are used, the maximum elevation difference between
any two emitters in the same distribution field shall be five (5) feet. The discharge
from pressure compensating emitters is relatively constant even when emitter
elevations vary. Discharge from turbulent flow emitters even when used with a
pressure regulator can be affected by elevation differences.
8.Emitters shall be located at no less than twelve (12) inches from the supply and return
manifolds.
B. DRIPFIELD ZONE CRITERIA
1. Drip fields may be divided into multiple zones which may be located in different areas of a
site as desired or needed to provide the required drip field size.
2. Differences in soil conditions and percolation rate characteristics from one zone to another
may require the use of correspondingly different wastewater application rates and drip
field sizing for each zone.
3. For systems with one thousand (1000) emitters at least two (2) separate distribution zones
are required. Separate zones are also recommended for Systems installed in any silt loams,
sandy clay loams, clay loams, silty clay loams.
4. Dosing must be automatically alternated between each zone with a distributing valve or
actuated valve and a controller.
29.6 PRESSURE DOSING REQUIREMENTS
A. GENERAL CRITERIA
1.Effluent treated by a supplemental treatment system shall be delivered to the dripfield by
pressure from a pump system and timed dosing. A minimum number of twelve (12) equally
spaced doses per day is required in all soil types.
2. The pressure distribution systems shall be designed in accordance with accepted industry
practices and manufacturer recommendations for subsurface drip dispersal systems to
achieve, at a minimum:
a.An adequate dosing volume and pressure per manufacturer’s guidelines;
b.A means of automatically flushing the filter and driplines at regular intervals;
3. Emitter discharge rates should be matched with soil conditions (slower discharge rates
work best in finer textured soils) to avoid effluent surfacing during dosing.
4. Additional requirements for design and construction of pump systems and pressure
distribution systems are contained in Chapter 26 of this Manual.
29.7 SYSTEM FLUSHING REQUIREMENTS
A. GENERAL CRITERIA
1. Subsurface drip dispersal systems must include a means to backwash filters and flush
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SUBSURFACE DRIP DISPERSAL SYSTEM REQUIREMENTS
driplines and manifolds.
2. Both supply and return manifolds are required on all systems.
3. Automated filter backwash and dripline flushing is recommended for all drip systems.
4. Filter backwash / line flush debris must be returned to primary treatment (septic tank). A
gravity return to the septic tank or primary treatment unit is recommended wherever
possible but may be delivered under pressure if necessary.
5. Hose bibs are not allowed for use as a flushing component (to prevent cross contamination
of potable water supply).
29.8 COMPONENT REQUIREMENTS
A. ROOT INHIBITOR CRITERIA
1. All subsurface drip dispersal systems must include a USDA approved root growth inhibitor
incorporated into a component (dripline or filter) during the manufacturing process to
prevent root intrusion into emitters.
B. DRIPLINE CRITERIA
1. Driplines shall be manufactured and intended for use with supplemental treatment systems,
with minimum forty-five (45) mil tubing wall thickness, bacterial growth inhibitor(s) and
means of protection against root intrusion.
2. Dripline must be color coded purple to identify that the pipe contains non-potable water
from a wastewater source.
3. Dripline may have either pressure compensating or turbulent flow emitters.
4. Driplines must incorporate emitters with a maximum nominal rated discharge of 1.3 gallons
per hour.
C. FILTER CRITERIA
1. All subsurface drip dispersal systems shall include a filtering device (disk or fine-mesh screen
type) capable of filtering particles in accordance with the dripline manufacturer
specifications;
2. Filters shall be located downstream of the supplemental treatment system.
3. The manufacturer must warrant filters for use with wastewater (resistant to corrosion).
4. All filters must be sized to operate at a flow rate at least equal to the maximum design
discharge rate of the system.
5. Filter backwash must be included in calculating the maximum discharge rate (where
applicable).
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SUBSURFACE DRIP DISPERSAL SYSTEM REQUIREMENTS
6. System flush volume and velocity must be in accordance with filter specifications.
7.Filters may require backwashing in accordance with manufacturer’s recommendations or
may be the continuously self-cleaning type.
8. All filters must be readily accessible for inspection and servicing.
D. AIR/VACUUM RELIEF VALVE CRITERIA
1. Air/vacuum relief valve(s) must be installed at the high point of each distribution sector.
2. All valves must be installed in a valve box with access to grade and include a gravel sump.
E. SUPPLY AND RETURN MANIFOLD CRITERIA
1. Supply and return manifolds must be installed to distribute effluent to driplines and to collect
filter backwash and line-flushing debris and return it to the primary treatment unit.
2. Supply and return manifolds and fittings must be schedule 40 or better.
F. FLOW METER CRITERIA
1. A flow meter or other means to monitor flow must be installed in a readily accessible
location for reading and servicing.
2. Flow meters must be warranted by the manufacturer for use with wastewater and be accurate
within the expected flow range of the installed system.
G. CHEMICAL INJECTION PORT CRITERIA
1. A chemical injector port must be installed to facilitate future connection of a chemical
injector pump if/when needed.
2. A mild acid solution can be injected to help scour scale accumulations and a mild chlorine
solution can combat bacterial slime accumulations.
3. If chemicals are injected, the flushed liquid must be returned to the primary treatment
tank.
H. CONTROLLERS
1. A controller capable of timed dosing is required for all systems.
2. Additional controller functions such as automatic line/filter flushing are recommended for
all systems.
3. Automatic control of actuated valves is required for systems with multiple distribution
zones.
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SUBSURFACE DRIP DISPERSAL SYSTEM REQUIREMENTS
I. VALVES
1. Valves must be readily accessible for inspection and/or service (such as in a valve box with
access to grade).
J. FITTINGS
1. Fittings used to join dripline to the distribution and flush manifolds must be in accordance
with manufacturer’s recommendations.
2. Both compression and barb fittings may be specified, depending on the manufacturer
recommendations and system operating pressure.
29.9 FINAL GRADING AND LANDSCAPING REQUIREMENTS
A. EROSION CONTROL & COVER FILL SYSTEM CRITERIA
1. Requirements for the design and placement of cover fill used in conjunction with drip
dispersal systems (if applicable) shall be in accordance with the criteria provided in
Chapter 32.
2. Erosion control measures must be implemented following installation.
B. LANDSCAPING CRITERIA
1. A ground cover (turf or other appropriate landscaping) must be planted over the dripfield
after installation to prevent erosion of the dripfield area.
29.10 OWTS PERFORMANCE MONITORING WELL REQUIREMENTS
A. MINIMUM CRITERIA
1.OWTS performance monitoring wells shall be installed around the dripfield in accordance
with the requirements in Table 25-4 and as shown on Figure 25-1 for the purpose of
checking groundwater levels periodically and water quality sampling, if needed.
29.11 DISPERSAL SYSTEM INSTALLATION REQUIREMENTS
A. GENERAL
1. Dripline installation methods are presented in Table 29-1. It is recommended that System
Designers specify the installation method.
2.Installation techniques that pull or stretch dripline are prohibited.
3.Disturbing the soil may affect the pore structure of the soil and create hydraulic
conductivity problems.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
Table 29-1
Dripline Installation Methods
Insertion Method Advantages Disadvantages
Hand Trenching Handles severe slopes and
confined areas
Uniform depth
Slow
Labor intensive
Disrupts existing turf and
ground
Back fill required
Oscillating or Vibrating Plow.
(Use the type that inserts the
dripline directly in place, not
one that pulls the dripline
through the soil.)
Fast in small to medium
installations
Minimal ground disturbance
No need to back fill the
trench
Depth has to be monitored
closely
Cannot be used on steeper
slopes >20%
Requires practice to set and
operate adequately
Tends to "stretch" pipe.
Shorter runs are required
Trenching Machine: Ground
Hog, Kwik-Trench, E-Z Trench
Faster than hand trenching
May use the 1" blade for
most installations
Uniform depth
Slower, requires labor
Disrupts surface of existing
turf
Back fill required
Tractor with Proprietary
Dripline Insertion Tool
Fast
Little damage to existing turf
because of the turf knife
Minimal ground disturbance
Does not stretch drip line
Adaptable to any tractor
The installation tool is
designed specifically for
this purpose and is available
from at least one of the
dripline manufacturers
Tractor Mounted 3-point Hitch
Insertion Implement
Fastest. Up to four plow
attachments with reels
A packer roller dumps back
soil on top of the pipe
Suitable for large
installations only
SEPTIC TANK
SUPPLEMENTAL TREATMENT
PVC SUPPLY MANIFOLD
P
PVC FLUSH RETURN LINE
PUMP CHAMBER
HEADWORKS, WITH FILTER, VALVES & PRESSURE
REGULATION
PVC FLUSH RETURN
MANIFOLD
FLUSH VALVE, SOLENOID OR
MANUAL, NORMALLY CLOSED
AIR/VACUUM RELIEF VALVE AT HIGH
POINTS (TYP.)
POLYETHYLENE DRIP TUBING; 24" DRIPLINE
SPACING; EMITTERS @ 24" O.C;
8-12" DEEP (TYP.)
DISPERSAL AREA PERIMETER
SUBSURFACE DRIP DISPERSAL SYSTEM
SCHEMATIC
FIGURE 29-1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
SOLENOID FIELD
FLUSH VALVE
VORTEX
FILTERPRESSURE
GUAGE AIR VENT
FROM SUBSURFACE
DRIP DISPOSAL FIELD
TO SUBSURFACE
DRIP DISPOSAL FIELD
TO SEPTIC
TANK
FROM PUMP
CHAMBER
AUTOMATIC HEADWORKS
PRESSURE
REGULATOR
PVC ELL TO
COMPRESSION
ADAPTER (TYP.)
PVC HEADER
SUPPLY MANIFOLD
PVC TEE
(TYP.)
BLANK
DRIPLINE
(TYP.)
GEOFLOW
DRIPLINE
END FEED/ FLUSH MANIFOLD
A 1.5' SEPARATION
IS REQUIRED
BETWEENT THE
SUPPLY MANIFOLD
AND 1ST DRIP
EMMITER
6"
ROUND
VALVE
BOX
1/2" PVC
COUPLING
1/2" SCH. 80 PVC
NIPPLE (LENGTH
AS REQUIRED)THREE
BRICK
SUPPORTS PEA
GRAVEL
SUMP
FINISHED GRADE
GEOFLOW
ARV 05
AIR/VACUUM
RELIEF
VALVE
1" AIR / VACUUM RELIEF
(PUMPED TO PVC)
PVC PIPING
AND FITTING
8" TO 12"
18"
SUBSURFACE DRIP DISPERSAL
SYSTEM DETAILS
FIGURE 29-2
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30.0 CHAPTER OVERVIEW
This chapter provides design criteria for at-grade and mound dispersal systems for new and replacement
OWTS and modifications or repairs to existing OWTS. In addition to the requirements in this chapter, at-
grade and mound dispersal systems must also comply with the general requirements for pressure distribution
systems presented in Chapter 26 of this Manual.
This chapter is organized in the following sections:
Section 30.1: At-Grade and Mound Dispersal System Overview
Section 30.2: Onsite Wastewater System Configuration Requirements
Section 30.3: Dispersal System Siting Requirements
Section 30.4: Pressure Dosing Requirements
Section 30.5: Gravel Distribution Bed Requirements
Section 30.6: Sand Fill Requirements (Mound Systems Only)
Section 30.7: Soil Cover Requirements
Section 30.8: Dispersal System Configuration Requirements
Section 30.9: Dispersal System Inspection Well Requirements
Section 30.10: OWTS Performance Monitoring Well Requirements
Section 30.11: Dispersal System Installation Requirements
Section 30.12: Reference Guidelines
30.1 AT-GRADE AND MOUND DISPERSAL SYSTEM OVERVIEW
A. DESCRIPTION
1 .An at-grade dispersal system consists of an elevated gravel distribution bed with pressurized
perforated pipes designed to distribute effluent evenly into the gravel distribution bed and
into the underlying native soil. The gravel distribution bed is placed directly on the soil
surface and is covered by soil fill. The discharge or infiltrative surface of the at-grade system
is at the interface of the gravel distribution bed and the preconstruction ground surface
elevation of the native soil.
2. A mound dispersal system is similar to an at-grade dispersal system, except that it includes
a sand bed (filter media) between the native soil and the gravel distribution bed to provide
treatment (sand filtration) of effluent before it reaches native soil.
3. Mound and at-grade dispersal systems utilize the shallow surface soil for broad distribution
of effluent, and can be used in areas with a high groundwater table and shallow soil
conditions on flat or gently sloping terrain.
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4. Schematic and cross-section diagrams are provided in Figure 30-1 and Figure 30-2
(included at the end of this chapter) to illustrate the key design features of at-grade dispersal
systems.
5. Schematic and cross-section diagrams are provided in Figure 30-3 through Figure 30-9
(included at the end of this chapter) to illustrate the key design features of mound dispersal
systems.
30.2 ONSITE WASTEWATER SYSTEM CONFIGURATION REQUIREMENTS
A. GENERAL REQUIREMENTS
1. Possible System configurations using an at-grade or mound dispersal system are presented
in Table 5-4 (at-grade systems) and Table 5-5 (mound systems) and summarized below.
2.Treatment Train Requirements.
a.Primary Treatment. Primary (septic tank) treatment shall be the minimum level of
treatment for at-grade and mound dispersal systems for wastewater meeting the
definition of domestic-strength wastewater per the criteria provided in Chapter 15
and in accordance with the criteria presented in Table 5-4 (at-grade systems) and
Table 5-5 (mound systems).
b.Supplemental Treatment.
(1) Supplemental treatment may be used to allow reduced vertical separation
distance requirements for effective soil and high seasonal groundwater.
(2) Supplemental treatment is required to reduce high-strength wastewater to
domestic strength wastewater prior to discharge to pressure dosed trench
dispersal systems.
3.Effluent Distribution Mechanism. Effluent from the treatment tanks is pressure dosed to
at-grade and mound dispersal beds.
4.Dispersal System Reserve Area Requirements. In lieu of the dual dispersal system
requirement for standard System configurations, pressure dosed trench dispersal systems
must have a reserve area identified and preserved for future use for installation of a
replacement dispersal system, if required in the future. The reserve area must be:
a.A dedicated area of land having suitable site conditions and sufficient area for
installation of a replacement dispersal system (sized for one hundred percent of
the wastewater design flow and able to meet all the design requirements of the
system proposed);
b. Totally separate from the installed dispersal system; and
c. Fully protected to prevent damage to soil and any adverse impact on the
immediate surroundings that may affect the future installation of the replacement
system and its function.
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30.3 DISPERSAL SYSTEM SITING REQUIREMENTS
A. HORIZONTAL SETBACK REQUIREMENTS
1. The minimum horizontal setback distances specified in Table 5-7 apply to the at-grade and
mound dispersal systems (as measured from the edge of cover soil) except where modified
below:
a.The setback distances to buildings, structures, parcel lines and underground utility
easements shall be:
(1) Upgradient and laterally: Ten (10) feet; and
(2) Downgradient: Twenty-five (25) feet.
B. VERTICAL SEPARATION REQUIREMENTS
1.Depth to Groundwater. The minimum separation to high seasonal groundwater for at-
grade and mound dispersal systems, as measured from ground surface, is provided in Table
5-4 (at-grade systems) and Table 5-5 (mound systems).
a.At-Grade Dispersal Systems. The minimum separation to high seasonal
groundwater for at-grade dispersal systems shall vary between two (2) and five (5)
feet according to the level of treatment and the soil percolation rate.
b.Mound Dispersal Systems. The minimum separation to high seasonal groundwater
for mound dispersal systems shall vary between two (2) and three (3) feet according
to the soil percolation rate.
2.Effective Soil Depth. The minimum effective soil depth for at-grade and mound dispersal
systems, as measured from ground surface, is provided in Table 5-4 (at-grade systems) and
Table -5-5 (mound systems). Effective soil depth requirements shall apply within the
dispersal field and in the adjacent area extending a distance of twenty-five (25) feet down-
slope of the edge of the soil cover on sloping sites, and a distance of fifteen (15) feet from
the edge of the soil cover on all sides on level sites.
a.At-Grade Dispersal Systems. The minimum effective soil depth for at-grade
dispersal systems shall vary between two (2) and three (3) feet according to the level
of treatment.
b.Mound Dispersal Systems. The minimum effective soil depth for mound dispersal
systems shall be two (2) feet.
C. MAXIMUM GROUND SLOPE REQUIREMENTS
1. The maximum ground slope for at-grade and mound dispersal systems is provided in Table
5-4 (at-grade systems) and Table 5-5 (mound systems) and shall be as follows:
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a.Soil Percolation Rates Between One (1) and Sixty (60) MPI: The maximum
ground slope in areas used for at-grade and mound dispersal systems with average
soil percolation rates between one (1) and sixty (60) MPI shall be twenty (20)
percent.
b.Soil Percolation Rates Greater than 60 MPI: The maximum ground slope in
areas used for at-grade and mound dispersal systems with average soil percolation
rates greater than sixty (60) MPI shall be fifteen (15) percent.
c.Where a geotechnical report including slope stability evaluation is provided an
increase in slope of up to five (5) percent over the slope maximums listed above
may be allowed.
30.4 PRESSURE DOSING REQUIREMENTS
A. MINIMUM CRITERIA
1. Wastewater effluent, from the septic tank or supplemental treatment system shall be applied
to the at-grade or mound dispersal system by pressure dosing utilizing a pump system.
2. The pressure distribution system shall be designed in accordance with accepted industry
practices and in accordance with the following minimum standards:
a.Uniform dosing of treated effluent over the surface application area of the at-
grade or mound gravel distribution bed;
b. Pressure manifolds shall enter only from the uphill side or end of the at-grade or
mound dispersal system;
c.Distribution laterals shall have a maximum length of one hundred (100) feet, shall
be spaced at least twenty-four (24) inches apart and be located at least eighteen (18)
inches from the end and sides of the gravel distribution bed;
d. Orifices shall face upward and shall be protected with orifice shields; and
e.Perforated distribution laterals shall have a balancing valve at the beginning of the
lateral and a purge valve at the end of the lateral.
3. Additional requirements for design and construction of pump systems and pressure
distribution systems are contained in Chapter 26 of this Manual, as applicable.
30.5 GRAVEL DISTRIBUTION BED REQUIREMENTS
A. GRAVEL DISTRIBUTION BED DESIGN CRITERIA
1.Material. The gravel distribution bed shall consist of pea gravel meeting the material
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AT-GRADE & MOUND DISPERSAL SYSTEM REQUIREMENTS
specifications provided in Chapter 35.
2.Depth. Pea gravel shall extend a minimum of six (6) inches below the invert and two (2)
inches above the top of the distribution piping.
3.Level (Mound Only). The bottom of the gravel distribution bed in a mound dispersal
system shall be level.
4.Natural Contour of Ground. The gravel distribution bed shall be parallel to the contour of
the natural ground and shall not deviate more than three (3) inches vertically per one-
hundred (100) feet horizontally.
5.Gravel Distribution Bed Configuration. The gravel distribution bed shall be as long
and narrow as possible to limit the linear loading rate of effluent to assure that all the
effluent infiltrates into the natural soil before it reaches the toe of soil cover of the at-grade
or mound dispersal system.
B. GRAVEL DISTRIBUTION BED DESIGN CALCULATIONS.
1.Basal Area Calculation. The minimum basal area of the gravel distribution bed (i.e., the
infiltration area of the bottom infiltrative surface of the bed) in at-grade and mound dispersal
systems shall be sized according to the following formula in Table 30-1 below.
Table 30-1
At-Grade and Mound Dispersal System
Gravel Bed Basal Area Sizing Formula
Gravel Bed Basal Area (ft2)=Wastewater Flow Rate (gpd)
Wastewater Application Rate (gpd
ft2 )
2.Wastewater Flow Rate. The wastewater flow rate used for sizing the gravel bed basal area
in at-grade and mound dispersal systems shall be the wastewater design flow rate for the
OWTS.
3.Wastewater Application Rate. The wastewater application rates used for sizing the gravel
bed basal area in at-grade and mound dispersal systems shall correspond to the infiltrative
surface (i.e., gravel/native soil infiltrative surface for at-grade dispersal systems and
gravel/sand infiltrative surface for mound dispersal systems) and shall be as follows:
a.At-Grade Dispersal Systems. The wastewater application rate at the native soil
infiltrative surface shall vary according to the soil percolation rate and the level of
wastewater treatment proceeding the at-grade dispersal system in accordance with
the criteria in Table 5-4.
b.Mound Dispersal Systems. The wastewater application rate at the gravel/sand
infiltrative surface shall be in accordance with the criteria in Table 30-2.
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AT-GRADE & MOUND DISPERSAL SYSTEM REQUIREMENTS
Table 30-2
Wastewater Application Rate Criteria
for Sizing Mound Dispersal System
Gravel Bed Area
Facility Type Wastewater Application Rate
(gpd/ft2)
Individual Residential 1.2
Non-Residential and
Multi-Unit Residential 1.0
c.Reduction in the above wastewater application rates to ensure the long term
integrity and performance of at-grade and mound distribution systems may be
required for high-strength wastewater flows or if warranted by soil conditions.
4.Basal Width & Length Calculations. The maximum width (A) and effective length (B) of
the gravel distribution bed basal area of at-grade and mound dispersal systems shall be
determined in accordance with the formula in Table 30-3.
Table 30-3
Gravel Bed Distribution Sizing Formulas
A =Basal Width =10 feet
B =Effective Length (ft)=Wastewater Flow Rate (gpd)
Linear Loading Rate (gpd/lineal foot)
a.Wastewater Flow Rate. The wastewater flow rate used for determining the
effective length of the basal area for at-grade and mound dispersal systems shall be
in accordance with the criteria in Table 30-4 below.
Table 30-4
Waste Water Flow Rate for Sizing Gravel Bed Basal Area
Facility Type Wastewater Flow Rate
(gpd)
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AT-GRADE & MOUND DISPERSAL SYSTEM REQUIREMENTS
b.Linear Loading Rate. The linear loading rate is defined as the wastewater flow
rate (in gpd) divided by the effective length of the dispersal system measured along
the slope contour. Maximum linear loading rates for at-grade and mound dispersal
systems vary according to ground slope, effective soil depth and percolation rate in
accordance with the criteria in the Table 30-5 (at-grade systems) and Table 30-6
(mound systems). If a variance from these criteria is proposed, it must be supported
by detailed groundwater mounding analysis carried out in accordance with accepted
methodology and/or scientific references dealing with water movement in soil and
utilizing site specific hydraulic conductivity data.
(1) At-Grade Dispersal Systems Maximum Linear Loading Rate. The
maximum linear loading rate for at-grade dispersal systems shall be in
accordance with the criteria in Table 30-5 below.
Percolation Rate (MPI)
1 - 30 31 - 60 61 - 120
2.0 to 3.0
0 - 10 5 4 3
11 - 20 6 5 4
3.1 to 4.0
0 - 10 7 6 5
11 - 20 8 7 6
4.1 to 5.0
0 - 10 9 8 7
11 - 20 10 9 8
>5.0
0 - 10 11 10 9
11 - 20 12 11 10
(2) Mound Dispersal Systems Maximum Linear Loading Rates. The
maximum linear loading rate for mound dispersal systems shall be in
accordance with the criteria in Table 30-6 below.
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AT-GRADE & MOUND DISPERSAL SYSTEM REQUIREMENTS
Table 30-6
Maximum Linear Loading Rate for Mound Dispersal Systems
Effective Soil
Depth
(feet)
Ground
Slope
(%)
Linear Loading Rate
(gpd/lineal foot)
Percolation Rate (MPI)
1 - 30 31 - 60 61 - 120
2.0 to 2.5
0 - 10 5 4 3
11 - 20 6 5 4
2.6 to 3.0
0 - 10 7 6 5
11 - 20 8 7 6
3.1 to 4.0
0 - 10 9 8 7
11 - 20 10 9 8
>4.0
0 - 10 11 10 9
11 - 20 12 11 10
30.6 SAND FILL REQUIREMENTS (MOUND SYSTEMS ONLY)
A. SAND SPECIFICATIONS
1. The sand media shall be a medium to coarse sand which meets the gradation specifications
in Chapter 35.
2. Documentation of laboratory sieve analysis results for the proposed sand fill material
shall be supplied to the Department to verify conformance with the above specifications.
B. SAND DEPTH
1. The minimum depth of sand fill below the gravel distribution bed shall be twelve (12)
inches.
2. The minimum depth of sand fill shall be increased to twenty-four (24) inches for sites
where the average percolation rate is between one (1) and five (5) MPI.
C. NATURAL CONTOUR OF THE GROUND
1. The sand fill shall follow the natural contour of the ground surface and not deviate more
than three (3) inches vertically per one-hundred (100) feet horizontally.
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AT-GRADE & MOUND DISPERSAL SYSTEM REQUIREMENTS
D. TOP AND SLOPE OF SAND FILL
1. The dimensions of the top and slopes of the sand fill bed shall be determined as follows and
in accordance with the formula in Table 30-7 and as shown on Figure 30-8 and
Figure 30-9 (included at the end of this chapter):
a.Level Sites. On level sites the top of the sand fill shall extend horizontally
beyond the gravel distribution bed a minimum of twenty-four (24) inches in all
directions, then slope uniformly as determined by the mound dimensions.
b.Sloping Sites. On sloping sites, the twenty-four (24) inch sand fill dimension on
the upslope side of the gravel distribution bed may be reduced to twelve (12)
inches, then slope uniformly as determined by the mound dimensions. The
downslope and upslope width of the sand fill shall be adjusted in accordance with
the formula in Table 30-7 and the slope length correction factors for mound
dispersal systems in Table 30-8 (included at the end of this chapter).
c.The maximum side slope of the top of the sand surface shall be three (3) horizontal
to one (1) vertical.
E. SAND FILL DESIGN CALCULATIONS
1.The sand fill basal area and the effective infiltrative area shall be sized in accordance with
the formulas provided in Table 30-7 and as shown on Figure 30-8 and 30-9.
a.Basal Area Calculation. The total sand fill basal area at the sand/soil interface is
dependent on the length and width of the gravel distribution bed, sand filter media
depth and side slopes of the filter media.
b.Effective Infiltrative Area Calculation. The minimum effective infiltrative area for
wastewater dispersal into native soil shall be determined according to the formula
in Table 30-9.
Table 30-9
Effective Infiltrative Area Formula
Effective Infiltrative Area(ft2)=Wastewater Flow Rate (gpd)
Wastewater Application Rate (gpd
ft2 )
(1) Wastewater Flow Rate. The wastewater flow rate used for sizing the
effective infiltrative area of the sand fill shall be the wastewater design
flow rate for the OWTS.
(2) Wastewater Application Rate. The wastewater application rate used for
sizing the effective infiltrative area of the sand fill shall be based on the
soil percolation rate in the upper twelve (12) to twenty-four (24) inches of
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AT-GRADE & MOUND DISPERSAL SYSTEM REQUIREMENTS
soil depth in accordance with Table 25-2 (enhanced wastewater
application rates).
(3) Reduction in Wastewater Application Rates. Reductions in the above
wastewater application rates to ensure the long term integrity and
performance of mound distribution systems may be required for high-
strength wastewater or if warranted by soil conditions.
(4) Level Sites. For level dispersal fields the effective infiltrative area is equal
to the total sand fill basal bed area (O).
(5) Sloping Sites. For sloping dispersal fields the effective infiltrative area (P)
includes the area beneath the gravel distribution bed and the area
immediately downslope from the gravel distribution bed. The upslope and
end slopes transmit very little of the effluent on sloping sites, and are
therefore disregarded.
30.7 SOIL COVER REQUIREMENTS
A. MATERIAL
1. A continuous soil cover shall be placed over the entire gravel distribution bed (for at-grade
dispersal systems) and the gravel distribution bed and sand fill (for mound dispersal
systems).
2. The soil cover shall consist of a medium, loamy-textured soil.
B. SILT BARRIER
1. The gravel distribution bed and sand fill shall be covered in their entirety with a geotextile
filter fabric silt barrier meeting the material specifications provided in Chapter 36.
C. DEPTH
1. The soil cover depth shall be a minimum of twelve (12) inches and a maximum of eighteen
(18) inches over the top of the gravel distribution bed, and twelve (12) inches minimum
over the side slopes of the gravel or sand fill portion of the dispersal system.
2. The soil cover over the distribution bed shall be crowned to promote rainfall runoff, and
compacted by track-rolling with a minimum of two passes.
D. LATERAL EXTENSION
1. The soil cover shall extend a minimum of four (4) feet beyond the perimeter edge of the
gravel bed in at-grade dispersal systems or the sand fill in mound dispersal systems in all
directions.
2. On sloping sites the soil cover of at-grade dispersal systems shall extend further beyond
the down-slope edge of the gravel bed and shall vary according to the native ground slope
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)30-11
CHAPTER 30
AT-GRADE & MOUND DISPERSAL SYSTEM REQUIREMENTS
in accordance with the criteria in Table 30-10.
Table 30-10
At-Grade Dispersal System Soil Cover Lateral Extension Lengths
Ground Slope
(%)
Soil Fill Extension
(feet)
30.8 DISPERSAL SYSTEM CONFIGURATION REQUIREMENTS
A. PLACEMENT CRITERIA
1.On sloping sites (greater than two [2] percent), at-grade and mound dispersal systems shall
be aligned with their longest dimension parallel to the natural ground surface site contours
so as not to concentrate the effluent into a small area as it moves laterally down slope.
2. The longest dimension of at-grade and mound dispersal systems shall not be aligned
perpendicular to the contours of the earth’s surface in the dispersal system area.
3. At-grade and mound dispersal systems shall not be placed in a concave landscape position.
B. MULTIPLE DISTRIBUTION BED CRITERIA
1. Where multiple distribution beds are used for dispersal of the effluent, beds may be placed
end-to-end or upslope/down-slope of one another, subject to meeting minimum sizing
requirements determined from basal area and linear loading criteria.
2. Where any portion of the distribution beds overlap in an upslope/downslope configuration
and are within twenty five (25) feet of each other the linear loading analysis must account
for the combined flow from the overlapping portions.
3. The beds may be placed with one continuous soil cover fill or with independent soil cover
fill.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)30-12
CHAPTER 30
AT-GRADE & MOUND DISPERSAL SYSTEM REQUIREMENTS
4. The minimum lateral (i.e., end-to-end) separation distance for distribution beds with one
continuous soil cover fill shall be six (6) feet.
C. OVERLAP OF DISPERSAL AREAS CRITERIA
1.In determining the necessary space for the reserve area for future replacement of the at-
grade or mound dispersal system the entire basal area (soil cover basal area) of the installed
dispersal system and the reserve area dispersal system shall not overlap.
D. SITE DRAINAGE CRITERIA
1. Site drainage shall be provided so that rainfall and runoff is directed away from or around
the at-grade or mound dispersal system. On sloped sites surface water or groundwater
drainage structures may be required to divert runoff away from the dispersal field.
30.9 DISPERSAL SYSTEM INSPECTION WELL REQUIREMENTS
A. INSPECTION WELL CONSTRUCTION
1.Inspection wells shall be constructed of two (2) inch to four (4) inch diameter pipe,
equipped with a wrench-tight cap or pipe plug and a bottom cap. Perforations shall
consist of hacksaw slots at nominal one (1) inch spacing, or equivalent commercially-
slotted pipe. To prevent surface water infiltration, inspection wells shall be sealed with a
bentonite or concrete annular seal (or equivalent) through the soil backfill zone.
B. AT-GRADE DISPERSAL SYSTEMS
1. A minimum of one (1) inspection well shall be installed near the center of the at-grade
dispersal system, extending from the surface of the soil cover to the bottom of the gravel
distribution bed and screened across the gravel bed, for the purpose of checking effluent
levels in accordance with the requirements in Table 25-4 and as shown on Figure 30-1 and
Figure 30-2.
C. MOUND DISPERSAL SYSTEMS
1. A minimum of two (2) inspection wells shall be installed within the mound dispersal system
for the purpose of checking effluent levels in accordance with the requirements in Table
25-4 and as shown on Figures 30-5 through 30-7.
a.One (1) inspection well shall be installed near the center of the mound dispersal
system extending from the mound surface to the bottom of the gravel distribution
bed and screened across the gravel bed.
b. One (1) inspection wells shall be installed within the effective sand basal area
(outside of the gravel distribution bed), extending from the mound surface to six (6)
inches into the native soil and screened across the sand fill bed.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)30-13
CHAPTER 30
AT-GRADE & MOUND DISPERSAL SYSTEM REQUIREMENTS
30.10 OWTS PERFORMANCE MONITORING WELL REQUIREMENTS
A. MINIMUM CRITERIA
1. OWTS performance monitoring wells shall be installed around the at-grade or mound
dispersal systems in accordance with the requirements in Table 25-4 and as shown on
Figure 30-1 and Figure 30-2 (for at-grade systems) and Figure 30-4 through Figure 30-
9 (for mound systems) for the purpose of checking groundwater levels periodically and
water quality sampling, if needed.
30.11 DISPERSAL SYSTEM INSTALLATION REQUIREMENTS
A. GENERAL CRITERIA
1. The use of wheeled vehicles is prohibited for the purpose of ripping or chisel plowing,
driving on areas that have been ripped or chisel plowed, driving on the sand fill, placing or
moving the soil cover, or anytime the soil conditions are wet, moist, or saturated.
2. Surface vegetation shall be mowed to native ground and the clippings removed.
3. The soil surface shall be ripped or chisel plowed to a depth of eight (8) to ten (10) inches,
with rippers set eight (8) to ten (10) inches apart. Initial ripping shall be performed in a
path parallel to the contour of the land and only within the limits of the gravel distribution
bed (for at-grade systems) or the limits of the gravel distribution bed and the sand fill base
(for mound systems). The interface of the native soil and the soil cover shall be ripped after
the gravel and/or sand has been placed and just prior to soil cover placement. On steeper
sloping sites, soil cover may be keyed into the native soil in lieu of ripping the soil at the
System Designer’s discretion.
4. The sand fill (in mound dispersal systems) shall be uniformly placed and compressed by
track rolling to a neat line to the elevation and slope specified on the plans with a horizontal
tolerance not exceeding one-quarter (1/4) foot horizontally.
5. No traffic is permitted on any ripped surface until after the gravel, sand or soil cover has
been placed.
6. Temporary form boards required for the placement of material shall be removed prior to
placement of the soil cover.
7. Finished soil cover surface elevation of the at-grade or mound dispersal systems shall be
established by track rolling and grooming by hand. Soil cover shall be conditioned with
sufficient moisture to allow track rolling to a firm and cohesive surface.
8. The soil cover shall be landscaped or seeded with shallow-rooted, drought tolerant plants,
shrubs or grasses.
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CHAPTER 30
AT-GRADE & MOUND DISPERSAL SYSTEM REQUIREMENTS
30.12 REFERENCE GUIDELINES
A. GENERAL
1. Additional guidelines for at-grade and mound dispersal system design are contained in the
following references
a.“Design and Construction Manual for Wisconsin Mounds”, Small Scale Waste
Management Project, University of Wisconsin, Madison, January 2000, including
any amendments.
b. "Wisconsin At-grade Soil Absorption System Siting, Design and Construction
Manual”, Small Scale Waste Management Project, University of Wisconsin-
Madison, 1990.
c.“At-grade Component Using Pressure Distribution Manual for Private Onsite
Wastewater Treatment Systems”, State of Wisconsin, Department of
Commerce, 1999.
2. When the requirements in this Manual conflict with the requirements of the reference
guidance documents the requirements of the Manual shall prevail unless otherwise approved
by the Department.
TABLE 30-7
MOUND DISPERSAL SYSTEM
SAND FILL SIZING
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
(Refer to Figures 30-8 and 30-9)
Note: All dimensions in formulas must be in feet
Variable Name Dimension (Value/Formula)
Gravel Distribution Bed Dimensions
Sand Fill Dimensions
Level Sites ≤ 2%: E = D
Level Sites ≤ 2%: J = I
TABLE 30-8
MOUND DISPERSAL SYSTEM
SLOPE CORRECTION FACTORS
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
Slope
(%)
Down Slope Correction
Factor
Up Slope Correction
Factor
0 1.0 1.00
1 1.03 0.97
2 1.06 0.94
3 1.10 0.92
4 1.14 0.89
5 1.18 0.88
6 1.22 0.85
7 1.27 0.83
8 1.32 0.80
9 1.38 0.79
10 1.44 0.77
11 1.51 0.75
12 1.57 0.73
13 1.64 0.72
14 1.72 0.71
15 1.82 0.69
16 1.92 0.68
17 2.04 0.66
18 2.17 0.65
19 2.33 0.64
20 2.50 0.62
21 2.70 0.61
22 2.94 0.60
23 3.23 0.59
24 3.57 0.58
25 4.00 0.57
SEPTIC TANK
DOSING PUMP
P
INSPECTION WELL (TYP.)
PEA GRAVEL DISTRIBUTION BED
PVC PRESSURE LINE
SOIL COVER FILL
SLOPE
SUPPLEMENTAL
TREATMENT
(OPTION)
AT-GRADE DISPERSAL SYSTEM
SCHEMATIC
FIGURE 30-1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018) PAGE 1 OF 1
BASAL AREA
10'TYP.
4' TO 20' BASED ON GROUND SLOPE
FOR SYSTEM SIZING
12" TO 18"
TOPSOIL COVER;
COMPACT BY
TRACK-ROLLING
INSPECTION
WELL (TYP.)
FILTER FABRIC SILT BARRIER
INSPECTION RISER W/
THREADED END CAP
TYP.UTILITY BOX (TYP.)
DISTRIBUTION BED; DOUBLE
WASHED PEA GRAVEL
MULCHED OR PLANTED WITH
NATIVE GRASSES FOLLOWING
CONSTRUCTION
EXISTING
GRADE
PRESSURE LINE FROM
DOSING PUMP
NATIVE SURFACE SOIL;
STRIP VEGETATION AND
PLOUGH OR RIP, 8" TO 12"
DEEP, PRIOR TO GRAVEL
AND SOIL PLACEMENT
DISTRIBUTION
MANIFOLD AND
LATERALS
AT-GRADE DISPERSAL SYSTEM
CROSS-SECTION
FIGURE 30-2
OWTS PERFORMANCE MONITORING WELL
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
31
1 3
FLOW LINE
INLET
COMPARTMENT
2/3 SEPTIC TANK
OUTLET
COMPARTMENT
1/3 SEPTIC TANK
SEPTIC TANK PUMP CHAMBER
MOUND DISPERSAL FIELD
GROUNDWATER TABLE
FILTER
GRAVEL BED
MOUND DISPERSAL SYSTEM
CROSS SECTION
FIGURE 30-3
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
OWTS PERFORMANCE MONITORING WELL (TYP.)
GRAVEL DISTRIBUTION BED
PVC PRESSURE LINE
FROM DOSING PUMP
SAND FILL EFFECTIVE
APPLICATION AREA EQUAL TO
ENTIRE SAND BASAL AREA
SOIL COVER
SHUT-OFF VALVE
PRESSURE DISTRIBUTION LATERALS (TYP.)
INSPECTION WELL/
CLEANOUT RISER (TYP.)
4' MIN.
MOUND DISPERSAL SYSTEM
SCHEMATIC - LEVEL SITE
FIGURE 30-4
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
3
1
1 3
18"
12" (TYP.)
2'2'
4' MIN.
(TYP.)
10'
(TYP.)
10'
(TYP.)12" MIN.
TOPSOIL COVER, COMPACT BY
TRACK-ROLLING
MULCHED OR PLANTED TO
NATIVE GRASSES
FOLLOWING CONSTRUCTION
GRAVEL DISTRIBUTION BED
MEDIUM SAND FILL
PLOUGH OR RIP NATIVE
SURFACE SOILS, 8" TO
12" DEEP PRIOR TO
SAND PLACEMENT
UTILITY BOX (TYP.)
INSPECTION
WELL/CLEANOUT
RISER (TYP.)INSPECTION WELL (TYP.)
PRESSURE LINE
FROM DOSING
PUMP
PRESSURE
DISTRIBUTION PIPING
FILTER
FABRIC
MOUND DISPERSAL SYSTEM
CROSS SECTION - LEVEL SITE
FIGURE 30-5
OWTS PERFORMANCE
MONITORING WELL
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
OWTS PERFORMANCE MONITORING WELL (TYP.)
GRAVEL DISTRIBUTION BED
PVC PRESSURE LINE
FROM DOSING PUMP
SAND FILL
SOIL COVERSLOPE
SAND FILL EFFECTIVE APPLICATION
AREA
PRESSURE DISTRIBUTION LATERALS (TYP.)
SHUT-OFF VALVE (TYP.)
INSPECTION
WELL/CLEANOUT
RISER (TYP.)
4' MIN.
MOUND DISPERSAL SYSTEM
SCHEMATIC - SLOPING SITE
FIGURE 30-6
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
31
1
3
3 1
4' MIN.
(TYP.)
10'
(TYP.)
2'
1'
10'
(TYP.)
12" MIN.
TOPSOIL COVER,
COMPACT BY
TRACK-ROLLING;
MULCHED OR PLANTED
TO NATIVE GRASSES
FOLLOWING
CONSTRUCTION
GRAVEL DISTRIBUTION BED
FILTER
FABRIC
UTILITY BOX (TYP.)
INSPECTION/
CLEANOUT
RISER (TYP.)
MEDIUM SAND FILL INSPECTION WELL
(TYP.)
PLOUGH OR RIP NATIVE
SURFACE SOILS, 8" TO
12" DEEP, PRIOR TO
SAND PLACEMENT
PRESSURE
DISTRIBUTION PIPING
PRESSURE LINE FROM
DOSING PUMP
MOUND DISPERSAL SYSTEM
CROSS SECTION - SLOPING SITE
FIGURE 30-7
OWTS PERFORMANCE
MONITORING WELL (TYP)
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
FIGURE 30-8
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (REVISED DRAFT 11-26-2016)
PAGE 1 OF 1
DIMENSIONS (SLOPING SITE)
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
MO
N
I
T
O
R
I
N
G
W
E
L
L
FIGURE 30-9
P
PAGE 1 OF 1
DIMENSIONS (LEVEL & SLOPING SITES)
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)31-1
CHAPTER 31
RAISED SAND FILTER BED DISPERSAL SYSTEM REQUIREMENTS
31.0 CHAPTER OVERVIEW
This chapter provides design criteria for raised sand filter bed systems. The criteria apply to replacement and
repair or modification of existing OWTS requiring corrective action. Raised sand filter bed dispersal systems
are allowed under limited circumstances and are subject to the requirements of an operating permit.
This chapter is organized in the following sections:
Section 31.1: Raised Sand Filter Bed Dispersal System Overview
Section 31.2: Onsite Wastewater System Configuration Requirements
Section 31.3: Dispersal System Siting Requirements
Section 31.4: Pressure Dosing Requirements
Section 31.5: Containment Structure Requirements
Section 31.6: Sand Filter Requirements
Section 31.7: Gravel Distribution Bed Requirements
Section 31.8: Soil Cover Requirements
Section 31.9: Dispersal System Inspection Well Requirements
Section 31.10: OWTS Monitoring Well Requirements
Section 31.11: Dispersal System Installation Requirements
31.1 RAISED SAND FILTER BED DISPERSAL SYSTEM OVERVIEW
A. GENERAL DESCRIPTION
1. Raised sand filter bed dispersal systems will be approved only for repair or other corrective
action of existing OWTS on severely constrained sites where site specific conditions limit
treatment and dispersal options.
2. A raised sand filter bed dispersal system, sometimes referred to as a bottomless sand
filter, combines features of an intermittent sand filter system and a mound dispersal
system. It consists of a raised or terraced sand bed, commonly supported by a low retaining
wall or bulkhead, where the bottom surface is even with or slightly below ground surface
and forms the absorption surface. The raised sand filter bed dispersal system provides
additional polishing treatment of effluent and final dispersal of wastewater into native soil.
3. Schematic and cross-section diagrams are provided in Figure 31-1 (included at the end of
this chapter) to illustrate the key design features of raised sand filter bed dispersal systems.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)31-2
CHAPTER 31
RAISED SAND FILTER BED DISPERSAL SYSTEM REQUIREMENTS
31.2 ONSITE WASTEWATER SYSTEM CONFIGURATION REQUIREMENTS
A. GENERAL
1. Possible System configurations using raised sand filter bed dispersal systems are presented
in Table 5-6 and summarized below.
2.Treatment Train Requirements.
a.Primary Treatment. Primary treatment shall be the minimum level of treatment
preceding a raised sand filter bed dispersal system.
b.Supplemental Treatment.
(1) Supplemental treatment may be used to allow reduced vertical separation
distance requirements for effective soil and high seasonal groundwater.
(2) Supplemental treatment is required to reduce high-strength wastewater to
domestic strength wastewater prior to discharge to pressure dosed trench
dispersal systems.
3.Effluent Distribution Mechanism. Effluent from the treatment tanks is pressure dosed to
the raised sand filter bed dispersal system.
4.Exception to Dispersal System Reserve Area Requirements. Raised sand filter bed
dispersal systems are allowed only on severely constrained sites where a reserve area is not
available.
31.3 DISPERSAL SYSTEM SITING REQUIREMENTS
A. HORIZONTAL SETBACK REQUIREMENTS
1. Minimum horizontal setback distances from raised sand filter bed dispersal systems to site
features are specified in Table 5-7.
2. Setback distances are measured from the edge of the containment structure.
B. VERTICAL SEPARATION REQUIREMENTS
1.Depth to Groundwater. The minimum separation to high seasonal groundwater, as
measured from the bottom of the raised sand filter bed shall vary between two (2) and three
(3) feet depending on the soil percolation rate and the level of treatment provided as specified
in Table 5-6.
2.Effective Soil Depth. The minimum depth of effective soil, as measured from the bottom of
the raised sand filter bed, shall be two (2) feet as specified in Table 5-6.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)31-3
CHAPTER 31
RAISED SAND FILTER BED DISPERSAL SYSTEM REQUIREMENTS
C. MAXIMUM GROUND SLOPE REQUIREMENTS
1. Maximum ground slope in areas used for raised sand filter bed dispersal systems shall be
thirty (30) percent as specified in Table 5-6.
a.An increase in slope of up to five (5) percent may be allowed if supported by a
geotechnical evaluation.
31.4 PRESSURE DOSING REQUIREMENTS
A. MINIMUM CRITERIA
1. Effluent shall be applied to the raised sand filter bed dispersal system by pressure dosing
utilizing a pump system.
2. The pressure distribution system shall be designed in accordance with accepted industry
practices to achieve, at a minimum:
a.Uniform dosing of treated effluent over the surface application area of the raised
sand filter bed dispersal system;
b.At least one distribution lateral for every thirty-six (36) inches of distribution bed
width; and
c.Additional requirements for design and construction of pressure distribution
systems and pump systems contained in Chapter 26 of this Manual, as applicable.
31.5 CONTAINMENT STRUCTURE REQUIREMENTS
A. CONTAINMENT LINER
1. The raised sand filter bed dispersal systems shall be provided with an impermeable
containment liner along all sides of the filter bed to prevent lateral leakage out of or into
the filter.
a.The liner shall extend a minimum of twelve (12) inches below the original ground
surface elevation.
b. The liner shall consist of either:
(1) thirty (30) mil plastic;
(2) reinforced poured-in-placed concrete; or
(3) an equivalent impermeable structure.
2. Plastic liners shall meet the material specification provided in Chapter 36.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)31-4
CHAPTER 31
RAISED SAND FILTER BED DISPERSAL SYSTEM REQUIREMENTS
B. RETAINING WALL
1. The finished surface elevation of the raised sand filter bed dispersal system shall be
above the surrounding ground elevation and shall be structurally supported with retaining
wall(s), as required.
2. Containment walls over four feet in height measured from the bottom of the footing to the
top of the walls must be designed by a Qualified Professional as allowed by their license
and registration.
C. BED DIMENSIONS
1. The maximum width of the sand bed shall be ten (10) feet.
2. The raised sand filter bed dispersal system shall not be restricted as to its shape in plan view.
D. MULTIPLE UNITS
1. The raised sand filter bed dispersal system may be divided into compartments or multiple
units.
31.6 SAND FILTER REQUIREMENTS
A. SAND SPECIFICATIONS
1. The sand media shall be a medium to coarse sand which meets the gradation specifications
for raised sand filter beds dispersal systems in Chapter 35.
2. Documentation of laboratory sieve analysis results for the proposed sand filter media material
shall be supplied to the Department to verify conformance with the specifications.
B. SAND DEPTH
1. The minimum depth of sand fill, below the gravel distribution bed, shall be:
a. Twenty-four (24) inches for septic tank effluent.
b.Twelve (12) inches for supplemental treatment effluent.
C. SAND FILL BASAL AREA SIZING
1.Basal Area Sizing. The minimum size (square feet) of the basal area of the raised sand filter
bed dispersal system shall be determined in accordance with the formula in Table 31-1.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)31-5
CHAPTER 31
RAISED SAND FILTER BED DISPERSAL SYSTEM REQUIREMENTS
Table 31-1
Raised Sand Filter Bed Sizing Formula
Sand Fill Basal Area(ft2)=Wastewater Flow Rate (gpd)
Wastewater Application Rate (gpd
ft2 )
a.Wastewater Flow. The flow used for sizing the basal area of the sand filter bed
shall be the wastewater design flow for the OWTS.
b.Wastewater Application Rate. The wastewater application rate used for sizing the
basal area of the sand filter bed shall be based on soil percolation rates in the upper
(12) to twenty- four (24) inches of soil depth in accordance with the criteria in Table
25-2 (enhanced wastewater application rates). Reduction in the wastewater loading
rates or other provisions to ensure the long term integrity and performance of the
raised sand filter bed dispersal system may be required for high-strength wastewater
flows.
2.Effective Length. The effective length (L) of the raised sand filter bed system shall be the
total length of the raised bed along the downslope edge. The length shall be calculated in
accordance with the formula in Table 31-2.
Table 31-2
Raised Sand Filter Bed Effective Length Formula
Effective Length (ft)=Wastewater Design Flow Rate (gpd)
Linear Loading Rate (gpd/lineal ft)
a.Linear Loading Rate. The maximum linear loading rate for raised sand filter bed
dispersal systems sizing shall vary according to available effective soil depth,
ground slope, and percolation rate as indicated in Table 31-3 below. If a change
from these criteria is proposed it must be supported by detailed groundwater
mounding analysis carried out in accordance with accepted methodology and/or
scientific references dealing with water movement in soil and utilizing site specific
hydraulic conductivity data.
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CHAPTER 31
RAISED SAND FILTER BED DISPERSAL SYSTEM REQUIREMENTS
Table 31-3
Raised Sand Filter Bed Linear Loading Rates
Effective Soil
Depth (feet)
Ground
Slope (%)
Linear Loading Rate
(gpd/lineal foot)
Percolation Rate (MPI)
1-30 31-60 61-120
2 to 2.5
0-10 5 4 3
11-20 6 5 4
2.5 to 3
0-10 7 6 5
11-20 8 7 6
3 to 4
0-10 9 8 7
11-20 10 9 8
> 4
0-10 11 10 9
11-20 12 11 10
b.Wastewater Flow (Q). The wastewater flow used for determining the effective
length shall be in accordance with the criteria in Table 31-4 below.
Table 31-4
Wastewater Flow Rate for Determining Linear Loading Rates
Facility Type Q (gpd)
31.7 GRAVEL DISTRIBUTION BED REQUIREMENTS
A. MATERIAL
1. The distribution bed shall consist of pea gravel meeting the material specifications in
Chapter 35.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)31-7
CHAPTER 31
RAISED SAND FILTER BED DISPERSAL SYSTEM REQUIREMENTS
B. DEPTH
1. Pea gravel shall extend a minimum of six (6) inches below the invert and two (2) inches
above the top of the distribution piping. If the distribution piping is installed with
gravelless chambers, the pea gravel depth below the distribution pipe may be reduced from
six (6) inches to four (4) inches, and the two (2) inch pea gravel cover may be eliminated.
C. SILT BARRIER
1. The gravel distribution bed shall be covered in its entirety with a geotextile filter fabric silt
barrier meeting the material specifications in Chapter 36.
31.8 SOIL COVER REQUIREMENTS
A. MATERIAL
1.A continuous soil cover consisting of a medium, loamy-textured soil shall be placed over
the entire gravel distribution bed.
B. DEPTH
1. The soil cover depth shall be a minimum of twelve (12) inches and a maximum of eighteen
(18) inches over the top of the gravel distribution bed.
2. The soil cover shall be crowned or sloped to promote rainfall runoff.
31.9 DISPERSAL SYSTEM INSPECTION WELL REQUIREMENTS
A. MINIMUM CRITERIA
1. A minimum of two (2) inspection wells shall be installed within the raised sand filter bed
dispersal system for the purpose of checking effluent levels in accordance with the
requirements in Table 25-4 and as shown on Figure 31-1.
a.One (1) inspection well shall be installed near the center of the raised sand filter bed
dispersal system extending from the fill surface to the bottom of the gravel
distribution bed and screened within the pea gravel fill.
b. One (1) inspection well shall be installed near the center of the raised sand filter bed
dispersal system extending from the fill surface to the soil-sand interface and
screened within the sand fill.
2. Inspection wells shall be constructed of two (2) inch to four (4) inch diameter pipe,
equipped with a wrench-tight cap or pipe plug and a bottom cap. Perforations shall
consist of hacksaw slots at nominal one (1) inch spacing, or equivalent commercially-
slotted pipe. To prevent surface water infiltration, inspection wells shall be sealed with a
bentonite or concrete annular seal (or equivalent).
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)31-8
CHAPTER 31
RAISED SAND FILTER BED DISPERSAL SYSTEM REQUIREMENTS
31.10 OWTS PERFORMANCE MONITORING WELL REQUIREMENTS
A. MINIMUM CRITERIA
1.OWTS performance monitoring wells shall be installed around the raised sand filter bed
dispersal system in accordance with the requirements in Table 25-4 and as shown on
Figure 31-1 for the purpose of checking groundwater levels periodically and water quality
sampling, if needed.
31.11 DISPERSAL SYSTEM INSTALLATION REQUIREMENTS
A. MINIMUM CRITERIA
1. The soil infiltrative surface should be broken up with the backhoe teeth to minimize the
formation of a distinct layer between the sand and the original, undisturbed soil.
2. Sand filter media must have a uniform density throughout and shall be installed in
accordance with the criteria provided in Chapter 35 of this Manual in order to prevent
differential settling when the raised sand filter bed dispersal system is put into service.
3. Plastic liners shall be installed in accordance with the criteria provided in Chapter 36 of
this Manual.
END CROSS-SECTION
SOIL FILL
EXISTING
GRADE
PEA GRAVEL DISTRIBUTION BED; 6" MIN.
BELOW PIPE, 2" MIN. ABOVE PIPE
FILTER FABRIC
SILT BARRIER
PVC PRESSURE LINE FROM
DOSING PUMP
INSPECTION WELL
(TYP.)
RETAINING STRUCTURE
WITH INTERIOR LINER
SECURED TO INSIDE
SURFACE (TYP.)
INSPECTION RISER
WITH THREADED END CAP
(TYP.)
EXTEND LINER BELOW
GRADE, 12" MIN.
PRESSURE DISTRIBUTION
PIPING
STRIP VEGETATION AND
PLOUGH OR RIP, 8" TO 12"
DEEP, PRIOR TO
PLACEMENT OF SOIL
COVER FILL
RAISED SAND FILTER BED
CROSS-SECTION
MEDIUM SAND FILL; 12" MIN.
12" MIN.
FIGURE 31-1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)32-1
CHAPTER 32
COVER FILL REQUIREMENTS
32.0 CHAPTER OVERVIEW
This chapter provides design criteria for cover fill that may be used in conjunction with gravity trench
dispersal systems, pressure dosed trench dispersal systems and subsurface drip dispersal systems presented in
Chapters 27 through Chapter 29 of this Manual. The requirements of this chapter are for new and
replacement OWTS and modifications or repairs to existing OWTS.
This chapter is organized in the following sections:
Section 32.1: Cover Fill Dispersal System Overview
Section 32.2: Dispersal System Siting Requirements
Section 32.3: Design and Construction Requirements
32.1 COVER FILL DISPERSAL SYSTEM OVERVIEW
A. GENERAL DESCRIPTION
1. The term “cover fill” refers to a trench dispersal system or subsurface drip dispersal system
where the dispersal trenches or dripline are excavated entirely below the natural ground
surface elevation, but up to twelve (12) inches of soil fill is placed on top of the original
ground surface to provide the required backfill cover over the trenches or driplines.
2. The wastewater is dispersed into the native soil, not into the fill soil. The purpose of cover
fill systems is to allow for shallower dispersal system depths where necessary or desirable to
meet soil depth and groundwater separation requirements.
3. Cover fill systems provide for improved use of the absorption capacity of the near surface
soil, which tend to be most permeable and most effective for absorption and treatment of
wastewater effluent.
4. A cross-section diagram of a cover fill trench dispersal system is provided in Figure 32-1
(included at the end of this chapter) to illustrate the key design features of cover fill dispersal
systems.
32.2 DISPERSAL SYSTEM SITING REQUIREMENTS
A. HORIZONTAL SETBACK REQUIREMENTS
1. Minimum horizontal setback distances for dispersal systems using cover fill to site features
are specified in Table 5-7. Setback distances are measured from the edge of the cover fill
soil.
B. VERTICAL SEPARATION REQUIREMENTS
1.Depth to Groundwater. The minimum separation to high seasonal groundwater, as
measured from the bottom of the trench or dripline, shall vary between two (2) and five (5)
feet depending on the type of dispersal system as specified in Table 5-1 through Table
5-3.
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CHAPTER 32
COVER FILL REQUIREMENTS
2.Effective Soil Depth. The minimum depth of effective soil as measured from the bottom of
the trench or dripline shall vary between two (2) and three (3) feet depending on the type of
dispersal system as specified in Table 5-1 through Table 5-3.
C. MAXIMUM GROUND SLOPE REQUIREMENTS
1. Maximum ground slope in areas used for cover fill systems shall be twenty (20) percent
as specified in Table 5-1 through Table 5-3.
a.An increase in slope of up to five (5) percent may be allowed if supported by a
geotechnical evaluation.
32.3 DESIGN AND CONSTRUCTION REQUIREMENTS
A. DISPERSAL TRENCHES & DRIPLINES
1. Trenches and driplines shall be installed entirely below the original ground surface
elevation.
2. All other aspects of the dispersal system shall be in accordance with requirements for the
particular type of system (e.g., pressure-dosed trench, subsurface drip dispersal system,
etc.).
B. SITE PREPARATION
1. Prior to placement of fill material, all vegetation shall be removed and the ground surface
ripped or ploughed to a depth approximately six (6) to ten (10) inches to permit good mixing
of native soil and fill material.
C. FILL MATERIAL
1.The soil used for fill shall be similar in texture to the native surface soil in the dispersal
system area.
2. Sand, gravel or rock do not qualify as acceptable material for cover fill.
3. Particle size analysis of proposed soil cover material shall be required and submitted to the
Department for review and approval, except in cases where the soil cover material is
obtained from similar soil on the parcel.
D. SEQUENCING
1. The cover soil fill shall be placed prior to dispersal trench or dripline excavation and
installation of dispersal piping and appurtenances.
E. AREAL COVERAGE
1. The cover soil fill shall be continuous and constructed to provide a uniform soil cover.
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CHAPTER 32
COVER FILL REQUIREMENTS
2. The cover soil fill (in combination with the trench backfill, if applicable), shall achieve a
total thickness of at least twelve (12) inches over the dispersal system piping and/or gravel.
3. The fill shall extend a minimum distance of fifteen (15) feet from the edge of the dispersal
system trenches or dripline in the down-slope direction and ten (10) feet in the upslope and
side-slope directions.
4. On level sites, the fill shall extend a minimum of ten (10) feet in all directions.
5. The toe of the fill shall be tapered at no less than a three (3) horizontal to one (1) vertical
slope, beginning at the required fifteen (15) foot or ten (10) foot distance, as applicable.
6. Where dual dispersal systems are installed and adjacent to one another, the cover fill should
be continuous over both fields.
F. FILL COMPACTION
1. Fill shall be placed in layers (“lifts”) of not more than six (6) inches and compacted to
approximately the same dry density as the native soil.
2. Normal compaction procedures to achieve this requirement shall consist of track-rolling
each lift with a minimum of two (2) passes.
3. Alternative compaction procedures may be allowed by the Department in accordance
with recommendations and supporting technical data supplied by the System Designer.
DISPOSAL TRENCHES;
INSTALL FOLLOWING
FILL PLACEMENT
10' MIN.
15' MIN.
12" MIN.
SOIL COVER FILL;
SIMILAR TO NATIVE SOIL TEXTURE; PLACE
AND COMPACT IN LIFTS OF 6" OR LESS;
COMPACT BY TRACK-ROLLING, TWO (2)
PASSES MIN.
ORIGINAL GRADE;
STRIP VEGETATION AND PLOUGH
OR RIP, 8" TO 12" DEEP, PRIOR TO
PLACEMENT OF SOIL COVER FILL
3
1
3
1
(UPSLOPE AND
SIDESLOPE
DIRECTIONS)
(DOWNSLOPE DIRECTION)
REVEGETATE SOIL FILL W/ GRASSES OR
OTHER GROUND COVER FOLLOWING
PLACEMENT AND COMPACTION
APPLY EROSION CONTROL
MEASURES, SUCH AS STRAW
WATTLES, AS NEEDED
NATIVE GROUND SLOPE,
20% MAX.
COVER FILL TRENCH DISPERSAL SYSTEM
(CONVENTIONAL TRENCH) CROSS-SECTION
FIGURE 32-1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018) PAGE 1 OF 1
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
PART 8
CONSTRUCTION MATERIAL & SYSTEM COMPONENT
REQUIREMENTS
CHAPTER TITLE
CHAPTER 33 PIPE REQUIREMENTS
CHAPTER 34 DISTRIBUTION DEVICE, VALVE, METER &
GAUGE REQUIREMENTS
CHAPTER 35 DRAIN ROCK, PEA GRAVEL & SAND FILTER
MEDIA REQUIRMENTS
CHAPTER 36 GEOSYNTHETIC MATERIAL
REQUIREMENTS
CHAPTER 37 GRAVELLESS DISTRIBUTION PRODUCT
REQUIREMENTS
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CHAPTER 33
PIPE REQUIREMENTS
33.0 CHAPTER OVERVIEW
This chapter provides requirements for pipes used in the construction of Systems. The criteria apply to new
and replacement Systems and modifications or repairs to existing Systems.
This chapter is organized in the following sections:
Section 33.1: Material & Construction Requirements
33.1 MATERIAL & CONSTRUCTION REQUIREMENTS
A. MINIMUM CRITERIA
1. Unless otherwise specified, building sewers and wastewater piping shall conform to the
standards of the most recent edition of the California Plumbing Code and with the following
criteria:
a.Labeling. All pipe throughout the Systems shall be clearly labeled and installed so
that the labeling can be readily identified by the Department.
b.Solid Pipe, Joints and Connections: Solid (non-perforated) pipe for Systems must
conform to the standards of the most recent edition of the California Plumbing
Code.
c.Perforated Distribution Pipe: Perforated pipe for gravity trench dispersal systems
must conform to the California Plumbing Code and must be three (3) or four (4)
inches in diameter.
d.Tightlines under Traffic Areas: Tightlines under traffic areas must be installed to
prevent deformation, which may include use of appropriate piping materials, burial
depth and sleeving.
e.Building Sewer Requirements: The building sewer from the structure to the septic
tank must meet California Plumbing Code requirements.
f.Setback Requirements. Wastewater piping shall conform to the California
Plumbing Code setback (horizontal and vertical) requirements to other utility
piping.
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CHAPTER 34
DISTRIBUTION DEVICE, VALVE, METER & GAUGE REQUIREMENTS
34.0 CHAPTER OVERVIEW
This chapter provides requirements for distribution devices, valves, meters and gauges used in System
design. The criteria apply to new and replacement Systems and modifications or repairs to existing Systems.
This chapter is organized in the following sections:
Section 34.1: Distribution Device Requirements
Section 34.2: Valve, Meter & Gauge Requirements
34.1 DISTRIBUTION DEVICE REQUIREMENTS
A. MINIMUM CRITERIA
1. Effluent distribution may be accomplished by the use of commercially available
pressurized flow splitter devices, distributing valves or by conventional distribution boxes.
2. Distribution devices shall be of sound construction, watertight, not subject to excessive
corrosion, and designed for the intended use.
3. Distribution devices must be fitted with risers and watertight lids or covers, extending to
grade, which will permit unobstructed access for maintenance, inspection and operation.
4. Distribution devices shall be designed to accommodate the necessary distribution laterals
and expected flows and placed in non-traffic areas.
5. Pressure distribution valves shall be designed to apply effluent uniformly over the entire
dispersal system.
B. DISTRIBUTION BOXES
1. Distribution boxes may be installed to divide effluent flows evenly among dispersal system
laterals.
2. Distribution boxes must be installed level to assure that each lateral in the drainfield is
receiving an equivalent amount of effluent.
3. Measures must be taken to dissipate the velocity of the wastewater delivered by a pump or
siphon and to prevent direct flow of effluent across the distribution box resulting in unequal
distribution among the outlets.
4. Distribution devices must be placed at a high point so that flow is by gravity in all lines
following the device.
5. The distribution box should be placed on a concrete pad or otherwise solidly anchored to
prevent it from tilting or shifting in place.
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DISTRIBUTION DEVICE, VALVE, METER & GAUGE REQUIREMENTS
C. LEVELING DEVICES
1. The use of commercially available outlet pipe leveling devices can compensate in elevation
differences in outlets and facilitate leveling adjustments.
2. Because of their constant radius and ease of adjustment, leveling devices may improve the
accuracy with which a distribution box can be leveled initially and in the future.
D. FLOW SPLITTING VALVES
1. A pressurized flow splitting device such as a pressure manifold can be used to provide
uniform distribution regardless of the drainfield lateral length or elevation.
2. Fitting the manifold with orifices sized to permit the percentage of flow desired
accommodates different lengths of laterals.
3. An air-release valve (swing-check valve installed in reverse) located at the high point(s) is
required if siphoning can occur through the device.
.
E. DISTRIBUTING VALVES
1. A pressurized distributing valve can be used as a means for distributing effluent to multiple
drainfield laterals or zones.
2. The water pressure in the transport line activates the distributing valves. Each time the
pump is turned on the distributing valve rotates to dose the next drainfield.
3. Distributing valves must be designed with the following features:
a.Unions to allow easy removal of the valve;
b. Clear sections of pipe for visual inspection of valve operation; and
c.A ball valve on the inlet for quick testing of valve operation.
4. The best location of a distributing valve for reliable operation is at the high point in the
system.
5. The transport line between the pump and valve should be kept full if possible. If the line is
empty at the beginning of each cycle, pockets of air during filling can cause random
rotation of the valve. To minimize air pockets, the transport line between the pump and
valve should be kept full, short and laid at a constant grade.
6. Because of the mechanical movements of distributing valves it is necessary to take steps
to prevent solids from reaching the valves, which may impede operation. Without
adequate septic tank effluent screening, distributing valves have very little chance of
reliable long term operation. Installation of a distributing valve should not be considered
unless a system monitoring program is required for inspecting the valve on a routine
frequency. Inspections are necessary to prevent system failure if the valve stops working
properly.
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DISTRIBUTION DEVICE, VALVE, METER & GAUGE REQUIREMENTS
7. Because liquid flow through a distributing valve passes fairly small openings with several
changes in direction head losses through the valve are high. To assure enough head is
available for proper system operation it is recommended that high head turbine pumps be
used to pressurize the valve. High pressures through the valve provide a large force for
proper seating of the rubber flap disk thus lowering the leakage that can occur through the
openings that are not being pressurized. High head turbine pumps are also recommended
because the use of a distributing valve typically requires more frequent pump cycling. The
System Designer should check with the manufacturer to determine the minimum required
flow rate through the valve to also assure proper seating of the rubber flap disk.
34.2 VALVE, METER & GAUGE REQUIREMENTS
A. DIVERSION VALVES
1. All diversion valves regardless of the type of distribution used (gravity or pressure) must:
a.Provide for independent flow to dual dispersal systems, but not both;
b. Be fitted with risers and watertight lids or covers, extending to grade, which will
permit unobstructed access for maintenance, inspection, and operation;
c.Have a valve box and either suitable length valve stems or long-handled keys or
tools so that they may be easily operated from the ground surface;
d. Be corrosion resistant, watertight, and designed to accommodate the inlet and
outlet pipes; and
e.Have a positive stop.
B. OTHER VALVES
1. The design, materials and construction of other valves (including but not limited to purge
valves, check valves, air/vacuum relief valves, pressure regulators) shall comply with all
requirements of the California Plumbing Code.
C. METERS AND GAUGES
1. Meter and gauge design, materials and construction (including but not limited to flow
meters and pressure regulators) shall comply with all requirements of the California
Plumbing Code.
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CHAPTER 35
DRAIN ROCK, PEA GRAVEL & SAND FILTER MEDIA REQUIREMENTS
35.0 CHAPTER OVERVIEW
This chapter provides requirements for gravel and sand used in sand filters and dispersal systems. The
criteria apply to new and replacement Systems and modifications or repairs to existing Systems.
This chapter is organized in the following sections:
Section 35.1: Gravel Specifications
Section 35.2: Sand Specifications & Placement Guidelines
35.1 GRAVEL SPECIFICATIONS
A. GENERAL
1. Gravel should be uniformly graded (particles of wide ranges of sizes) to maximize pore
space.
2. Gravel shall be clean, washed, non-deteriorating and substantially free of fines (defined as
less than one [1] percent fines passing the No. 200 sieve).
3. Gravel must be accepted by the System Designer prior to placement.
B. DRAIN ROCK (DISPERSAL TRENCHES)
1. Gravel used for drain rock in trench dispersal systems shall be three quarter (¾) inch to two
and one-half (2½) inches in diameter.
C. FILTER/BACKFILL MATERIAL (CURTAIN DRAINS)
1. Gravel used as filter/backfill material in curtain drains shall be three-quarter (¾) to one and
one-half (1½) inches in diameter.
2. Caltrans Class 2 permeable filter material may be substituted for the gravel.
D. PEA GRAVEL FILTER MATERIAL (ISF, RSF, PDST, MOUND, AT-GRADE & RAISED
SAND FILTER BED SYSTEMS)
1. Pea gravel used for pressure-dosed sand trench dispersal system filter material (below the
distribution pipe), gravel distribution beds and underdrains in ISF and RSF systems, and gravel
distribution beds in at-grade, mound and raised sand filter bed dispersal systems shall be three
eighths (3/8) inch double-washed pea gravel.
E. GRANULAR MEDIA COVER (RSF)
1. Granular Media used for cover over the gravel distribution bed in RSF systems shall range
in size from three-eights (3/8) inch pea gravel to two and one-half (2 1/2) inch rounded
rock.
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DRAIN ROCK, PEA GRAVEL & SAND FILTER MEDIA REQUIREMENTS
35.2 SAND SPECIFICATIONS & PLACEMENT GUIDELINES
A. SAND FILTER MEDIA
1.Sieve Analysis. Sand filter materials used in ISF/RSF systems and PDST, raised sand filter
bed and mound dispersal systems shall fall within the limits of the specifications shown in
the Table 35-1 for the amounts of material retained/passing (by weight).
2.Additional Requirements for Recirculating Sand Filter Systems. The following
additional sand specifications shall apply for RSF:
a.Effective size of sand/gravel, D10: 1.5 to 2.0 millimeters (mm)
b. Uniformity coefficient, Uc < 2.5
3. Documentation of laboratory sieve analysis results for the proposed sand fill material shall
be supplied to the Department to verify conformance with the above specifications prior
to placement.
B. SAND FILTER PLACEMENT GUIDELINES
1. In order to prevent differential settling when the sand filter is put into service, the filter
media must have a uniform density throughout.
2. Uniform density may be accomplished one of two ways, depending on the moisture content
of the filter media during construction.
Table 35-1
Sand Filter Media Specifications
Sieve
Size
Percent Passing Sieve
ISF & RSF
Systems
PDST,
Mound
& Raised Sand Filter Bed
Dispersal Systems
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DRAIN ROCK, PEA GRAVEL & SAND FILTER MEDIA REQUIREMENTS
a.If the filter media is so dry that it can be poured (like salt or sand in an hourglass),
it can be poured to fill the sand filter frame, then settled lightly (not compacted) to
allow about five (5) percent settling (i.e., volume reduction).
b. If the filter media is moist enough that it cannot be poured, it should be placed in
successive six (6) inch lifts with each lift lightly settled.
3. The intent of the light settling in both cases is to eliminate large voids in the media that may
collapse later when effluent is added.
4. The light settling may be accomplished by walking on the sand, then raking (with hand
tools) into the corners, along the sides, around the pump well (if applicable) and around
inspection wells. Higher densities will reduce infiltration rates and oxygen exchange
potential.
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CHAPTER 36
GEOSYNTHETIC MATERIAL REQUIREMENTS
36.0 CHAPTER OVERVIEW
This chapter provides requirements for geosynthetic materials used in sand filters and dispersal systems.
The criteria apply to new and replacement Systems and modifications or repairs to existing Systems.
This chapter is organized in the following sections:
Section 36.1: Geotextile Filter Fabric Requirements
Section 36.2: Polyvinyl Chloride (PVC) Liner Requirements
36.1 GEOTEXTILE FILTER FABRIC REQUIREMENTS
A. MINIMUM CRITERIA
1. Geotextile filter fabric shall either be polyester, nylon or polypropylene, or any combination
thereof, and shall be suitable for use in subsurface dispersal systems and underdrain
applications.
2.The fabric shall be free of any chemical treatment or coating which reduces permeability and
shall be inert to chemicals commonly found in soil.
3.Filter fabric shall be non-woven, shall not act as a wicking agent and shall be permeable and
shall meet or exceed the specifications listed in Table 36-1.
Notes:
(1) For soil with fifty (50) percent or less particles by weight passing the No. 200 sieve,
the Apparent Opening Size (AOS) shall be less than 0.6 mm (greater than the No.
30 Sieve).
(2) For soil with more than fifty (50) percent particles by weight passing the No. 200
Sieve, the AOS shall be less than 0.297 mm (greater than the No. 50 Sieve).
36.2 POLYVINYL CHLORIDE (PVC) LINER REQUIREMENTS
A. MINIMUM CRITERIA
1.PVC liners used in sand filter design shall meet or exceed the specifications provided in
Table 36-2.
–
Property Test Procedure Unit Minimum Value
Grab Strength ASTM D4632 lb 60
Puncture Tear ASTM D4833 lb. 18
Trapezoid Tear ASTM D4533 lb. 25
Apparent Opening Size ASTM D4751 Sieve See Note (1),(2)
Flow Rate ASTM D4491 gal/ft2/min 100
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GEOSYNTHETIC MATERIAL REQUIREMENTS
Table 36-2
Polyvinyl Chloride Liner Specifications
Property Test Method Value
Thickness ASTM D1593, Para 9.1.3 30 mil
minimum
Specific Gravity (Minimum) ASTM D792 Method A
Minimum Tensile Properties (each
direction) ASTM D882
Breaking Factor (pounds/inch width) Method A or B (1 inch wide) 69
Elongation at Break (percent) Method A or B 300
Modulus (force) at 100% elongation
(pounds/inch width) Method A or B 27
Tear Resistance (pounds, minimum) ASTM D1004, Die C 8
Low Temperature ASTM D1790 -20°F
Dimensional Stability (each
direction, percent change maximum) ASTM D1204, 212°F, 15 min. ± 5
Water Extraction ASTM D1239 -0.35% max
Volatile Loss ASTM D1203, Method A 0.7% max
Resistance to soil Burial (percent
change maximum in original
value)
ASTM D3083
Breaking Factor -5
Elongation at Break -20
Modulus at 100% Elongation ±10
Bonded Seam Strength (factory
seam, breaking factor, ppi width ASTM D3083 55.2
Hydrostatic Resistance ASTM D751, Method A 82
B. INSTALLATION GUIDELINES
1. Site Considerations and Preparation.
a.The supporting surface slopes and foundation to accept the liner shall be stable and
structurally sound including appropriate compaction. Particular attention shall be
paid to the potential of sink hole development and differential settlement;
b. Potentially abrasive soil stabilizers such as cementations or chemical binding agents
shall not adversely affect the membrane.
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GEOSYNTHETIC MATERIAL REQUIREMENTS
c.The liner must be protected by being fully buried to avoid deterioration caused by
exposure to weather or sunlight. In cases where portions of the liner may be subject
to direct exposure to the weather (e.g., in an ISF or RSF system in which the top
edges of the liner may not be buried due to system design requirements) the exposed
portions of the liner must be covered (e.g., by construction of a finish rim over the
exposed liner); and
d. Strain (or elongation) shall be minimized anywhere in the flexible membrane liner.
Non-reinforced liners have high elongation and can conform to irregular surfaces
and follow settlements within limits. Unreasonable strain reduces thickness and
may reduce life expectancy by lessening the chemical resistance of the thinner
(stretched) material.
2. Construction and Installation.
a.The bottom of the pit shall be graded to provide a sloping liner surface from the
outer edge of the filter toward the point of underdrain collection.
b.The sides of the pit shall be smooth and free of possible puncture points.
c.The liner shall be protected from puncture by placing a minimum of three (3) inches
of sand or non-woven needle-punched geotextile fabric in the bottom of the pit prior
to liner placement;
3. Climatic Conditions.
a.Temperature. The desirable temperature range for membrane installation shall be
in accordance with the manufacturer’s recommendations. Placing liner outside the
desirable temperature range shall be avoided to prevent adverse effects on
transportation, storage, field handling and placement, seaming, backfilling and
attaching boots and patches.
b.Wind. Wind may have an adverse effect on liner installation. Placing the liner in
high wind shall be avoided to prevent damage to the liner and cleanliness of areas
for boot connection and patching.
c.Precipitation. Seaming, patching and attaching ‘boots’ shall be done under dry
conditions. When field seaming is adversely affected by moisture, portable
protective structures and/or other methods shall be used to maintain a dry sealing
surface to facilitate proper surface preparation for bonding boots and patches.
4.Boots: When boots are used (required when using a gravity-flow underdrain), the boot and
exit pipe must be installed with the following criteria:
b.The boot shall be installed by the manufacturer or the manufacturer's representative;
c.The boot outlet shall be bedded in sand;
d.The boot shall be sized to accommodate a four (4) inch underdrain outlet pipe;
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GEOSYNTHETIC MATERIAL REQUIREMENTS
e.The boot shall be secured to the four (4) inch outlet pipe with two (2) stainless steel
bands and screws and sealant strips as recommended by the manufacturer;
f.An inspection port must be installed in the pipe from the sand filter to the dispersal
field;
g.The trench from the sand filter to the drainfield must be backfilled with a minimum
five (5) lineal feet clay dam to prevent the trench from acting as a conduit for ground
water movement towards the dispersal field;
h.Performance testing of the sand filter/boot for leakage must be conducted if the boot
may be submerged in a seasonal high water table; and
i.Testing of the sand filter/boot for leakage must be conducted in accordance with
the following protocol:
(1) Fill the underdrain gravel with water;
(2) Measure and record elevation of water through observation/inspection port;
(3) Let stand for twenty four (24) hours minimum;
(4) Measure and record elevation of water through observation/inspection port;
(1) There shall not be any loss of water in the twenty four (24) hour test period.
5. Liner Placement.
a. Size. The final cut size of the liner shall be determined and ordered to generously
fit the container geometry without field seaming or excess straining of the liner
material.
b.Transportation, Handling and Storage. Transportation, handling and storage
procedures shall be planned to prevent material damage. Material shall be stored in
a secured area and protected from adverse weather.
c. Site Inspection. A site inspection shall be carried out by the System Designer and
the installation Contractor prior to liner installation to verify surface conditions.
d.Deployment. Panels shall be positioned to minimize handling. Seaming should not
be necessary. Bridging or stressed conditions shall be avoided with proper slack
allowances for shrinkage. The liner shall be secured to prevent movement and
promptly backfilled.
e. Anchoring Trenches. The liner edges shall be secured in backfilled trenches or
with manufacturer recommended fastening devices.
f. Field Seaming. Field seaming, if absolutely necessary, shall only be attempted
when weather conditions are favorable. The contact surfaces of the materials should
be clean of dirt, dust, moisture or other foreign materials. The contact surfaces shall
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GEOSYNTHETIC MATERIAL REQUIREMENTS
be aligned with sufficient overlap and bonded in accordance with the suppliers
recommended procedures. Wrinkles shall be smoothed out and seams should be
inspected by non-destructive testing techniques to verify their integrity. Field seams
shall be inspected continuously and any faulty area repaired immediately.
g.Field Repairs. Traffic on the lined area shall be minimized. Any necessary repairs
to the liner shall be patched using the same lining material and following the
recommended procedure of the supplier.
h.Final Inspection and Acceptance. Completed liner installations shall be visually
checked by the System Designer for punctures, rips, tears and seam discontinuities
before placement of any backfill. The installation contractor shall also manually
check all factory and field seams with an appropriate tool. In lieu of or in addition
to manual checking of seams by the installer, either of the following tests may be
performed:
(1) Wet Test. The lined basin shall be flooded to the one (1) foot level with
water after inlets and outlets have been plugged. There shall not be any loss
of water in a twenty four (24) hour test period; or
(2) Air Lance Test. Bonded seams shall be checked using a minimum fifty
(50) pounds per square inch (gauge) air supply directed through a three
sixteenths (3/16) inch (typical) nozzle held not more than two (2) inches
from the seam edge and directed at the seam edge. Riffles indicate
unbonded areas within the seam or other undesirable seam construction.
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CHAPTER 37
GRAVELLESS DISTRIBUTION PRODUCT REQUIREMENTS
37.0 CHAPTER OVERVIEW
This chapter provides specifications for gravelless distribution products that may be used as alternatives
to gravel in dispersal systems or sand filter systems. The criteria apply to new and replacement Systems
and modifications or repairs to existing Systems.
This chapter is organized in the following sections:
Section 37.1: Gravelless Distribution Product Overview
Section 37.2: Types of Gravelless Distribution Products
Section 37.3: Performance Criteria
Section 37.4: Gravelless Dispersal System Design Requirements
Section 37.5: Installation Requirements
37.1 GRAVELLESS DISTRIBUTION PRODUCT OVERVIEW
A. GENERAL
1. Gravelless distribution products may be used in subsurface dispersal systems in lieu of
gravel-filled trenches or beds.
2. Gravelless distribution products include pipe, chamber, gravel-substitute and
geocomposites.
(3) Plastic chamber systems or other gravelless alternatives substituted for drain rock in
dispersal systems or sand filters must be certified by IAPMO, UPC, NSF or other
nationally recognized certification organization.
(4) Trench dimensions and specifications for gravity and pressure-dosed trench dispersal
systems provided in Chapter 27 and Chapter 28 shall apply to trenches with drain rock
alternatives, as applicable.
B. ADVANTAGES
1. Gravelless dispersal systems can be advantageous when gravel is either unavailable,
expensive, or where site conditions make gravel placement difficult or time consuming.
2. The use of gravelless distribution products address some of the concerns associated with
gravel including but not limited to:
a.The detrimental effect of gravel impacting and compressing the infiltrative surface
when dumped into the dispersal system area from the front-end loader of a
backhoe, which may lower the infiltrative capacity of the soil.
b. A reduction in infiltrative capacity if the quality of the gravel washing process is
poor. Silt particles remaining on the surface of the gravel may be washed off when
the dispersal system is placed into use, resulting in a silt layer on the infiltrative
surface and thereby reducing its infiltrative capacity.
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GRAVELLESS DISTRIBUTION PRODUCT REQUIREMENTS
c.The damaging effect that the transportation of gravel across yards can have on
landscaping and the reduced air transport to the infiltrative surface from compacted
soils due to the weight of the material and size of the heavy equipment needed to
transport the gravel from the stock pile to the dispersal system area.
37.2 TYPES OF GRAVELLESS DISTRIBUTION PRODUCTS
A. GRAVELLESS CHAMBERS OVERVIEW
1. Gravelless chambers are plastic molded chambers of various dimensions.
2. The chambers replace the gravel-supported void space with chamber-supported void space.
3. The trench, or bed bottom infiltrative surface is fully exposed; sidewalls are generally
louvered and the top is generally solid.
4. The chambers are connected end-to-end in the bottom of the trench (or placed side-by-side
in a bed) and backfilled with native material or as otherwise directed by the manufacturer
depending upon soil conditions.
5. Solid end plates are installed at the end of each trench or bed chamber line for structural
support and as a barrier to soil backfill.
6. The use of a geotextile barrier between the chamber and the soil backfill varies from
manufacturer to manufacturer and model to model depending upon sidewall louver design
and the type of soil in which the dispersal system is installed.
B. GRAVELLESS PIPE OVERVIEW
1. Gravelless pipes are corrugated slotted plastic pipes covered by a geotextile fabric.
2. Pipe-based gravelless dispersal fields are typically installed in single-pipe or multiple pipe
configurations.
a.Single-pipe gravelless dispersal systems typically consist of large diameter pipe,
typically ten (10) to twelve (12) inch outside diameter, wrapped in a layer of
geotextile material. Serial distribution (drop boxes or crossovers) is more
commonly used than parallel distribution (distribution boxes).
b. Multiple-pipe gravelless dispersal systems typically consist of medium diameter
pipe typically four (4) inch outside diameter, bundled together in groups in various
configurations to accommodate different widths and depths of trenches or beds.
C. GRAVEL SUBSTITUTE OVERVIEW
1. Gravel substitute media may be loose or contained in bundles that are held together with
netting for ease of installation and/or as an element of design.
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GRAVELLESS DISTRIBUTION PRODUCT REQUIREMENTS
2. The particular shape and configuration of the substitute media may provide additional void
space within the trench or bed depending on how the units are placed and the depth and
width of the dispersal system trench or bed.
D. GEOCOMPOSITE OVERVIEW
1. Geocomposites consist of geogrid and geotextile products.
2. Dispersal system void space is created by the assembly of multiple layers of geogrid and
geotextile bundled together in size and shape to facilitate handling and placement.
3. Structural integrity is imparted by the design and material elements of the geocomposites.
4. Geocomposite dispersal systems may incorporate a layer of sand media between the
geogrid/geotextile bundle and the bottom and sides of the dispersal system trench or bed.
5. A geotextile material is placed on top of the geocomposite drain field as a barrier to soil
backfill infiltration.
37.3 PERFORMANCE CRITERIA
A. GENERAL REQUIREMENTS
1. Gravelless distribution technologies are, for the most part, proprietary. As such, other than
the performance criteria identified below there are few specific design requirements for the
manufactured products.
2. Gravelless distribution products shall meet or exceed the following attributes provided by
gravel in gravel filled dispersal systems:
a.Be constructed or manufactured from materials that are nondecaying and
nondeteriorating and do not leach chemicals when exposed to wastewater and the
subsurface soil environment;
b. Provide liquid storage volume at least equal to the storage volume provided within
the thirty (30) percent void space in a twelve (12) inch layer of drain rock in a drain
rock filled dispersal system. This storage volume must be established by the
gravelless distribution products, system design and installation and must be
maintained for the life of the system. This requirement may be met on a lineal-
foot, or on an overall system design basis;
c.Provide suitable effluent distribution to the infiltrative surface at the soil interface;
and
d. Maintain the integrity of the trench or bed. The material used, by its nature and its
manufacturer-prescribed installation procedure, must withstand the physical forces
of the soil sidewalls, soil backfill and the weight of equipment used in the
backfilling.
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GRAVELLESS DISTRIBUTION PRODUCT REQUIREMENTS
37.4 GRAVELLESS DISPERSAL SYSTEM DESIGN REQUIREMENTS
A. GENERAL
1. With the exception of the infiltrative surface area reductions and inspection well
requirements provided below, all other dispersal system design features (e.g., trench
separation, maximum lateral lengths, maximum width of trench or bed, minimum depth of
soil backfill, cover material, setbacks, etc.) must meet the dispersal system requirements
provided in Part 7 of this Manual.
B. INFILTRATIVE SURFACE AREA PER LINEAL FOOT
1. The lineal amount of gravelless distribution product required to provide the total dispersal
system area depends on the amount of bottom area infiltrative surface area per lineal foot
provided by the gravelless distribution product. The maximum infiltrative surface allowed
for dispersal systems using gravelless distribution products shall meet the requirements for
the gravel dispersal systems.
a.Gravelless Chambers. The infiltrative surface area per lineal foot shall be
equivalent to the outside dimensional width of the chamber in contact with the
bottom of the trench or bed. Gravelless chambers with louvered sidewalls may
include a portion of the sidewall area.
b.Single-Pipe Gravelless Distribution Products. The infiltrative surface area per
lineal foot shall be equivalent to the outside diameter of the pipe in contact with
the bottom of the trench and allowable sidewall area for trench distribution system
or the bottom of the bed.
c.Multiple-Pipe Gravelless Distribution Products. The infiltrative surface area
per lineal foot shall be equivalent to the outside dimensional width of the bottom
layer of pipe bundle(s) in contact with the bottom of the trench and allowable
sidewall area for trench distribution systems or the bottom of the bed.
d.Gravel Substitute Distribution Products. The infiltrative surface area per lineal
foot shall be equivalent to the width of bottom of the trench and allowable sidewall
area for trench distribution systems or the width of the bed covered by the gravel
substitute.
e.Geocomposite Distribution Products. The infiltrative surface area per lineal foot
shall be equivalent to the outside dimensions of the bundle(s) in contact with the
bottom of the trench and allowable sidewall area in trench dispersal systems or the
bottom of the bed. If a sand layer is required between the geocomposite and the
infiltrative surface at the bottom of the trench or bed by the manufacturer the
infiltrative area per lineal foot shall be equal to the outside bottom dimensions of
the bundle(s) in contact with the sand layer.
C. ALLOWABE REDUCTIONS IN INFILTRATIVE SURFACE AREA
1. When proposing the use of a gravelless distribution product in a dispersal system the
System Designer may choose to install less than one hundred (100) percent of the total
required infiltrative area for a gravel dispersal system.
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GRAVELLESS DISTRIBUTION PRODUCT REQUIREMENTS
2. Reductions may be considered for the following types of gravelless distribution products:
a.Chambers;
b. Gravel Substitutes; or
c.Geocomposites.
3. Dispersal system size reductions for gravelless distribution products may not be combined
with drainfield size reductions based on effluent quality.
4. Dispersal system size reductions of up to thirty (30) percent are allowed. The reserve areas
shall be sized to at least one hundred (100) percent of the required gravel dispersal system
size.
5. When a gravelless distribution product is used in a treatment component, such as an
intermittent sand filter, and media is used to meet a treatment level, no size reduction can
be taken for the treatment component.
6. The System Designer should evaluate on a case by case basis the appropriateness of using
manufacturer literature suggested allowances for dispersal system area reductions based on
soil and site characteristics.
7. System design, layout and installation using gravelless distribution product reductions
must be done in a manner easily facilitating the installation of additional gravelless
dispersal system area if future conditions necessitate such action.
8. For Systems using pressure distribution, if additional dispersal system area is needed in the
future, elements of the System (such as the pump or controls) may need to be modified in
order to meet the hydraulic performance requirements of pressure distribution throughout
the expanded dispersal system.
D. INSPECTION WELLS
1. The installation of inspection wells in gravelless dispersal fields is for the purpose of
monitoring system status and aiding in problem analysis.
2. To be effective inspection wells must be installed in a representative location on each
dispersal system line.
3. Some lines may require additional inspection wells to achieve observations representative
of the entire dispersal system.
4. Inspection wells must provide visual access to the trench-bottom in gravelless dispersal
systems as follows:
a.Single-Pipe: to the interior of the pipe;
b. Multiple-Pipe: to the infiltrative surface;
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GRAVELLESS DISTRIBUTION PRODUCT REQUIREMENTS
c.Chamber: to the interior of the chamber;
d. Gravel Substitute: to the infiltrative surface; or
e.Geocomposite: to the infiltrative surface.
37.5 INSTALLATION REQUIREMENTS
A. GENERAL
1. Gravelless distribution products must be installed according to the manufacturer's
instructions, in a manner that is consistent with the standards in this Manual.
2. If the manufacturer's instructions and the standards in the Manual are in conflict, the matter
must be discussed with, and decided by the Department.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
PART 9
NON-DISCHARGING TOILET UNIT
REQUIREMENTS
CHAPTER TITLE
CHAPTER 38 VAULT TOILET REQUIREMENTS
CHAPTER 39 PORTABLE TOILET REQUIREMENTS
CHAPTER 40 WATERLESS TOILET REQUIREMENTS
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CHAPTER 38
VAULT TOILET REQUIREMENTS
38.0 CHAPTER OVERVIEW
This chapter provides guidelines for vault toilets. Vault toilets are allowed under limited circumstances
and are subject to the requirements of an operating permit.
This chapter is organized in the following sections:
Section 38.1: Vault Toilet Overview
Section 38.2: Vault Toilet Requirements
38.1 VAULT TOILET OVERVIEW
A. DESCRIPTION
1. A vault toilet is a non-discharging toilet unit and consists of a structure with a self-
contained, watertight subsurface vault used to collect and store human waste and drainage
from its hand washing sink prior to it being pumped and removed from the property by a
Septage Pumper.
38.2 VAULT TOILET REQUIREMENTS
A. SITING CRITERIA
1. Vault toilets shall only serve non-residential facilities and non-commercial facilities in areas
where it is the preferable method of wastewater disposal for the protection of public health
and environmental resources due to such factors as remote location, limited water supply
and site constraints for an OWTS.
2. Limited use application examples include but are not limited to primitive type picnic
grounds, campsites, camps and remote recreation areas.
3. Vault toilets shall not be used for seasonal dwellings, non-residential facilities or single
family dwellings.
4. Vault toilets shall meet the same horizontal setbacks requirements for tanks as provided
in Table 5-7.
B. GENERAL REQUIREMENTS
1. The vault shall be watertight and tested for water tightness at the time of installation using
the methods in Chapter 42 for tank water tightness.
2. All handwashing within a vault shelter must be plumbed to the vault. No other water-carried
wastewater may be piped to or placed in vault toilets.
3. The capacity of the vaults shall be adequately sized to accommodate the proposed usage
and frequency of pumping.
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VAULT TOILET REQUIREMENTS
4.Vault toilets shall be designed and installed in accordance with applicable building codes.
5. Vaults toilets must be installed in accordance with the manufacturer’s recommendations.
C. PERMIT REQUIREMENTS
1. Vault toilets require an installation and operating permit.
2.Vault toilets shall be installed and maintained in accordance with the manufacturer’s
recommendations.
3. Vault toilets shall be maintained to prevent health hazards and contamination of soil, surface
water and groundwater.
4. Wastewater shall be regularly pumped from the vault by a Septage Pumper as necessary to
prevent overflow. The vault shall not be allowed to fill with waste above the manufacturer
recommended level.
5. Vault toilet structures shall display the business name and phone number of the owner and
the Septage Pumper that is responsible for servicing the vault toilet.
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CHAPTER 39
PORTABLE TOILET REQUIREMENTS
39.0 CHAPTER OVERVIEW
This chapter provides guidelines for portable toilets. Portable toilets are allowed under limited
circumstances and are subject to the requirements of a special permit.
This chapter is organized in the following sections:
Section 39.1: Portable Toilet Overview
Section 39.2: Portable Toilet Requirements
39.1 PORTABLE TOILET OVERVIEW
A. DESCRIPTION
1. A portable toilet is any self-contained chemical toilet facility that is housed within a
portable toilet shelter that collects human waste and any drainage from its hand washing
sink.
39.2 PORTABLE TOILET REQUIREMENTS
A. SITING CRITERIA
1. Portable toilets may be allowed for temporary or limited use areas, such as construction
sites (for use by on site employees), mobile or temporary agricultural uses, temporary
campsites and special events.
2. Portable toilets must meet the same horizontal setback requirements for tanks provided in
Table 5-7.
3. When associated with a land use permit issued by a local planning department, a copy of
the land use permit must be provided to the Department with a site plan which indicates the
placement of the portable toilets relative to required setbacks.
4. Portable toilets shall not be allowed for seasonal dwellings, non-residential facilities or
single-family dwellings.
B. GENERAL REQUIREMENTS
1. All handwashing within a portable toilet shelter must be plumbed to the waste detention
chamber. No other water-carried wastewater may be piped to or placed in portable toilets.
2. Documentation shall be provided to the Department on the minimum number of portable
toilets required determined based on the site use and/or estimated attendees and duration of
events and relevant published industry guidance such as the Portable Sanitation Association
International Special Event Extended Chart Breakdown.
3. Biocides and oxidants must be added to waste detention chambers at rates and intervals
recommended by the manufacturer.
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PORTABLE TOILET REQUIREMENTS
C. PERMIT REQUIREMENTS
1. A special permit is required for the use of portable toilets. An exception to this requirement
may be allowed for temporary use (less than seven [7] days) of portable toilets and in
agricultural field activities.
2. Portable toilets shall be installed and maintained in accordance with the manufacturer’s
recommendations.
3. Portable toilet shelters shall display the business name and phone number of the owner and
the Septage Pumper that is responsible for servicing the portable toilet.
3. Wastewater shall be regularly pumped from the portable toilet by a Septage Pumper as
necessary to prevent overflow. The portable toilet shall not be allowed to fill with waste
above the manufacturer recommended level.
4. Portable toilets shall be maintained to prevent health hazards and contamination of soil,
surface water and groundwater.
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CHAPTER 40
WATERLESS TOILET REQUIREMENTS
40.0 CHAPTER OVERVIEW
This chapter provides guidelines for waterless toilets. Waterless toilets are allowed under limited
circumstances and are subject to the requirements of a special permit.
This chapter is organized in the following sections:
Section 40.1: Waterless Toilet Overview
Section 40.2: Waterless Toilet Requirements
40.1 WATERLESS TOILET OVERVIEW
A. DESCRIPTION
1. A waterless toilet includes a composting toilet, an incinerating toilet or similar device for
the holding and processing of wastewater from a toilet.
40.2 WATERLESS TOILET REQUIREMENTS
A. SITING CRITERIA
1. Waterless toilets are only allowed in limited instances for example outbuildings not used as
a residence or sleeping quarter or as part of a corrective action for repair or replacement of
a failed OWTS on severely constrained sites.
2. Waterless toilets must meet each the following conditions:
a.Five (5) acre minimum parcel size;
b. Setbacks from the unit and the burial area (if applicable) must meet the minimum
requirements for OWTS dispersals system setbacks provided in Table 5-7 with the
additional requirement that setbacks from the all property lines must be at least one
hundred (100) feet;
c.The parcel is not located in a designated Area of Concern as identified in Chapter
10; and
d. The waterless toilet does not create a public nuisance.
3. A Qualified Professional must conduct a site evaluation in the area of the proposed burial
area of the waterless toilet waste. The site evaluation shall verify a vertical separation of
at least five (5) feet to groundwater or other limiting layer from the bottom of the burial area.
B. GENERAL REQUIREMENTS
1. Waterless toilets shall be installed and maintained in accordance with the manufacturer’s
recommendations.
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WATERLESS TOILET REQUIREMENTS
2. The waterless toilet shall be certified and currently listed by the NSF under NSF/ANSI
Standard 41.
3.The model of the waterless toilet shall be appropriate for the number of users and intended
demand.
4. The Applicant or designee shall submit the following documentation to the Department for
approval:
a.Site map demonstrating compliance with the siting requirements;
b. Waterless toilet manufacturer specification sheet showing that the toilet is
appropriately sized for the planned use; and
c.An OM&M manual for the waterless toilet and, if applicable, the burial area. The
OM&M Manual must include the following:
(1)Manufacturer’s name and model number;
(2)Manufacturer’s NSF listing and certification;
(3)Manufacturer’s recommended operational capacity;
(4)Manufacturer’s operation and maintenance guidance;
(5) Minimum burial depth;
(6) The location of the burial area;
(7) Schedule and timing for burial;
(8) Method of handling and site for disposal of the waste product of the
waterless toilet;
(9) Manufacturer contact information in case of the need of repair or
replacement;
(10) Trouble-shooting information; and
(11) Other items as requested by the Department.
C. PERMIT REQUIREMENTS
1. A special permit is required for use of a waterless toilet. The owner must renew the special
permit on an annual basis.
2.No material shall be placed in a waterless toilet other than the material for which it has
been designed.
3. The owner must maintain the waterless toilet in accordance with the OM&M manual and
comply with all of the special permit conditions.
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WATERLESS TOILET REQUIREMENTS
4.A person selling a parcel on which there is a special permit for a waterless toilet must notify
the Department of the transfer and disclose to the prospective purchaser the presence of the
waterless toilet and the requirements to maintain a special permit. A special permit for a
waterless toilet is issued to the owner of the property and any change in ownership requires
a new permit application be filed with the Department and a new permit be issued, which is
done at the discretion of the Department.
5. The waste product of the waterless toilet shall only be handled and disposed of after
the digestion process is complete as specified in the manufacturer’s instructions.
6. The waste product of the waterless toilet digestion must be transported and/or disposed of
in a manner that does not create a public nuisance and is in accordance with the
requirements of the OM&M manual.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
PART 10
SYSTEM DESIGN APPROVAL,
INSTALLATION/REMOVAL & OPERATING
REQUIREMENTS
CHAPTER TITLE
CHAPTER 41 SYSTEM DESIGN APPROVAL REQUIREMENTS
CHAPTER 42 SYSTEM INSTALLATION & REMOVAL
REQUIREMENTS
CHAPTER 43 SYSTEM OM&M REQUIREMENTS
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CHAPTER 41
SYSTEM DESIGN APPROVAL REQUIREMENTS
41.0 CHAPTER OVERVIEW
This chapter provides the submittal requirements for Department approval of Onsite Wastewater System
designs and issuance of installation or repair/modification permits.
This chapter is organized in the following sections:
Section 41.1: Design Plan Requirements
Section 41.2: Basis of Design Report Requirements
Section 41.3: OM&M Manual Requirements
41.1 DESIGN PLAN REQUIREMENTS
A. GENERAL REQUIREMENTS
1. The Onsite Wastewater System design plans must include sheets with scaled plan views,
profile views, cross sections, and details sufficient to allow:
a.Review by Department staff for compliance with the requirements of the
Ordinance and this Manual.
b. Onsite Wastewater System installation, operation, monitoring and maintenance.
B. SPECIFIC REQUIREMENTS
1. The design plans must be prepared in accordance with the following requirements.
a.Sheet Size. Plans must be clearly and legibly drawn to scale on ANSI “D” sized
sheets measuring twenty-two (22) inches by thirty-four (34) inches. Other sheet
sizes may be allowed for consistency with building permit plan sets.
b.Title Block. The title block shall include the following information:
(1) Assessor’s parcel number and address of the parcel;
(2) Name, address, telephone number, signature and wet stamp of the System
Designer;
(3) Name, address, telephone number and signature of the individual who
prepared the site plan and topographic base map and the date of the survey,
if different from the System Designer;
(4) Date of design plans and subsequent revisions on each plan sheet; and
(5) Name, address, and telephone number of the property owner.
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SYSTEM DESIGN APPROVAL REQUIREMENTS
c.Scale. The scale of the plans must not be smaller than one (1) inch equals twenty (20)
feet and shall correspond to a scale provided on an engineer’s scale to facilitate
Department plan review. The design plans shall include a statement of the nominal
scale as a ratio or fraction and provide a bar scale to represent the nominal scale.
d.North Arrow. The plans shall include a north arrow.
2. The plans must present at a minimum the following information, as applicable:
a.Site Plan. The plans shall utilize the site plan prepared in accordance with the
requirements of Chapter 6 of this Manual as the base map. If the site plan is
prepared by a Qualified Professional other than the System Designer a copy of the
site plan and topographic base map, signed and stamped by the individual who
prepared the plan, must be provided to the Department with the design documents.
b.Treatment Train Components. The plans shall show:
(1) The layout and location of all existing and proposed System components
including but not limited to OWTS dispersal system reserve areas; tanks,
supplemental treatment systems, dispersal systems, flow divider assemblies,
valves, distribution boxes, meters and gauges, alarms and control panels;
and
(2) A treatment train schematic.
c.Tanks Details. The plans shall provide plan views, cross-sections and details of the
tanks in the treatment showing tank configurations and depths, working volumes,
emergency storage volumes, nominal tank sizing charts and slope of finished ground
surface in the vicinity of tank(s) to demonstrate adequate grading to prevent storm
water infiltration.
d.Dispersal System Details. The plans shall provide plan, profile and cross sections
views and details of the dispersal system area that show the ground slope, dispersal
line dimensions, material specifications including gravelless distribution product
information if applicable (e.g., trench lengths, number of chambers, length of
chambers, length of endcaps, total length of chamber system, etc.) and any benching
necessary to install the system.
e.Pump System Details. The plans shall show pump system components, float
settings, dosing calculations (i.e., volumes, pumping rate and runtime, frequency,
drawdown per dose cycle, etc.) and control panel programming and timer functions.
f.Pipe Alignments. The plans shall show:
a.Building sewer and lateral alignments, gradient designations and direction
of flow for piping from all structures connected to the System and between
the tank(s) and the dispersal system; and
b.Cross sections of pipe trenches with the dimensions of the trench, depth of
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SYSTEM DESIGN APPROVAL REQUIREMENTS
pipe burial, backfill specifications and vertical distances between
wastewater piping and other site utilities.
g.Performance Monitoring Components. The plans shall provide plan views and
cross section details showing the location, design and depths of OWTS performance
monitoring and inspection wells and groundwater monitoring wells.
h.Material Specifications. The plans shall provide specifications for all construction
materials.
i. Manufacturer Specifications. The plans shall specify the make, model and
manufacturer of all System components.
j. Horizontal Setback Distances. The plans shall provide horizontal dimensions
from System components to pertinent features to facilitate determination of
compliance with horizontal setback requirements in Table 5-7.
k.Vertical Separation to Groundwater Distances and Effective Soil Depth. The
plans shall provide cross-sections showing the vertical separation to groundwater
and effective soil depth beneath the bottom of OWTS dispersal systems.
l. Slope Designations. The plans shall show slope designations in the vicinity of
tanks and dispersal systems (percent and arrows for direction).
m.System Sizing Calculations. The plans shall show the design wastewater flow and
strength characteristics, dispersal sizing reduction allowances (e.g., low flow
fixtures, gravelless chambers, etc.), wastewater application rates, effective
infiltration area, flow equalization calculations, tank and dispersal system sizing,
etc.
n.System Hydraulic Calculations. The plans shall show:
(1) Spot elevation data to confirm the hydraulic design of the System;
(2) Elevations of building sewers as they exit building(s) or structure(s)
connected to the System to demonstrate adequate fall to the septic tank or
other appurtenances;
(3) Tank outlet invert elevations;
(4) Pump pickup elevations or siphon invert elevations;
(5) Friction loss data including pipe lengths/diameters/material, number and
type of pipe fittings and friction coefficients and head loss data for pipes,
fittings, valves, distribution components, orifices etc.;
(6) Total dynamic head;
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SYSTEM DESIGN APPROVAL REQUIREMENTS
(7) Pump curves with system operating points; and
(8) Orifice dimensions and spacing.
o.Electrical Wiring Diagrams. The plans shall show electrical wiring diagrams
specific to the project.
p.Site Modification Measures. The plans shall provide plan, profile and cross
section views showing lateral and vertical dimensions and details of site
modification measures including but not limited to surface drainage structures and
curtain drains.
q.Erosion Control Plans. The plans shall include an erosion control plan,
incorporating measures consistent with guidelines and requirements contained in
Chapter 15.36 (grading, erosion and sediment control) of the Alameda County
General Ordinance.
r.Geotechnical Report Recommendations. The plans must incorporate applicable
recommendations contained in associated geotechnical reports regarding the
avoidance or mitigation of slope stability concerns, including, as applicable,
recommended horizontal setback distance(s) from cut banks, embankments, steep
slopes or any identified unstable land masses within the horizontal setback
requirements for dispersal systems and tanks.
s.System Protection Measures. The plans shall include guidelines and notes for use
by the owner and Contractors during:
(1) Installation of the System;
(2) Site development activities. Measures shall be identified to protect
existing Systems or proposed System areas during site demolition and
development activities such as installation of construction fencing,
stockpiling prohibitions, etc.; and/or
(3) Prohibited activities on the dispersal system.
t. System Installation Notes. The plans shall include a list of critical control point
inspections and requisite testing.
u.Other Pertinent Information. The plans shall include other pertinent information
and features that could affect System installation and performance.
v.List of Non-Compliance. The plans shall include a list of items that do not comply
with the requirements of the Ordinance and this Manual and that will require
granting of a variance.
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41.2 BASIS OF DESIGN REPORT REQUIREMENTS
A. REQUISITE ELEMENTS
1. System design plans shall be accompanied by a design report documenting the basis of the
System design. The basis of design report shall include but not be limited to the following:
a.Legible field data sheets documenting the results of the soil profile, percolation
tests, wet weather testing, etc.;
b. Manufacturer specification sheets, installation instructions and warranty
information for System components;
c.Hydraulic calculation sheets;
d. Supporting calculations for storm water diversion structures; and
e.Other pertinent data required to support the System design.
2. Reports documenting geotechnical evaluations, cumulative impact assessments,
hydrogeological studies, curtain drain installation or other evaluations must be appended
to the basis of design report.
41.3 OM&M MANUAL REQUIREMENTS
A. REQUISITE ELEMENTS
1.An OM&M manual shall be submitted with the System design plans and the basis of design
report.
2.The content of the OM&M manual will differ depending on the type and complexity of the
System.
3. The OM&M manual shall include requisite maintenance, monitoring and reporting
activities for the System, including the following elements as applicable:
a.Diagrams of the System and list of components;
b. Manufacturer name and model number for key equipment and proprietary system
components;
c.Explanation of general System function, operational expectations, owner
responsibility, etc.;
d. Specifications of all electrical and mechanical components installed;
e.Names and telephone numbers of the System Designer, installation Contractor, the
Department, component manufacturer and/or the management entity to be
contacted in the event of a failure;
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f. Half sized copy (11 inch x 17 inch) of the design plans, updated with as-built
plans as applicable at the conclusion of System installation (any changes must be
approved by the Department);
g.Routine maintenance schedule; and
h. Information on troubleshooting common operational problems that might occur
with the specific System. This information should be as detailed and complete as
needed to assist the System owner to make accurate decisions about when and how
to attempt corrections of operational problems and when to call for professional
assistance.
4. The OM&M manual must be supplemented or updated by a System Designer as
appropriate including after repairs or modifications to the System.
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42.0 CHAPTER OVERVIEW
This chapter provides the requirements for System Designer and Department inspections and approval of
System installation, repairs, modifications and tank abandonment.
This chapter is organized in the following sections:
Section 42.1: Department Inspection Requirements
Section 42.2: Tank Destruction/Removal Requirements
Section 42.3: Tank Installation Requirements
Section 42.4: System Installation Requirements
Section 42.5: Final System Installation Approval Requirements
42.1 DEPARTMENT INSPECTION REQUIREMENTS
A. GENERAL
1. Department inspections of System installation and abandonment are required to ensure
conformance with the standards in this Manual. The System must be ready for the type
of inspection requested or specified in each step in the installation process.
2. If more than one site visit is required to observe a requisite inspection, a fee may be charged
for each additional visit.
3.No portion of the System shall be covered without prior inspection and approval by the
Department unless specific written authorization has been provided.
4. Written notice must be given to the Department and an inspection requested at least forty-
eight (48) hours prior to reaching required System installation or tank destruction/removal
destruction inspection points. Additional time may be required to schedule the presence of
a Department representative.
4. Notification and the request must include the Applicant’s name, assessor’s parcel number,
street address and installation or repair/modification permit number. Failure to provide
sufficient notice may result in delay of System installation or tank removal/destruction
and/or duplication of work.
5. The Department may authorize System installation and/or tank destruction/removal to
proceed without a Department representative, however, such authorization must be in
writing.
42.2 TANK DESTRUCTION/REMOVAL REQUIREMENTS
A. PERMIT REQUIRED
1.Destruction or removal of a tank requires an abandonment permit from the Department.
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2.Tanks shall be destroyed or removed under an abandonment permit from the Department
within thirty (30) days from the date of one of the following circumstances:
a.When a System is permanently disconnected from the building or structure served
and has not been approved for subsequent use by another building or structure;
b.When the building sewer has been disconnected from the System and connected to
a sanitary sewer that is part of a municipal treatment works; and/or
c.When the tank has been determined to be failing and cannot be repaired.
3.Abandoned tanks that have not been properly destroyed or removed can pose hazards and
create undesirable situations.
a.Tanks that have collapsed pose safety hazards for people, pets and other animals.
b.Tanks that are not properly destroyed may fill with water over time and cause an
entrapment or drowning hazard.
4.Improperly destroyed tanks may not be able to support the weight of vehicular traffic,
building foundations or other structures built on the property.
B. TANK DESTRUCTION/REMOVAL PROCEDURE
1.Tank destruction/removal shall be done under the responsible charge of a Contractor.
2.The procedures for the tank destruction or removal shall be as follows:
a.The tank shall be pumped by a Septage Pumper and all contents removed and
disposed of at a permitted facility;
b.All equipment (e.g., pumps, filters, vaults, etc.) shall be removed from the tank;
c.Electrical connections shall be disconnected;
d.For tank destruction, several holes shall be made in the tank bottom and the tank lid
shall be completely broken and placed in the tank pit;
e.For tank removals, the tank lid and tank shall be completely removed from the
excavation;
f.Hydrated lime or chlorine shall be spread over the tank or excavation area;
g.After inspection by the Department, the tank or void shall be completely filled with
soil, sand, gravel, concrete or other suitable material and then completely covered
with soil or material similar to that at the surface in the immediate surrounding;
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h.When the tank is to be destroyed or removed and subsequently covered with a
foundation or other structure, a Qualified Professional as allowed by their
registration and license shall determine the method of destruction and backfill;
i. Tank pieces removed from the excavation shall be taken to a permitted sanitary
landfill or appropriate facility for recycling. A copy of the receipt shall be submitted
to the Department; and
j. The building or structure wastewater plumbing system shall be permanently capped
unless the building or structure is connected to an approved Onsite Wastewater
System or a public sewer system. If the building or structure is not connected to an
approved Onsite Wastewater System or a public sewer system all plumbing fixtures
and all water inlets shall be removed from the structure.
42.3 TANK INSTALLATION REQUIREMENTS
A. PERMIT REQUIRED
1. Tank installation requires an installation permit from the Department.
2. Tank installation may be done in conjunction with replacement of a failed tank, System
upgrades or a new System installation.
B. INSTALLATION INSPECTIONS AND FUNCTIONAL TESTING REQUIREMENTS
1.Tank installation inspections and functional testing requirements are dependent on the type
and complexity of the tank and associated pump and treatment systems.
2.Tank watertightness tests shall be conducted under the oversight of the System Designer
in accordance with the procedure below. A watertight test certification form must be
submitted by the System Designer prior to the Department granting final approval of the
tank installation.
C. WATERTIGHTNESS TEST PROCEDURE
1.New Tanks. Watertight testing for new tanks shall be done in accordance with the
following procedures:
a.Tanks, inlet and outlet connections, risers and riser covers shall be completely
watertight.
b.The watertightness test shall be performed after tank installation is complete
including connecting inlet and outlet piping (with caps) and installing risers (if
applicable);.
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c.Whenever possible, risers shall be installed as one continuous piece.
d. Backfill may or may not be in place depending on whether the backfill is integral
to the structural design of the tank.
e.The tank shall be filled with water to two (2) inches above the highest connecting
inlet or outlet piping or the tank and riser connection (if installed). If multiple riser
connections or concrete grade rings are used, water shall be added to two (2) inches
above the highest riser connection.
f.The level of the water in the tank or riser shall be marked and after a predetermined
“test time” applicable to the material or assembly, the water level in the tank (or
riser) shall be checked and a visual inspection shall be made on the outside of the
tank for leakage (if possible).
g.If no visual evidence of leaking and no measurable loss of water is observed the
tank shall be considered watertight.
(1) Fiberglass or Plastic Tanks. If there is no measurable loss of water in the
tank or one (1) hour and no visual signs of leakage, the tank is considered
watertight.
(2) Concrete Tanks. Concrete tanks shall be left for twenty-four (24) hours
after filling the tank to allow for a period of time for natural absorption
into the material prior to beginning the watertightness test. After twenty-
four (24) hours the tank shall be refilled to two (2) inches above the
piping or riser connection. If there is no measurable loss after one (1) hour
and no visual signs of leakage, the tank is considered watertight.
2.Existing Tanks. If watertightness testing of existing tanks is required due to System
modifications or repairs, the tank shall be pumped by a Septage Pumper to remove its
contents prior to conducting the test (as described above).
3.Tank Repairs. Repairs can be made to tanks failing the watertightness test provided the
structural integrity has not been compromised and the tank passes the watertightness test
after the repairs have been made. If the bedding under the tank is uneven or has rocks
protruding, the tank may crack causing failure of the test.
42.4 SYSTEM INSTALLATION REQUIREMENTS
A. PERMIT REQUIRED
1. System installation requires an installation permit from the Department.
2.Protection of Utilities. The Contractor shall be responsible for the prevention of damage
to any public or private utilities or services.
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3.Protection of Adjacent Property. The Contractor shall be responsible for the prevention
of damage to adjacent property. No person shall excavate on land sufficiently close to the
property line to endanger any adjoining public roadway, right-of-way, private or public
property, without first supporting and protecting such property from damage that might
result.
4.Construction Site Control. The Contractor shall implement seasonally appropriate best
management practices for the control of erosion, the control of storm water run-on and run-
off, the control of sediment, good site management, and the control of non-storm water
discharges from the site.
B. REQUIRED INSTALLATION INSPECTIONS
1. The type and number of System installation inspections and functional testing is dependent
on the type and complexity of the System design.
2. System installation inspections are required to be performed by the System Designer.
3. The Department may be at each inspection, or may respond to an inspection request by
approving that the System Designer may proceed with the inspection and notify the
Department of the results. The Department may combine one or more required inspections
into a single field visit if possible.
4. Inspection cannot occur until the Department has confirmed that it will be attending or that
the inspection may proceed. The Department may require specific documentation be
provided (such as photos) by the System Designer if the Department allows an independent
inspection.
5. System installation inspections shall include, but not be limited to the following, as
applicable depending on System type:
a.Preconstruction Meeting. At the time of the preconstruction meeting the Contractor
shall have the ground in the System area marked with the layout of the System
components, including but not limited to tanks, dispersal systems, pipes and
transport lines. The footprints of all proposed buildings, structures or utilities
which could affect the System and reserve area must also be marked. Minimum
horizontal setbacks must be confirmed during the preconstruction meeting.
b.Open Excavation and Material Inspection. At the time of open excavation and
material inspection all the following shall be completed:
(1) All excavations necessary for System installation are complete at designed
depth, width and length;
(2) Bottom of the dispersal trenches/beds are level and all smeared or
compacted surfaces have been corrected;
(3) Clearing and ripping/plowing of the soil basal area of at-grade, mound,
raised sand bed filter dispersal systems is complete; and
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(4) Drain rock, pea gravel and sand is stockpiled onsite and available for
inspection.
c.System Installation Inspection(s). At the time of System installation inspections
all the following shall be completed:
(1) Dispersal trenches/beds filled with drain rock, pea gravel or sand to the
specified level (or gravelless distribution products installed);
(2) Dispersal system piping installed level in trenches/beds with ends capped
and trench inspection wells and cleanout sweeps installed;
(3) All other pipe installed with proper gradient and sealing to adjacent
components;
(4) Distribution boxes/assemblies and covers installed level on undisturbed
soil and at the proper elevation;
(5) All tanks in the treatment train set level in place on undisturbed soil, risers
installed and sealing to tank complete;
(6) All components of the pressure distribution system installed; and
(7) Containment structure/liner and/or underdrain system installed, as
applicable (i.e., sand filter systems and raised sand bed dispersal systems).
d.Functional Testing. At the time of functional testing inspection all test preparation
activities must be complete. The Department may elect to be present during all or
part of the functional testing.
(1) Water Tightness Tests. Watertightness testing of tanks and System
components.
(a) System components required to be filled with water to the flow line
prior to requesting inspection. All seams or joints shall be left
exposed and the System components and tanks shall remain
watertight.
(b) Watertightness testing of tanks shall be done in accordance with
the test procedures in Section 42.3.
(2) Flow & Hydraulic Squirt Tests. Flow tests and hydraulic squirt tests (for
pressure distribution systems) of the System. All lines and components
shall be watertight and distribution to dispersal system according to the
approved System design.
(3) Control Panel Setting. Functional testing and setting of all System
control devices and alarms.
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(4) Treatment System Testing. Testing of proprietary treatment units in
accordance with manufacturer requirements.
(5) Other System Testing. Other System testing if required as a permit
condition by the Department complete.
e.Final Inspection. Final inspection to verify that all construction elements are in
conformance with the approved plans and specifications, functional testing is
complete, tank venting systems, lids, covers and locking mechanisms are
installed, inspection wells and OWTS performance monitoring wells are installed
and backfill and erosion control has been completed.
C. PERMITS REVISIONS OR CHANGES
1. If revisions or changes are proposed to the approved System design during construction
(e.g., different type of system, new system location, etc.), they must be approved by the
Department prior to performing the work.
2. Any changes in the approved system design are subject to the following:
a.Minor Revisions. A minor change in tank location, a change in distribution box
location or line location adjustments for contour or obstructions within the
approved dispersal system area shall be considered minor revisions. Minor
revisions shall be drawn clearly and to-scale on the original approved system
design plans and signed and stamped by the System Designer and Contractor as an
"as-built" of the system.
b.Major revisions. Changes in the design or location of major system components
shall be considered major revisions. A revised system design shall be prepared,
showing these major revisions, and shall be re-approved by the Department prior
to any work being performed.
3.Requirements of Submitting As-Built Plans. If changes have been made to the approved
System design, at completion of construction and prior to receiving final approval by the
Department, the Contractor and System Designer shall provide to the Department and
System owner, a set of as-built drawings of the completed System installation.
4. All revisions are subject to an additional review fee and new permit conditions may be
required.
42.5 FINAL SYSTEM INSTALLATION APPROVAL
1.General. Final System installation approval is issued by the Department in the form of a
letter that indicates the System was installed in compliance with the requirements of this
Manual and relevant County codes, and all installation permit conditions of approval have
been fulfilled, including issuance of any required operating permit.
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2. Prior to the issuance of the final installation approval by the Department the following must
occur:
a.The System Designer and installation Contractor have submitted written
certification that the System has been installed in accordance with the approved
System design and permit conditions and is operating in conformance with the
design specifications.
b. For Systems with an operating permit a copy of an executed agreement for
maintenances services with a Service Provider or System Designer.
c.The System Designer has provided the owner with an OM&M manual that outlines
the operation of the System, including the owner’s responsibilities for maintaining
the System.
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43.0 CHAPTER OVERVIEW
This chapter provides an overview of operation, maintenance, monitoring and reporting requirements for
Onsite Wastewater Systems.
This chapter is organized in the following sections:
Section 43.1: General System Performance Requirements
Section 43.2: System Inspection and Monitoring Requirements
Section 43.3: System Operating Permit Requirements
Section 43.4: System Reporting Requirements
43.1 GENERAL SYSTEM PERFORMANCE REQUIREMENTS
A. ALL SYSTEMS
1. All Systems shall be operated in compliance with applicable performance requirements
particular to the type of system, the facility served and the site conditions.
2.All Systems shall function in such a manner as to:
a.Be sanitary and not create a health hazard or nuisance;
b. Prevent backup or release of wastewater into the building and structure(s) being
served by the System; and
c.Prevent release of wastewater onto the ground surface or into surface water, or in
such a manner that groundwater may be adversely impacted.
3. All Systems and the individual components shall meet the performance requirements for the
specific site conditions and applications for which they are approved.
B. STANDARD OWTS
1. All components of the OWTS shall be functional and in proper working order.
2. All septic tanks shall be:
a.Structurally sound;
b. Watertight;
c.Provide clarified effluent;
d. Have adequate space available for sludge and scum storage;
e.Operate in such a manner as to not create odors or vector attraction;
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f.Be properly vented; and
g.Have a functional baffle(s).
3. Dispersal systems shall:
a.Have adequate dispersal capacity for the structures and/or uses served;
b. Not result in seepage or saturated soil conditions within twelve (12) inches of the
ground surface in or adjacent to the dispersal system;
c.Be free from soil erosion or instability; and
d. Not have effluent continuously pond at a level above the invert (bottom) of the
perforated distribution pipe in the dispersal trench or serial distribution overflow
line, as applicable.
C. ADVANCED OWTS
1.In addition to the requirements in A and B above, advanced OWTS shall also comply
with the requirements listed below, as applicable.
2.Pressure Distribution Systems. Pressure distribution systems shall comply with the
following:
a.Pump tanks, risers and lids shall be structurally sound, watertight and store
wastewater effluent in such a manner as to not create odors or vector attraction.
b. Pumps, floats, alarms and associated controls shall be in good condition and operate
in accordance with design specifications.
c.Dispersal systems and components shall:
(1) Be operable and in good condition;
(2) Maintain uniform distribution of effluent throughout the dispersal system;
(3) Not result in continuously ponded effluent in the dispersal trench (or bed)
to a level above the invert of the distribution pipe; and
(4) In the case of pressure-dosed sand trenches, not result in continuously ponded
effluent above the sand interface.
3.Subsurface Drip Dispersal Systems. Subsurface drip dispersal systems and components
shall:
a.Not result in seepage or saturated soil conditions above the depth of the dripline
within or anywhere along the perimeter of the dripfield;
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b. Be free from erosion, slumping or any other soil disturbance that threatens to expose or
cause damage to drip dispersal tubing or appurtenances;
c.Conform to applicable requirements for pressure distribution in item C.2 above; and
d. Be operated and maintained in accordance with manufacturer recommendations.
4.Mound, At-Grade and Raised Sand Bed Dispersal Systems. Mound, at-grade and raised
sand filter bed dispersal systems shall:
a.Not result in seepage or saturated soil conditions within twelve (12) inches of the
ground surface anywhere along the perimeter toe or edge of the system;
b. Be free from erosion, slumping or damage to the soil cover;
c.Not result in continuously ponded effluent within the gravel distribution bed or in
the sand fill (for mounds and raised sand bed systems); and
d. Conform to applicable requirements for pressure distribution in item C.2 above.
5.Proprietary Treatment Units. Proprietary treatment units shall comply with the
following:
a.The unit and its components shall be structurally sound, free from defects, be
watertight, and not create odor or vector attraction nuisance; and
b. The unit shall be operated in accordance with the approved manufacturer and
certification/listing organization standards.
6.Sand Filter Systems. Sand filter systems shall:
a.Be operated to maintain uniform effluent distribution throughout the sand filter
bed;
b. Not result in continuously ponded effluent on the distribution bed infiltrative
surface;
c.Be operated and maintained to prevent channeling of flow, erosion of the sand
media or other conditions that allow short-circuiting of effluent through the
OWTS;
d. Not result in leakage of effluent through the sand filter liner or supporting
structure; and
e.Conform to applicable requirements for pressure distribution.
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D. OWCU
1. All components of an OWCU shall be functional and in proper working order in compliance
with the requirements listed in Chapter 21 (holding tanks) and Part 9 (non-discharging toilet
units) of this Manual.
43.2 SYSTEM INSPECTION AND MONITORING REQUIREMENTS
A. INSPECTION FREQUENCY REQUIREMENTS
1. Systems shall meet the inspection frequencies and maintenance checks as specified in
Table 43-1, or as otherwise required by the operating permit.
a.Nothing contained in this provision shall prevent the Department from requiring
more frequent inspections and maintenance checks for Systems with operating
permits as deemed necessary to ensure proper System performance or to protect
water quality or public health.
b. Complexity and frequency of inspection will be related to the complexity and
maintenance requirements of the System components, recommendations of the
manufacturer and industry standards.
2. System components shall be inspected and monitored at a minimum in accordance with the
criteria listed in Table 43-2 and Table 43-3, as applicable. The monitoring requirements
will vary depending on the specific System.
B. COMPLIANCE MONITORING REQUIREMENTS
1. Supplemental treatment systems shall be inspected and monitored for performance at a
minimum annually. Specific monitoring requirements will be contained in each operating
permit however, the following guidelines will generally be followed:
a.Individual Residential OWTS. For individual residential OWTS semiannual
sampling and analysis for BOD and TSS of effluent for the first two years of
operation is required. Thereafter sampling frequency may be reduced or eliminated
based on satisfactory OWTS performance and reporting. The sampling is
recognized to be a spot check of OWTS operation and not to be interpreted for
purposes of compliance of thirty (30) day average performance standards.
b.Multi-Unit Residential and Non-Residential OWTS. For multi-unit residential
and non-residential small OWTS (less than one thousand five hundred [1,500)]
gallons per day) semiannual sampling and analysis for BOD and TSS of wastewater
effluent for the first two years of operation is required. Thereafter sampling
frequency may be reduced to annual based on satisfactory OWTS performance and
reporting. The sampling is recognized to be a spot check of OWTS operation and
not to be interpreted for purposes of compliance of thirty (30) day average
performance standards.
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c.High-Strength and High-Flow OWTS. For high-strength wastewater and high-
flow OWTS, sampling parameters will include at least sampling and analysis for
BOD and TSS of wastewater effluent and may also include nitrogen, FOG and other
constituents as applicable. Sampling frequency may be increased and will be
dependent on the size, location and features of the OWTS. Sampling may include
analysis used for both spot check as well as compliance with performance
standards.
d.OWTS Near Public Water Supplies. For OWTS within the setbacks for a public
water supply intake or well, testing of wastewater treated by disinfection units for
total fecal coliform shall be required.
2.Effluent Quality. Effluent produced by OWTS requiring supplemental treatment systems
shall comply with the maximum constituent limitations provided in Table 43-4.
BOD (mg/L) 30 30
TSS (mg/L) 30 30
Fecal Coliform (MPN/100 ml) N/A 200
a.When compliance monitoring results exceed the operating permit system
performance limits the following will typically be required.
(1) Repeat sampling and analysis until compliance is demonstrated; and
(2) If needed, adjustments to the OWTS operations to bring wastewater
quality into conformance with performance limits.
C. GROUNDWATER QUALITY MONITORING REQUIREMENTS
1. Groundwater monitoring wells must be sampled for nitrates at least annually or as
frequently as determined by the Department.
2. Sampling may be required for other contaminants at the discretion of the Department.
3. An OWTS is considered to be failing or having an adverse effect on groundwater quality
when monitoring well nitrate levels are above ten (10) milligrams per liter (mg/l) of nitrate
as nitrogen.
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43.3 SYSTEM OPERATING PERMIT REQUIREMENTS
A. MINIMUM CRITERIA
1. All advanced OWTS and all OWCU require an annual operating permit or qualifying
public agency permit.
2. Maintenance and performance monitoring shall be performed by a Service Provider or
System Designer.
3. Permit Exemptions.
a.Standard OWTS do not require an operating permit unless required as a condition
of approval for corrective action(s) on an existing OWTS.
b.An operating permit is not required for: (1) temporary use (less than seven [7]
days) of portable toilets, and (2) use in temporary agricultural field activities.
4. Prior to issuance of a final approval of the system installation the property owner shall
obtain an operating permit from the Department.
a.The operating permit shall be renewed annually and any required fees shall be paid.
The owner of the property shall keep the operating permit valid for the life of
the System.
b. The operating permit renewal frequency for advanced OWTS may be extended to
a period of three (3) years contingent upon compliance with all of the following
conditions:
(1) The System has been functioning properly for two (2) consecutive years
in compliance with the approved design plans and the operation,
monitoring and maintenance (OM&M) manual; and
(2) The owner is in compliance with the terms of the operating permit
including but not limited to the annual reporting requirements to the
Department.
5. The property owner shall notify the Department, in writing, of any change in property
ownership within ten (10) days of the change and provide the name and contact information
for the new owner.
a.When the property changes ownership, the new owner must apply to the
Department for a new operating permit on or before the anniversary of the
operating permit issuance date.
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b. The new owner will not be required to pay either an application or permit fee for
the transfer of ownership, however, a nominal administrative fee may be charged
for transferring the operating permit. The new owner will be responsible for any
annual operating permit renewal fees.
c.The Department strongly encourages the new property owner to submit an
application as soon as possible and not wait until the renewal date, in order for the
Department to have all the information required in the application.
6. All Systems issued an operating permit shall be operated, maintained, and monitored
pursuant to the requirements of the standards/conditions found in the Ordinance and this
Manual and the issued operating permit.
7. A monitoring program is required and shall be included in the OM&M manual and as a
condition of the operating permit. The monitoring program may be amended at the time of
a permit renewal.
8. The permit holder is responsible for contracting with a Service Provider or System Designer
for monitoring to ensure that the System is functioning satisfactorily to protect water quality
and public health and safety.
B. NON-COMPLIANCE WITH OPERATING PERMIT REQUIREMENTS
1. Non-compliance with System operating permit requirements may result in enforcement
action and administrative fines and penalties.
2. Actions that may be taken by the Department include:
a.Issuance of notice of non-compliance to the System owner with:
(1) Request to participate in an informal meeting with the Department to
review the lack of compliance and corrective actions;
(2) Requirements for the owner to conduct additional testing, inspections, or
other monitoring until the Onsite Wastewater System is compliant;
and/or
(3) Restriction or prohibition of the use of the Onsite Wastewater System.
43.4 SYSTEM REPORTING REQUIREMENTS
A. SYSTEMS WITHOUT OPERATING PERMITS
1.For standard OWTS that do not require an operating permit, the property owner shall
submit a homeowner’s questionnaire to the Department once every five (5) years with
information on the System to assist the County in complying with State reporting
requirements.
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SYSTEM OM&M REQUIREMENTS
a.The Department will send at least one notice to the property owner requesting
submittal of the homeowner’s questionnaire.
b. Failure to submit the questionnaire to the Department may result in a requirement
to provide the information by the Regional Water Board.
B. SYSTEMS WITH OPERATING PERMITS
1. For Systems with operating permits, the property owner must submit an annual report
prepared by the Service Provider or System Designer to the Department, or as otherwise
required by the operating permit. Reports will typically include the following:
a.Actual wastewater flows for operating permit period, or an estimate based on water
usage.
b. Inspection findings of the System components submitted on a form provided by
the Department, or similar documentation.
c.Information requested by the State.
(1) Failure to submit information required by the State may result in fines or
penalties.
(2) Prior to any fine or penalty the Department will send at least one notice to
the property owner and direction to provide the required information.
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
Table 43-1
OWTS Required Inspection Frequency
Inspection
Interval
Residential
Standard
Gravity System
Pressure
Dosed
Non-
Residential
Standard
Gravity System
or Pressure
Dosed
Steep Slope,
Mound or
Sand Filter
Proprietary
Supplemental
Treatment Unit
Disinfection Units
First
6 weeks
PL or SP
(required)
First
3 Months
PL or PU or SP
or Installer
(recommended)
SP
(recommended)
SP
(required)
PL or SP
(required)
Monthly
PL or SP
(if no telemetry)
(required)
Annually SP
(recommended)
SP
(required)
As required
by the
manufacturer
or NSF, but
not less than
once per year
PL or PU or SP
or Installer
(recommended)
PL or SP
(required)
PL or SP
(with telemetry)
(required)
Every
3-7 years PU or SP
(recommended)
Notes:
(1) Supplemental Treatment Systems, other than single pass Sand Filters, used for Treatment prior to disinfection must be monitored monthly for
the first year of operation and longer if necessary to assure Treatment requirements are reliably met
PL= Proprietary Device Licensee (also must be an approved Service Provider)
PU= Septage Pumper
SP= Service Provider
Table 43-2
System Inspection Requirements
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
Element Description of Work
Site
Inspection
Inspect site to assess current site development (buildings, structures, decks, fences,
ponds, pools, spas, ground-mounted solar panels, driveways, retaining walls, animal
pens, etc.) against conditions on approved System plans.
Inspect site topography in the vicinity of System components including cut/fill areas,
steep slopes, and graded areas for signs of instability or effluent seepage.
Verify horizontal setbacks to site development structures for compliance with
System plans and the requirments of this Manual.
Inpect the site in the vicinity of the System components for cave-in or exposed
components and wastewater odors.
Wastewater
Plumbing
Inspection
Inspect site to ensure that all graywater and blackwater plumbing is routed to the
System or for graywater to an permitted graywater systems.
Inspect plumbing fixtures for leakage.
Verify if garbage disposal is routed to the System.
Verify if a water treatment appliance backflushes to the System.
Drainage
Inspection
Inspect site in vicinity of System components for drainage issues including location
and integrity of stormwater diversion structures (swales, inlets, dissipation devices,
etc), sump pumps, foundation drains, roof runoff and other drainage related features
that could impact or be impacted by the System.
Dispersal
System
Inspection
Inspect dispersal system for compliance with approved System plans. Inspect surface
conditions in dispersal system area (including downslope and surrounding areas) for odors,
effluent leakage, wet areas, soil erosion, burnt out grass or ground staining, gopher holes,
abnormal vegetation, trees, landscaping, irrigation, signs of heavy objects or vehicular
traffic (impressions or tracks), etc.
Tanks and
Risers
Inspection
Inspect area around tank(s) for odors, effluent leakage, wet areas, soil erosion,
drainage/infiltration, abnormal vegetation, signs of vehicular traffic, landscaping,
irrigation, etc.
Inspect conditon of risers for integrity, accessibiltiy, secure covers, etc. and
compliance with approved System plans.
Inspect tank(s) for compliance with approved System plans. Inspect conditon of
tanks, baffles, inlet and outlet tees, effluent filters etc. for integrity, signs of water
intrusion, material/component type and tanks size.
Supplemental
Treatment
System
Inspection
Inspect proprietary treatment unit components for compliance with approved plans
and manufacturer’s specifications.
Inspect sand filter systems for compliance with approved System plans. Inspect
surface conditions in sand filter system area (including downslope and surrounding areas)
for effluent leakage, wet areas, soil erosion, gopher holes, abnormal vegetation, trees,
landscaping, irrigation, signs of vehicular traffic, etc.
Pumps, Control
Panels,
Telemetry
Systems and
Alarms
Inspection
Inspect pumps, float switches, control panels, alarms, electrical wiring and other
appurtenances for compliance with the approved System Plans.
Other System
Components
Inspections
Inspect pipes, valves, headworks, valve boxes, distribution boxes, OWTS
performance monitoring wells, inspection wells, groundwater monitoring wells, etc.
for integrity, functionality and compliance with approved System plans.
Table 43-3
System Maintenance & Monitoring Requirements
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 1 OF 1
Element Description of Work
Routine
Maintenance
Activities
Perform all maintenance work as recommended by System Designer or
equipment Manufacturer.
Replace all components as necessary with equivalent materials and/or equipment in
accordance with the requirements of this Manual.
Purge and balance laterals.
Clean and check operation of valves to ensure functionality and repair and/or
replace as necessary.
Perform all maintenance work on pumps and siphons, float switches, hose and
valve assemblies, and other pump related components.
Check functionality of alarms (audio and visual), flow meters, and control boxes
and replace and/or repair as necessary. Record flow, dose counter, and/or
elapsed time meter readings.
Remove and clean and/or replace filters.
Measure liquid, scum and sludge levels in tanks and have tanks pumped by a
Septage Pumper as required. In a properly functioning OWTS, the level in the
septic tank should be even with the invert of the outlet pipe. If the liquid level is
below the outlet pipe, the tank may be leaking. If the liquid is above the pipe, the
dispersal field may either be flooded or the line to the field obstructed or possibly
set with an improper gradient.
Uncover and/or replace damaged valve boxes and tank riser covers.
Repair irrigation and storm water diversion structure problems in the vicinity of
System components creating storm water run-on or run-off problems,
infiltration, erosion or other deleterious effects to System components.
Control rodents causing damage to System components.
Maintain fill area landscape vegetation and erosion control measures.
Repairs and
Corrective Action
Report findings to the Department and perform System repairs or corrective
action work after obtaining requisite approvals and/or permits from the
Department.
In the case of emergency or System failure conditions, immediately perform
corrective actions necessary to abate human health, water quality, or other
environmental impacts and immediately report to the Department.
Water Monitoring
& Sampling
Measure and record water levels in OWTS performance monitoring wells and
inspection wells located in and around dispersal system and sand filter areas.
Obtain and analyze water samples from OWTS performance monitoring wells and
inspection wells, as applicable, per operating permit requirements.
Measure and record water levels in groundwater monitoring wells and obtain
and analyze water samples per operating permit requirements.
Obtain water samples from surfacing liquid in the vicinity of System
components and analyze for bacteria indicator parameters (total coliform, fecal
coliform and e. coli).
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)
PART 11
EXISTING SYSTEM
REQUIREMENTS
CHAPTER TITLE
CHAPTER 44 EXISTING SYSTEM PERFORMANCE
EVALUATION REQUIREMENTS
CHAPTER 45 EXISTING SYSTEM CORRECTIVE ACTION
REQUIREMENTS
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44.0 CHAPTER OVERVIEW
This chapter provides procedures and requirements for conducting performance evaluations of existing
Onsite Wastewater Systems and is organized in the following sections:
Section 44.1: Performance Evaluation Overview
Section 44.2: Level of Evaluation Required
Section 44.3: Records Search Guidelines
Section 44.4: Site & System Inspection Requirements
Section 44.5: Hydraulic Load Test Guidelines
Section 44.6: Pump Test Guidelines
Section 44.7: System Evaluation Criteria
Section 44.8: Reporting with Findings and Recommendations
44.1 PERFORMANCE EVALUATION OVERVIEW
A. PURPOSE
1.The purpose of a performance evaluation is to determine, on an individual basis, whether
an existing Onsite Wastewater System is safe and functional, is in compliance with
permitted conditions, can be repaired/modified to meet the minimum performance
standards in this Manual and/or requires replacement.
2. Nothing contained in this Manual shall be deemed a requirement to alter, change,
reconstruct, remove or demolish an existing Onsite Wastewater System provided the
system meets all of the following criteria:
a.Was installed in accordance with any applicable law in effect at that time;
b. Continues to comply with previously imposed permitting conditions; and
c.Is properly functioning and appropriately sized.
44.2 LEVEL OF EVALUATION REQUIRED
A. WHEN REQUIRED
1.A performance evaluation of an existing Onsite Wastewater System may be required in
connection with:
a.Corrective action of a System; or
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b. Site development and/or building permit applications.
2. A performance evaluation may also be useful and is recommended for other circumstances
such as System inspections in connection with property transfers for lending institutions,
etc.
B. LEVEL OF EVALUATION REQUIRED
1. Performance evaluation tasks and reporting requirements are dependent on the purpose of
the performance evaluation.
a.Site Development and Building Projects. Performance evaluations conducted to
support proposed site development and building projects must evaluate the
compatibility of the project with existing and/or proposed Onsite Wastewater
Systems for two main purposes:
(1) Design and Capacity of System. Evaluation of the capacity of existing
and/or proposed Systems to handle the wastewater loading associated with
the project including but not limited to the sizing and design of the System
to treat the wastewater strength and flow from existing and proposed site
usage; and/or
(2) Physical Impacts to the System. Evaluation of potential physical impacts
to existing Systems including areas reserved for dispersal system
replacement (reserve areas) and compliance with requisite setbacks from
proposed site development and building projects to System components.
b.Corrective Actions on Existing Systems. Performance evaluations conducted
to evaluate an existing System requiring corrective action and support
recommended repairs, modifications or replacement of the System. Evaluations
to support repairs and modifications to an existing System must be conducted
in accordance with the site evaluation activities presented in Part 2 of this
Manual and the corrective action criteria presented in Chapter 45 of this
Manual, as applicable.
2. Performance evaluation tasks and reporting requirements are also dependent on whether
System design documents/permits are on file with the Department.
a.Documented Systems. Performance evaluations of existing Systems with design
documents/permits on file with the Department must be conducted to evaluate the
System and current site conditions for compliance with the design
documents/permits. If discrepancies are found between the System design
documents/permits and site conditions, additional steps for the evaluating the
discrepancies will be required in accordance with the procedures for evaluating
undocumented Systems below.
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b.Undocumented Systems. Performance evaluations of undocumented Systems
must be conducted to evaluate the siting and construction of the System. These
additional tasks may include but not be limited to:
(1) Selective exploration including probing with a metal rod, potholing or
excavation, camera or tracer line inspections or other similar methods to
locate subsurface components; and/or
(2) A site evaluation in accordance with the criteria presented in Part 2 of
this Manual to determine at a minimum:
(a) Vertical separation distance to groundwater from the bottom of
the dispersal system;
(b) Effective soil depth;
(c) Horizontal setback distances from System components to site
features; and
(d) Replacement area for future dispersal systems replacement.
C. PRACTITIONER QUALIFICATIONS
1. Performance evaluations of existing Systems may be conducted by a Contractor or a
System Designer with the exception of the following activities which must only be
conducted by a System Designer:
a.Site evaluation tasks as defined in Part 2 of this Manual to evaluate the siting of
existing dispersal system(s) and reserve areas; and
b. Evaluation of the sizing or design of an existing System to determine its capacity
to treat wastewater from existing or proposed site usage.
44.3 RECORDS SEARCH GUIDELINES
A. GENERAL
1. Prior to conducting a performance evaluation, the owner, Contractor or System Designer
should compile and review all available background information pertaining to the property
and structures connected to Onsite Wastewater Systems.
2. Information that should be reviewed includes records of the System design and permit
information, System as-built plans, prior inspection results or reports, site plans, site
development and building permit plans, etc.
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3. Databases that may have pertinent information include but are not limited to the owner
records, Department files, building department files and the County assessor’s office
records. The level of database search is dependent on the records available as listed below:
a.System Permits Located. If System permits are located, then proceed with site
and System inspection (see Section 44.4); else proceed to Item 3.b below.
b.System Permits Not Located. If System permits are not located, then search for
building permits for the structure(s) connected to the System. If permits for the
structure(s) are found then proceed with site and System inspection (see Section
44.4); else proceed to Item 3.c below.
c.System Permits and Structure Permits Not Located. If permits for the System
and for the structure(s) connected to the System are not located, then search the
County assessor’s office database for records of the structure. If records for the
structure(s) are found then proceed with site and System inspection (see Section
44.4); else procced to Item 3.d below.
d.System Permits, Structure Permits, and Assessor Records Not Located. If
permits for the System and for the structure(s) connected to the System are not
located, and the structure(s) are not recorded with the County’s assessor’s office
then contact the local building department for requirements regarding the buildings
or structure(s) before proceeding with the site and System inspection.
44.4 SITE & SYSTEM INSPECTION REQUIREMENTS
A. GENERAL
1. After a records search is completed, a site inspection must be performed by a Contractor
or System Designer.
2. Depending on the purpose of the performance evaluation and whether there are design
document/permits on file with the Department a System inspection and/or System design
evaluation may also be required.
3. If imminent health hazards and/or unsafe conditions are observed during site and System
inspection activities, the Department must be notified within twenty-four (24) hours and
immediate emergency repair work completed to abate the risk, provided the owner
immediately thereafter applies for a repair/modification permit, if applicable.
B. MINIMUM REQUIREMENTS
1. A site and System inspection shall be performed by a Contractor or System Designer in
accordance with the requirements of this chapter and the inspection requirements presented
in Chapter 43. The performance evaluation inspections shall include but not be limited to:
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a.Locating the System components including tanks, supplemental treatment systems,
the extents of the primary and secondary/replacement dispersal system area(s) and
location of associated components (distribution boxes, valves, inspection ports,
OWTS monitoring wells, etc.). If the location of the System components are
undocumented or cannot be identified from design document/permits then
selective exploration must be conducted as part of a System inspection;
b. Verifying field conditions and reconciling discrepancies between records of the
System and buildings, structures and property features (if any);
c.Verifying that the System is adequately sized and functioning properly and is in
compliance with approved design documents/permits (if available) or other
minimum standards as applicable;
d. Identifying conditions that may suggest an existing or impending failure; and
e.Identifying and conducting System testing to verify the functionality and
performance of the System including but not limited to hydraulic load testing,
pump testing and other testing required by an operating permit, if applicable.
44.5 HYDRAULIC LOAD TEST GUIDELINES
A. OVERVIEW
1. A subsurface dispersal system may be undersized for the buildings or structures it serves
or may lose hydraulic capacity due to excessive flows or waste strengths, crushed pipes,
root intrusion or blockages or other causes.
2. A hydraulic load test may be used to assess the hydraulic capacity and effectiveness of a
gravity dispersal system to absorb and treat wastewater.
3. The results of the test must be interpreted within the context of the entire site, OWTS
inspection and current site use. A hydraulic load test may give unreliable results under the
following conditions:
a.When the structure is unoccupied during the last twelve (12) months, or for a
continuous period of one month or more; and/or
b. When there is evidence that the OWTS has had a procedure (usually evidenced by
chemical scouring or a bleached-out appearance on concrete components)
indicating an attempt to fix a major OWTS failure.
4. If a system is showing signs of failure, certain hydraulic load test procedures may actually
aggravate the problem and should not be performed.
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B. HYDRAULIC LOAD TESTING PROCEDURE
1. The hydraulic load test should be designed to approximate the peak one (1) hour flow. For
a residential structure, the peak one-hour flow shall be estimated to reflect the number of
bedrooms. For a typical residential structure the test should be conducted with
approximately one hundred and fifty (150) gallons of water over a twenty (20) to thirty
(30) minute period. Building occupants should refrain from using plumbing fixtures during
the test.
2. Prior to starting the test the following shall be determined:
a.Depth of both the scum and sludge layers. If the OWTS appears to be in good
working order, the flow test volume may be added via either the inlet (using water
from plumbing fixtures) or the outlet of the septic tank. If inspection of the septic
tank indicates backflow from the dispersal system area, evidence of solids
carryover, or other situations of concern, the test should be conducted by running
water through the tank outlet. The test should not be conducted at the inlet by using
water from plumbing fixtures.
b. Flow rate from the hose (e.g., with 5-gallon bucket and stop watch) to properly
gauge the amount of surcharge water added to the tank. Alternatively, a portable
water meter can be installed between the house faucet and the hose to directly
measure the water volume added.
c.Location (measurement) of the static water line in the septic tank (at the outlet side)
for use as an initial reference point.
3. The hydraulic load test should then proceed in accordance with the following procedure:
a.Surcharge the tank with water to start the hydraulic load test. If a garden hose is
used to discharge into the outlet side of the tank, the hose outlet should remain at
least twelve (12) inches above the water level in the tank to prevent cross-
contamination.
b. During surcharging, observe rises in the liquid level at the outlet pipe and measure
the final level at the end of filling. Typically, the liquid level will rise one (1) or
two (2) inches, at which point the liquid level should stabilize for the reminder of
filling, and then return to the initial level in a matter of minutes after filling is
stopped.
c.After the filling cycle is finished, observe the water level decline in the septic tank
until the initial level is reached and the time to achieve this is recorded. If the initial
level is not attained within thirty (30) minutes, the test should be terminated and
the final water level noted. The time it takes to add the flow test volume should be
recorded, or alternatively, if water begins to back up (i.e., rises more than two
inches above the outlet bottom), the time it took for this to occur.
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4. At the completion of the hydraulic load test, the dispersal system area and downslope areas
should be checked again for indications of surfacing wastewater, wetness or odors. If any
of these conditions exist as a result of the hydraulic load test, this would likely be
considered evidence of dispersal system failure.
5. If the field observations of wetness are not obviously the result of the hydraulic load test,
further investigation may be needed by a System Designer to determine if the dispersal
system is failing and the cause of the failure.
6. Although not always conclusive, tracer dye added to the tank may be used to assist in
investigating the possible contribution of wastewater where surface wetness/seepage is
suspected or observed.
C. OWTS RATING BASED ON HYDRAULIC LOAD TEST
1. A hydraulic performance rating shall be assigned to the OWTS based upon the water
level readings during the hydraulic load test in accordance with the guidelines in the
Table 44-1 below.
Table 44-1
Hydraulic Load Test Rating Guidelines
Rating Septic Tank Response To Hydraulic Loading
2. If an OWTS receives a marginal rating, a more detailed examination by a System Designer
will be required to determine the cause of the sluggishness.
3. The hydraulic performance ratings in Table 44-1 are guidelines only; special
circumstances may be cause for modifying the evaluation and rating of a particular system.
An OWTS receiving a "failed" rating will likely require corrective action and/or additional
investigation by a System Designer to determine the underlying cause(s).
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44.6 PUMP SYSTEM TEST GUIDELINES
A. OVERVIEW
1. A pump test is conducted to assess the functionality of a pump system, integrity of the
pressure piping system and pressure-dosing of the dispersal field.
B. PROCEDURE
1. Prior to starting the test the pump access cover and basin lid should be removed and signs
of scum or sludge buildup, indications of previous pump failure (such as scum line above
the high water alarm switch) or evidence of soil or roots entering the basin observed.
2. The float controls should be inspected to see that they have free movement and the
electrical junction box (if located in the basin or access riser) checked for signs of
corrosion.
3. If the water level in the basin is normal (i.e., between the high and low water controls) the
testing of the pump system should proceed according to the following steps:
a.Add sufficient water to the basin to activate the pump "ON" control, and observe
the performance of the system over at least one pumping cycle. The total amount
of water added should be about one hundred and fifty (150) gallons to approximate
the same hydraulic loading of the dispersal field as for gravity dispersal systems.
b. The water may be added to the outlet side of the septic tank or directly to the pump
basin. If filling the basin directly, care should be taken to minimize turbulence and
disturbance of sediment or sludge that may have collected in the basin. This can
be best accomplished by directing the stream of water against the interior side of
the chamber rather than directly toward the bottom of the pump chamber.
c.Observe the filling of the basin and note and measure the point at which the pump
is activated. Immediately stop the filling operation and observe the pumping cycle
until the pump shuts off.
d. While the pump is discharging, examine the piping system (where exposed) for
any leaks. Even small leaks could be a forewarning of possible breaks in the
pressure line at some point in the future; and these should be corrected as soon as
possible.
e.Note and measure the depth at which the pump shuts off and calculate the volume
of water between the "ON" and “OFF” measurements. Compare this dose with the
design dose volume specified for the System. If the dose is too high or too low,
float controls should be adjusted to correct the dose.
f.The pumping cycle (from "ON" to "OFF') level should be timed and the pump
discharge rate determined (in gpm).
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g.Test the pump system audio and visual alarm to confirm that it can be heard at the
house if mounted at the pump tank.
4. Typically, if the pump is sized and operating properly, pump operation lasts about one (1)
to five (5) minutes per dose. Pump cycles lasting longer than this may indicate a flooded
dispersal field and/or pump or piping deficiencies. If this is observed, it should be noted
and further investigation of the pump and dispersal field should be conducted by a System
Designer to determine the specific cause. The observed pump rate should be checked
against the design requirement for the System and any discrepancy noted.
5. If during filling of the pump basin, the pump does not activate when the water reaches the
high liquid level control (i.e., "ON" float), discontinue the pump test. This indicates a pump
failure, defective float switch or wiring problems and may require the repair service of a
Contractor. The pump system failure should be noted, communicated immediately to the
owner and followed up with prompt corrective action.
44.7 SYSTEM EVALUATION CRITERIA
A. MINIMUM PERFORMANCE CRITERIA
1.Evaluation of System Functionality. The site and System inspection and functional
testing results must document that the System meets the following minimum criteria:
a.There is no surfacing effluent at any time.
b. There is always positive flow to the dispersal system from the septic tank with no
backup to the tank or building/structure plumbing.
c.Tanks are watertight, structurally sound and serviceable.
d. There is no indication that the existing System is adversely affecting surface water
or groundwater.
2.Additional Testing Required by Operating Permit (if applicable). Additional criteria
must also be met for Systems with operating permits. Compliance with these conditions
must be evaluated in the performance evaluation or documented in an annual OM&M
report.
3.Evaluation of System Design and Capacity. An evaluation of the System by a System
Designer may also be required to verify that the System is:
a.Adequately sized and designed to treat the wastewater flow and strength from
existing and/or proposed uses. System evaluation may require collection of
information on the wastewater influent to the System including but not limited to:
(1) Flow volume and wastewater type from each structure connected to the
System based on the number of bedrooms for residential structures, flow
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and wastewater characteristics from multi-unit residential and non-
residential facilities; water use/wastewater flow rates for the property, etc.;
and
(2) Flow volumes of graywater diverted from the wastewater stream to
permitted systems.
b. In compliance with approved design documents/permits (if available) or other
minimum standards as applicable.
(1) Systems with approved System design documents/permits: The System
must comply with the approved System design documents/permits on file
with the Department; or
(2) Systems where approved System design documents/permits could not
be located but building permits for structures are available. The
Department may consider use of the minimum standards contained in the
building or California Plumbing Code in effect at the time the structure(s)
were permitted; or
(3) Systems where approved System design plans or building permits for
the structure could not be located, but the structure is recorded with
the Assessor’s Office. The Department may consider use of the minimum
standards contained in the building or California Plumbing Code in effect
at the time the structure(s) was first recorded in the County Assessor’s
database. If the date of the recording of the structure predates 1946 (the
date when the County began issuing building permits) then the System
may be evaluated against criteria established in the 1952 Plumbing Code
adopted by Alameda County Board of Supervisors through Ordinance 644.
44.8 REPORTING WITH FINDINGS AND RECOMMENDATIONS
A. REPORT REQUIREMENTS
1.A performance evaluation report documenting the findings of the performance evaluation
and recommendations must be prepared and filed with Department. The performance
evaluation report must contain the following as applicable:
a.Record search results;
b. Site and System inspection findings;
c.System functional testing results;
d. Site map and System as-built plans; and/or
e.System evaluation findings and recommendations.
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2. Performance evaluations conducted to support building or development permits must also
submit the following:
a.A statement certifying that the proposed project will not impact existing Systems
on the site; or
b. Recommendations for additional site assessment and/or corrective action if
necessary for project clearance by the Department for site development or building
permits.
3. If the System requires corrective action or replacement the results of the performance
evaluation may be incorporated into the design documents for repairs/modifications to the
existing System or a replacement System.
B. SITE MAPS AND SYSTEM AS-BUILT PLANS
1. A site map must be prepared for undocumented Systems or permitted Systems where site
conditions were observed that differ from the approved System design documents/permits
but do not negatively impact or encroach on the approved System or dispersal system
replacement area(s).
2. The site map must be a scaled drawing utilizing site development, building plans,
topographic maps, and/or aerial photographs as a base map if available and must include
the following:
a.Location of System components;
b. Extent of the primary and secondary/replacement dispersal area(s) and subsurface
dispersal system details, as applicable;
c.Setbacks to site structures and development features, wells/springs, surface water
bodies, and other pertinent features in the vicinity of the System and replacement
area(s); and
d. Any other conditions which may affect the functionality of the System.
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EXISTING SYSTEMS CORRECTIVE ACTION REQUIREMENTS
45.0 CHAPTER OVERVIEW
This chapter provides the requirements for existing Onsite Wastewater Systems that require corrective
action and is organized in the following sections:
Section 45.1: Systems Requiring Corrective Action
Section 45.2: Corrective Action Requirements
Section 45.3: Corrective Action Permitting Requirements
Section 45.4: Failed Systems and Abatement Requirements
45.1 SYSTEMS REQUIRING CORRECTIVE ACTION
A. REQUIREMENTS
1. An existing Onsite Wastewater System that requires corrective action is defined by the State
OWTS Policy as a System that exhibits any of the following conditions:
a.Dispersal System Failure. Any System that has pooling wastewater, discharges
wastewater to the surface or has wastewater backed up into plumbing fixtures,
because its dispersal system is no longer adequately percolating the wastewater is
deemed to be failing and is no longer meeting its primary purpose to protect public
health.
b.Tank Failure. Any tank failure, such as a baffle failure, tank structural integrity
failure such that either wastewater is exfiltrating or groundwater is infiltrating or
other failure such that the tank is not functioning as designed is deemed to be failing
and is no longer meeting its primary purpose to protect public health.
c.Component Failure. Any System that has a failure of one of its components other
than a dispersal system or tank failure such as a distribution box or broken piping
connection is deemed to be failing and no longer meeting its primary purpose to
protect public health.
d.Groundwater or Surface Water Degradation. Any System that has affected or
will affect groundwater or surface water to a degree that makes it unfit for drinking
or other uses or is causing a human health or other public nuisance condition.
45.2 CORRECTIVE ACTION REQUIREMENTS
A. POTENTIAL REMEDIES
1. Corrective action may include repair, modification, replacement or abandonment of the
System or components of the System.
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EXISTING SYSTEMS CORRECTIVE ACTION REQUIREMENTS
2. Potential remedies may include but not be limited to the following:
a.Source Control Measures: Potential source control measures include but are not
limited to:
(1) Modification of water use habits;
(2) Installation of low, ultra-low flow plumbing fixtures;
(3) Repair or replacement of leaking plumbing lines, fittings, etc;
(4) Installation of flow equalization tanks in the treatment train;
(5) Installation of pump systems to time-dose the dispersal system;
(6) Installation of graywater systems;
(7) Installation of waterless toilets; and/or
(8) Maintenance pumping of tanks.
b.Site Modifications: Potential site modifications include but are not limited to:
(1) Removal of trees, conflicting landscaping, irrigation, or structures;
(2) Installation of surface water drainage diversion structures; and/or
(3) Installation of curtain drains or other measures to intercept/divert
groundwater from the dispersal system.
c.Tank Repairs/Modifications/Replacement. Potential improvements to tanks
include but are not limited to:
(1) Installation of effluent filters;
(2) Repair or replacement of risers and lids;
(3) Repair or replacement of inlet and outlet tees and baffles;
(4) Installation of waterproofing materials; and/or
(5) Replacement of tanks with watertight tanks.
d.Treatment Improvements: Potential improvements to the treatment train include
but are not limited to:
(1) Installation of supplemental treatment; and/or
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EXISTING SYSTEMS CORRECTIVE ACTION REQUIREMENTS
(2) Installation of sand filtration dispersal systems to provide additional
wastewater polishing prior to dispersal to the ground (e.g., mound
dispersal systems; raised sand bed filter systems, pressure-dosed sand
trenches).
e.Dispersal System Improvements: Potential improvements to existing dispersal
systems include but are not limited to:
(1) Increasing the capacity of the dispersal system by installing additional
dispersal trenches or beds;
(2) Utilizing reserve areas or other suitable area (e.g., installation of additional
dispersal trenches, etc.);
(3) Reconstructing or modifying existing trench systems by:
(a) Converting gravity trench dispersal systems to pressure
distribution systems;
(b) Replacing drain rock with new rock;
(c) Replacing drain rock with gravelless distribution products to
allow dispersal area sizing reductions;
(d) Using cover fill with shallow in-ground trenches to provides
requisite soil cover depth; and/or
(e) Replacing the existing dispersal system with a new dispersal
system.
f.Discharge Elimination. Installation of holding tanks and regular pumping by a
Septage Pumper or abandonment of the System and connection to the sewer.
B. MAXIMUM EXTENT PRACTICABLE STANDARDS ON CONSTRAINED SITES
1. On constrained sites where site specific conditions including but not limited to small parcel
size, site development, poor soil characteristics, steep slopes, close proximity to surface
water bodies and shallow groundwater table conditions limit treatment and dispersal
System options, corrective action measures must be made to the maximum extent
practicable with the requirements of this Manual.
2. Reduced horizontal setbacks from System components to sensitive receptors and vertical
separation to groundwater distances may be allowed subject to Department approval,
incorporation of supplemental treatment and/or advanced dispersal systems and
compliance with the following criteria:
a.The setback from System components to property lines may be reduced to less than
ten (10) feet provided the location of the property line is identified by a Qualified
Professional as allowed by their license or registration and impacts to the adjacent
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property have been evaluated and appropriate mitigation measures proposed.
b. All existing tank deficiencies must be repaired so the tanks are watertight,
structurally sound and in good operating condition.
c.The System must incorporate advanced dispersal systems and/or supplemental
treatment unless sufficient evidence is provided to support that there is no impact
or significant threat to groundwater or surface water or a monitoring program is
proposed and approved by the Department as part of a phased corrective action
plan to monitor surface water and/or groundwater conditions and modify the
System at a later date if warranted by monitoring data.
d. An OWTS may not be located any closer to any well, spring or surface drainage
or other sensitive receptor than the existing OWTS.
e.In no case shall a repair create the potential of an increased threat to groundwater
or surface water than that of the existing OWTS.
f.For a new System on an existing lot of record that is tributary to and upstream of
a public water supply intake the System must incorporate supplemental treatment
for pathogens (i.e., disinfection) in accordance with the State OWTS Policy.
3. In determining the level of corrective action required, the following factors shall be taken
into consideration, generally according to the following priorities:
a.Public health and safety;
b. Soil characteristics and groundwater separation;
c.Setbacks from wells and streams;
d. Ground slope and horizontal setback from unstable landforms;
e.System sizing standards; and
f.Other setback criteria (e.g., foundations, pipelines, trees, etc.).
C. FLOOD PROTECTION MEASURES
1. Where suitable area outside of the horizontal setback distances and flood hazard areas is
not available, repairs to existing OWTS located with floodplains shall include design
features to prevent damage to the System components by associated flood events and
infiltration of flood waters into the OWTS or discharge from the OWTS into flood waters.
2. The flood plain measures must be incorporated into the design plans for replacement
Systems or corrective action plans for existing Systems and must include:
a.Protection of OWTS components from flood damage using structural tie-downs;
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EXISTING SYSTEMS CORRECTIVE ACTION REQUIREMENTS
b. Elevation of critical components above the one hundred (100) year flood level;
c.Prevention of wastewater discharge into flooded dispersal system areas from pump
systems (e.g., using flood-activated float switches to override/disable pump
operation during high water conditions);
d. Additional emergency storage capacity for flood periods; and
e. Plan, profile and cross sections delineating the flood plain.
45.3 CORRECTIVE ACTION PERMITTING PROCESS REQUIREMENTS
A. CORRECTIVE ACTION PLAN SUBMITTALS
1. Proposed corrective action design documents must be submitted to the Department for
approval.
2. Repairs and modifications to an existing System must be supported by a performance
evaluation of the existing System conducted in accordance with the criteria presented in
Chapter 44 and site evaluation activities conducted in accordance with the criteria
presented in Part 2 of this Manual as applicable.
B. PERMIT REQUIREMENTS
1. Permit requirements for Onsite Wastewater System corrective action will depend on the
nature of the failure condition, the property location, the type of occupancy and the type of
corrective work needed.
a.In order to perform corrective actions on an existing System the property owner or
designee shall obtain a repair/ modification permit from the Department except
where exempt as described in Chapter 2.
b. If an existing System cannot be repaired or modified but can be replaced with a
new System the property owner or designee shall obtain an installation permit from
the Department;
c.If an existing System cannot be repaired, modified or replaced with a new System
the property owner or designee shall eliminate wastewater discharge at the site by
obtaining:
(1) An installation permit for a holding tank with regular pumping by a
Septage Pumper; or
(2) An abandonment permit of the System and connection to the sewer.
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EXISTING SYSTEMS CORRECTIVE ACTION REQUIREMENTS
C. CORRECTIVE ACTION IMPLEMENTATION TIMELINE
1. Owners of Onsite Wastewater Systems shall address any corrective action requirements
as soon as is reasonably possible and must comply with the time schedule of any
corrective action notice received from the Department.
2.Interim Measures. Interim measures such as installation of a holding tank and pumping
of septage may be required for failed Systems that require replacement and submittal of
a design plans for repair, modification or replacement.
3.Emergency Repair Work. Nothing in this chapter shall preclude the property owner from
performing any emergency repair work necessary to protect against an imminent threat to
human health and safety or the environment provided the owner immediately thereafter
applies for a permit if applicable.
4.Phased Corrective Action Plan. A phased corrective action plan may be submitted to the
Department for consideration to allow property owners time to plan for the costs of
implementing corrective action measures. Phased corrective action plans shall be prepared
by a System Designer and shall include immediate, intermediate and long-term
recommendations, as applicable, based on the results of system inspections, performance
evaluations and site evaluations. Phased corrective action plan approvals will be
conditioned upon issuance of an operating permit with monitoring and reporting
requirements during the period of corrective action implementation.
a.Immediate Measures. Immediate measures shall be implemented within one (1)
to three (3) months and shall include measures to eliminate surface discharge and
safety issues and may include but not be limited to source control measures,
plumbing and tank repairs and pump and haul by a Septage Pumper.
b.Intermediate Measures. Intermediate measures shall be implemented within one
(1) year and may include but are not limited to additional source control measures,
site modifications, septic tank replacement, dispersal system repairs/modifications,
monitoring well installation and continued pump and haul as needed.
c.Long-Term Measures. Long-term measures shall be implemented within one (1)
to three (3) years and may include but are not limited to additional source control
measures such as installation of graywater systems, treatment train modifications
including but not limited to addition of flow equalization tanks, pump tanks,
supplemental treatment, and/or dispersal system redesign or replacement. Longer
time frames (up to nine [9] years) may be approved for communities with plans for
a public sewer system or community OWTS.
5.Regional Water Board Oversight
a.If the owner of the Onsite Wastewater System is not able to comply with corrective
action requirements of this chapter, the Regional Water Board may require the
owner of the System to submit an application and information (Report of Waste
Discharge) to the Regional Water Board for evaluation on a case-by-case.
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EXISTING SYSTEMS CORRECTIVE ACTION REQUIREMENTS
45.4 FAILED SYSTEMS & ABATEMENT REQUIREMENTS
A. OWNER REQUIRMENETS
1.A property owner must immediately abate conditions that pose a threat to human health
and/or the environment due to a failing Onsite Wastewater System. At a minimum the owner
must hire a Contractor, Septage Pumper and/or Qualified Professional to assist in
immediately implementing the following interim abatement measures:
a.Stop all wastewater flows to the System;
b. Collect surfacing or ponding wastewater (must be done by a Septage Pumper);
c.Contain surfacing wastewater as close as practical to the failed System through the
use of berms or other measures;
d. Isolate storm drain collection systems if wastewater has the potential to enter inlets;
e.Conduct general cleanup measures including removing all impacted debris;
f.Prevent public contact with wastewater by installing fencing or hazard tape and
warning signs around the impacted area;
g.Wash down impacted impervious surfaces and collect and dispose of wash water in
a sanitary sewer;
h. Notify adjacent property owners that have the potential to be directly affected by the
failed System and or cleanup activities; and
i. Take other actions as directed by the Department.
2.Depending on the extent of the failing or failed System impacts, the owner may be required
to implement additional measures including but not limited to:
a.Investigation and/or monitoring the source and/or movement of wastewater;
b.Collection of well water, surface water, and/or soil samples for analysis of fecal
indicator bacteria to determine the extent of the release and threat to public health
and the environment;
c.Identification of appropriate cleanup action(s). Depending on the extent of impact of
the wastewater release to the environment, oversight by other regulatory agencies
may be required including but not limited to the Regional Water Board, State Water
Board, California Department of Fish and Wildlife, or the U.S. Army Corp of
Engineers; and
d.Implementation of additional soil cleanup measures including but not limited to
covering the impacted area with clean soil, excavation, aeration, or disinfection of
the impacted soil.
APPENDIX A
LIST OF TABLES
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LIST OF TABLES
Table
No Table Title
2-1 Professional, Contractor, Service Provider and Septage Pumper Licensing, Registration &
Certification Requirements
2-2 Professional, Contractor, Service Provider and Septage Pumper Qualifications & Scope of
Work Allowed by Registration, Certification or License
5-1 Gravity Trench Dispersal Systems – Configurations & Siting Criteria
5-2 Pressure-Dosed Trench Dispersal Systems – Configurations & Siting Criteria
5-3 Subsurface Drip Dispersal Systems – Configurations & Siting Criteria
5-4 At-Grade Dispersal Systems – Configurations & Siting Criteria
5-5 Mound Dispersal Systems – Configurations & Siting Criteria
5-6 Raised Sand Filer Bed Dispersal Systems – Configurations & Siting Criteria
5-7 Minimum Horizontal Setback Distances
8-1 Stabilized Percolation Rate Formula
8-2 Adjusted Percolation Rate Formula
8-3 Design Percolation Rate Formula
8-4 Soil Types and Associated Percolation Rate Guidelines
10-1 Projects Requiring Cumulative Impact Assessments
10-2 Nitrogen Loading Analysis - Minimum Average Wastewater Flow & Nitrogen
Concentration Criteria
10-3 Minimum Cumulative Nitrogen Loading Criteria from Proposed OWTS
10-4 Maximum Allowable Annual Nitrogen Loading Per Parcel for Parcels Located in Zone 7
Jurisdiction
14-1 Wastewater Design Flow Criteria – Residential Facilities
14-2 Wastewater Design Flow Guidelines – Multi-Unit Residential & Non-Residential Facilities
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LIST OF TABLES
Table
No. Table Title
15-1 Domestic-Strength Wastewater Strength Criteria
15-2 Wastewater Strength Guidelines – Multi-Unit Residential & Non-Residential Facilities
17-1 Minimum Septic Tank Capacity Criteria – Residential Facilities
17-2 Grease Interceptor and Primary Tank Sizing Chart Guidelines for Non-Residential
Facilities Based on Hydraulic Residence Time
19-1 Minimum Grease Interceptor Tank Capacity Formula
21-1 Holding Tank Sizing Formula
24-1 Wastewater Application Rate for Sand Filter Basal Area Sizing
24-2 Sand Filter Basal Area Formula
25-1 Subsurface Dispersal System Sizing - Standard Wastewater Application Rates
25-2 Subsurface Dispersal System Sizing - Enhanced Wastewater Application Rates
25-3 Subsurface Drip Dispersal Systems - Wastewater Application Rates -
25-4 OWTS Performance & Dispersal System Monitoring Wells Requirements
27-1 Gravity Trench Infiltrative Area Formula
27-2 Gravity Trench Length Formula
27-3 Gravity Trench Design Criteria (Drain Rock)
27-4 Gravity Trench Spacing Criteria
28-1 Pressure Dosed - Trench Infiltrative Area Formula
28-2 Pressure Dosed - Trench Length Formula
28-3 PDST Gravel-Sand Interface Wastewater Application Rate Criteria
28-4 Pressure Dosed - Trench Design Criteria (Drain Rock)
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LIST OF TABLES
Table
No. Table Title
28-5 PDST - Trench Design Criteria
28-6 PDST – Sand & Gravel Depth Criteria
28-7 Pressure Dosed - Trench Spacing Criteria
29-1 Dripfield Infiltration Area Formula
29-2 Drip Installation Methods
30-1 At-Grade and Mound Dispersal System Gravel Bed Basal Area Sizing Formula
30-2 Wastewater Application Rate used for Sizing At-Grade and Mound Dispersal System
Gravel Bed Areas
30-3 At-Grade and Mound Gravel Bed Distribution Sizing Formulas
30-4 At-Grade and Mound Waste Water Flow Rate for Sizing Gravel Bed Basal Area
30-5 Maximum Linear Loading Rate for At-Grade Dispersal Systems
30-6 Maximum Linear Loading Rate for Mound Dispersal Systems
30-7 Mound Dispersal System Sand Fill Sizing Requirements
30-8 Mound Dispersal System Slope Correction Factors
30-9 Mound System Effective Infiltrative Area Formula
30-10 At-Grade Dispersal System Soil Cover Lateral Extension Lengths
31-1 Raised Sand Filter Bed Sizing Formula
31-2 Raised Sand Filter Bed Effective Length Formula
31-3 Raised Sand Filter Bed Linear Loading Rates
31-4 Raised Sand Bed Filter Wastewater Flow Rate used for Determining Linear Loading Rates
35-1 Sand Filter Media Specifications
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LIST OF TABLES
Table
No. Table Title
36-1 Geotextile Specifications – Minimum Average Roll Values
36-2 Polyvinyl Chloride Liner Specifications
43-1 OWTS Required Inspection Frequency
43-2 System Inspection Requirements
43-3 System Maintenance, Monitoring & Reporting Requirements
43-4 Effluent Quality Maximum Constituent Concentrations
44-1 Hydraulic Load Test Rating Guidelines
APPENDIX B
LIST OF FIGURES
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)B-1
APPENDIX B - FIGURES
Figure
Number Figure Title
7-1 USDA Soil Textural Triangle
7-2 Soil Profile Classification
8-1 Percolation Test Hole Schematic – Standard Method of Construction
8-2 Percolation Test Hole Schematic – Alternative Method of Construction
10-1 Nitrate Impacted Groundwater Areas of Concern – Alameda Creek Watershed Above Niles
10-2 Nitrogen Loading Requirements within Zone 7 Water Agency Jurisdictional Boundaries
12-1 Curtain Drain Schematic Detail
17-1 Typical Septic Tank Cross-Section
24-1 Intermittent Sand Filter Schematic
24-2 Intermittent Sand Filter with Pump Basin Cross-Section
24-3 Recirculating Sand Filter Cross-Section
25-1 OWTS Performance Monitoring Well Schematic
27-1 Gravity Trench Dispersal System (Gravel Trench) Cross-Section
27-2 Gravity Trench Dispersal System (Gravel Trench) Overflow Pipe on Sloping Site
28-1 Pressure Distribution Trench Dispersal System Schematic
28-2 Pressure Distribution Trench Dispersal System (Gravel Trench) Cross-Section
28-3 Pressure-Dosed Sand Trench Dispersal System Cross-Section
29-1 Subsurface Drip Dispersal System Schematic
29-2 Subsurface Drip Dispersal System Details
30-1 At-Grade Dispersal System Schematic
30-2 At-Grade Dispersal System Cross-Section
30-3 Mound Dispersal System Cross-Section
30-4 Mound Dispersal System Plan View – Level Site
30-5 Mound Dispersal System Cross-Section – Level Site
30-6 Mound Dispersal System Schematic – Sloping Site
30-7 Mound Dispersal System Cross-Section – Sloping Site
30-8 Mound Dispersal System Cross Section – Dimensions (Sloping Site)
30-9 Mound Dispersal System Plan View – Dimensions (Sloping & Level Site)
31-1 Raised Sand Filter Bed Dispersal System Cross-Section
32-1 Cover Fill Trench Dispersal System (Conventional Trench) Cross-Section
APPENDIX C
LIST OF ACRONYMS
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LIST OF ACRONYMS
Acronym Definition
AOC Areas of concern
AOS Apparent opening size
ANSI American National Standards Institute
ASTM American Society for Testing and Materials
ATU Aerobic Treatment Unit
BOD Biochemical oxygen demand
BOD5 Biochemical oxygen demand exerted after a five days of a BOD test
CBOD5 Carbonaceous biological oxygen demand
CIMIS California Irrigation Management Information System
COWA California Onsite Wastewater Association
D10 Effective size
FEMA Federal Emergency Management Act
FOG Fats, oil and grease
ft2/ft Square feet per lineal foot
gpd Gallons per day
gal/ft2 Gallons per square foot
gal/ft2-day Gallons per square foot per day
gal/ft2-min Gallons per square foot per minute
gpm Gallons per minute
IAPMO International Association of Plumbing and Mechanical Officials
ISF Intermittent sand filter
L/gal Liters per gallon
lb/mg Pounds per milligram
lb/year Pounds per year
MCL USEPA maximum contaminant level drinking water standard
mg/L Milligrams per liter
Mg-N/L Milligrams of nitrate per liter
ml Milliliters
MPI Minutes per inch
MPN Most probable number
NAWT National Association of Waste Transporters
N Nitrogen
NH3-N Ammonia nitrogen
NH4-N Ammonium nitrogen
NMP Zone 7 Nutrient Management Plan
NO2-N Nitrite-nitrogen
NO3-N Nitrate-nitrogen
NSF National Sanitation Foundation
OM&M Operations, monitoring and maintenance
Ordinance Alameda County Onsite Wastewater Treatment Systems Ordinance
Organic-N Nitrogen
OWCU Onsite Wastewater Containment Unit
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)PAGE 2 OF 2
LIST OF ACRONYMS
Acronym Definition
OWTS Onsite Wastewater Treatment System
PDST Pressure Dosed Sand Trench
RV Recreational Vehicle
ROWD Report of waste discharge
RRE Rural residential equivalence
RSF Recirculating sand filter
SRA Service request application
TKN Total Kjeldahl Nitrogen
TSS Total suspended solids
Uc Uniformity coefficient
UPC Uniform Plumbing Code
USDA United States Department of Agriculture
USGS United States Geological Survey
USEPA United States Environmental Protection Agency
Zone 7 Zone 7 Water Agency
APPENDIX D
DEFINITION OF TERMS
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)D-1
DEFINITION OF TERMS
Definitions are provided for terms used in this Manual.
Abandoned system: An OWTS or OWCU that will no longer be used to receive effluent or the Department
has issued notice to destroy the OWTS or OWCU. Also referred to as Abandoned OWTS or OWCU.
Abandoned well: A well whose original purpose and use has been permanently discontinued or which is in
such a state of disrepair that it cannot be used for its original purpose. If an abandoned well has been properly
destroyed so that it will not produce water nor act as a conduit for the movement of water, it will not be
subject to well setback requirements.
Abandonment permit: The administrative document issued by the Department allowing abandonment of
an existing OWTS or OWCU.
Advanced OWTS: An Advanced OWTS utilizes either a method of Wastewater treatment or supplemental
treatment other than a septic tank and/or a method of wastewater dispersal other than a gravity trench
dispersal system. Advanced OWTS are designed to allow siting of an OWTS where a standard OWTS is
not suitable due to site constraints or wastewater strength.
Applicant: A property owner or the property owner’s authorized representative that applies for a permit for
an OWTS or OWCU.
Application: Service Request Application
As-built plans: Scaled plan(s) prepared by a Contractor and/or Qualified Professional identifying the
location and configuration of the installed System components and the horizontal setbacks to structures
and other features on the property. As-built plans are submitted to the Department if changes have been
made to the approved OWTS design, at completion of construction and prior to receiving final approval by
the Department and to support performance evaluations of undocumented or unpermitted Systems.
At-grade dispersal system: A dispersal system with a discharge point located at the preconstruction grade
(ground surface elevation). The discharge from an at-grade system is always subsurface.
Authorized representative: A person or persons authorized by the property owner to act on the property
owner’s behalf on matters pertaining to application for permits and services, or holder of an easement
sufficient to authorize the work on the land on which the System is to be installed, in order to represent the
owner’s or easement holder’s interests.
Average annual rainfall: The average of the annual amount of precipitation for a location over a year as
measured by the nearest National Weather Service station for the preceding three decades. For example the
data set use to make a determination in 2012 would be the data from 1981 to 2010.
Basis of design report. A bound design report documenting the basis of the OWTS or OWCU design.
Reports documenting geotechnical evaluations, cumulative impact assessments, hydrogeological studies or
other evaluations must be appended to the basis of design report. Also referred to as design report.
Biochemical oxygen demand (BOD): The amount of dissolved oxygen needed by aerobic biological
organisms in a body of water to break down organic material present in a given water sample at certain
temperature over a specific time period. BOD5 is the five (5) day biochemical oxygen demand exerted after
five (5) days of a BOD test.
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DEFINITION OF TERMS
Blackwater: Wastewater contaminated with human or kitchen wastes, generally originating from toilets
and kitchen sinks. It includes, but is not limited to, wastewater discharges from kitchen sinks, garbage
grinders, water closets, toilets, urinals or similar fixtures alone or in combination with other wastewater.
Building: A structure built, erected and framed of component structural parts designed for the housing,
shelter, enclosure or support of persons, animals or property of any kind.
Building department: A local building agency of a city or county which has the jurisdiction to issue
building permits to construct, alter, repair or destroy structures.
Building sewer: The drainage piping which conveys sewage from a building to the septic tank or public
sewer. That part of the horizontal piping of a drainage system that extends form the end of the building drain
and that receives the discharge of the building drain and conveys it to a public sewer, private sewer or Onsite
Wastewater System.
California Plumbing Code: Part 5 of the California Code or Regulations, Title 24 also referred to as the
California Building Standards Code, published in its entirety every three years by order of the California
legislature with supplements published in intervening years. A city, county or city and county may establish
more restrictive building standards reasonably necessary because of local climate, geological or topographic
conditions.
Cesspool: An excavation in the ground receiving wastewater designed to retain the organic matter and
solids while allowing the liquids to seep into the soil. Cesspools differ from seepage pits because cesspool
systems do not have septic tanks. The term cesspool does not include pit-privies and out-houses.
Chemical toilet facility: See portable toilet.
Cleanout: A fitting inserted into a piping system with a removable plug whereby access to the pipe is
obtained for the purpose of cleaning or clearing blockages.
Community OWTS: An OWTS that accepts wastewater from buildings or structures on two or more parcels
or an OWTS shared by buildings or structures under separate ownership whether or not they are on the same
Parcel. A community OWTS may be either privately or publicly owned or operated.
Composting toilet: A type of dry toilet that uses a predominantly aerobic processing system to treat human
excreta by composting or managed aerobic decomposition.
Constrained sites: Sites where specific conditions including but not limited to small parcel size, poor soil
characteristics, close proximity to surface water bodies and shallow groundwater table conditions limit
treatment and dispersal system options. May require maximum extent practical measures to be implemented
during corrective actions due the inability to meet vertical separation to groundwater and horizontal setback
distance requirements.
Contamination: Impairment to the quality of the waters of the State from wastewater to a degree which
creates a hazard to public health through toxicity or through the spread of disease. Contamination shall
include any equivalent effect resulting from the disposal of wastewater, whether or not waters of the state
are affected.
Contractor: An individual licensed as a General Engineering Contractor (Class A), a General Building
Contractor (Class B), a Plumbing Contractor (Class C-36) or a Sanitation System Contractor (Class C-42)
ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL (06-05-2018)D-3
DEFINITION OF TERMS
license in accordance with the provisions of the California Business and Professions Code. Contractors
engaged in the modification, repair or installation of Onsite Wastewater Systems are expected to possess
basic knowledge and skills regarding applicable codes, siting, construction and operation of Onsite
Wastewater Systems.
Corrective action plan: A written document supporting a repair/modification permit application describing
corrective actions required to return an OWTS to a properly functioning system. The corrective action plan
may include a timeline for phased implementation.
County. Alameda County.
Cover fill dispersal system: Dispersal systems that use “cover fill” or soil fill placed on top of original grade
to provide the required backfill cover over the pipe and drain rock in trench dispersal systems or subsurface
drip dispersal systems where the dispersal trenches or driplines are excavated entirely below grade. The
wastewater is dispersed into the native soils, not into the fill soil.
Cumulative impacts: The persistent and/or increasing effect resulting from the density of OWTS
discharges in relation to the assimilative capacity of the local environment. Examples include, but not
limited to:
Nitrate, salt additions, or other indicator of human excreta to groundwater or surface water;
and/or
Rise in groundwater levels that interfere with the performance of the OWTS, causing drainage
problems or results in other adverse hydrological or soil conditions affecting public health, water
quality or public safety; and/or
Bacteriological Contamination from animal and human waste in surface water, Groundwater,
and drinking water wells.
Curtain drain: A sub-surface gravel-filled trench installed uphill of a dispersal system designed to intercept
shallow perched groundwater flow and divert it away from or around the dispersal field.
Cut or embankment: Any altered area of land surface where the height (h) of the manmade cut or
embankment is greater than two (2) feet, with a slope greater than fifty (50) percent, and any part of which
is lower in elevation than the ground surface at the nearest point of the System. The required setback
distance shall not be less than twenty five (25) feet nor more than fifty (50) feet from the top of the cut or
embankment. Cuts supported by retaining walls or similar structures shall be included in this definition as
shall steep natural ground surfaces where a sharp break in the ground slope is discernible.
Department: See Department of Environmental Health.
Department of Environmental Health (Department): The Alameda County Department of
Environmental Health.
Design plans: The OWTS or OWCU design plans prepared by a System Designer utilizing the site map as
a base map and presenting the engineering details of the OWTS or OWCU design. Also referred to as
OWTS or OWCU Design Plans.
Design report: See basis of design report.
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DEFINITION OF TERMS
Director of Environmental Health: The director of the Department of Environmental Health or his or
her designated representative.
Dispersal field: The area occupied by the OWTS Dispersal System.
Dispersal system: The OWTS dispersal system including a trench, subsurface drip, at-grade, mound, raised
sand filter bed, evapotranspiration and infiltration bed, or other type of system for final wastewater treatment
and subsurface discharge.
Dispersal trench: A trench with vertical sides and substantially flat bottom designed to receive effluent
and disperse the effluent into the surrounding soil through the bottom and/or sidewall area of the trench. It
may also be referred to as a trench.
Domestic-strength wastewater: Wastewater with a measured strength less then high-strength wastewater
and is the type of wastewater normally discharged from, or similar to, that discharged from plumbing
fixtures, appliances and other household devices including, but not limited to toilets, bathtubs, showers,
laundry facilities, dishwashing facilities, and garbage disposals. Domestic wastewater may include
wastewater from commercial buildings such as office buildings, retail stores, and some restaurants, or from
industrial facilities where the domestic wastewater is segregated from the industrial wastewater. Domestic
wastewater may include incidental recreational (RV) holding tank dumping but does not include wastewater
consisting of a significant portion of RV holding tank wastewater such as at RV dump stations. Domestic
wastewater does not include wastewater from industrial processes.
Drainage swale: Any course of concentrated drainage water that has formed over time by either natural or
man-made forces or where flow of water is either at or near the ground surface. For purposes of this Manual,
drainage swales are treated as ephemeral watercourses. OWTS and OWCU horizontal setback distances are
measured from the high water mark.
Drainage way: An unlined channel with definite bed or banks which conveys storm water runoff and
provides surface hydraulic continuity with either intermittent or perennial watercourses. For purposes of
this Manual, drainage ways are treated as ephemeral watercourses. OWTS and OWCU horizontal setback
distances are measured from the high water mark.
Dump Station: A facility intended to receive the discharge of wastewater from a holding tank installed on
a recreational vehicle (RV). A dump station does not include a full hook-up sewer connection similar to
those used at a RV park.
Dwelling: Any structure or building or any portion thereof which is used, intended, or designed to be
occupied for human living purposes including, but not limited to, houses, houseboats, boathouses, mobile
homes, travel trailers, hotels, motels and apartments.
Effective infiltrative area: The surface area measured in square feet that is required/allowed, for design
purposes, to be considered for receiving the wastewater effluent dispersal in the dispersal system.
Effective soil: Permeable, unsaturated soil located beneath the bottom of the dispersal system having suitable
texture and other properties for absorption and adequate filtration of effluent. It is the undisturbed unsaturated
naturally occurring soil located beneath the bottom of the dispersal system and above the high seasonal
groundwater level and/or other the limiting layer.
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DEFINITION OF TERMS
Effluent: Untreated, partially or completely treated wastewater flowing out of a septic tank, supplemental
treatment system, dispersal system or other OWTS component.
Ephemeral watercourse. See Watercourse.
Existing lot of record: A lot or parcel legally created prior to the effective date of this Manual.
Existing OWTS or OWCU: An OWTS or OWCU that was in place, operating, and properly functioning
on the effective date of Alameda County’s Local Agency Management Plan (LAMP). Also referred to as
an Existing Onsite Wastewater System or System.
Expansion: An increase in the size or capacity of an OWTS for the purpose of accommodating a planned
or potential increase in the amount or strength of wastewater flow from the facility or facilities served by the
OWTS.
Expansive clay soil: Soil that swells and shears when wet and shrinks and develops cracks when dry,
forming slickened sides and wedge-shaped structures. Expansive clay soil is very hard or extremely hard
when dry, very firm when moist and very sticky and very plastic when wet. When dry, there is normally clear
visual evidence of soil shrinkage cracks. When wet, expansive clay soil is massive and cracks and structure
are not evident. Expansive, high shrink-swell soil may exhibit suitable soil percolation rates during the
dry season due to shrinkage cracks in the Soil; but when it becomes wet, the same soil may swell to the
point of providing little or no percolation.
Failed OWTS or OWCU: A failed OWTS or OWCU requires corrective action, in some cases repair in
others replacement. Also referred to as a failed System.
Final approval: The document, issued by the Department that certifies the OWTS or OWCU was installed
in compliance with the provisions of this Manual and all permit conditions of approval have been met,
including issuance of an operating permit, as applicable.
Flood hazard area: The greater of the following two areas:
The area within a floodplain subject to a one (1) percent or greater chance of flooding in any given
year.
The area designated as a flood hazard area on a community’s flood hazard map, or otherwise legally
designated.
Flow equalization: The process of controlling the rate of wastewater flow through an OWTS by providing
storage capacity to hold surges of incoming flow, with timed-release of the accumulated wastewater to
even-out the flow to downstream Treatment and/or dispersal components.
Flow equalization tank. Flow equalization tanks are installed following the septic tank to aid in better
OWTS performance by allowing peak surges in wastewater flow (e.g., from a weekend event) to be
temporarily stored and metered into the supplemental treatment system and/or dispersal system at a
relatively even (“average”) rate over an extended number of days (e.g., during the subsequent week).
Flowing water body: A body of running water flowing over the earth in a natural water course, where the
movement of the water is readily discernible or if water is not present it is apparent from review of the geology
that when present it does flow, such as in an ephemeral drainage, creek, stream, or river.
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DEFINITION OF TERMS
Geotechnical report: A written document prepared by a Qualified Professional used to communicate soil
and geologic site conditions, interpretations, analysis and recommendations pertinent to the design,
installation and operation of an OWTS where required by this Manual.
Grade: The slope or fall of a line of pipe in reference to a horizontal plane. In drainage, it is usually expressed
as the fall in a fraction of an inch or percentage of slope per foot length of pipe.
Gravity trench dispersal system: A dispersal system consisting of a series of gravity-fed trenches that use
perforated pipe for subsurface dispersal of effluent into the soil.
Graywater: Pursuant to Health and Safety Code Section 17922.12, graywater means untreated wastewater
that has not been contaminated by any toilet discharge, has not been affected by infectious, contaminated, or
unhealthy bodily waste and does not present a threat of contamination by unhealthful processing,
manufacturing or operating wastes. Graywater includes but is not limited to wastewater from bathtubs,
showers, bathroom washbasins, clothes washing machines and laundry tubs, but does not include Wastewater
from kitchen sinks or dishwashers.
Graywater system: A system designed to collect graywater to be treated onsite for reuse or distribution
to an irrigation or disposal field. A graywater system may include onsite treated non-potable water devices
or equipment, tanks, valves, filters, pumps or other appurtenances along with piping and receiving landscape.
Grease interceptor: A passive interceptor that has a rate of flow exceeding fifty (50) gallons per minute and
that is located outside a building. Grease interceptors are used for separating and collecting oil and grease
from wastewater.
Grease interceptor tanks: Tanks used to collect fats, oils and greases (FOG) before they enter the septic
tank.
Groundwater: Water below the land surface that is at or above atmospheric pressure.
Groundwater mounding: A rise in the groundwater table which may occur beneath or down-gradient of
an OWTS dispersal system as a result of the concentrated or high volume of hydraulic loading (wastewater
discharge) from one or more OWTS in a limited area.
Groundwater table. That level of groundwater where the hydraulic pressure is zero. It may also be described
as the upper surface of the zone of saturation.
High-flow OWTS: An OWTS with a wastewater design flow greater than one thousand five hundred
(1,500) gallons per day.
High-strength wastewater: Wastewater having a thirty (30) day average concentration of biochemical
oxygen demand (BOD) greater than three hundred (300) milligrams-per-liter (mg/L) or of total suspended
solids (TSS) greater than three hundred and thirty (330) mg/L or a fats, oil, and grease (FOG) greater than
one hundred (100) mg/L prior to the septic tank or other treatment component.
High seasonal groundwater: The highest level of saturation in the soil in a year with normal rainfall.
Holding tank: A self-contained watertight receptacle used to collect and store wastewater prior to it being
pumped and removed from the property by a Septage Pumper and are only allowed in limited circumstances.
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DEFINITION OF TERMS
Horizontal setbacks: Minimum horizontal distance requirements from pertinent features to OWTS or
OWCU components.
Incinerator toilet: A type of dry toilet that burns human feces instead of flushing them away with water.
Individual OWTS: An OWTS that serves building(s) or structure(s) under the same ownership on one Lot
or parcel.
Industrial wastewater: Liquid or water-borne waste from industrial or commercial processes, except
domestic wastewater.
Inspection well: Wells installed within dispersal systems and sand filter systems for the purpose of checking
effluent levels periodically.
Installation permit: The administrative document issued by the Department that conveys approval of
and conditions for the installation of an OWTS or OWCU or component thereof.
Installer: A person meeting the definition of Contractor as defined this Manual.
Intermittent sand filter (ISF) system: A sand filter system is used to provide supplemental treatment of
septic tank effluent prior to discharge to the dispersal system. They are used to improve or restore the capacity
of the dispersal system, reduce pathogenic bacteria loading and can provide additional nitrogen removal. An
ISF consists of a packed-bed filter of medium-grained sand designed for single pass-through treatment of
septic tank effluent; it is sometimes referred to as a “single pass filter”.
Intermittent watercourse: See Watercourse.
Limiting layer or condition: A subsurface layer or condition that can severely limit the function of a
dispersal system. Includes hardpan, claypan, fragipan, saprolite, clay soil, permeable fractured rock,
compacted soil, soil containing rock or coarse fragments greater than fifty (50) percent, sandy or gravelly
soil with very rapid permeability, high seasonal groundwater and other subsurface conditions such as buried
foundations, abandoned dispersal Systems, piping, etc. (Reference the USDA Natural Resources
Conservation Service Soil Survey Manual for definition of soil terms).
Listed (third-party certified): Equipment or materials included in a list published by a listing agency
(accredited conformity assessment body) that maintains periodic inspection on current production of listed
equipment of materials and whose listing states either that the equipment or material complies with approved
standards or has been tested and found suitable for use in a specified manner.
Listing agency: An agency accredited by an independent and authoritative conformity assessment body to
operate a material and product listing and labeling (certification) system which is in the business of listing
or labeling. The system includes initial and ongoing product testing, a periodic inspection on current
production of listed (certified) products, and that makes available a published report of such listing in which
specific information is included that the material or product is in accordance with applicable standards and
found safe for use in a specific manner.
Lot: A legally recognized and defined area of land that can be sold individually, as described on an
instrument or a map recorded or filed with the County Recorder. A lot may also be referred to as a parcel.
A single or individual parcel or area of land legally recorded or validated by other means acceptable to the
authority having jurisdiction on which is situated a building or which is the site of any work regulated by
Onsite Wastewater Treatment System Manual (Manual): The document developed, maintained
and amended by the Alameda County Department of Environmental Health containing policy, procedural
DEFINITION OF TERMS
this code, together with the yards, courts, and unoccupied spaces legally required for the building or works,
and that is owned by or is in the lawful possession of the owner or the building or works.
Manual: See Onsite Wastewater Treatment System Manual.
Mound dispersal system: An aboveground dispersal system (covered sand bed with effluent leachfield
elevated above original ground surface inside) used to enhance soil treatment, dispersal and absorption of
effluent discharges from an OWTS treatment unit such as a septic tank. Mound systems have a subsurface
discharge.
Multi-Unit Residences: Apartments, condominiums, mobile home parks, etc.
National Sanitation Foundation (NSF): A non for profit non-governmental organization that develops
health and safety standards and performs product certification.
New Onsite Wastewater System: An OWTS or OWCU permitted after the effective date of Alameda
County’s Local Agency Management Plan (LAMP).
Non-discharging toilet unit: A self-contained, watertight container designed to hold wastewater until it is
pumped out and hauled to an approved receiving facility for disposal. A non-discharging toilet unit includes
but is not limited to a vault toilet, portable toilet and waterless toilet.
Non-residential facility: Any structure or building (excluding single-family residential units) or any portion
thereof intended for commercial or industrial use.
Nuisance: Includes, but is not limited to:
A public nuisance known at common law or in equity jurisprudence.
Where work regulated by this Manual and the Ordinance is dangerous to human life or is
detrimental to health and property.
Inadequate or unsafe water supply or Wastewater disposal system.
Onsite Wastewater Containment Unit (OWCU): A self-contained, non-discharging unit used to collect
and store wastewater for removal, hauling and disposal at an approved septage receiving facility, and
includes holding tanks, vault toilets, portable toilets and waterless toilets. The short form of the term may be
singular of plural.
Onsite Wastewater Systems: Onsite Wastewater Systems (or Systems) as referenced herein include Onsite
Wastewater Treatment Systems (OWTS) as defined by the State OWTS Policy and Onsite Wastewater
Containment Units (OWCU) as defined by Alameda County General Ordinance Code Chapter 15.18.
Onsite Wastewater Treatment System(s) (OWTS): Individual disposal systems, community collection and
disposal systems, and alternative collection and disposal systems that use subsurface disposal. The short form
of the term may be singular or plural. OWTS do not include “graywater” systems pursuant to Health and
Safety Code Section 17922.12.
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DEFINITION OF TERMS
and technical details for implementation of the Chapter 15.18 of the County Ordinance as approved by the
San Francisco Bay Regional Water Quality Control Board and adopted by the Board of Supervisors of
Alameda County.
Operating permit: The administrative document issued by the Department authorizing the initial and/or
continued use of OWTS or OWCU in conformance with the provisions of the Ordinance and this Manual
and may contain both general and specific conditions of use.
Operation, maintenance and monitoring (OM&M) manual: A manual prepared by a System Designer
in connection with the development of an OWTS or OWCU that provides technical information and
guidance for the owner and Service Provider regarding the components, operation and maintenance of the
OWTS or OWCU, including recommended inspections, monitoring and/or servicing to ensure long-term
performance and water quality and public health protection.
Ordinance: Alameda County Onsite Wastewater Treatment Systems Ordinance codified in Chapter 15.18
of the Alameda County General Ordinance Code.
Owner: Any person who alone, or with others:
Has legal title to any single parcel, dwelling, dwelling unit, non-residential facility or an easement
sufficient to allow installation and maintenance of an Onsite Wastewater System; or
Has care, charge or control of any real property as Applicant, executor, executrix,
administrator, trustee or other holder of legal title.
OWTS performance monitoring well: A monitoring well installed upslope, downslope or laterally from
the dispersal system for the purpose of monitoring fluctuations in groundwater levels, quality of
groundwater or the concentration of contaminants in groundwater.
Parcel: See lot.
Percolation rate: The liquid absorption rate of soil in the dispersal field as determined by a percolation test
used for designing the dispersal system.
Percolation test (or testing): A method of testing water absorption of the soil. The test is conducted with
clean water and test results can be used to establish the dispersal system design.
Perennial watercourse: See Watercourse.
Performance evaluation. A System inspection and evaluation to determine, on an individual basis, whether
an existing OWTS is functional and meets minimum standards of performance contained in this Manual.
Performance evaluation report. A written document prepared by a Qualified Professional documenting
the findings of a performance evaluation of an existing System and recommendations for corrective action(s),
if applicable.
Permit: A document issued by the County or Regional Water Board that allows the installation and use of
an OWTS or OWCU.
Person: Any individual, firm, association, organization, partnership, corporation, business trust, company,
Pressure-dosed sand trench dispersal system: A variation of a pressure-dosed trench dispersal system
that utilizes pea gravel and a medium-grade sand in lieu of a portion of the drain rock in the dispersal
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DEFINITION OF TERMS
state agency or department or unit of local government.
Piezometers: An observation well installed in the dispersal field to measure high seasonal groundwater
levels during wet weather testing.
Planning department: A local agency of a city or county which has the jurisdiction over land use approvals
including but not limited to lot creation, subdivisions, lot line adjustments, conditional use permits, or other
site development reviews;
Plans. OWTS or OWCU design plans, repair/modification plans, corrective action plans or as-built plans.
Plumbing fixture: An approved-type installed receptacle, device or appliance that is supplied with water or
that receives liquid or liquid-borne wastes and discharges such wastes into the drainage system to which it
may be directly or indirectly connected. Industrial or commercial tanks, vats and similar processing
equipment are not plumbing fixtures, but may be connected to or discharged into approved traps or plumbing
fixtures where and otherwise provided for elsewhere in this code.
Plumbing system: Includes all potable water, building supply and distribution pipes; all plumbing fixtures
and traps; all drainage and vent pipes; and all building drains and building sewers including their respective
joints and connections, devices, receptors and appurtenances within the property lines of the premises.
Portable toilet: A portable toilet is a chemical toilet with a self-contained watertight container housed
within a portable toilet shelter that collects wastewater from the toilet and/or hand washing facilities. A
portable toilet is a non-discharging toilet unit.
Potable water: Water that is satisfactory for drinking, culinary and domestic purposes and that meets the
requirements of the health authority having jurisdiction.
Premises: A building and the area of land that it is on.
Pressure distribution: A method of effluent distribution to a supplemental treatment system (such as a
sand filter) and/or a dispersal system designed to spread the effluent equally and evenly throughout the
distribution area by placing the Effluent under pressure in a small diameter piping network. It may also be
referred as pressure dosing.
Pressure distribution system: A system employing pressure distribution that includes the following
elements:
Pump or dosing siphon that generates pressurized flow and a prescribed dose volume;
Transport piping that conveys the effluent from the pump or dosing siphon to the distribution area;
Manifold and fittings that divide the flow from the transport piping amongst a series of laterals;
Lateral pipes placed throughout the supplemental treatment system or dispersal system with a
prescribed number, sizing and spacing of drilled holes (orifices) along the length of each lateral
pipe to release the effluent evenly under pressure to the distribution area during each dosing cycle.
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DEFINITION OF TERMS
trench to improve treatment of effluent.
Pressure-dosed trench dispersal system: A trench dispersal system that uses a pump or dosing siphon and
small-diameter pressure piping to achieve broad and uniform distribution of effluent for improved soil
absorption and better treatment of effluent as compared to a gravity trench dispersal system.
Primary treatment: Wastewater treatment occurring in the septic tank.
Process water: Wastewater that is generated from any manufacturing, processing institution, commercial,
or agricultural operation, or any operation that discharges other than blackwater and graywater.
Property: See Lot
Proprietary treatment units: A category of manufactured or “packaged” supplemental treatment systems
specifically developed for residential and other small-scale wastewater treatment applications.
Public health hazard: A condition created by a discharge of biological, chemical, physical and/or
radiological agents which are likely to cause human illness, disorders or disability or as otherwise defined
by law.
Public nuisance: Includes but not be limited to, anything which:
Is injurious to public health or is indecent or offensive to the senses or any obstruction to the free
use of property so as to interfere with the comfortable enjoyment of life or property; and
Affects at the same time an entire community or neighborhood or any considerable number
of persons, although the extent of the annoyance or damage inflicted upon individuals may
be unequal; and
Is an attractive nuisance which may prove detrimental to children or others, whether in a building,
on the premises of a building or upon an unoccupied lot. This may include, for example, any
abandoned but improperly decommissioned well, OWTS or OWCU, cesspool, or open seepage Pit;
and
Is dangerous to human life or is detrimental to health, as determined by the Director of
Environmental Health; and
Inadequate or unsanitary or unapproved wastewater or plumbing facilities.
Public sewer system: Any sanitary sewer system constructed, installed, maintained, operated and
owned by or for a municipality or other public entity having authority for collection, treatment and disposal
of wastewater.
Public water system: A water system regulated by the California Department of Public Health of a Local
Primacy Agency pursuant to Chapter 12, Part 4, California Safe Drinking Water Act, Section 116275(h) of
the California Health and Safety Code.
Public water well: A groundwater well serving a public water system. A spring which is not subject to the
California Surface Water Treatment Rule (SWTR), California Code of Regulations CCR Title 22, Sections
64650 through 64666 is a public well.
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DEFINITION OF TERMS
Pump tank: A watertight tank constructed of approved materials designed to receive and temporarily collect
and store wastewater and serves as a temporary reservoir for a pump that doses or discharges the collected
effluent to a subsequent OWTS component by means of a pump or automatic dosing siphon.
Qualified Professional: An individual licensed or certified by a State of California agency to design Onsite
Wastewater Systems and to practice as professionals for other associated reports, as allowed under their
license or registration. Depending on the services to be performed and the various licensing and registration
requirements, this may include an individual who possesses a registered environmental health specialist
certificate or is currently licensed as a professional engineer or professional geologist.
Qualifying public agency: A public agency with local, full-time sanitation and water quality staff who
are trained and have the capability to operate and maintain OWTS and OWCU.
Raised sand filter bed dispersal system: A dispersal system that combines features of an intermittent
sand filter system and a mound dispersal system. It consists of a raised or terraced sand bed, commonly
supported by a low retaining wall or bulkhead, where the bottom surface is even with or slightly below
ground surface and forms the absorption surface. The raised sand filter bed dispersal system provides
additional polishing treatment of effluent and final dispersal of wastewater into native soil. Raised sand
filter bed dispersal systems will be approved only for repair or other corrective action of existing OWTS on
severely constrained sites where site specific conditions limit treatment and dispersal options.
Recirculating sand filter (RSF) system: A sand filter system used to provide supplemental treatment of
septic tank effluent prior to discharge to the dispersal system. RSFs are used to improve or restore the
capacity of the dispersal system, reduce pathogenic bacteria loading and can provide additional nitrogen
removal. An RSF utilizes coarse-grained sand and a recirculation system, usually controlled by a timer
that causes the effluent to pass through the sand media several times prior to final dispersal. RSFs have
the ability to produce effluent quality similar to intermittent sand filter systems, except that they are less
effective in bacteria removal. However, RSFs typically provide greater nitrogen removal than ISFs,
on the order of fifty (50) percent reduction as compared with standard tank effluent.
Recreational vehicle (RV): A vehicular-type unit primarily designed as temporary living quarters for
recreational, camping, travel or season use that either has its own motive power, or is mounted on or towed
by another vehicle. The basic entities are camping trailer, fifth-wheel trailer, motor home, park trailer, travel
trailer and truck camper.
Regional Water Board: The Regional Water Quality Control Boards designated by Water Code Section
13200. Any reference to an action of the Regional Water Board in this Manual also refers to an action
of its Executive Officer, including the conducting of public hearings, pursuant to any general or
specific delegation under Water Code Section 13223. The San Francisco Bay and Central Valley
Regional Water Boards have jurisdiction over Alameda County.
Repair/Modification Permit. The administrative document issued by the Department allowing repairs or
modifications to an existing OWTS or OWCU.
Replacement OWTS: A new OWTS replacing an existing failing OWTS.
Report of waste discharge (ROWD): Application, technical information and filing fee submitted to
Regional Water Board to receive waste discharge requirements (or a permit) authorizing operation and
OWTS discharges.
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DEFINITION OF TERMS
Reserve area: A dedicated area of land having suitable site conditions and sufficient area for installation
of a replacement dispersal system (sized for one hundred (100) percent of the wastewater design flow
and able to meet all the design requirements of the dispersal system proposed) should it be required in
the future.
Restrictive layer: See Limiting layer
Rural residential equivalent (RRE): Zone 7 Water Agency groundwater nitrogen loading estimate of
thirty-four (34) pounds of nitrogen per year from a typical, single family home served by a standard OWTS.
Sand filter system: A packed-bed sand filter to treat septic tank effluent to an “advanced level” prior to
dispersal into the soil. The sand filter system consists of a lined excavation or structure filled with uniform
clean sand, with an under-drain system at the bottom to collect and direct the water for dispersal or additional
treatment. In some cases, sand filter systems may have an open bottom to allow percolation directly into the
soil below where conditions are suitable.
Scum: A mass of organic or inorganic materials floating on the surface in a septic tank, largely comprised
of oil and grease from animal and vegetable fats.
Seepage Pit: A drilled or dug excavation that receives the effluent discharge from a septic tank or other
OWTS treatment unit for dispersal. Seepage pits are not authorized in Alameda County.
Septage: Accumulated wastewater solids and liquid in OWCU or OWTS tanks that require periodic
removal, hauling and disposal at an approved septage receiving facility.
Septage Pumper: A person who is qualified to pump and haul waste from OWCU and OWTS. To operate
in Alameda County a Septage Pumper must be registered pursuant to the California Health and Safety Code.
Septic Tank: A watertight, covered receptacle designed for primary treatment of wastewater and
constructed to:
Receive wastewater discharged from a wastewater drainage system;
Separate settleable and floating solids from the liquid;
Digest organic matter by anaerobic bacterial action;
Store digested solids; and
Clarify wastewater for further treatment with final subsurface discharge.
Serial Distribution: The distribution of effluent to the dispersal system by gravity flow that
progressively loads one section of the dispersal system to a predetermined level before overflowing to the
succeeding lower section(s).
Service Provider. An individual capable of operating, monitoring and maintaining an Onsite Wastewater
System in accordance with the provisions of this Manual. To operate in Alameda County a Service Provider
must be registered with the Department.
Single family residence: A dwelling designed for and commonly occupied exclusively by one household or
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DEFINITION OF TERMS
family.
Site: See Parcel or Lot.
Site evaluation: An assessment of the characteristics of a parcel sufficient to determine its suitability for an
OWTS to meet the requirements of this Manual.
Slope: The rise or fall in feet per one hundred (100) feet of horizontal distance. Slope is expressed as a percent
of grade. For example: a land surface with a rise of one hundred (100) feet over a horizontal distance of one
hundred (100) feet (45-degree angle) has a slope of 100 percent. Also referred to as grade.
Sludge: The residual, semi-solid material that is produced as a byproduct of wastewater treatment.
Soil: The naturally occurring body of porous mineral and organic materials on the land surface, which is
composed of unconsolidated materials, including sand-sized, silt-sized and clay-sized particles mixed with
varying amounts of larger fragments and organic material. The various combinations of particles
differentiate specific soil textures identified in the soil textural triangle developed by the USDA...
Soil profile: An evaluation of the characteristics of a vertical section of the soil extending through all its
horizons into the underlying parent material. It is conducted in areas proposed for wastewater dispersal,
including reserve area(s), to ascertain its suitability for that purpose. Characteristics of soil examined in a
soil profile may include structure, texture, color, impervious layers, and evidence of groundwater as
determined by direct observation or presence of indicators, such as mottling. Also referred to as a soil profile
study.
Soil profile study. See Soil profile.
Soil profile test pits: An excavation dug for the purpose of a soil profile study of sufficient size and depth
to allow thorough examination of the soil to evaluate its suitability for wastewater dispersal.
Soil texture: The relative proportions of sand, silt and clay particles found in a mass of Soil, as described
by the twelve (12) basic textural classes defined by the United States Department of Agriculture (USDA).
Special permit: The administrative document issued by the Department for approval and conditions for
use of portable toilets and waterless toilets.
Standard OWTS: An OWTS comprised of primary (septic tank) treatment and gravity-fed trenches
(gravity trench dispersal system) installed in native soil below original grade. Effluent flows to the dispersal
trenches by gravity or may be pumped to the first distribution box of the dispersal system.
State OWTS Policy: The Water Quality Control Policy for Siting, Design, Operation and Maintenance
of Onsite Wastewater Treatment Systems adopted by the State Water Resources Control Board on June 19,
2012, which became effective May 13, 2013.
Storm water: Water that originates during precipitation events and snow/ice melt. Storm water can soak into
the soil (infiltrate), be held on the surface and evaporate or runoff and end up in nearby surface waterbodies.
Subdivision: Subdivision as defined by the Subdivision Map Act of the State (Government Code Section
66410 et seq.).
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DEFINITION OF TERMS
Subsurface drip dispersal system: A method for disposal of treated wastewater that uses special drip
tubing (dripline) designed for use with wastewater. The dripline is placed normally eight (8) to twelve
(12) inches below ground surface and makes use of the most biologically active soil zone for distribution,
nutrient uptake and evapotranspiration of the wastewater.
Sump: A tank that receives liquid waste and which is located below the normal grade of the gravity system
and which must be emptied by mechanical means.
Supplemental treatment systems. Any OWTS or component of an OWTS, except a septic tank or dosing
tank, that performs additional wastewater treatment so that the effluent meets a predetermined performance
requirement prior to discharge of effluent into the dispersal field.
Surface water drainage structures: Manmade structures such as lined drainage ditches,
infiltration/percolation trenches, vegetated swales, non-perforated drain pipes, watertight culverts or
conduits, etc., used for dispersal of roof runoff or other Site drainage, OWTS and OWCU horizontal setback
distances are measured from the edge of the conveyance structure.
Swale: See Drainage swale.
Systems: See Onsite Wastewater Treatment Systems.
Total suspended solids (TSS): Suspended solids in water and are a constituent of total solids. TSS can
include a wide variety of material such as soil particles, decaying plant, animal matter and wastewater.
The total amount of suspended solids in a liquid is determined by a laboratory test that measures the dry
weight of TSS residue retained on a filter after drying the sample and is a measure of the level of treatment
being achieved. TSS can be inorganic particles, which are difficult for biological processes to break
down, resulting in mechanical clogging. In wastewater with high TSS, inorganics are less easily broken
down and can accelerate mechanical clogging of the infiltrative surface of the dispersal system.
Treatment: Any process or action that accomplishes a measureable reduction in wastewater strength or
separation of liquid from solids, such as in the reduction of solids or organics, dewatering, coagulation,
settling, filtration, aeration or disinfection.
Trench(es). See Dispersal trench.
Unstable land mass: Land prone to subsidence, erosion or movement as indicated by evidence of historical
landslide events, published maps or reports, or evidence of characteristics such as surface rupture, scarps,
creep or other irregularities in ground slope conditions
Variance: An administration exception to the provisions of the Ordinance and the Manual.
Vault toilet: A structure used for disposal of human waste without the aid of water. It consists of a shelter
built above a subsurface vault into which human waste is deposited. A vault toilet has no water connection
and is a non-discharging toilet unit.
Vertical separation: The measured depth of effective soil for effluent absorption and filtration that
exists between the bottom of a dispersal system and the restrictive or limiting layer or groundwater.
Waste discharge requirement (WDR): An operation and discharge permit issued by a Regional Water
Board for the discharge of waste pursuant to Section 13260 of the California Water code.
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Wastewater: Water-carried waste that is intended to be removed and generally produced by fixtures such
as toilets, sinks, showers or bathtubs, clothes washing machines, dish washing machines, floor drains or
other fixtures or fittings intended to drain organic or inorganic waste material from residential and non-
residential (including commercial and industrial) processes. The term wastewater as referenced in this
Manual includes both untreated, partially treated and treated wastewater.
Wastewater design flow: The quantity of peak daily wastewater flow assigned to a building or structure for
the purpose of sizing an OWTS or OWCU. For OWTS with flow equalization tanks, the wastewater design
flow used for sizing the supplemental treatment system and/or the dispersal system may be based on the
equalized (“average”) flow rate rather than the peak daily flow rate for the building or structure;
Watercourse: A body of running water flowing over the earth in a natural watercourse, where the movement
of water is readily discernible or if water is not present it is apparent from review of the geography that when
present it does flow.
Ephemeral watercourse: A watercourse that may or may not have a well-defined channel that is
dry most of the year and flows only during or briefly following a period of rainfall in the immediate
locality. Ephemeral watercourses receive no water from springs or groundwater and no sustained
supply from melting snow or other surface source. Ephemeral watercourses are not defined on
United States Geological Survey (USGS) topographic maps and must be identified in the field based
on characteristic features. For purposes of this Manual, ephemeral watercourses includes drainage
swales and drainage ways. Horizontal setback distances are measured from the high water mark.
Intermittent watercourse. A natural watercourse with a well-defined channel with bed and banks
in which water flows for only part of the year, typically during winter and spring when the bed is
below the groundwater table, during years of normal rainfall. The flow may be heavily supplemented
by storm water runoff. For purposes of this Manual, intermittent watercourses are identified as
dotted blue lines on USGS topographic maps. Horizontal setback distances are measured from the
natural or levied top of bank).
Perennial watercourse: A watercourse with a well-defined channel with bed and banks that has
continuous flow all year round during years of normal rainfall. The channel bed is located below the
groundwater table for most of the year. Groundwater is the primary source of water for a perennial
watercourse, but it also carries storm water runoff. For purposes of this Manual, perennial
watercourses are identified as solid blue lines on USGS topographic maps. Horizontal setback
distances are measured from the natural or levied top of bank).
Waterless toilet: A composting toilet, incinerator toilet or similar device for the holding and processing
of waste from a toilet. A waterless toilet is a non-discharging toilet unit.
Water supply system: The building supply pipe, the water distribution pipes, and the necessary connecting
pipes, fittings, control valves, backflow prevention devices and all appurtenances carry or supply potable
water in or adjacent to the building or premises.
Well: A groundwater well that provides water for human consumption and is not regulated by the California
Department of Public Health.
Wet weather season: See wet weather testing period.
Wet weather testing: Direct observation of groundwater levels during the time of year when the highest
groundwater conditions are expected or known to occur.
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Wet weather testing period: The period from October through April and after at least fifty (50) percent of
the average annual rainfall (as measured from October 1st through September 30th) has fallen and within a
ten (10) day period following rainfall of at least one-half (0.5) inch in a forty-eight (48) hour period. The wet
weather testing period may be extended or shortened by the Department depending on rainfall patterns in a
given year. Also referred to as wet weather season.
Zone 7: Alameda County Zone 7 Water Agency.