Onsite Wastewater Treatment Systems (OWTS) Policy

  (Page last updated 4/15/24)

Table of Contents

1. Accessory Dwelling Unit Permitting Guidelines Onsite Wastewater Treatment
2. Local Agency Reporting of Groundwater Monitoring Data
3. Local Agency Monitoring and Reporting Requirements
4. Water Quality Control Policy for Siting, Design, Operation and Maintenance
5. Commercial Food Service Wastewater Issues
6. OWTS Policy Guidance Timeline Table
7. LAMP Contact List

Accessory Dwelling Unit Permitting Guidelines Onsite Wastewater Treatment

This section addresses permitting guidelines for accessory dwelling units (ADUs) under the Water Quality Control Policy for Siting, Design, Operation and Maintenance of Onsite Wastewater Treatment Systems (OWTS Policy). The State Water Resources Control Board (State Water Board) adopted the OWTS Policy in June 2012. The OWTS Policy authorizes local agencies (e.g., county environmental health departments) to issue OWTS permits. Local agency permitting activities must be consistent with the requirements of the OWTS Policy. Proposed ADUs should be evaluated as described below; local agencies should refer questions about permitting ADUs to Regional Water Quality Control Board (Regional Water Board) staff as needed. Additional evaluation is necessary because ADUs added to an existing development changes the initial analysis of the threat to water quality performed by the Regional Water Board.

ADUs may be attached to an existing structure or constructed as separate buildings on an existing subdivided lot. ADUs are also known as in-law units, backyard cottages, etc. The California Department of Housing and Community Development has promoted ADUs as an affordable housing option, more information is available under Accessory Dwelling Units. For ADUs served by an OWTS (e.g., septic system), approval from the local health officer is required per Government Code 65852.2(a)(1)(D)(ix). Local health officers must implement the requirements of the OWTS Policy when considering approval of an ADU. Additional information is available under the OWTS Policy.  

Local Agency Permitting of ADUs

Local agencies have some discretion in how they implement the OWTS Policy. They may:

1. Implement the OWTS Policy default permitting program (Tier 1). Local agencies implementing Tier 1 permitting programs should refer all ADU proposals to the Regional Water Board for evaluation and permitting as appropriate.
2. Implement a Regional Water Board approved local agency management program (LAMP) (Tier 2). Local agencies implementing a Tier 2 permitting program may permit ADUs consistent with the LAMP; if a LAMP does not address ADUs, then local agencies should refer all ADU proposals to the Regional Water Board for evaluation and permitting as appropriate.
3. Implement a program associated with an OWTS Policy Attachment 2 listed impaired surface water body (Tier 3). An OWTS located in the geographic area associated with an impaired surface water body is subject to additional treatment, monitoring, and oversight requirements. Local agencies implementing Tier 3 permitting programs can either implement the OWTS Policy Tier 3 default permitting requirements, a Regional Water Board approved advanced protection management program (APMP), or an approved total maximum daily load (TMDL) implementation program. Local agencies implementing an APMP or TMDL program may permit ADUs consistent with the program requirements. If an APMP or TMDL does not address ADUs, or if the local agency is implementing the default Tier 3 permitting requirements, then local agencies should refer all ADU proposals to the Regional Water Board for evaluation and permitting as appropriate.

Local Agency Reporting of Groundwater Monitoring Data

This section provides assistance to local agencies required to submit local agency generated surface water or groundwater monitoring data pursuant to the Water Quality Control Policy for Siting, Design, Operation and Maintenance of Onsite Wastewater Treatment Systems (OWTS Policy). Adopted by the State Water Resources Control Board in June 2012, the OWTS Policy authorizes local agencies (e.g., county environmental health departments) to issue OWTS permits. It also establishes certain monitoring and reporting requirements. Link to the OWTS Policy and the May 13, 2018 adopted conditional OWTS Policy waiver Resolution. OWTS Policy section 9.3.3 requires a local agency with an approved local agency management program (LAMP) to submit all local agency generated groundwater monitoring data for inclusion into GeoTracker. All local agency generated surface water monitoring data is required to be submitted to the California Environmental Data Exchange Network (CEDEN). All data shall be submitted by February 1 each year.

Information on how to submit the data for each system is provided below.

Groundwater Data Submittals – GeoTracker
Local agency generated groundwater data related to the OWTS Policy shall be submitted to the Regional Water Board in electronic deliverable format (EDF). EDF is a comprehensive data standard designed to facilitate the transfer of electronic files between data producers and users. Because GeoTracker requires an associated global identification number to upload data, and staff anticipate most OWTS Policy related groundwater data uploads to be isolated events (e.g., at the time of a real estate transfer), a simplified method to upload groundwater data to GeoTracker is described herein.

Local agencies shall ensure that the analytical laboratory selected to perform the sample analysis will produce the results in EDF. The EDF file shall be transmitted electronically to the Regional Water Board as part of the local agency’s annual report. Regional Water Boards will provide the EDF file to the State Water Board for uploading to GeoTracker. Additional information regarding EDF is available on the GeoTracker webpage. Two special procedures shall be employed regarding the EDF file:

• The “field point name1” shall be the physical site address, number and street name with no spaces (e.g., if the address is 123 Main Street, the field point name should be 123mainst).
•  The “global identification number2” shall be left blank. State Water Board staff will add a proxy global identification number before uploading the data to GeoTracker.

Surface Water Data Submittals - CEDEN
Local agency generated surface water data related to the OWTS Policy shall be submitted to CEDEN in a surface water ambient monitoring program (SWAMP) comparable format. Data is submitted to CEDEN through one of three regional data centers. Specific instructions and contact information is available under the CEDEN webpage.

Local Agency Monitoring and Reporting Requirements

This section provides assistance to local agencies required to submit monitoring reports to the Regional Water Quality Control Board (Regional Water Board). The State Water Resources Control Board (State Water Board) adopted the Water Quality Control Policy for Siting, Design, Operation and Maintenance of Onsite Wastewater Treatment Systems (OWTS Policy) for wastewater treatment systems in June 2012. The OWTS Policy authorizes local agencies (e.g., county environmental health departments) to issue OWTS permits. All local agencies that issue OWTS permits are required to report information to the Regional Water Board on February 1 each year.

Tier 1 Local Agencies
Local agencies that do not have an approved local agency management program (LAMP) are only required to report the information listed in OWTS Policy section 3.3.

Tier 2 and 3 Local Agencies
Local agencies implementing a Regional Water Board approved LAMP are required to report the information listed in OWTS Policy section 3.3 and section 9.3. Additional monitoring and reporting requirements may exist in the local agency’s LAMP, advanced protection management program (APMP), and/or total maximum daily load (TMDL) monitoring specified by the Regional Water Board.

Tier 2 local agencies are also required to:

• Maintain a water quality assessment program described in OWTS Policy section 9.3.2. The water quality assessment shall be submitted on February 1 every fifth year after the date of the Regional Water Board LAMP approval.
• Submit groundwater monitoring data generated by the local agency to GeoTracker in electronic deliverable format (EDF) as described in OWTS Policy section 9.3.3. More details are available under Electronic Submittal of Information. Contact your Regional Water Board representative for further information.
• Submit surface water monitoring data generated by the local agency to the California Environmental Data Exchange Network (CEDEN) as described in OWTS Policy section 9.3.3. Information about data submittal is available on the CEDEN webpage. Contact your Regional Water Board representative for further information

To assist local agencies in submitting the required monitoring reports, the State Water Board has developed template forms addressing the requirements of OWTS Policy section 3.3 and 9.3. The example word document contains four templates, each titled consistent with the OWTS Policy section number.

• Example Monitoring and Reporting Template (.docx)
• Example Monitoring and Reporting Template (.pdf)

Water Quality Control Policy for Siting, Design, Operation and Maintenance

General OWTS Policy Information

• Onsite wastewater treatment systems (OWTS) commonly known as septic systems that primarily treat domestic wastewater and employ subsurface disposal.
• There are an estimated 1.2 million OWTS in California

• The effective date of the Policy was May 13, 2013.
• Except for Tier 3, local agencies may continue to implement their existing OWTS permitting programs for 60 months after the effective date of the Policy.
• Owners of OWTS with projected flow over 10,000 gallons per day (gpd) or receives high-strength wastewater shall notify the Regional Water Boards. These OWTS may be required to submit a Report of Waste Discharge for coverage of Waste Discharge Requirements (WDR) or a Waiver of WDR.

• To allow continued use of OWTS, while protecting water quality and public health
• Assembly Bill 885 amended California Water Code section 13290, which required the State Water Board to develop statewide standards or regulations for permitting and operation of OWTS.

• OWTS owners
• Local agencies that permit OWTS (county environmental health dept., etc.)
• Regional Water Boards
• State Water Board

OWTS Policy Tiers

The OWTS Policy establishes a statewide, risk-based, tiered approach for regulation and management of OWTS installations and replacements, and it recognizes the effectiveness of local permitting agencies. Tiers are briefly summarized below, refer to the OWTS Policy for a complete discussion of the requirements.

Tier 0: Existing OWTS (OWTS Policy Section 6)

• Applies to properly functioning systems that do not need corrective action and are not near an impaired water body subject to TMDL, local agency’s special provisions, or located within 600 feet of a water body listed on OWTS Policy Attachment 2.
• Maximum flow rate is 10,000 gpd.

Tier 1: Low Risk New or Replacement OWTS (OWTS Policy Sections 7 & 8)

• Applies to new or replacement OWTS that comply with conservative siting and design standards described in the OWTS Policy.
• Tier 1 applies when a Local Agency Management Program (LAMP) has not been approved by the Regional Water Board.
• Maximum flow rate is 3,500 gpd.

• Applies to new or replacement OWTS that comply with the siting and design standards in an approved LAMP. LAMPs are developed by Local Agencies based on local conditions; siting and design standards may differ from Tier 1 standards.
• Maximum flow rate is 10,000 gpd.

• Applies to OWTS located near impaired surface water bodies that are subject to a Total Maximum Daily Load (TMDL) implementation plan, a special provision contained in a LAMP, or is located within 600 feet of a water body listed on OWTS Attachment 2.
• Supplemental treatment requirements may apply to a Tier 3 system.
• Maximum flow rate is 10,000 gpd.

• Applies to systems that are not properly functioning (failing).
• Failure may be indicated by surfacing effluent, wastewater backing up in plumbing fixtures, OWTS component/piping structural failure, or significant groundwater or surface water degradation

OWTS Policy Update Information

The OWTS Policy was adopted by the State Water Resources Control Board (State Water Board); the Policy became effective May 13, 2013. The Policy established a statewide, risk-based, tiered approach for regulation and management of OWTS. More information is available on the OWTS Policy program webpage

• The Policy includes a conditional waiver of waste discharge requirements for systems in compliance with the Policy, which by law expires after five years. The State Water Board renewed the conditional waiver on April 17, 2018 and on April 18, 2023
• OWTS Policy Attachment 2 contains a list of impaired waterbodies for which OWTS discharges are likely to be a contributing source of pathogens or nitrogen. Since the adoption of the OWTS Policy, technical studies performed and other factors justify changes to Attachment 2. The list of water bodies was amended to reflect the changes.

• Resolution No. 023-0012

• OWTS located near waterbodies removed from Attachment 2 are no longer subject to Tier 3 requirements unless a local agency has developed an advanced protection management program (APMP) for the area. Your local agency will inform you of APMP requirements if they are applicable.

• Definitions are updated to include the definition of Domestic wastewater, Accessory dwelling units (or ADUs), CWSRF, and LAMP.  
• References to California Department of Public Health in the policy are replaced with “State Water Board”
• Clarification in Tier 2 includes that Differing system design requirements; including but not limited to, alternative collection and disposal systems that use subsurface disposal.  
• Revised LAMPs five-year water quality assessment reporting period from five years after LAMP approval dates to a fixed five years beginning in 2018.
• Waterbodies removed or their TMDL completion dates were extended in the impaired water body Attachment 3 list.

Commercial Food Service Wastewater Issues

In June 2012, the State Water Resources Control Board (State Water Board) adopted the Water Quality Control Policy for Siting, Design, Operation and Maintenance of Onsite Wastewater Treatment Systems (OWTS Policy) for wastewater treatment systems. The OWTS Policy addresses onsite systems that primarily treat domestic wastewater and employ subsurface disposal, but it also addresses commercial food service buildings (such as restaurants) with similar wastewater treatment systems. This Fact Sheet provides guidance on simple and cost-effective methods for source control at commercial food service buildings to comply with the OWTS Policy.

Historically, most small wastewater systems were permitted through a local agency - typically a county environmental health department. The OWTS Policy does not change that procedure, but certain changes in local wastewater ordinances may be required to comply with the OWTS Policy requirements. In addition, the OWTS Policy imposes some requirements that a local agency must comply with. One of those requirements affects commercial food service buildings.

OWTS Policy section 2.6 requires owners of commercial food service buildings with onsite wastewater treatment systems to apply to the Regional Water Quality Control Board (Regional Water Board) for waste discharge requirements (WDRs) if the wastewater system:

1. Receives wastewater with a biochemical oxygen demand (BOD) greater than 900 milligrams per liter (mg/L), or
2. Does not have a properly sized and functioning oil/grease interceptor.

Owners of these systems must comply with both requirements (and other requirements such as flow limits) to avoid having to apply for WDRs.

Commercial food service operators have several alternatives to reduce the concentration of BOD in their wastewater. Employing these relatively inexpensive best management practices is likely to maintain the BOD concentration below 900 mg/L. An operator can train employees to employ the following good work practices:

1. Scrape plates and cookware to dispose of residual food in the trash before rinsing dishes.
2. Use screens in drains to capture food waste. Maintain drains and traps as needed.
3. Minimize the use of a sink mounted garbage disposal.
4. Recycle or properly dispose of cooking oils and other food items that cannot be used, rather than pouring them down the drain.
5. Sweep and/or mop floors rather than washing spills down the drain.
6. If needed, consider installing an in-kitchen passive interceptor.

Commercial food service operators have fewer options regarding the oil/grease interceptor requirement of the OWTS Policy. An operator can:

1. Connect to a regional wastewater collection system (if possible).
2. Install a properly sized and functioning oil/grease interceptor.
3. Submit an application to the Regional Water Board for issuance of WDRs.

OWTS Policy Guidance Timeline Table

Policy and Waiver Adoption: June 2012
Effective Date (Section 13.0): May 2013

State Water Board Renews Waiver* (Section 3.1) Year 5
Effective Date - May 13, 2018

State Water Board Renews Waiver* (Section 3.1) Year 10
Effective Date - May 13, 2023

State Water Board Renews Waiver* (Section 3.1) Year 15
Effective Date - May 13, 2028

*Waiver renewal per CWC Section13269