Onsite Wastewater Treatment Systems (OWTS) / Septic Systems

Statewide Policy on the Regulation of OWTS

Onsite wastewater treatment systems (OWTS), commonly known as septic systems, treat domestic wastewater and employ subsurface disposal. On June 19, 2012, the State Water Resources Control Board (State Water Board) adopted Resolution No. 2012-0032, thereby adopting the Water Quality Control Policy for Siting, Design, Operation, and Maintenance of Onsite Wastewater Treatment Systems (OWTS Policy).  The OWTS Policy applies to discharges from new or replacement systems (excluding cesspools) with a maximum flow rate of 3,500 gallons per day (gpd). The OWTS Policy uses a risk-based, tiered approach (Tiers 0-4) for the regulation and management of OWTS installations and replacements. These Tiers are summarized in the table below.

The OWTS Policy contains a General Waiver of Waste Discharge Requirements (General Waiver) that authorizes discharges from OWTS that comply with the conditions of the OWTS Policy. The OWTS Policy must be readopted by the State Water Board every five years to renew the General Waiver. The most recent version of the OWTS Policy can be found on the State Board’s OWTS Policy webpage (https://www.waterboards.ca.gov/water_issues/programs/owts/index.html). The OWTS Policy was incorporated by reference into the North Coast Water Board’s Basin Plan (as well as all other Regional Boards’ Basin Plans) and is effective in the North Coast Region.

Local Agency Management Plans

The OWTS Policy establishes a framework in Tier 2 that promotes Local Agency Management Plans (LAMPs) developed by local governments, typically counties, to implement OWTS standards that differ from those prescribed in the OWTS Policy. LAMPs may apply to discharges from new or replacement OWTS up to 10,000 gpd. LAMPS are reviewed by Regional Board staff and approved by the Regional Board through resolution or through signature of the Executive Officer following public notice and comment. LAMPs may be revised by the local agency and submitted to the Regional Board for approval in their revised form.

The OWTS Policy grants each Regional Board the primary approving authority over LAMPS proposed by specific counties. The status of LAMPs in counties where the North Coast Region has the primary approval authority can be found in the table below.

Replacement OWTS with Inadequate Separation to Groundwater

Replacement OWTS that do not meet minimum groundwater separation requirements established by the OWTS Policy or a LAMP may be eligible for coverage under the Conditional Waiver of Waste Discharge Requirements for Specific Categories of Low Threat Discharge in the North Coast Region (Conditional Waiver). For the most recent version of this Conditional Waiver, see Adopted Orders (https://www.waterboards.ca.gov/northcoast/board_decisions/adopted_orders/). OWTS owners seeking coverage under the Conditional Waiver should first engage with local permitting authorities before contacting Regional Board staff for assistance.

OWTS in Areas with an Advanced Protection Management Program (APMP)

The OWTS Policy prescribes APMP requirements and sets APMP area boundaries for OWTS within Tier 3 of the OWTS Policy. APMPs are required for areas that are both on the Impaired Waters list (https://www.waterboards.ca.gov/northcoast/water_issues/programs/tmdls/303d/), a.k.a.  the 303(d) list, for pathogens or nitrogen, and are deemed to have a possible OWTS contribution to the impairment. The OWTS Policy also authorizes LAMPs to prescribe alternative requirements and create additional APMPs. Finally, APMPs and their requirements can be established by Total Maximum Daily Load (TMDL) regulations and an associated TMDL implementation plan.

In the absence of a LAMP or TMDL that addresses APMPs, the APMP area and its requirements are prescribed in the OWTS Policy. Where a LAMP exists but a TMDL does not, the LAMP may set requirements for APMP areas, but it may also defer to the OWTS Policy’s requirements. Finally, where a TMDL exists, whether or not a LAMP exists, the TMDL may define APMP boundaries and requirements. However, the TMDL may defer to a LAMP, if it exists, or the OWTS Policy.

In the North Coast Region, the only TMDL with APMP requirements is found in the Russian River watershed. The Russian River Pathogen TMDL (https://www.waterboards.ca.gov/northcoast/water_issues/programs/tmdls/russian_river/) defers APMP requirements to the Sonoma County and Mendocino County LAMPs or the OWTS Policy if no LAMP requirements exist. Therefore, OWTS owners in the Russian River watershed seeking information on OWTS requirements should contact the appropriate county prior to contacting Regional Board staff.

Cesspools

Cesspools have not been an authorized method of waste disposal since the adoption of the first Interim Basin Plan in 1971. Cesspools are not covered by the General Waiver contained in the OWTS Policy. Owners of cesspools should work with septic system design professionals and the appropriate county government to identify the best means of replacing the cesspool with an OWTS that qualifies for the General Waiver contained in the OWTS Policy.