Sanitary Sewer Overflow Reduction Program

A sanitary sewer overflow (SSO) is any overflow, spill, release, discharge or diversion of untreated or partially treated wastewater from a sanitary sewer system. SSOs often contain high levels of suspended solids, pathogenic organisms, toxic pollutants, nutrients, oil, and grease. SSOs pollute surface and ground waters, threaten public health, adversely affect aquatic life, and impair the recreational use and aesthetic enjoyment of surface waters. Typical consequences of SSOs include the closure of beaches and other recreational areas, inundated properties, and polluted rivers and streams.



Issuance of Informal Staff Draft Statewide Sanitary Sewer Systems Order Reissuance

The State Water Resources Control Board (State Water Board) has issued a public notice announcing: (1) the availability of an informal staff draft Statewide Sanitary Sewer System General Order, and (2) two public workshops to provide stakeholders and interested parties information regarding the preliminary informal staff draft General Order. Stakeholders and interested parties are encouraged to provide oral feedback to staff during these workshops. Please see the Public Notice below for more details.


In April and May 2019, State Water Board staff conducted outreach workshops in the cities of San Diego, Sacramento, Chino, Redding, and Fresno to hear stakeholder input on the proposed reissuance of the existing Statewide Sanitary Sewer Systems General Order.

Links to 2019 Workshop Documents:

To receive up-to-date information regarding the proposed Sanitary Sewer Systems Order reissuance, please subscribe to the following email list service: (Under the Water Quality heading, select “Sanitary Sewer Overflow Reduction Program Order Review”)

General Order Information

To provide a consistent, statewide regulatory approach to address SSOs, the State Water Resources Control Board (State Water Board) adopted Statewide General Waste Discharge Requirements (WDRs) for Sanitary Sewer Systems, Water Quality Order No. 2006-0003 (Sanitary Sewer Systems WDR) on May 2, 2006. The Sanitary Sewer Systems WDR requires public agencies that own or operate sanitary sewer systems to develop and implement sewer system management plans and report all SSOs to the State Water Board’s online SSO database. The Sanitary Sewer Systems WDR and its supporting documents can be viewed through the links below:

All public agencies that own or operate a sanitary sewer system that is comprised of more than one mile of pipes or sewer lines which conveys wastewater to a publicly owned treatment facility must apply for coverage under the Sanitary Sewer Systems WDR. The application or Notice of Intent (NOI) for coverage under the Sanitary Sewer Systems WDR should have been submitted to the State Water Board by November 2, 2006 and is available at the link below:

Sewage Spill Incident Maps

These interactive geographic information system (GIS) maps, updated nightly, plot all certified sanitary sewer overflows (SSOs) and Private Lateral Sewage Discharges from sanitary sewer collection systems (not including any spills from wastewater (sewage) treatment plants), reported by agencies into the state’s online California Integrated Water Quality System. This includes the spill location, amount, source, and name of the responsible or reporting agency.

A second map allows users to see Private Lateral Sewage Discharges, voluntarily reported from enrollees in the program from pipes which empty into public sewer collection systems. Private lateral spills are caused from failures in pipes that tie private businesses and homes into the public sewer collection system, and are maintained by individual property owners. They often suffer from overflows which can affect public sewer collection systems.

Online SSO Database Access and Use

The SSO database is accessed through the California Integrated Water Quality System (CIWQS), which is the State Water Board’s regulatory and water quality information management system.

The collection system questionnaire gathers information related to an enrollee’s agency and facilities. This information will allow the performance of an enrollee’s sanitary sewer system to be put into the context of site-specific characteristics. The information collected includes population served, miles of pipe, and age of the sanitary sewer system. To view a copy of the collection system questionnaire, please refer to the Dischargers Users Guide.

The SSO report collects detailed information on a specific overflow event. Enrollees are required to report all SSOs that result from a failure in any portion of a sanitary sewer system under their management. For the purposes of reporting, SSOs fall into one of three categories. The definitions for each Category are listed in Table 1, below.

CATEGORIES DEFINITIONS [see Section A on page 5 of SSS WDRs for SSO definition]

Discharges of untreated or partially treated wastewater of any volume resulting from an enrollees sanitary sewer system failure or flow condition that:

Reach surface water and/or reach a drainage channel tributary to a surface water; or

Reach a municipal separate storm sewer system and are not fully captured and returned to the sanitary sewer system or not otherwise captured and disposed of properly. Any volume of wastewater not recovered from the municipal separate storm sewer system is considered to have reached surface water unless the storm drain system discharges to a dedicated storm water or ground water infiltration basin (e.g., infiltration pit, percolation pond).

CATEGORY 2 Discharges of untreated or partially treated wastewater of 1,000 gallons or greater resulting from an enrollee’s sanitary sewer system failure or flow condition that do not reach surface water, a drainage channel, or a municipal separate storm sewer system unless the entire SSO discharged to the storm drain system is fully recovered and disposed of properly.
CATEGORY 3 All other discharges of untreated or partially treated wastewater resulting from an enrollees sanitary sewer system failure or flow condition.

SSO information reported by enrollees includes location of overflow, volume of sewage spilled, and cause of the overflow. A copy of the Category 1, Category 2 SSO, and Category 3 can be found in the Dischargers User Guide.

If an enrollee does not have any SSOs in a calendar month, they are required to complete a no spill certification. The no spill certification form can be viewed at the link below:

Sewer System Management Plan Development/Implementation

Every enrollee is required to develop and implement a sewer system management plan (SSMP). The SSMP documents an enrollee’s program to properly operate and maintain its sanitary sewer system.; Each SSMP should address the following elements:

  1. Goal
  2. Organization
  3. Legal Authority
  4. Operation and Maintenance Program
  5. Design and Performance Provisions
  6. Overflow Emergency Response Plan
  7. Fats, Oils, and Grease (FOG) Control Program
  8. System Evaluation and Capacity Assurance Plan
  9. Monitoring, Measurement, and Program Modifications
  10. SSMP Program Audits
  11. Communication Program

For a detailed explanation of the SSMP elements, please refer to the Sanitary Sewer Systems WDR above.

The Sanitary Sewer Systems WDR gives enrollees a reasonable amount of time to develop and implement their SSMP with smaller communities having more time than larger ones.

The SSMP must be updated every five (5) years, and must include any significant program changes. Re-certification by the governing board of the Enrollee is required in accordance with D.14 of the SSS WDR when significant updates to the SSMP are made. To complete the re-certification process, the Enrollee shall enter the data in the Online SSO Database. Enrollees are required to provide an electronic copy of their SSMP to the Online SSO Database. 

Sanitary Sewer Systems WDR Enrollee Training

The State Water Board signed a memorandum of agreement (MOA) with California Water Environment Association (CWEA) to develop a training course for the Sanitary Sewer Systems WDR. CWEA will offer the courses statewide to educate enrollees about the terms of the Sanitary Sewer Systems WDR, use of the online SSO database, and development of a sewer system management plan (SSMP). For details about the course content and schedule, please visit the CWEA Website.

Related Links:

Historical Information


Permit Information

Reporting/SSMP/Spill Event Requests Information

SSO Compliance & Enforcement Information Annual Compliance Report