Sanitary Sewer Overflow

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What is a Sanitary Sewer Overflow (SSO)?
Do you know your Sewer System? Do you know who’s responsible and who to call?
Check out this diagram that illustrates the difference between private laterals, local city sewer lines, OCSD’s regional sewer trunklines, and storm drains.

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.

What is the Waste Discharge Requirement (WDR)?
To provide a consistent, statewide regulatory approach to address SSOs, the State Water Resources Control Board (SWRCB) 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 Statewide General Waste Discharge Requirements and its supporting documents can be viewed through this link:

What is a Sewer System Management Plan?
OCSD's Sewer System Management Plan (SSMP) describes the activities we use to manage the wastewater collection system effectively. Effective management of a wastewater collection system includes:

1. Maintaining or improving the condition of the collection system infrastructure in order to provide reliable service into the future.
2. Cost-effectively minimizing infiltration/inflow (I/I) and providing adequate sewer capacity to accommodate design storm flows.
3. Minimizing the number and impact of sanitary sewer overflows (SSOs) that occur.

What are the required elements of a Sewer System Management Plan?

The required elements of an SSMP include:
1. Collection system management goals
2. Organization of personnel, including the chain of command and communications
3. Overflow emergency response plan
4. Fats, oils, and grease (FOG) control program
5. Legal authority for permitting flows into the system, inflow/infiltration control as well as enforcement of proper design, installation, and testing standards, and inspection requirements for new and rehabilitated sewers
6. Measures and activities to maintain the wastewater collection system
7. Design and construction standards
8. Capacity management
9. Monitoring plan for SSMP program effectiveness
10. Periodic SSMP Audits, periodic SSMP updates, and implementation of program improvements

What reports need to be generated?

If an SSO occurs, it must be reported to the SWRCB using an online reporting system developed the SWRCB. This online reporting system is called CIWQS - the California Integrated Water Quality System. Note: All spills greater than 1000 gallons still must be called in to the California Emergency Management Agency (CalEMA), as is currently required.

State Water Resources Board 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. The following links will take you to the State Water Resources Control Board’s spill maps.

What is the CA WDR Quarterly General Meeting?
The CA WDR General Group meets quarterly to discuss topics related to the WDR, SSMP, and Sewer Collections Systems. There may also  be opportunities for technical training. It is open to OCSD staff, satellite agencies, and the general public. For meeting dates go to the OCSD district calendar. 

We hope this provides you with a general overview and an opportunity to explore links to more detailed information.

If you have any questions or would like to provide input, please contact:

  • Ron Coss, Program Manager for the SSMP, (714) 593-7508
  • Lisa Frigo, Environmental Supervisor for SSMP, (714) 593- 7405
  • Dindo Carrillo, Regulatory Liaison for SSMP, (714) 593-7476
  • Peggy Echavarria, WDR Committee Liaison, (714) 593-7256