Rehabilitate four Combined Sewer Discharge (CSD) structures and install backflow preventers and monitoring sensors to keep seawater from entering the City's combined sewer system during high tide conditions.
A program-wide assessment was performed of the CSD structures through the Collections System Reliability (CSR) programmatic effort. Based on video inspections and physical studies by a specialized consultant, four CSD structures along Mission Creek at 5th, North 6th, and Division Street, and Sansome at Embarcadero were identified as priority structures due to their age, the importance of the CSD structure based on amount of discharge and sensitivity of the receiving water body, structural conditions, compliance with permit requirements, and other operational deficiencies.
What is a Combined Sewer Discharge (CSD)?
San Francisco is the only coastal city in California with a combined sewer system that collects and treats both sewage and stormwater in the same network of pipes and treatment facilities. This combined system means the debris and pollutants in stormwater runoff is treated to secondary treatment standards before being discharged into the Bay or Ocean. However, during intense storms the system can reach capacity and combined wastewater that is treated to primary standards is discharged through CSD structures around the City.
These CSD events are monitored and the SFPUC is in compliance with all regulatory and permitting agencies. Under the Sewer System Improvement Program, projects such as Baker Beach Green Streets, are being constructed to further reduce CSD events. Visit the Beach Water Quality Monitoring Program for more information on CSDs and water quality at beaches.
Project Purpose and Need
This project will rehabilitate four Combined Sewer Discharge (CSD) structures and install backflow preventers and monitoring sensors to keep seawater from entering the City's combined sewer system during high tide conditions. The completion of the structures at Mission Creek at 5th, North 6th, and Division Street were completed in 2019, but additional rehabilitation work was needed for the structure located along the Embarcadero at Sansome Street. This construction work began in May 2020 and is anticipated to complete in early 2021.
About the SSIP
The San Francisco Public Utilities Commission (SFPUC) recently launched the Sewer System Improvement Program (SSIP), a 20-year citywide investment to upgrade our aging sewer system and provide a more reliable, sustainable, and seismically safe system now and for future generations. The SSIP includes a series of facility upgrades at the Southeast Treatment Plant (SEP) located in the Bayview neighborhood of San Francisco. Click here to learn more about the SSIP.