Orange Memorial Park Regional Stormwater Capture Project

South San Francisco, Ca March 16, 2021 City Website


In 2015, the San Francisco Regional Water Quality Control Board (RWQCB) issued the countywide Municipal Regional Stormwater Permit (MRP) to regulate stormwater discharges in San Mateo County. The MRP requires all permittees to implement green infrastructure improvements to reduce the amount of mercury and polychlorinated biphenyl (PCB) in stormwater discharges to the San Francisco Bay. The San Mateo County Stormwater Resource Plan (SRP) was developed to identify projects that could help meet the requirements of the MRP.  The SRP identified the proposed project as a high-priority regional project that can capture water from a large multi-jurisdictional drainage area.

Additional details on the SRP are located here.


Colma Creek Water Shed

Rain falling east of the Santa Cruz Mountain range drains into the San Francisco Bay, while rain falling on the western side drains to the Pacific Ocean.  This project helps clean water flowing from our cities to the Bay.  The reach of Colma Creek running through Orange Memorial Park drains over 6,500 acres of land from six different municipalities, including the City of South San Francisco.


This regional stormwater capture project, the first-of-its-kind in Northern California, diverts all dry-weather flow and the dirty first flush of urban stormwater runoff from Colma Creek into an underground system integrated within the park.

The project supports the City’s park Master Plan by co-locating stormwater capture, storage, and treatment facilities in Orange Memorial Park with the park renovations which will follow this project.

Orange Memorial Park Stormwater Capture Educational Placard


Project Summary

Orange Memorial Park Stormwater Capture project will provide water quality improvements to meet the requirements of the San Francisco Bay MRP. The project is designed to reduce discharges of PCBs and mercury to San Francisco Bay and is the first regional stormwater project of its kind in the Bay Area.



The project will capture runoff through the installation of an instream diversion and pre-treatment structure (trash screen and sediment removal chamber) at the upper end of the Colma Creek flood control channel within the park. Pre-treated water will then enter a diversion pipe leading to an underground stormwater storage reservoir. A portion of the storage facility will function as a cistern, holding water for eventual non-potable irrigation use in the park and for water trucks, and the remainder will function as an infiltration chamber to recharge groundwater in the Westside Basin. Construction of these storage facilities will occur underneath a portion of the existing baseball and softball fields. A flow splitter is located just upstream of the storage facilities to discharge treated overflow back into the channel when storage capacity is exceeded.




The project is currently in the Construction phase and scheduled to begin construction early 2021.  For additional information, please contact our Construction Hotline at (650) 829-4600, or email us at

Project Timeline

Storm water timeline


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