Sewer System Modeling

Client: San Francisco Public Utilities Commission

San Francisco is the only coastal city in California with a combined sewer system that collects and treats both wastewater and stormwater in the same network of pipes. This means the rain that runs off roofs and streets gets treated just like the wastewater that goes down the toilet.

Since much of San Francisco is paved over, most of the rainwater that falls from the skies usually ends up in the City’s sewers. There are almost 1,000 miles of sewer beneath the City's roadways, including large storage/transport boxes that are about 50 feet deep and as wide as the streets they run under. San Francisco's hilly geography adds to the complexity of the combined sewer system.

WRE engineers participated in the development of a comprehensive computer model that simulates the performance of the City’s combined sewer system. The model has been used to analyze potential system improvements by allowing the simulation of “what if” scenarios.