Wastewater flows from the west side of the City are transported to the Oceanside Plant, which is located at 3500 Great Highway in San Francisco. The Oceanside Plant has the capacity to treat 65 MGD of combined storm water and wastewater during wet weather conditions. Up to 43 MGD receive secondary treatment, and the remaining flow receives primary treatment. All dry weather and wet weather flow from the Oceanside WPCP is discharged into the Pacific Ocean via a 80-feet deep and 3.75 miles long pipe (Southwest Ocean Outfall-SWOO ) to ensure adequate dilution.

The storage/transport structures operate to transport combined sewage and street runoff to the Oceanside Plant during dry weather periods. During wet weather, these structures provide storage for additional storm water and wastewater flow, while pumping facilities continue to transfer flow to the treatment facility. In the event that the capacities of the treatment plant and storage structures are exceeded, the combined storm water and wastewater receive the equivalent of primary treatment in the transport structures and are discharged into the Pacific Ocean via the SWOO or any of the seven shoreline combined sewer overflow structures.