Central San advances studies for long-term wastewater diversion to regional recycled water program

Central San advances studies for long-term wastewater diversion to regional recycled water programThe Central Contra Costa Sanitary District has approved an agreement with regional partners to evaluate diverting up to 2.7 million gallons per day of wastewater to support summer irrigation demands.

The board authorized a Memorandum of Agreement with the DSRSD-EBMUD Recycled Water Authority (DERWA) to fund technical studies for a potential 50-year diversion term.

Studies will assess the feasibility of diverting full flows from a local pump station without causing downstream impacts or odor issues in Central San's collection system.

The initial agreement spans one year with two possible one-year extensions, replacing a recently expired temporary five-year arrangement.

The Central Contra Costa Sanitary District (Central San) is moving forward with plans to potentially supply a neighboring recycled water program with seasonal wastewater flows. During its March 19, 2026 meeting, the Central San board authorized a Memorandum of Agreement (MOA) with the DSRSD-EBMUD Recycled Water Authority (DERWA), the Dublin San Ramon Services District (DSRSD), and the East Bay Municipal Utility District (EBMUD). DERWA, which provides recycled water to the San Ramon Valley, has sought additional wastewater supplies to meet summer irrigation demands. While a temporary five-year agreement previously allowed DERWA to access flows via an existing 18-inch sewer line interconnection, the agencies are now exploring a permanent solution. The newly approved MOA establishes a one-year term with two possible one-year extensions to facilitate technical studies, which will be funded by the DERWA partners. Currently, DERWA has access to approximately 0.6 to 0.7 million gallons per day (MGD) that flows by gravity through the interconnection. The upcoming studies will evaluate the operational feasibility of diverting the full flow from the associated force main pump station, which currently handles 2.7 MGD from the Doherty Valley area. Volumes are expected to increase due to regional development. Central San staff and board members emphasized that any long-term diversion must not harm the utility's existing infrastructure or customer base. The technical studies will specifically examine how to maintain the integrity of the force main pump station during summer months when it may not be running, as well as any downstream impacts on the collection system, such as odor generation. Staff noted that an adaptive management approach—including a flushing protocol funded by the DERWA partners—will be evaluated to mitigate potential issues. Pending the outcome of the technical studies, the agencies aim to negotiate a 50-year seasonal wastewater diversion agreement, providing the long-term certainty required for future infrastructure investments.