MVSD’s wastewater treatment plant provides advanced secondary level treatment which includes sand filtration and ultraviolet disinfection for approximately 1.45 million gallons per day (mgd) of domestic and commercial wastewater; the plant has a design capacity of 3.2 mgd. The District manages 151 acres of constructed and natural marshland to provide for wastewater disposal. The treated effluent enters a constructed marshland west of I-680 known as Moorhen Marsh, flows to Peyton Slough, which then combines with surface runoff to supply natural marshland east of I-680 known as McNabney Marsh. Flows from the natural marshland re-enter Peyton Slough and ultimately reach the Carquinez Strait. Because of the water quality requirements for this process, the District maintains strict pretreatment standards and prohibits the discharge of heavy industrial waste into its sewerage system.

The District provides wetlands programs within the 21-acre constructed Moorhen Marsh and the 130-acre McNabney Marsh. These programs include environmental education as well as non-contract recreational use for residents of Contra Costa and Solano Counties.