In the San Francisco Bay Area, where most freshwater wetlands have been lost, Moorhen Marsh is a shining example of a community success story.

In 1974, MVSD created Moorhen Marsh, the first wetlands on the West Coast dependent solely on treated effluents as its primary water source. The 21-acre constructed wetland saved the District’s rate payers millions of dollars by avoiding the construction of a deep-water outfall to transport MVSD’s treated wastewater to the Carquinez Strait, all while creating critical habitat for wildlife.

Moorhen Marsh is a part of the wastewater treatment process by reducing nutrients as the effluent travels through the wetland before flowing into Peyton Slough and eventually out to the Carquinez Strait. MVSD installed 42 floating islands, fully stocked with native plant species, in Moorhen Marsh to act as a natural treatment system, taking advantage of the natural processes of plants and robust microbial activity in the roots. Additionally, the riparian zones throughout the marsh were planted with native species to establish a fully native habitat as a beneficial use for desired animal species

Moorhen Marsh is completely dependent on MVSD’s advanced secondary treated effluent for its water. Without the approximately 1 million gallons of effluent provided by MVSD’s treatment plant every day, this historic marsh would cease to exist.

To increase awareness, appreciation, and understanding of the functions and values of wetland habitats and the wildlife they support, MVSD started the Wetlands Education Program in 1996. The program began with field trip experiences for Martinez elementary schools. Over the years it has grown and now includes a classroom program and is available to students from schools throughout Contra Costa County. Learn more about the program at https://www.mvsd.org/wetlands-education-program.

Moorhen Marsh provides important open space in a heavily industrialized area, while offering visitors an opportunity to learn about wetlands, their important role in our community, and how we can protect them for future generations.

Moorhen Marsh is open by appointment only during MVSD business hours, Mondays-Thursdays, 7 am - 4 pm, and Fridays, 7 am – 3 pm. To make an appointment contact the Public Outreach Coordinator at rmitchell@mvsd.org. There is no access on the weekends or during observed holidays.