An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

San Francisco Bay Delta

Improving Water Quality in Suisun Marsh

The Suisun Marsh is the largest contiguous brackish marsh remaining on the west coast of North America and is a critical part of the San Francisco Bay-Delta estuary ecosystem. The marsh is also impaired by mercury, nutrients, and organic enrichment/low dissolved oxygen (DO). The project will implement water quality improvement BMPs on Peytonia and Boynton sloughs and evaluate their efficacy. Based on hydrologic modeling of the slough systems, a mix of physical, operational, and management modifications BMPs will be implemented for the managed wetlands and treatment plant discharges. Community involvement is essential for long‐term attainment of TMDL objectives, as land use decisions that affect Suisun Marsh are made by numerous private landowners and a few public and non‐profit organizations.

Project Facts

Recipient: San Francisco Estuary Partnership
Funding:   $843,982 (non-federal match = $843,982)
Project Period:  July 2015 – December 2019
Partners: California Department of Fish and Wildlife, Fairfield Suisun Sewer District, Bay Conservation and Development Commission, Delta Conservancy, Delta Science Program, SFBay Regional Water Quality Control Board, Suisun Resource Conservation District, Siegel Environmental, Tetra Tech Inc.

Environmental Results Summary: Improving Water Quality in Suisun Marsh

OUTPUTS (Activities, efforts, and/or work product during project period)

OUTCOMES (Environmental results)

(1-5 yrs)


Develop an Experimental Design and Modeling Plan (EDMP) to guide HEC-RAS (hydrodynamic) and reactor model development, BMP implementation, and BMP field data collection and laboratory analysis

Complete the hydrodynamic model for predicting DO levels in Peytonia and Boynton Sloughs

Develop a reactor model for the managed wetlands representing the hydrology and kinetics affecting DO, BOD and MeHg concentrations and loading.

Field test BMPs along Peytonia and Boynton sloughs

Use an integrated HEC-RAS / Reactor-based modeling approach to characterize managed wetland field DO responses to imposed and hypothetical hydrologic and vegetation BMPs. This approach will allow testing the effectiveness of BMPs beyond what can be done through field studies due to resource limitations and confounding data

Analyze model results and publish technical report

Reduced occurrences of low DO events in tidal sloughs

Progress toward achieving (a) 75% reduction in occurrences of 1‐hour average DO concentrations ≤3.0 mg/L from fall flood‐up to spring draw‐down, and (b) DO levels that are protective of aquatic life

Full List of Project Summaries