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 This website is no longer updated and links to external websites and some internal pages may not work.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

Water Quality Improvement

A major objective in EPA's work to restore the San Francisco Bay Delta Watershed is to improve water quality by reducing or preventing contamination of rivers and streams, using a watershed approach.

EPA has worked with local partners to reduce the pesticide diazinon levels in the Sacramento and Feather River systems. As a result, levels of diazinon have dropped below water quality criteria on 79 miles of these rivers. Selenium loads have been reduced by two-thirds since 1996 in Salt Slough and Grasslands Marsh through water management improvements and redirecting contaminated flow.

In 2015, EPA produced 14 water quality progress reports that assess TMDL implementation progress and water quality improvement. We will use these reports and work with our partners to identify actions that accelerate water quality improvements and restore protection for beneficial uses.