The 303(d) List of Impaired Water Bodies


The Federal Clean Water Act (CWA) gives States the primary responsibility for protecting and restoring surface water quality. Under the CWA, States that administer the CWA must review, make necessary changes, and submit the CWA section 303(d) list (list of waters not meeting water quality standards) to the U.S. Environmental Protection Agency (U.S.EPA). CWA Section 305(b) requires each State to report biennially to U.S.EPA, on the condition of its surface water quality. The U.S.EPA has issued guidance to States which requires the two reports to be integrated. For California, this combined report is called the California 303(d)/305(b) Integrated Report.

For 303(d), State and Regional Water Boards assess water quality monitoring data for California’s surface waters every two years to determine if they contain pollutants at levels that exceed protective water quality standards. Water body and pollutants that exceed protective water quality standards are placed on the State’s 303(d) List. This determination in California is governed by the Water Quality Control Policy for developing California’s Clean Water Act Section 303(d) List. U.S.EPA must approve the 303(d) List before it is considered final.

Placement of a water body and pollutant that exceeds protective water quality standards on the 303(d) List, requires the development of a Total Maximum Daily Load (TMDL). In some cases other regulatory programs will address the impairment instead of a TMDL, or the water quality may improve as a result of other circumstances.

For the 305(b) Report, State and Regional Water Boards place the water body segment that were assessed into one of U.S.EPA’s five Integrated Report beneficial use report categories (see 2016 Staff Report below for more details). For this assessment, available data are used to evaluate beneficial uses including aquatic life, drinking water supply, fish consumption non-contact recreational, and swimming.

California has been developing 303(d)/305(b) Integrated Reports every two years since 1976, and these reports are available in electronic format on the State Board's Water Quality Assessment web page.

2018 Section 303(d) List Changes

The Regional Board approved limited changes to the Section 303(d) list at its March 13, 2019 meeting. The State Board approved the these limited changes when they approved the 2018 Integrated Report at its October 20, 2020 Meeting. You can find out more about the 2018 Integrated Report by visiting this website. Please see the Staff Summary Report and appendices below for more information.

2016 Section 303(d) and 305(b) Integrated Report

This is the Section 303(d) and Section 305(b) Integrated Report that was approved by the San Francisco Bay Regional Board on April 12, 2017. The Final Staff Report is available in PDF form, and the appendices link to web pages containing the described information on 303(d) list changes and 305(b) assessment of waterbody segments in the San Francisco Bay Region.

Proposed De-Listings

Napa River and Sonoma Creek Delisting Project:
The San Francisco Bay Regional Water Quality Control Board approved at its February 12, 2014 meeting a proposal to delist Sonoma Creek for nutrients resulting in excessive algae growth and to remove this water body from the EPA 303(d) list. The staff report detailing recent water quality assessments, lines of evidence, and interpretation of data are provided below. This de-listing will not be included in the Integrated Report submitted to U.S. EPA for the 2016 listing cycle because the data on which the de-listings are founded were collected after the 2010 data solicitation period for the 2016 list. These de-listings will be included in a subsequent (2018) 303(d) cycle. See the Napa River Nutrients and Sonoma Creek Nutrients project pages for more information.

Past 303(d) Lists (2010 List)

Evaluation of Water Quality Conditions for San Francisco Bay Region. Proposed Revisions to federal Clean Water Act Section 303(d) List of Impaired Waters.

The last complete 303(d) list for the San Francisco Bay Region was completed in 2010. View and query the final 2010 303(d) list on the State Board website. For information about the San Francisco Regional Water Board process in preparing the 2010 303(d) list, see the documents below.


Past 303(d) Lists (2006 List)