Richardson Bay Pathogen TMDL

On December 18, 2009, the federal Environmental Protection Agency approved a Basin Plan amendment incorporating a TMDL for pathogens in Richardson Bay and an implementation plan to achieve the TMDL. The amendment was formerly adopted by the San Francisco Bay Water Board and the State Water Resources Control Board. The TMDL was approved by the State Office of Administrative Law and became effective on November 2, 2009. It is now officially incorporated into the Water Quality Control Plan for San Francisco Bay Basin (Basin Plan), the region’s mater planning document for protecting water quality. Electronic versions of the following documents are available upon request. However, in accordance with Section 11546.7 of the California Government Code, electronic versions cannot be posted online as they do not meet specified accessibility standards. For an electronic copy of the order, please contact the staff person listed at the bottom of this web page.

  • Adopted and approved Basin Plan amendment
  • State Water Board Resolution No. 2009-0063
  • Regional Water Board Resolution R2-2008-0061
  • Staff Report


Richardson Bay (also known as Richardson’s Bay) is an arm of San Francisco Bay located just northeast of the Golden Gate in southern Marin. It is enclosed by the cities of Sausalito, Mill Valley, Tiburon and Belvedere, as well as an unincorporated portion of Marin County. The Richardson Bay Audubon Sanctuary includes 900 acres of marine habitat between Belvedere and Tiburon.

The Bay is widely used for recreational activities including boating, kayaking, rowing, and swimming. Historically, Richardson Bay supported shellfish such as oysters, mussels, and clams. Because it is shallow and enclosed, with little tidal action or freshwater inflow from local creeks, the Bay has only a limited ability to disperse or dilute pollution.

Richardson Bay is listed by U.S. EPA as impaired by pathogens. The listing was made in response to observations of elevated bacteria levels in the Bay, which indicate the presence of fecal contamination and health risks from water-borne pathogens to shellfish harvesters and recreational users of the Bay. The Richardson Bay TMDL examines these water quality issues, identifies sources of pathogen contamination, and specifies actions to restore the health of the Bay.
view of Sausalito from the water

NEW - Fall 2023 - Long-term Bacteria Water Quality Monitoring Map
The San Francisco Bay Regional Water Board has created a map to illustrate the results of the long-term bacteria water quality monitoring in Richardson Bay. The map visually demonstrates pre- and post-TMDL bacteria levels, as well as the rate at which they exceed the applicable water quality objective for water-contact recreation at various sites within the Bay.

More information about Richardson Bay and Preventing Pollution
Richardson Bay Audubon Center and Sanctuary
Marin County Stormwater Pollution Prevention Program (MCSTOPPP)
Richardson Bay Special Area Plan (1984) (pdf, 7MB)

For more information contact:
Farhad Ghodrati
Water Resources Control Engineer
San Francisco Bay Regional Water Quality Control Board
1515 Clay Street, Suite 1400
Oakland, CA 94612
Phone: 510-622-2300
Fax: 510-622-2460