Why is This Important?
San Mateo County borders the San Francisco Bay to the east and the Pacific Ocean to the west. Both water bodies support unique aquatic ecosystems that are easily impacted by onshore activities. Bay and ocean resources support local economies through tourism and fisheries, and provide residents with recreational opportunities. Pollution and degradation of water quality in the Bay or Ocean can adversely impact economic growth through restrictions on development, fines to local governments, or loss of tourism revenues.
What is a Sustainable State?
In a sustainable state the presence of harmful pollutants in the county's water is minimized, and marine habitats are healthy and support native species.
How Are We Doing?
Bay water quality
Major historical contamination of the Bay includes mercury (used in gold mining operations) and PCBs (which were used widely as industrial insulators before being banned in 1979). Both of these contaminants are still present in significant quantities in bay sediments, and are also found in samples of fish tissue in quantities that can harm humans and animals. New contamination comes from inflows from the Delta, atmospheric deposition, and municipal and industrial wastewater effluent. Contaminants of concern today include selenium, pesticides, and petroleum products such as oils and greases. Many of these contaminants enter the county's water as "nonpoint source" pollution, primarily stormwater runoff from roads and other paved areas.
Sanitary Sewer Overflows
Another significant source of contamination in the Bay and Ocean is sanitary sewer overfl ows. These typically occur when sewer collection lines overflow from blockages, breaks, or high flow conditions caused by rainfall particularly in the oldest pipelines. There were 468 sanitary sewer overflows in San Mateo County in 2009, as reported by the State Water Resources Control Board.
Beach quality
San Mateo County frequently tests public beaches for waterborne contamination, and warning signs are posted when samples test high for indicator bacteria.
• In 2009, no Pacifi c beaches were closed for contamination. Two bayside beaches were closed for approximately two weeks, because of sanitary sewer overflows.
• For the 18 Pacific beaches monitored, 11 (about 61 percent) were posted with warning signs for at least one week of the year, with a total of 60 weeks of posting cumulative for those
beaches (about 6.4 percent of all Pacific beach-days).
