Why is This Important?
San Francisco Bay to the east and the Pacific Ocean to the west border San Mateo County. Both water bodies’ unique aquatic ecosystems are sensitive to 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 water is minimal, 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. Much of this pollution enters the county’s water as “non-point source” pollution, primarily stormwater runoff from roads and other paved areas, and is more difficult to control than “point source” pollution sources (so called “end of pipe” contamination).
Sanitary Sewer Overflows
A significant and growing source of contamination in the Bay and Ocean is sanitary sewer overflows. These typically occur when sewer collection lines overflow from blockages, breaks, or high flow conditions cause by rainfall. These events occur more frequently with older, aged pipelines, and many of the sewer lines in San Mateo County are 50 or even 75 years old. There were 391 reported sanitary sewer overflows in San Mateo County in 2010, a reduction from 468 in 2009.
San Mateo County frequently tests public beaches for waterborne contamination, and warning signs are posted when samples test high for indicator bacteria. Occasionally, beaches must be closed for public health reasons.
· In 2010, three Pacific beaches were closed for contamination for a total of 13 days. Two bayside beaches (Aquatic Park Beach and Lakeshore Park Beach) were closed for a combined total of 84 days, because of sanitary sewer overflows.
· For the 18 Pacific beaches monitored, 9.5 percent of all days were posted with warning signs in 2010. For the bayside beaches, 31.5 percent of all days were posted.