Water: Bay and Ocean Water Quality

Why Is This Important?
San Mateo County is bordered by the San Francisco Bay to the east and the Pacific Ocean to the west.  Both support marine ecosystems, local economies, recreational activities, tourism, and food resources.

What Is A Sustainable State?
A sustainable state is one where harmful pollutants do not run into the Bay and Pacific Ocean, and marine habitats are healthy and support native species.

How Are We Doing?
Bay water quality
Mercury and polychlorinated biphenyls (PCBs) are the primary drivers of ongoing fish consumption advisories in the Bay.  New contamination comes from inflows from the Delta and urban runoff.  However, high concentrations of these pollutants are bound in the Bay’s sediment from past pollution and persist as the major source of contamination. 

Through pollution prevention and cleanup efforts, the long-term trend for mercury and PCBs is expected to be positive.  However, as concentrations are extremely high and the pollutants are bound in the Bay’s sediment, it will be many years before concentrations of these pollutants decline significantly.

The primary source of new pollution entering the Bay is stormwater runoff.  Examples of pollutants that can run into the Bay include:

  • Mercury from broken fluorescent lights, old batteries, and thermometers
  • Leaking oil, antifreeze, and gasoline from automobiles
  • Pesticides and herbicides
  • Motor oil waste from automobiles, lawn mowers, and small equipment
  • Soaps and chemicals used to wash cars
  • Copper dust from automobile brake pads
  • Rubber tire dust from automobiles

Beach quality
In San Mateo County, beach closures are primarily due to sewage spilled in waterways that flow to either the Pacific or the Bay. 

  • In 2007, there were no beach closures due to sewage spills, a decline from the five closures in 2006 (four on the Pacific side of the county and one
    on the Bay side). 
  • In 2007, there were six beaches closed because of the Cosco Busan oil spill.  With each of the six beaches closed for four days, there was a total of 24 total closed beach days.


Data source: San Mateo County Health Department, Environmental Health

Warning signs are posted at county beaches when water samples test high for fecal indicator bacteria. 

  • In 2007, beach warnings occurred on 8 percent of the total beach days in the county, down from 13 percent of days in 2006.
  • Warnings occurred more frequently on Bay side beaches than Pacific side beaches (25 percent of beach days compared to only 5 percent).

The source for these bacteria is primarily wildlife fecal matter that is deposited by water fowl or washed to the Bay or the Pacific in waterways during storms.


See appendix page 79, CLICK HERE. .  Researchers: Harry Symonds and Joe Rois

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From the 2014 Indicators Report

The county’s population is expected to grow by 185,000 before 2040.

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‟The nation behaves well if it treats the natural resources as assets which it must turn over to the next generation increased, and not impaired in value.”—Theodore Roosevelt