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large chlorine-caustic plants. Even the brine drawn from the salt 

 ponds in the last stages of the solar evaporation process is consid- 

 dered important. It is called bittern and from it are extracted 

 magnesium chloride and bromine as well as chemicals used in the 

 manufacture of gypsum. The salt ponds are located in San Mateo, 

 Santa Clara, Alameda, and Napa Counties. 



Deposits of oyster shells and blue clay found in the Bay are less 

 important economically than the salt and other chemicals. The 

 shells are sold to chemical companies and firms manufacturing soil 

 conditioners and poultry feed. 



Sand deposits in the Bay have served as a basic source of fill for 

 tideland areas, but have been of too-poor quality for general 

 industrial use. Sand for industrial purposes is largely extracted 

 from pits in ancient river beds in Alameda County. Approximately 

 5 million tons come from these sources each year for building and 

 paving in the Bay area. 



The Bay provides a matchess natural harbor and habitat for probably 

 the greatest variety of fish and wildlife of any comparable body of 

 water in California. The area's marshlands, mudflats, and permanent 

 water areas (an important resting spot for migratory birds in the 

 Pacific flyway) support large populations of waterfowl. At least 

 six species of anadromous fish run into or through the Bay going 



