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What About MTBE?

In 1996, the California Air Resources Board mandated that all gasoline sold in California be reformulated to contain 11 percent oxygenates, most commonly methyl tertiary butyl ether (MTBE), in order to reduce levels of automobile exhaust emissions. While air quality in California has improved since the gasoline was reformulated, MTBE has been found in some drinking water supplies in California. MTBE is particularly problematic because it causes taste and odor concerns even in trace concentrations, and it is highly mobile in water and difficult to remove.

We are monitoring all of our wells and local surface supply for MTBE, and to date it has not been detected. We draw our groundwater from very deep aquifers that are protected by impermeable confining layers of soil. Our local mountain surface water supplies originate from a very pristine and well protected watershed, that allows very little opportunity for pollution. We are also working very closely with the Santa Clara Valley Water District (SCVWD), a wholesale water agency that supplies treated surface water to San Jose Water Company and seven other water retailers in the county, to monitor the occurrence of MTBE in our imported water sources. SCVWD has previously detected trace levels of MTBE in Calero and Anderson Reservoirs and in water from the State Water Project supplying their three water treatment plants. The levels found in SCVWD's treated drinking water are extremely minute, approximately 1 part per billion (1 microgram per liter) and do not represent a public health risk. This is well below the State Action Level of 35 parts per billion and the USEPA's Drinking Water Advisory Level of 20-40 parts per billion. The California Department of Public Health considers levels below 5 parts per billion to be non-detectable for reporting purposes.

The use of MTBE as a gasoline additive was completely phased out in California at the end of 2002. San Jose Water Company and SCVWD will continue to monitor our supplies and pursue long-term solutions to this potential problem. For more information about MTBE and other drinking water issues check the homepage of the California Department of Public Health Division of Drinking Water and Environmental Management (DDWEM). The home page is available at: