Gas Additive MTBE Found in O.C. Aquifer

A gasoline additive that makes drinking water taste bad and may cause cancer at high concentrations has been detected for the first time at the top of a deep Orange County aquifer.

The presence of MTBE--an additive that has helped reduce air pollution--at a site in Fountain Valley does not immediately threaten Orange County’s drinking water, said officials from the Orange County Water District. It would have to travel about a mile before reaching a drinking water well, and that could take from five to 10 years, officials said.

But it does give credence to alarms raised about the threat posed by numerous leaks from underground gasoline storage tanks.

“This is proof that the threat is real,” said Ron Wildermuth, public information officer for the Orange County Water District. “We think it’s a real future threat which justifies cleaning up all these gasoline spills as soon as possible.”

In the mid-1990s, California’s efforts to produce cleaner-burning fuels led to widespread use of MTBE--methyl tertiary butyl ether--in gasoline. But the additive was soon found to travel through the soil more quickly and be harder to clean up than other gasoline additives. Acting on an executive order by Gov. Gray Davis, the state Air Resources Board ordered it removed from California’s gasoline supply by 2003.

The Fountain Valley MTBE contamination was found 60 feet underground in the Talbert Aquifer, and is likely related to leakage from a Fountain Valley ARCO station’s underground storage tank system, said Karen Hodel, a program manager for the environmental health division of the Orange County Health Care Agency.

Though drinking water is usually drawn from 300 to 1,000 feet below the surface, MTBE’s presence at the top of the deep aquifer signals it can migrate to the ground water’s lower depths, she said. Previous Orange County tests have found MTBE only in shallow aquifers, less than 50 feet below the surface.

The contamination is spreading, posing a greater potential risk to drinking water, Hodel said. In north and central Orange County, the potential impact is substantial because 75% of the drinking water there is drawn from county aquifers, she said.

The ARCO station is one of more than 100 included in a lawsuit brought by prosecutors against the Atlantic Richfield Co. and Thrifty Oil, alleging contamination of ground water. The suit seeks millions of dollars in civil penalties. Prosecutors also are calling for more stringent regulations for monitoring the underground tanks.