Tank Leaks May Threaten Water

A toxic gasoline additive that was designed to fight smog is leaking from scores of fuel tank sites in Ventura County and poses a long-term hazard to drinking water, officials said Monday.

The chemical compound MTBE has been detected in half the county’s 316 leaking tank sites, mostly located at gas stations. So far, however, the county’s drinking water supplies have been spared from contamination, officials said.

Only one well, the Fairview well in Moorpark, which is operated by the Calleguas Creek Municipal Water District, has shown traces of the fuel additive. The Feb. 25, 1997, finding was well within limits, and the well was not in service at the time.

The pollutant is gone from the site now, and no one in the county is believed to be drinking water contaminated with MTBE, said Douglas A. Beach, manager of the hazardous materials section for the Ventura County environmental health division.

Dozens of MTBE-contaminated sites are clustered in Oxnard and Ventura, atop a critical aquifer that provides drinking water to 300,000 consumers. For now, the chemical is blocked by a layer of clay above the deep water table where wells draw water.

As long as the pollutant remains in shallow soils, it may be flushed to the ocean. The danger is that the contaminant, which has been shown to cause cancer in rats, could filter down through 1,000 abandoned water well shafts, explained Steve Bachman, ground water programs manager for the United Water Conservation District in Santa Paula.

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People living on the Oxnard plain, as well as in Santa Paula and Fillmore, get half their water from these underground basins threatened by MTBE. Still, officials attending a water conference Monday in Ventura said there is no cause for alarm.

“It’s not as significant an issue here as in L.A. County or other parts of the state. We’re concerned about the potential, and we are trying to keep ahead of the problem,” said David A. Bacharowski, environmental program manager for the Los Angeles Regional Water Quality Control Board.

MTBE, short for methyl tertiary butyl ether, is an oxygen-rich additive oil companies add to gasoline so fuel burns more efficiently in cars, reducing air pollution. The state Air Resources Board says the chemical, which has been in use since 1996, has resulted in emissions reductions equivalent to eliminating 3 million cars from the highways.

But the chemical has become a scourge of water districts in much of California. Around the state, 10,000 sites are contaminated with MTBE. Of 4,430 public drinking wells tested in California, 533 showed traces of MTBE. Only 5% of those wells, however, contained enough of the substance to alter the taste, color or odor of the water, according to a state auditor’s report released in December.

South Lake Tahoe has lost about one-third of its wells, and Santa Monica lost the use of half of its ground-water supplies due to MTBE.

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A report by University of California scientists released in November estimates annual costs of cleaning up MTBE could reach $1 billion. Water officials did not have an estimate on what it would cost to clean Ventura County’s MTBE-contaminated sites.

Gov. Gray Davis in March declared the chemical a serious threat to California’s water supply and ordered its elimination as a fuel additive by 2002. Meanwhile, Sen. Dianne Feinstein and Rep. Brian Bilbray (R-San Diego) have introduced bills in Congress to eliminate the federal requirement for oxygenated fuels in California.

What makes MTBE so troublesome is that it can rapidly invade shallow wells. Beneath the Oxnard plain, MTBE is moving at nearly 3 feet per day, maybe faster close to the surface, Bachman said.

“It’s so soluble that it moves at the same rate as the ground water does. It doesn’t follow any of the rules people who do cleanups are used to,” Bachman said.

MTBE is also difficult to clean up because it clings to water molecules more stubbornly than other chemicals in gasoline. To prevent more pollution, state and local regulators are focusing on fixing underground fuel tanks and pipes, including installing interior tank lining, corrosion protection, overfill prevention, alarms and leak detectors.

About 400 leaking tanks have been removed or replaced in Ventura County in the last 12 years, Beach said.

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The average cost to remove three, 10,000-gallon tanks at a typical gas station is about $35,000, and the cost to clean polluted soil and ground water ranges from $80,000 to $150,000, said David Deaner, manager of the underground storage tank cleanup fund for the state Water Resources Control Board.

Human health effects from MTBE are not well understood. A study by the Centers for Disease Control and Prevention showed that acute exposure causes headaches, nausea and dizziness.

The current MTBE limit allows no more than five parts of the chemical per billion parts of water, because at higher concentrations it causes taste and odor problems.

“Nobody’s really sure what the health effects are. At the very least, we know it’s not something people want in their water,” Beach said.