Ethanol and MTBE polluting Lake Tahoe

Plagued by leaks of both ethanol and methyl tertiary butyl ether from gasoline service stations that are polluting groundwater sources, the Lake Tahoe, Calif., resort area is headed into another summer of water use restrictions.


Sam Fletcher
OGJ Online

Plagued by leaks of both ethanol and methyl tertiary butyl ether from gasoline service stations that are polluting groundwater sources, the Lake Tahoe, Calif., resort area is headed into another summer of water use restrictions.

Earlier this year, California officials ordered that ethanol replace MTBE in all reformulated gasoline sold around Lake Tahoe. Traces of MTBE were found in tests of groundwater sources in that area in September 1998, forcing the South Tahoe Public Utility District (STPUD) to shut in 12 of its 34 wells, or 27% of the water supply for area residents.

Now ethanol also is showing up in water tests, in concentrations as high as 130,000 ppb. That quickly prompted a near "I-told-you-so" response from the Oxygenated Fuels Association Inc., a trade group of fuel-additive manufacturers based in Arlington, Va.

"We have said all along that you cannot blame a single component for gasoline leaks from substandard tanks. But our groundwater resources are too precious, and the problem of leaking underground storage tanks is too serious for us to say 'I told you so.' Still, the fact that ethanol has replaced MTBE in Lake Tahoe and is now in the groundwater speaks for itself," said Charles Drevna, government affairs director for the association.

Some claim ethanol moves through groundwater faster and in a less predictable fashion than MTBE. But MTBE is detectable by its offensive taste and smell in much smaller quantities, as little as 2 ppb, said Dennis Cocking, STPUD spokesman. He said El Dorado County officials are asking the state to ban use of all oxygenates in gasoline sold in that area.

Leaking storage tanks
Actually, the double-walled underground tanks at service stations in the Lake Tahoe area are holding up well, Cocking told OGJ Online.

The leaks are occurring at valves and elbows of lines connecting the underground gasoline tanks with the pump outlets at the stations. In some cases, Cocking said, "We know to the moment when some leaks occurred during pressure testing."

The response by gasoline suppliers and station operators has been mixed, he said Thursday. Big companies "like Shell, Chevron, and Tosco" moved quickly to halt the use of MTBE and to try to remedy the problem, he said. But "six or seven independents" were slow to move until the El Dorado County board of directors last month implemented a criminal law banning MTBE.

That is probably the first law in the US to criminalize use of MTBE, Cocking said.

The water utility district serves a base area population of some 30,000 people. But that population escalates to about 200,000 during the summer as people flock to the scenic mountain lake.

Tourist trade hasn't yet been affected, because the utility district shut in the polluted wells before MTBE or ethanol could get into the public water system, Cocking said. But loss of 12 wells eliminated the utility district's excess supply, leaving it just enough water to meet peak demand.

As part of the area's standard conservation effort even before the pollution was discovered, restaurants were serving water to diners only on request, and hotels were encouraging guests to reuse towels to reduce laundry. Last summer, local officials implemented additional restrictions, primarily limiting watering of lawns and other outdoor irrigation on a schedule of even or odd days. Similar restrictions will be implemented this summer, said Cocking.

Local authorities are still mulling over possible cleanup efforts. "The trouble is, the remediation technology hasn't caught up with the problem," said Cocking. "But I have faith in the enterprise system that the situation will change."

Meanwhile, a civil lawsuit is pending in US District Court in San Francisco against refiners, station operators, and "anyone else who might be involved" in the Lake Tahoe pollution. Clean-up costs are expected to run into millions of dollars.

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