Contamination not limited to MTBE |

Contamination not limited to MTBE

by Andy Bourelle

While the South Tahoe Public Utility District’s battle with MTBE has drawn attention in California, Nevada and many parts of the nation, the controversial fuel additive has contaminated other sites within the Lake Tahoe Basin.

The only difference is that, except at South Shore, the contaminant plumes have not affected drinking water supplies.

Lauri Kemper, chief of the Lake Tahoe unit of the Lahontan Regional Water Quality Control Board, said that there are more than 80 sites where gasoline or diesel fuel have leaked from storage tanks on the California side of the Tahoe Basin. Thirty-one of those involve MTBE, and 11 of the MTBE cases are on North Shore.

No drinking water sources have been affected there, a contrast to numerous wells shut down on South Shore. STPUD – which supplies about 30,000 people with water, through about 12,500 connections – has closed more than one-third of its wells since September 1997.

The Lukins Brothers Water Company, which serves 900 South Lake Tahoe customers, also closed one of its five wells in October 1997 when MTBE was discovered there.

On the eastern side of Lake Tahoe, the Nevada Division of Environmental Protection is investigating at least three contamination sites: one on Kingsbury Grade, one in Incline Village and one in Cave Rock. Except for the Cave Rock site, where two private wells have been contaminated, drinking water is not affected by the plumes.

Soil and groundwater contamination are not the only concerns in a place like Lake Tahoe, however.

Whether it was caused by leaks from marinas, contaminated groundwater running into the lake or the 1.5 million gallons of gasoline used by boaters on Lake Tahoe in 1998, researchers found MTBE and other gasoline compounds in the lake last summer, just as they had the year before.

The U.S. Geological Survey found MTBE in Lake Tahoe last summer at concentrations of 0.54 to 5.6 parts per billion at near-shore sites. The highest concentration was detected at Emerald Bay. At a depth of 100 feet in the middle of Lake Tahoe, MTBE was detected at 0.31 parts per billion. In 1997 at the same site, it was detected at 0.26 parts per billion.

In Lower Echo Lake, USGS found MTBE at levels of 9.8 parts per billion.

No known regulatory levels for MTBE were exceeded, according to USGS, but California’s taste and odor threshold of 5 parts per billion was exceeded in some cases.

At that level, most people can begin to detect the additives presence in water; it smells and tastes like turpentine.

Several public utility providers in the basin take their water from Lake Tahoe, and at least two South Shore providers have served water with low levels of MTBE contamination – below 5 parts per billion and below any state or federal action requirements. The Round Hill General Improvement District, which serves about 460 customers, and the Lakeside Water Utility District, serving 137 customers, found traces of MTBE last summer.

Researchers have found that MTBE and other gasoline compounds are most prevalent in the waters of Tahoe during the summer, the peak boating season. After summer is over, the presence of the compounds fades.

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