MTBE causes 13th well to be closed | TahoeDailyTribune.com
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MTBE causes 13th well to be closed

The South Tahoe Public Utility District has closed another well because of the controversial fuel additive MTBE. It is the 13th well shut down since September 1997.

And like the unlucky No. 13 might suggest, the circumstances surrounding the closure are “mysterious.”

The mystery arises from the fact that MTBE has not been detected in the groundwater used by the well, but traces of the potentially hazardous substance are coming out of the system.



“The pervasiveness of MTBE is absolutely startling,” said Bob Baer, STPUD general manager. “We can’t find it in the groundwater, and yet it still manages to get into the drinking water.”

The Clement well, located in Gardner Mountain, has consistently tested clean for MTBE. However, the water produced by the well is put through an air stripper, and concentrations of MTBE have been found in the water as it leaves the air stripper.




The air stripper was installed in the early 1990s to treat a contamination plume of PCE, a cleaning solvent. The Clement well is the only well currently putting water through the stripper. The district’s nearby Tata Lane well which is contaminated by MTBE pumped water through it last year, and the stripper successfully treated the water for several months. However, MTBE levels increased in the well to about 35 parts of the additive per billion parts water, and small traces were coming through the stripper. The Tata Lane well was closed in July.

STPUD cleaned the air stripper, and, until this month, the Clement well’s water came out with no traces of MTBE.

District officials now are confused as to where the MTBE is coming from. One possibility, officials believe, is that the stripping tower, which draws in air, is actually pulling in MTBE-contaminated air.

STPUD is in the process of obtaining special air-sampling equipment to test whether or not that is the case.

The stripper itself is being thoroughly disinfected because of the remote possibility that some MTBE is lodged somewhere in the system.

The levels of MTBE in the water ranged from 0.3 to 1.5 parts per billion. Although the levels are below California’s taste and odor threshold of 5 parts per billion, the district has a policy of serving no water with any MTBE in it.

STPUD’s water system supplies about 30,000 people through about 12,500 connections, and at times the total population served is as high as 60,000.

STPUD required water-usage restrictions for much of the 1998 summer and likely will have to this summer, too. For now, the latest closure will not significantly affect the district’s ability to serve water.

“Obviously, every time a well goes down, we have to do some shuffling,” said Dawn Forsythe, STPUD information officer. “But we’re looking at ways to address (the MTBE problem).”

MTBE – methyl tertiary butyl ether – is a synthetic chemical oxygenated gasoline additive comprising significant portions of California gasoline. It is classified by the U.S. Environmental Protection Agency as a possible cancer-causing agent and has a horrible taste and odor.

MTBE travels very quickly in the ground, unlike other gasoline contaminants, spreading at the same rate as water. It does not degrade in water like other contaminants, either. It has a half life of 26 years, meaning it will last in water for more than 100 years.

To the utility district, the problems with the Clement well reinforces its belief that MTBE should be banned.

“There should be no doubt that the only way to prevent MTBE contamination of our drinking water is to keep MTBE out of the Tahoe Basin, period,” Baer said.

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