WATER SUPPLY/California city begins MTBE removal efforts

South Lake Tahoe, Calif., is known for its pristine lake, clean air and pure water. However, that reputation was threatened a few years ago when the city’s drinking water was contaminated with the gasoline additive Methyl Tertiary Butyl Ether (MTBE).

MTBE has been used as a fuel oxygenate since 1979 to reduce carbon monoxide and ozone levels caused by automobile emissions. According to the U.S. Environmental Protection Agency, it is a potential carcinogen, and it can contaminate groundwater supplies through fuel storage tank and pipeline leaks, spills and stormwater runoff. Additionally, very low levels of MTBE, which smells and tastes like turpentine, can make drinking water unpalatable.

In 1996, the South Tahoe Public Utility District (STPUD) detected trace amounts of MTBE in 13 of its 34 drinking water wells, and by 1998, it closed each of the contaminated sites. The district found that leaking underground storage tanks were the sources of the contamination. (The district continues to provide safe drinking water to its 28,000 residents by rerouting water from uncontaminated wells.)

Soon after the wells were closed, the district sued 31 companies, including MTBE manufacturers and oil companies, alleging that their product spoiled the city’s drinking water. Twenty-six of those companies settled last year for a total of $33 million, allowing the district to begin its cleanup efforts.

In July 2001, the district purchased an 800-gpm HiPOx system from Pleasant Hill, Calif.-based Applied Process Technology. The system destroys MTBE by injecting hydrogen peroxide and ozone into the contaminated water. Those chemicals combine to form hydroxil ions, which break apart the MTBE molecules.

In June 2002, after receiving a permit from California’s Department of Health Services, STPUD began operating the system at one of its wells. There, the district expects the system to reduce the MTBE levels from two parts per billion to non-detectable levels.

STPUD estimates that the long-term cleanup costs for removing MTBE from its wells will be close to $35 million.