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Charnock MTBE Cleanup
After discovering the gasoline additive methyl tert-butyl ether (MTBE) in a number of its Charnock Sub-Basin drinking water wells, the City of Santa Monica shut down several of its wells in 1996 and sought assistance from EPA.
Working with the Los Angeles Regional Water Quality Control Board 
, EPA required responsible parties to investigate and cleanup individual sources of MTBE contamination, pay over $3 million per year to provide replacement water to Santa Monica and Culver City residents, and perform engineering evaluations of methods to restore the Charnock Sub-Basin to its beneficial use as a drinking water supply.
Under a settlement with the City of Santa Monica in 2003, responsible parties are funding the design and construction of a wellhead treatment plant under oversight from the California Department of Health Services . Including past costs, responsible parties will spend more than $200 million to address the contamination.
In February 2005, EPA and the U.S. Department of Justice filed a $1.5 million settlement in district court. This settlement requires various oil companies to reimburse EPA's past costs in connection with the Charnock MTBE cleanup and is the largest Leaking Underground Storage Tank Fund cost recovery settlement by EPA since Congress created the fund in 1986. The settlement document can be found on the Regional Enforcement page.
The Charnock groundwater sub-basin is located in Southern California within the communities of West Los Angeles and Culver City Site Location Map (PDF) (1 pp, 111K, About PDF) and is an important source of drinking water for the cities of Santa Monica and Culver City.