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EPA Transfers Operations of Whittier Narrows Treatment Plant to State of California

Release Date: 05/17/2013
Contact Information: DTSC: Jim Marxen, 916-324-6544, EPA: Nahal Mogharabi, 213-244-1815,

Billions of Gallons of Groundwater Treated To Date

LOS ANGELES-- Today, responsibility for operation and maintenance of the groundwater treatment system at the Whittier Narrows Operable Unit (OU) was transferred from the U.S. Environmental Protection Agency (EPA) to the California Department of Toxic Substances Control (DTSC). The Whittier Narrows OU encompasses approximately four square miles in the southern portion of the San Gabriel Valley Area 1 Superfund Site in South El Monte, Calif.

EPA began investigating groundwater contamination in this area in the late 1980s. In 2002, EPA and DTSC constructed and began operation of a $12 million treatment plant that treats 1.8 billion gallons annually. The treatment plant removes volatile organic compounds (VOC) from groundwater and prevents the VOCs from moving into the Central Basin, thereby protecting drinking water for more than two million customers in Los Angeles and Orange counties. The groundwater treated by this system is used for drinking water and to maintain the water level in Legg Lakes.

During the past decade, EPA, in partnership with DTSC, has made significant progress in cleaning up the aquifer. Since 2002, thousands of pounds of VOCs have been removed from the shallow and deep groundwater zone at Whittier Narrows at a cost of $20 million. VOCs at the site consist of predominately trichloroethylene (TCE) and tetrachloroethylene (PCE). Drinking water containing TCE and PCE above federal health standards for extended periods of time could increase risk of cancer and liver problems.

DTSC has contributed an additional $2.5 million toward the construction and operation of this system. The Superfund law provides for transfer of responsibility for long-term operation of cleanups from EPA to the state. EPA and DTSC selected the San Gabriel Valley Water Company (SGVWC) to serve as the new operator for the ground water treatment system. After EPA constructs new infrastructure to connect the existing treatment plant to SGVWC’s drinking water distribution system in the coming months, the treated water will become part of the valuable water supply for the surrounding communities.

EPA and the State continue to investigate and clean up contaminated ground water in other areas of the San Gabriel Valley including Baldwin Park, South El Monte, and other parts of the 170 square-mile area.

For more information on the San Gabriel Valley Superfund Site, please visit: Or,