san gabriel valley (area 2)


The San Gabriel Valley Area 2 Superfund Site is one of four Superfund sites addressing groundwater contamination in the San Gabriel Valley. The four sites address multiple areas of contamination in the San Gabriel Basin aquifer, a critical source of drinking water for water-scarce Southern California. The Superfund sites include areas of soil and groundwater contamination underlying portions of the cities of Alhambra, Arcadia, Azusa, Baldwin Park, Industry, Irwindale, El Monte, La Puente, Monrovia, Rosemead, South El Monte, and West Covina. The San Gabriel Valley covers approximately 170 square miles. Groundwater contamination was first detected in the San Gabriel Valley in 1979. Following this discovery, the California Department of Public Health (CDPH, formerly the Department of Health Services) analyzed water samples collected from water supply wells throughout the Valley to assess the extent of contamination. By 1984, 59 wells were found to be contaminated with volatile organic compounds (VOCs). In the late 1990s, perchlorate, N-nitrosodimethylamine (NDMA), and 1,4-dioxane were also discovered in the groundwater. Despite the widespread contamination, the San Gabriel Basin aquifer continues to provide the majority of the domestic water supply for the Valley's one and one-half million residents. Water utilities in the area have continued to provide their customers with clean water by obtaining water from unaffected portions of the basin and neighboring utilities, blending contaminated water with clean water to meet drinking water standards, and installing wellhead treatment systems. EPA's Superfund projects are providing additional water supplies, by providing treated groundwater to several water utilities for local use. EPA's efforts at the sites began in the mid-1980s with studies needed to understand the sources, nature and extent of soil and groundwater contamination. In the 1980s and early 1990s, EPA also developed a basin-wide plan to set cleanup priorities, and led State and Federal efforts to develop the institutional framework necessary to address the contamination. In the early 1990s, EPA divided the San Gabriel Valley into eight project areas, including the Baldwin Park area. In 1994, EPA adopted the cleanup plan for the Baldwin Park project. Between 1990 and 1997, EPA identified Potentially Responsible Parties (PRPs) at the site. In the late 1990s, PRPs engaged in negotiations with local water agencies and began initial design work on the project. After reaching a detailed agreement with seven local water agencies in March 2002, design work was completed and construction work began. Construction of the four planned groundwater extraction and treatment facilities was largely completed in 2006. As of October 2014, more than $200 million has been spent to construct and operate the groundwater cleanup facilities, more than 75 billion gallons of contaminated groundwater has been treated, more than 60,000 pounds of contamination removed from the ground water, and more than 40,000 pounds of contamination removed from the soil. Additional details are provided below. EPA conducted its first "Five-Year review" of the project in 2007 and its second "Five-Year Review" in September 2012. Reports summarizing the findings of the 2007 and 2012 reviews are available in the "Technical Documents" section below. Comprehensive annual performance evaluation reports for 2007, 2008, 2009, 2010, 2011, 2012, and 2013 are also available on-line (see Site Documents and Reports below). The most recent annual performance evaluation report (for the calendar 2013) was completed in April 2014.

Hazardous Ranking Score

42 / 100

A score of 28.5 or higher qualifies a site for the Superfund National Priority List.

Regional Contact

Region 9
Phone: (415) 947-4251

Contact Region



Site Inspection
Preliminary Assessment
Final Listing On NPL

Contaminants & Health Effects

      Endocrine Disrupter
      Reproductive Toxin
      Persistent, bioaccumulative and toxic


        African American
        American Indian and Alaska Native
        Native Hawaiian


        People living
        within a 1 mile radius


        Average Income


        Occupied homes

        Potentially Responsible Parties

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