san gabriel valley (area 1)


The San Gabriel Valley (Area 1) site is an area of contaminated groundwater over 4 miles long and 1½ miles wide located in the San Gabriel Valley. In 1984, the EPA identified four large areas of groundwater contamination in the San Gabriel Valley; each area is a separate Superfund site. The sites include four large areas of groundwater contamination that underlie significant portions of the Cities of Alhambra, Arcadia, Azusa, Baldwin Park, Industry, El Monte, La Puente, Monrovia, Rosemead, South El Monte, West Covina, and other areas of the 170 square-mile San Gabriel Valley. Over 30 square miles of groundwater under the Valley may be contaminated. Contamination of the groundwater by volatile organic compounds (VOCs) was first detected in 1979 when Aerojet Electrosystems in Azusa sampled nearby wells in the Valley County Water District. Subsequently, the California Department of Health Services (CDHS) initiated a well sampling program to assess the extent of contamination. By 1984, 59 wells were found to be contaminated with high levels of VOCs. Hundreds of individual facilities could be contributing to the contamination in the basin through improper handling and disposal practices. The area of contamination parallels the San Gabriel River to the east. The basin's groundwater provides approximately 90 percent of the domestic water supply for over 1,000,000 people who live in the Valley. Over 400 water supply wells are used in the basin to extract groundwater for industrial, business, agricultural, and domestic uses. Forty-five different water suppliers operate in the basin and provide drinking water to more than 1,000,000 people. In 1992, EPA completed construction of a water treatment plant for the Richwood Mutual Water Company to assist them in providing water that meets drinking water standards.

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

        Similar Sites

        Add Story


        No stories have been submitted for this site.