San Gabriel Valley (Area 3) Alhambra

Description and History

The San Gabriel Valley Superfund Sites include multiple areas of contaminated groundwater in the 170-square-mile San Gabriel Valley. The contamination in groundwater underlying the San Gabriel Valley may extend over an area of 30 square miles, including 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 San Gabriel Valley. Groundwater in the San Gabriel Basin provides approximately 90 percent of the domestic water supply for over 1,000,000 people who live in the San Gabriel Valley. Forty-five different suppliers of water operate over 400 water supply wells in the basin to extract groundwater for industrial, business, agricultural, and domestic uses.

Within the San Gabriel Valley Superfund Sites, the San Gabriel Valley Area 3 Superfund Site or "Area 3" (formerly identified as the Alhambra Operable Unit) includes an approximate 18-square-mile area of groundwater contamination underlying the cities of Alhambra, San Gabriel, San Marino, South Pasadena, Rosemead, and Temple City.

Contamination from volatile organic compounds (VOCs) was first detected in 1979 in the San Gabriel Groundwater Basin within the Valley County Water District, when Aerojet Electrosystems in Azusa sampled wells. The California Department of Health Services (CDHS) then initiated a well sampling program to assess the extent of contamination. By 1984, testing at 59 wells confirmed the presence of contamination with high levels of various VOCs. Currently, contamination in groundwater at many wells in the area exceeds EPA's standards for water quality. Hundreds of individual facilities could be contributing to the contamination in the basin through improper chemical handling and disposal practices.

EPA currently is evaluating the results of a remedial investigation of regional groundwater contamination in Area 3 to identify cleanup options. This assessment also involves facility investigations in cooperation with the Los Angeles Regional Water Quality Control Board (RWQCB) as part of an effort to identify Potentially Responsible Parties (PRPs) and associated sources of groundwater contamination. EPA's review of investigation data and historical records will help to identify PRPs.

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Contaminants and Risks

Groundwater is contaminated with VOCs, including trichloroethene (TCE) and tetrachloroethene (PCE), at concentrations that exceed 20 times the maximum contaminant levels (MCLs) allowed by federal and state law. Soil also is contaminated with various VOCs. People who inhale vapors from groundwater or soil that contains VOCs could be exposed to hazardous substances.

Currently, all drinking water served within the San Gabriel Valley Area 3 Superfund Site meets federal and State drinking water standards. While EPA works to identify possible options for addressing regional groundwater contamination in Area 3, the state is working with facilities to address soil contamination.

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Who is Involved

This site is being addressed through federal and state actions.

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Investigation and Cleanup Activities

This site is being addressed in two long-term remedial phases focusing on cleanup of area-wide contamination and identification and control of the source of contamination.

Area-wide Contamination: In 1984, EPA began a study of the nature and extent of contamination throughout the San Gabriel Valley. This investigation identified specific areas within the San Gabriel Valley Superfund Sites for focused study and for further support of ongoing activities. This investigation may lead to additional required groundwater cleanup or monitoring.

Source Identification and Control: The California Regional Water Quality Control Board, Los Angeles Region, working under a Cooperative Agreement with EPA, is identifying sources of contaminants in San Gabriel Valley Area 3. To date, nearly 400 individual facilities throughout San Gabriel Valley have confirmed the presence of soil contamination.

Remedial Investigation: EPA started the Remedial Investigation (RI) for Area 3 in 1999, including the collection of extensive data over a seven year period. The RI report, completed in June 2009, assesses the nature and extent of groundwater contamination in Area 3 and the potential for harm to public health or the environment caused by the contamination. The conclusions of the RI will form the basis of a Feasibility Study (FS) to evaluate cleanup alternatives to prevent and eliminate the release or the threat of release of contaminants in groundwater at the site.

Feasibility Study: The next step in the Superfund process will involve completing a Feasibility Study (FS) for Area 3 to develop, screen and evaluate cleanup alternatives. Potential cleanup alternatives will focus on preventing and eliminating the release or the threat of release of contaminants at the site. During development of the FS, EPA may collect additional data to address remaining uncertainties identified in the RI.

Technical Assistance Grant: In 2007, EPA awarded a Technical Assistance Grant (TAG) to the San Gabriel Valley Oversight Group, a nonprofit organization formed by community representatives living within the area. The San Gabriel Valley Oversight Group will use the grant funding to provide a public-driven assessment of groundwater contamination data that is independent of federal, state, and municipal agencies and to conduct community outreach.

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Cleanup Results to Date

After adding the San Gabriel Valley Area 3 Site to the NPL, EPA confirmed through preliminary investigations that no immediate actions are required while studies are ongoing and potential cleanup actions are under evaluation. EPA now is conducting additional investigations to identify PRPs responsible for contamination of the groundwater within Area 3 and to support evaluation of cleanup alternatives.

Since 2003, EPA has installed eight groundwater monitoring wells and conducted routine groundwater sampling to evaluate groundwater contamination. EPA's RI report assesses water quality data collected from these wells, along with data collected from monitoring wells installed at over 10 facilities under investigation in Area 3 and from production wells throughout Area 3. The report also includes a site conceptual model that will help EPA in evaluating cleanup alternatives.

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Potentially Responsible Parties

Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.

Online information about the PRPs for the site is not yet available.

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Documents and Reports

Administrative Records
		Alhambra Operable Unit
		Removal Action
Fact Sheets
	09/01/02	EPA to begin field work to investigate groundwater quality in Alhambra (English/Spanish/Vietnamese/Chinese)
	05/01/03	EPA to Install Groundwater Monitoring Well in the City of San Gabriel(English/Spanish/Chinese/Viatnamese)
	05/01/04	Community Involvement Plan
	05/01/04	EPA Ground Water Testing Underway
	11/01/04	EPA to Install Additional Groundwater Monitoring Wells in the San Gabriel Valley
	07/01/05	Information Workshop
Technical Documents
	06/01/09	Final Report Remedial Investigation San Gabriel Valley Area 3

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Community Involvement

Public Meetings:

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Public Information Repositories

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Additional Links

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Contacts

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