Superfund Information Systems: Site Profile

Superfund Site:

ORANGE COUNTY NORTH BASIN
ORANGE COUNTY, CA

Cleanup Activities

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Background

The site, located in northern Orange County, California, is a comingled groundwater plume of chlorinated solvents and other contaminants covering approximately five square miles beneath parts of the cities of Anaheim and Fullerton. In the past, the plume was also partially beneath part of the city of Placentia, but the plume has since moved southwest. Seventy percent of the water served in Orange County is from groundwater, making the basin a critical water resource for 2.4 million residents in 22 cities. The water supply is closely monitored by the water purveyors, with regulatory oversight, and continues to provide drinking water that meets federal and state standards to all consumers.

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What Has Been Done to Clean Up the Site?

In 2014 and 2015, several state and local agencies asked that EPA commit resources to help clean up the area of groundwater contamination in northern Orange County. In response, EPA proceeded concurrently on three parallel paths: 1) entering into an administrative agreement with the Orange County Water District to complete a remedial investigation and feasibility study (RI/FS) for an interim remedy at the site; 2) evaluating whether to finalize the site’s listing on the NPL; and 3) reviewing technical and legal information to identify potentially responsible parties (PRPs) responsible for the contamination.

EPA and OCWD entered into an administrative agreement in October 2016 that requires OCWD to draft an RI/FS, the document that characterizes the extent of contamination and evaluates a range of remedial alternatives.  This document is only to address the most contaminated portion of the site and is called the Interim RI/FS. The OCWD is conducting the Interim RI/FS work under EPA oversight. It is expected to be completed in 2021. To view the administrative agreement click here.

As part of the Interim RI, OCWD has collected data to determine the nature and extent of site contamination. The Interim FS will provide EPA with information needed to develop a cleanup plan for the site. The interim remedy will address the drinking water aquifer (princial zone) in the most contaminated portion of the site. The Interim RI included the installation of a limited number of groundwater monitoring wells to characterize the site, but it is not intended to characterize the full extent of site groundwater contamination.

EPA has initiated the first phase of the Comprehensive (site-wide) RI/FS, which will involve the installation of additional monitoring wells in 2021 to further characterize the entire site.

The California Department of Toxic Substances Control and the Santa Ana Regional Water Quality Control Board continue to actively initiate and oversee facility-led investigation and remediation of surface contamination (soil and shallow groundwater) at several of the facilities identified as possible contributors to the plume.

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What Is the Current Site Status?

EPA received a letter from the State of California on June 28, 2017, in support of placing this site on the National Priorities List. To view the letter of state concurrence on this listing please click here. EPA proposed the site be added to the National Priorities List (NPL) on January 18, 2018.

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Enforcement Information

The Orange County North Basin groundwater plume is contaminated with chlorinated solvents and other contaminants. The government agencies believe that contamination in the North Basin is the result of spills and leaks from industrial activities over the last several decades. Specifically, many properties in the North Basin where historical industrial activity occurred have soil and groundwater contaminated with tetrachloroethene (PCE), trichloroethene (TCE), 1,1-dichloroethene (1,1-DCE), and 1,4-dioxane.  

EPA is reviewing state files, historical documents, and other sources of information to identify Potentially Responsible Parties (PRPs) at the site. PRPs refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site, as provided by the Superfund statute, EPA expects that the PRPs will perform and/or pay for site investigation and cleanup.

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