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Pacific Southwest, Region 9: Superfund

Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations


EPA #: CAT080012826

State: California(CA)

County: Riverside

City: 1 mile north of Glen Avon

Congressional District: 43

Other Names:

Bulletin Board

On 10/13/17, this website will no longer be updated. Site information will be migrated to the new web page at: http://www.epa.gov/superfund/stringfellow .
EPA appreciates your patience through this transition. If you have questions, please contact EPA staff listed below.

Description and History

NPL Listing History

NPL Status: Final

Proposed Date: 12/30/82

Final Date: 09/08/83

Deleted Date:

The Stringfellow Superfund Site is located in the City of Jurupa Valley, California, about six miles northwest of Riverside, California. The city includes the community of Glen Avon. The Site includes a hazardous waste disposal facility operated by the Stringfellow Quarry Company from 1956 until 1972 and a several-mile long plume of groundwater contamination originating from the former disposal facility. More than 34 million gallons of liquid industrial waste were disposed in unlined ponds in the 16 years that the facility operated. The wastes included spent acids and caustics, metals, solvents, and pesticide byproducts from metal finishing, electroplating, and pesticide production.

In the 1960s and 70s, liquid wastes in the disposal pits overflowed or were discharged into an adjacent surface water channel known as Pyrite Creek. In 1972, Site contaminants were detected in groundwater thousands of feet downgradient of the waste disposal ponds. Following the discharge of wastes from the ponds in 1978, Site-related contaminants were detected in surface water flowing in the Creek as far as four miles downstream of the disposal ponds. .

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Contaminants and Risks

Contaminated Media
  • Groundwater
  • Surface Water
  • Soil and Sludges

Numerous environmental sampling efforts have been completed at the Site since the 1970s. The testing has demonstrated that Site contaminants were released into soil, surface water, and groundwater, probably beginning soon after the facility began operation in 1956. Contaminants have been carried downstream in Pyrite Creek, and percolated into and moved with the underlying groundwater.

            Thousands of soil, surface water, and groundwater samples have been collected and analyzed. Currently, there are more than 400 active groundwater monitoring wells and piezometers at the Site.

            Laboratory tests indicate that Site contaminants include a variety of chemicals including trichloroethene (TCE) and other volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), pesticides, sulfate, perchlorate, N-nitrosodimethylamine (NDMA), 1,4-dioxane, parachlorobenzene sulfonic acid (pCBSA), and metals including cadmium, nickel, chromium, copper, manganese, and zinc. Groundwater near the former disposal pits is highly acidic, with a pH as low as 2. A plume of contaminated groundwater extends approximately five miles from the former disposal pits to the Santa Ana River.

            To prevent contact with wastes or contaminated soil, the former disposal pits have been drained, covered, and fenced. To prevent ingestion of and contact with contaminated groundwater, private drinking water supply wells have been closed and the community in the affected area provided with water from the Jurupa Valley Community Services District, a local public utility.

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Who is Involved

From the 1970s into the 1990s, EPA, the Santa Ana Regional Water Quality Control Board, the California Department of Toxic Substances Control (DTSC), and Potentially Responsible Parties (PRPs) carried out or funded cleanup work at the site.
Currently, the State of California (the “State"), through the DTSC, is implementing all cleanup work at the Site. The State became the primary response party at the Site in 2002, as described further below. The State operates and maintains three groundwater treatment systems, has made numerous improvements to the three systems since they were constructed, has completed several technology evaluations, conducts periodic groundwater and surface water monitoring, and prepares a variety of Site-related technical reports.

EPA is responsible for overseeing all remediation work at the Site.

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Investigation and Cleanup Activities

The Site is geographically divided into four zones. Zones 1 through 3 include the former Stringfellow disposal ponds and an area of contamination extending to Highway 60, about 1 miles to the southwest of the disposal pits. Zone 4 includes an area of groundwater contamination extending about four miles from Highway 60 to the vicinity of the Santa Ana River. Investigations into sources of groundwater contamination other than the Stringfellow disposal ponds are also underway in Pyrite Canyon north of Highway 60.

Initial Actions

Initial Actions: Efforts to stabilize and remediate the Site began in the 1970s, with the removal of about 6 million gallons of liquid wastes. The Site was added to the Superfund "National Priorities List" (NPL) in 1983. Between 1983 and 1990, EPA adopted four Records of Decision (RODs) that have guided subsequent remediation efforts.

Stringfellow Site Operable Units and Records of Decision
Operable Unit (OU)Record of DecisionKey Elements of Selected Remedy
01July 22, 1983Offsite disposal of liquid wastes, groundwater extraction, surface water control, erosion control, fencing (Zone 1)
02July 18, 1984Groundwater migration control, construction of onsite groundwater treatment plant (Zone 2)
03June 25, 1987Groundwater migration control (Zone 3), surface water control (Zone 1)
04Sept 30, 1990Groundwater dewatering (Zone 1), groundwater restoration (Zone 4)

Copies of the four RODs, and an update to the July 18, 1984 ROD known as an “Explanation of Significant Differences,” are available below, in the Documents and Reports section. A fifth ROD is expected in 2021.

Cleanup Ongoing

Cleanup is underway in Zones 1 through 4.

In Zone 1, remediation efforts have included draining, filling, and capping the disposal pits; construction of an upgradient groundwater and surface water interception system; construction of a subsurface clay barrier dam; and a groundwater control and dewatering system. Contaminated groundwater is routed through a series of water treatment processes at the "Pre-Treatment Plant" (PTP) to remove the contaminants.

The PTP began operation in 1985, removing metals, pesticides, and other organic contaminants from groundwater extracted in Zones 1 and 2. Treatment includes lime precipitation for removal of heavy metals, and granular activated carbon (GAC) treatment for removal of volatile organic compounds (VOCs). The treated water is discharged to an industrial sewer line known as the Inland Empire brine line. The State has constructed a new treatment plant (the Pyrite Canyon Treatment Facility (PCTF)) to replace the PTP. The PCTF is expected to begin operation in 2016. Other improvements in Zone 1 are described in a July 2009 report known as the Supplemental Feasibility Study.

A second groundwater treatment system, the "Lower Canyon Treatment Facility (LCTF)," began operation in 1990, treating groundwater with GAC. The LCTF treats groundwater extracted in Zone 3 and the northern portion of Zone 4. The treated water is discharged to the Inland Empire brine line.

A third groundwater treatment system, the "Community Wellhead Treatment System (CWTS)," began operation in 1998. It treats groundwater extracted from Zone 4 using GAC (and resin, since 2003). The treated water is discharged to Pyrite Creek or used for local irrigation. The CWTS does not fully remediate the groundwater contamination in Zone 4; there is perchlorate-contaminated groundwater that has moved past the CWTS. Studies are underway in accordance with an EPA-State agreement reached in April 2014 to determine what additional cleanup is needed, with a proposed plan expected in 2019. The nature and approximate extent of perchlorate contamination in Zone 4 groundwater are described in two draft reports prepared for the DTSC (the Zone 4 RI report in February 2010 and Zone 4 FS report in March 2012).

Recent technical reports prepared for DTSC include: “Final Phase I Evaluation, Zone 1 Barrier Systems and Hydraulic Containment in Zone 1b” (4/10/15); “Final Groundwater Monitoring Optimization Report” (2/12/2026; “Final 2014 Annual Groundwater Remedy Effectiveness Evaluation” (6/16/2016).

EPA is conducting studies in Pyrite Canyon to investigate perchlorate sources other than the Stringfellow disposal pits. Field work began in July 2013 and was completed in 2015. Sample results collected during these investigation will be analyzed in remedial investigation reports. These reports are expected to be finalized in 2017..

The Documents and Reports section below includes key site documents. A more complete set of documents is available on DTSC's site webpage at: http://www.envirostor.dtsc.ca.gov/public/profile_report.asp?global_id=33490001

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Cleanup Results to Date

The removal of liquid waste, connection of affected residences to an alternate water supply, and installation of groundwater capture and treatment systems have reduced the potential for exposure to contaminated soil, groundwater and surface soil at the Stringfellow Site while the remaining cleanup activities are being planned and conducted.

EPA regularly reviews progress made in cleaning up the Site. Formal reviews are completed every five years to evaluate whether the cleanup continues to protect human health and the environment and is achieving EPA's cleanup goals. EPA has completed four "five-year reviews" at the Site. The most recent, will be completed in September 2016, and available in the Documents and Reports section below.

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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.

EPA began identifying PRPs at the Stringfellow Site in the 1980s. More than 100 PRPs have been identified. Under the Superfund law, PRPs include the owner and operator of a site, and companies that arranged for the disposal of wastes that ended up at the Site.
In 1983, EPA and the State of California filed a lawsuit against 32 PRPs believed to be responsible for the costs of cleanup at the Site. The enforcement effort included a series of judicial judgments and settlements between 1987 and 2004. The settlements include eight agreements that provided commitments by PRPs to complete cleanup work at the site and/or reimburse money that EPA had spent on the cleanup. The eight settlements are as follows.

Date Entered by the CStringfellow Site Consent Decreesourt
October 23, 1992United States, the State, and 16 PRPs, including the Site operator and most of the major generator PRPs (later known as the Pyrite Canyon Group)
October, 1992United States and Alcan Aluminum Corporation (subsequently a member of the Pyrite Canyon Group)
March 14, 1994United States, the State, and General Steel and Wire, Co., Inc.
April 25, 1997United States, the State, and 80 PRPs (the “de minimis” parties)
June 1, 2001United States, the State, and Rainbow Canyon Manufacturing, Inc.
July 20, 2001United States and the State of California
August 2002State of California and the Pyrite Canyon Group
June 21, 2004United States, the State, the Pyrite Canyon Group, and additional PRPs known as "Third-Party Defendants"

Following litigation between the defendants and the State, the court ruled in 1995 that the State was a Responsible Party at the Site, and that its fair share (“allocation”) of the costs is 100% (under State law, 60% under federal law). Currently, after settlements with other PRPs, the State of California is the principle Responsible Party at the Site. The State began work at the Site in 1983 through a Cooperative Agreement with EPA (since ended). DTSC implements work on behalf of the State. The State of California is currently implementing all remediation work at the Site.

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Documents and Reports

Show details for Administrative RecordsAdministrative Records
Show details for Community InvolvementCommunity Involvement
Show details for Fact SheetsFact Sheets
Hide details for ImagesImages
Show details for Legal DocumentsLegal Documents
Show details for MapsMaps
Show details for Records of DecisionRecords of Decision
Show details for Technical DocumentsTechnical Documents

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Community Involvement

Public Meetings: EPA and DTSC periodically prepare and distribute fact sheets describing progress and highlighting issues at the site. DTSC fact sheets are available on on DTSC's site webpage at: http://www.envirostor.dtsc.ca.gov/public/profile_report.asp?global_id=33490001 (Look under the "Community Involvement" tab.)

The Stringfellow Advisory Committee (SAC) has been meeting regularly since the 1980s. Meetings generally occur quarterly at the DTSC Stringfellow Information Center (10247 Bellegrave Avenue, Suite 131, Mira Loma, CA 91752). Minutes of the meetings are available on the DTSC website. Contact EPA or DTSC staff for more information.

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Public Information Repositories

The public information repositories for the site are at the following locations:

Glen Avon Public Library
9244 Galena St.
Riverside, CA 92509
(951) 685-8121

The most complete collection of documents is the official EPA site file, maintained at the following location:

Superfund Records Center

Mail Stop SFD-7C

95 Hawthorne Street, Room 403

San Francisco, CA 94105

(415) 820-4700

Enter main lobby of 75 Hawthorne street, go to 4th floor of South Wing Annex.

Additional Links

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EPA Site Manager
Daewon Rojas-Mickelson
US EPA Region 9
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Community Involvement Coordinator
Viola Cooper
US EPA Region 9
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
State Contact
Susan Fears
Stringfellow Branch Chief
Department of Toxic Substances Control
P.O. Box 806
Sacramento, CA 95812-0806
PRP Contact
Susan Fears
Stringfellow Branch Chief
Department of Toxic Substances Control
P.O. Box 806
Sacramento, CA 95812-0806
Community Contact
Center for Community Action and Environmental Justice
Center for Community Action and Environmental Justice
P.O. Box 33124
Jurupa Valley, CA 92519
Other Contacts
After Hours (Emergency Response)
(800) 424-8802

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