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Pacific Southwest, Region 9: Superfund

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

Koppers Co., Inc. (Oroville Plant)

EPA #: CAD009112087

State: California(CA)

County: Butte

City: Oroville

Congressional District: 02

Other Names: Koppers Company, Inc., Koppers Feather River Plant

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/koppers .
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: 09/08/83

Final Date: 09/21/84

Deleted Date:

Since 1948 until March 15, 2001, the 205-acre Koppers Company, Inc. (Oroville Plant) site was used to conduct wood treating operations to prevent wood deterioration by insects or fungi. Koppers purchased the plant from the National Wood Treating Company in 1955 and closed the facility March 15, 2001. Chemical and waste water handling procedures and wood treatment and storage operations contaminated the soil and groundwater on and off site. Fires at the Koppers facility occurred in 1963 and 1987, causing increased contamination at the site. Groundwater, surface water, and soils on and off site were contaminated with pentachlorophenol (PCP) and other hazardous substances used in Koppers' wood treating activities. The contaminated groundwater was located beneath this site and off-property south of the Koppers site. In 1973, PCP was discovered in nearby residential wells that were used as a source of drinking water. In 1988, the Koppers Company, Inc. was bought by the parent company of Beazer East, Inc (BEI). BEI later sold the wood treating plants to Koppers Industries, Inc. (KII). After KII closed its wood treating operation in March 2001, KII resold the site back to BEI in November 2002. In November 2006, BEI sold all the 205 acre site (exclusive of parcel #1 containing the site's contaminated soils consolidated into two RCRA landfills) to Gold Line Express, Inc. of Woodland CA for development as an industrial park (see attached 49 lot parcel plan). In 2016 several of the parcels were sold to parties that do not have active plans for redevelopment. BEI remains the recognized potentially responsible party provided the new owner complies with the insitutional controls contained in the deed restrictions. Approximately 10,650 people live within a three mile radius of the site. These people also depend on groundwater as their source of drinking water. The nearest downgradient private water supply well is just off-property to the south, and there are numerous private water supply wells within three miles of the site. Contamination of groundwater from site-related chemicals is limited to on site property.

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Contaminants and Risks

Contaminated Media
  • Groundwater
  • Surface Water

Groundwater on property, contains pentachlorophenol (PCP), dioxins, furans, polycyclic aromatic hydrocarbons (PAHs), and heavy metals including copper, chromium, and arsenic. Potential health risk pathways include drinking contaminated groundwater, or dermal exposure via excavation of soil below five feet on site.

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Who is Involved

This site is being addressed through Federal and potentially responsible parties' actions.

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Investigation and Cleanup Activities

This site is being addressed in three stages: 1. the consolidation of contaminated soil in two corrective action management units which has been completed, 2) contain contaminated groundwater and restore the aquifer using pump and treat technology augmented by nutrient addition to enhance natural biological degradation of the groundwater contamination which is operating, and 3) monitor a technical impracticability waiver granted for a 4 acre on property area upgradient of the on-property pump and treat system.

Initial Actions

Initial Actions: An alternative water supply was provided by BEI to residents south of the site in areas of potential groundwater contamination since 1986. Between 1987 and 1988, the EPA directed the construction of a temporary chip seal cap over the contaminated soil in the process area. The cap functioned to stabilize the site and to prevent contact with contaminants after a fire spread hazardous substances. In 1994, the EPA directed BEI to build an on-site landfill for disposal of surface soils containing high levels of dioxins. The 15,000 cubic yard landfill Cell #1 was completed in 1995. Subsequent detailed investigations determined dioxin soil contamination was widespread preventing the planned soil remedies.

Cleanup Ongoing

Entire Site: The potentially responsible party for site contamination completed a study of the site in 1989. The EPA used the results of this study to select the following methods to address site contamination: removing and treating contaminated groundwater with a carbon adsorption process; treating the contaminated soil in place; capping the wood treating area; providing a permanent water supply to those residents with contaminated wells; and discharging treated groundwater to the aquifer. Two groundwater extraction and treatment systems were installed: one on-site (400 gpm system still operating) and one off-site (600 gpm system shutdown in Dec. 1995 when the plume retreated) using carbon absorption followed by recharge to the aquifer using injection wells. In 1989, the EPA selected three different treatment technologies to clean up approximately 335,000 cubic yards of contaminated soil. However, treatability tests conducted during the design phases showed that the selected technologies could not achieve cleanup goals for all contaminants. BEI initiated a focused feasibility study to evaluate other cleanup alternatives for soils in 1995. In August of 1996, a Record of Decision (ROD) Amendment #1 was issued changing the soil remedy to on-site landfilling of the remaining contaminated soils. ROD Amendment #1 changed the cleanup standard to industrial use and required deed restrictions to prohibit future residential development.

In September 23, 1999, the EPA issued a ROD Amendment #2 to modify the remedy to 1) provide for a Technical Impracticability Waiver due to Dense Non-Aqueous Liquid for 4 acres of the 200 acre site, 2) add enhanced in-situ bioremediation to the remedy, and 3) provide for Monitored Natural Attenuation (MNA) as a contingency remedy. A modification to the Consent Decree modification for ROD Amendments #1 and #2 was completed September 22, 2003. The land use covenant provision of the ROD restricting the site to industrial use and restricting access and use of groundwater under the site were recorded with the Butte County Recorder on November 12, 2003.

Koppers Industries, Inc. closed the wood treating facility in March 15, 2001 and completed its Resource Conservation and Recovery Act (RCRA) closure under State of California oversight July 2002. Remediation of the area beneath the process area became accessible after the RCRA closure. Final soil remediation was completed in September 2002.

With soil remediation complete and groundwater contamination under control a Preliminary Closeout Report was issued September 4, 2003. To review this preliminary report double click on its title below under Site Documents and Report section. A Final Closure Report cannot be issued until the groundwater aquifer is restored to the cleanup levels specified in the ROD which will be some years in the future.

In 1982, the State issued two orders to Koppers to clean up contaminated soil and groundwater at the site. In 1986, the EPA and Koppers signed a Consent Order, which required the company to conduct a study into the nature and extent of contamination at the site. In December 1990, BEI signed a Consent Decree to perform the engineering design and cleanup activities at the site. An Explanation of Significant Differences was issued January of 1991 which limited soils cleanup to five feet unless a potential source to groundwater were found. In August of 1996, a ROD Amendment #1 was issued changing the soil remedy to an on-site landfill. In September 1999, a ROD amendment #2 was issued modifying the groundwater remedy to provide for 1) 4 acre Technical Impracticability Zone, 2) adding enhanced in-situ bioremediation to the remedy and 3) providing MNA as a contingency remedy.

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Cleanup Results to Date


To prevent exposure to contaminated groundwater from domestic wells, city water was provided in 1986 to residents with potential for exposure and was paid for by BEI. As the off-property remediation progressed, there was no need for the alternative water supply program to continue.

The off-property pump and treatment facility was taken off-line in December of 1995 as the plume degraded and no contaminants were being removed by the extraction wells. In August 1998 a pilot in-situ bioremediation program to assist in PCP degradation was initiated and incorporated into the remedy September 1999. The program was initiated with the addition of two nutrients (diammonium phosphate) and oxygen (magnesium peroxide) to three wells and monitoring at five wells. In the first quarter 2004 nutrient addition was reduced to adding only magnesium peroxide. Contaminant concentrations in off-property groundwater fell below cleanup standards in 2007. As of June 2013, off-property groundwater is no longer being monitored.

        The on-property pump and treatment facility is still in operation preventing contaminated groundwater from moving off-property. In April 1998 a pilot in-situ bioremediation program was initiated on-property to degrade PCP and incorporated into the remedy in September 1999. The program initially added two nutrients (diammonium phosphate) and oxygen (magnesium peroxide) to six wells and monitoring at five wells. The magnesium peroxide addition was stopped the first quarter 2004. The PCP concentrations in the on-property wells are continuing to decrease. The on-property pump and treat facility will continue to operate until the ROD cleanup standards are met and then will be held in reserve as long as the Technical Impracticability Waiver remains in effect.

        March 8, 1999 BEI submitted a Final Evaluation of Technical Impracticability (TI) of Groundwater Restoration in the Former Creosote Pond and Cellon Blowdown Areas On-property. The TI waiver for the four acres was incorporated into the remedy with ROD Amendment #2 in September 1999. TI zone area and just downgradient is monitored for contaminant movement.

        With the demolition of the wood treating facility in 2001 and 2002, boron was mobilized from the DriCon/CCA area and detected by monitoring well MW-8 above the action level. The downgradient on-property treatment plant does not treat for boron. MW-8 was converted to an extraction well to dilute the boron concentration to continue reinjection below the cleanup level. Boron readings are monitored at MW-8 and prior to reinjection for compliance with the ROD.


        In 1987/88 a temporary chip seal cap was placed over the process area. In 1992, two concrete drip pads were installed in the process area to contain wood treating chemicals and prevent any further soil contamination. The cap and drip pads were demolished in 2002 as part of KII's facility closure. Two landfill cells were constructed for disposal of contaminated soils on site. Cell #1 (13,000 cubic yards) was completed in August 1995 as a Removal Action. Cell #2 (147,000 cubic yards capacity) was closed September 2002 with the completion of the soil remediation efforts for the site. 6,000 cubic yards of boron impacted soil was removed from the newly discovered Dri-Con/CCA source and placed in Cell #2 prior to its closure. With soil remediation complete and control of groundwater in place a Preliminary Closeout Report was issued for the site September 4, 2003. A land use covenant was recorded with the Butte County Recorder on November 12, 2003 restricting the site to industrial use and the access and use of groundwater under the site.

        In November 2006, BEI sold all the 205 acre site exclusive of parcel #1 containing the site's contaminated soils consolidated into two RCRA landfills to Express, Inc. of Woodland CA for development as an industrial park (see attached 49 lot parcel plan).

        The Fourth Five Year Review Report, completed in August 28, 2013, concluded that currently, all implemented remedies are found to be functioning as intended by the decision document and, therefore, are protective of human health and the environment.

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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.

As agreed to in the 1992 Consent Decree for the Koppers Site Remediation, Beazer East, Inc. is the PRP for the Koppers Site in Oroville.

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Documents and Reports

Show details for Administrative RecordsAdministrative Records
Show details for Fact SheetsFact Sheets
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:

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Public Information Repositories

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

Butte County Public Library,
1820 Mitchell Ave.,
Oroville, CA 95965

Meriam Library,
California State University at Chico,
Chico, CA 95929-0295

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
Heather Parker
US EPA Region 9
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
State Contact
DTSC - Deena A. Stanley

RWQCB - Bill Bergmann


8800 Cal Center Drive
Sacramento, 95826-3200
PRP Contact
Michael Tischuk

Jennifer Abrahams


Beazer East, Inc.

Tetra Tech
Community Contact
Other Contacts
After Hours (Emergency Response)
(800) 424-8802

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