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The Koppers Company, Inc. (Koppers) site is located in Oroville, Butte County, California, approximately 50 miles north of Sacramento. Since 1948, on-site wood treatment activities coupled with fires resulted in varying amounts and types of contamination in groundwater, soil, sediment, and surface water. The fires also resulted in episodic air releases.

In the past, area residents voiced concerns regarding possible health effects associated with site-related contamination. A local community group, Citizens for Clean Water, requested that the Agency for Toxic Substances and Disease Registry (ATSDR) conduct a public health assessment for the site. In response, ATSDR reviewed and evaluated environmental sampling data collected as part of site investigations. ATSDR studied the ways in which people may have been exposed to site-related contamination and evaluated biologic monitoring (blood and urine) data and local health outcome data (documentation of disease occurrence) collected by state health officials.

Contaminants detected on site during site investigations include arsenic, benzene, pentachlorophenol (PCP), polychlorinated dibenzodioxins (dioxins) and polychlorinated dibenzofurans (furans), and polycyclic aromatic hydrocarbons (PAHs), all of which are associated with the wood treatment process. Groundwater south of the Koppers plant (including some domestic wells) was found to be contaminated, primarily with PCP. In addition, limited testing of backyard-raised eggs and livestock revealed the presence of dioxins/furans.

Site workers and site neighbors may have been exposed in the past to site-related contaminants as a result of 1) drinking or contacting water from domestic or on-property supply wells; 2) breathing smoke resulting from site fires; 3) eating home-produced chicken or eggs containing elevated levels of dioxins/furans; or 4) contacting on-site soils, sediment, and surface water. ATSDR's evaluation of these exposures is summarized below:

  • Certain past exposures to domestic well water, smoky air, and on-site soils may have resulted in some short-term (acute) reversible adverse health effects, such as skin irritations, headaches, etc. However, area residents and workers were unlikely exposed to site-related contaminants at high enough concentrations or for enough time to suffer long-term health effects. Lack of exposure data, however, makes definitive links between health effects and past exposures impossible.

  • Currently, the site poses no apparent public health hazards. No persons are currently exposed to harmful levels of contaminants. Residences are connected to public water or are using wells that meet drinking water standards. Groundwater and site soil clean-up efforts have been implemented and have largely reduced contaminant levels. Measures that are in place to ensure the continued protection of public health include on-property groundwater treatment, regular monitoring of area groundwater, and certain land use restrictions.

  • Some uncertainties exist regarding the extent and significance of dioxin/furan levels detected in backyard-produced chicken/eggs. The California Department of Health Services (CDHS) issued a Health Advisory in 1989 recommending that community members reduce their exposures to potentially contaminated products. This advisory serves as a preventive measure while investigations continue.


Activities at the Koppers Company, Inc. Feather River Plant (the Koppers site) in Oroville, California have resulted in varying amounts of contamination of site and area groundwater, air, and soil. Over the years, local residents have voiced many concerns about the Koppers site and possible health effects associated with exposures to pentachlorophenol (PCP) in groundwater, pollutants released to the air during past fires, dioxins detected in home-produced eggs, and contaminated soil and debris on site. In response, site investigations have been ongoing since the mid-1980s and site clean-up activities are in progress.

Citizens for Clean Water, a local community group concerned with the contamination and cleanup of this site, requested that the Agency for Toxic Substances and Disease Registry (ATSDR) perform a public health assessment (PHA) of the site. The purpose of this PHA is to evaluate community concerns by 1) identifying ways in which people may have been exposed to contaminants related to the Koppers site; 2) assessing the findings of environmental sampling, biologic monitoring, and health outcome studies; 3) providing the community with ATSDR's conclusions regarding potential public health impacts associated with the Koppers site; and 4) providing recommendations for the continued protection of the health of site users and neighbors.


A. Site Description

The Koppers site is in Butte County, California, one-quarter mile south of the city limits of Oroville. Wood treatment activities have taken place on this 200-acre site since 1948. The Koppers site lies in the Feather River flood plain, which is approximately 2.7 miles wide. The Feather River is approximately 3,000 feet west of Koppers. The Louisiana-Pacific Corporation (L-P) facility, a wood products plant, borders the Koppers site on the west and the Western Pacific Railroad runs east of the site. See Appendix A for maps of the site and surrounding area.

Access to the site is relatively unrestricted. Although the site is fenced, the two entrance gates are kept open and not guarded. Access to outdoor process areas is possible but not likely because facility personnel would deter trespassers (EPA 1997b).

B. Site History

The site was developed as a lumber mill in 1920. In 1948, National Wood Treating Corporation began operations at the site, and in 1955 the property was purchased by Koppers Company of Pittsburgh, Pennsylvania. Over the years, many different processes and chemicals were used to treat wood. The chemicals used include the following:

Cellon: Cellon is the commercial name for a mixture of PCP, #2 diesel oil, liquefied butane, and isopropyl ether.

Penta-in-oil: Penta-in-oil is the common name for a mixture of PCP and #2 diesel oil.

Chromated Copper Arsenic (CCA): CCA is a 1% - 2% solution of chromium, copper, and arsenic in water.

Creosote-in-#6 diesel oil: This mixture contains 30% creosote and 70% oil.

NCX: NCX is the commercial name for a mixture of phosphorus, melamine, formaldehyde, and dicyanodiamide in water.

Dricon: Dricon is the commercial name for a mixture of phosphorus, boron, and dicyanodiamide.

In 1963, a fire occurred in the Cellon process treatment area. In the aftermath, fire debris was buried on site. In 1971, PCP contamination was discovered in groundwater on and off property. In 1973, the fire debris, which was suspected as the source of the PCP groundwater contamination, was excavated and transported off site to an approved waste facility. Measures taken in 1973 and 1974 to minimize the release of contaminants from the site include 1) the installation of two recovery wells to intercept and recover contaminated groundwater, and 2) the installation of a wastewater treatment system (Dames & Moore 1988a). Groundwater monitoring continued on and near the site throughout the 1970s.

In 1984, Koppers discovered additional groundwater contamination (including contamination of domestic wells in areas further south from the Koppers property line). Between 1984 and 1985, Koppers provided bottled water to approximately 40 homes whose wells were or had the potential to be affected (Dames & Moore 1988b). The site was placed on the U.S. Environmental Protection Agency's (EPA's) National Priorities List (NPL) in 1984, and EPA initiated a Remedial Investigation (RI) of the site. In February 1986, affected residences were connected to the Oroville-Wyandotte Irrigation District (OWID) municipal water supply (Ebasco 1988).

In 1987, another fire occurred in the Cellon treatment area. Residents exposed to the resulting smoke complained of nausea and of skin and eye irritations. The California Department of Health Services (CDHS) responded by documenting complaints and organizing a health screening within a week of the fire. Results of the screening are presented in the Discussion section of this public health assessment. To further evaluate the potential impact of the fire, EPA and CDHS analyzed a limited number of off-site soil samples, and CDHS sampled eggs and livestock raised in nearby yards.

Between June and November 1988, Beazer Materials and Services, Inc. (Beazer) purchased Koppers Company, Inc. On December 28, 1988, Beazer sold a portion of the corporation, including the Koppers/Oroville Superfund site, to Koppers Industries, Inc., but retained responsibility for site investigation and remedial activities required by EPA under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA).

The RI was completed in 1988. In May 1989, EPA released the proposed plan to clean up contaminated groundwater and soil. Beazer is conducting these cleanup actions under the terms of an agreement (known as a consent decree) with EPA that was approved in 1992. As part of this effort, Beazer constructed two pump and treat treatment systems to address PCP groundwater contamination: one system located on-property, and the other off-property near the intersection of Lone Tree and Prince Roads up gradient from any domestic wells that could be affected by contaminants. The systems consist primarily of extraction wells to pump contaminated water to a treatment plant, where contaminants, including PCP, are removed. Off-property treatment began in March 1993, and on-property treatment started in 1994 (EPA 1989, 1999a).

As of December 1995, EPA determined that the area of PCP-contaminated groundwater had receded to the extent that the off-property pump and treat system operation could be suspended. As described in EPA's amended Record of Decision for the Koppers site, the residual off-property PCP contamination is presently being treated by use of enhanced in-situ bioremediation, which is a type of aboveground treatment consisting of water recirculation and conditioning the water with nutrients and an oxygen source (EPA 1999a, 1999b). It is anticipated that the off-property aquifer will be fully restored for drinking water within 30 years under this type of treatment (EPA 1999a).

In April 1998, EPA removed restrictions on well use for domestic drinking water on 26 of 34 properties that had been the subject of closest scrutiny. EPA continues to require monitoring of off-property groundwater to ensure that the water quality is maintained. Treatment of groundwater beneath the Koppers property continues to reduce PCP levels and prevent the migration of remaining on-property contamination to off-property areas (EPA1997a,1998).

To clean up site soils, Beazer has excavated approximately 107,000 cubic yards of soil from existing storage locations. These soils have been placed in an on-site landfill, which is equipped with a liner system, leachate collection system, and leak detection system (TRC 1998). Figure 2 of Appendix A illustrates the areas of soil remediation and the location of the on-site disposal area.

C. Demographics and Land Use

The total population within a one-mile radius of the Koppers site is 2,626, based on statistics from the 1990 U.S. Census Bureau. The population is predominantly white and the area contains primarily middle-income households in single-family homes. According to the census data, 889 housing units are located within this area. Demographic statistics are presented in Appendix A.

Approximately 250 homes are located immediately south of the site, including 120 mobile homes and 130 individual residences (Butte County 1993). The nearest residence is approximately 500 feet from the southern edge of the Koppers facility. Land use south of the site is generally rural residential and includes agricultural and grazing lands. Some of those households maintain gardens and keep a limited number of backyard poultry and animals such as rabbits and goats. No commercial farms are located in the areas immediately adjacent to Koppers, but some are present in the Oroville area. However, a limited number of eggs have historically been sold from backyard operations (CA Dept. of Food and Agriculture 1993).

The L-P sawmill and particle board plant is located west of Koppers. Further west are California Highway 70 and the Feather River. A partially developed industrial area is north of Koppers, including an electric co-generation plant. The Western Pacific Railroad runs east of the site (Figure 1 in Appendix A).

Area groundwater and surface water provide water for drinking or irrigation throughout the county. The municipal water supply is fed by water from surface reservoirs in foothills east and upgradient of the site. The site habitat does not support any wildlife, nor do the water bodies on site (including a fire safety pond and drainage ditches) support any fish (Dames & Moore 1988a). Although water in the streams and ditches on the western periphery of the site are not designated for recreational use, neighborhood children play in these areas.


Community members living near the Koppers plant have expressed a variety of health concerns over the years including:

  • Potential health effects associated with PCP in domestic well water and the safety of existing drinking water supplies.

  • The possible association of reported skin, respiratory, and gastrointestinal disorders with site-related air and groundwater contamination.

  • Potential long-term health effects resulting from possible exposure to low levels of chemicals--perhaps over many years--in soil, air, and homegrown farm products.

  • Potential health effects from exposures to smoke during and immediately following fires at the Koppers plant.

  • Effectiveness of Koppers clean-up efforts and the proper disposal of fire debris from the on-site fires.

These concerns are addressed in the Discussion section of this document.

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