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There are four Kerr-McGee Superfund sites in the West Chicago, IL, area that were contaminated by radioactive thorium waste material. The waste was generated by a processing facility (now closed and owned by the Kerr-McGee Chemical Corporation) that operated in West Chicago between 1932 and 1973.

Sand-like waste materials known as mill tailings were stored at the facility. The mill tailings were available as free fill material from the 1930s through the 1950s and were used throughout the West Chicago area for landscaping projects and to fill low-lying areas. It was later determined that the radioactive material was potentially hazardous.

Wastes from the Kerr-McGee facility also entered Kress Creek through a storm sewer, contaminating sediments (river mud) in the creek and the West Branch DuPage River.

The Kress Creek/West Branch DuPage River site is located in DuPage County, Ill., about 30 miles west of Chicago, and includes almost seven miles of creek and river sediment, banks and floodplain soils contaminated with radioactive thorium residue. The Kress Creek site includes about a mile and a half of Kress Creek stretching from a storm sewer outlet to where the creek empties into the West Branch DuPage River. From there the site stretches about five miles down the West Branch DuPage River past the Warrenville Dam to the McDowell Dam. The site is shown in the figure on page 3. Land use along the creek and river is a mixture of residential areas, parks, county forest preserves, and property owned by religious groups and government entities.

The sewage treatment plant site is located in West Chicago, also in DuPage County. The sewage treatment plant site is divided into two different parts: an upland portion and a river portion. The upland portion of the site consists of the West Chicago Sewage Treatment Plant, which is owned and operated by the city of West Chicago and located northeast of the intersection of Illinois Routes 59 and 38. The river portion of the site consists of a little over a mile of the West Branch DuPage River from the northern edge of the sewage treatment plant property to where Kress Creek joins the river. The site is shown in the figure on page 3. Land use along the river portion of the site is mostly recreational, but there are some homes and a church on the eastern side of the river south of the sewage treatment plant.

Portions of both the Kress Creek site and the sewage treatment plant site are contaminated with the radioactive thorium residue. The residue came from a facility in West Chicago that processed radioactive thorium from 1931 through 1973. The facility originally was owned by Lindsay Light and Chemical Co. but changed hands several times. Kerr-McGee owned and operated the facility from 1967 to 1973 when it closed the plant. Thorium and other elements were separated from ores at the plant using an acid process. The Kerr-McGee facility is not part of the Kress Creek site and is being cleaned up under the supervision of the Illinois Emergency Management Agency, Division of Nuclear Safety.

Over many years, thorium-contaminated soil particles from the Kerr-McGee facility entered a nearby storm sewer during rainstorms and traveled to Kress Creek. From there the pollution moved downstream in the creek and into the West Branch DuPage River, settling into the creek and river sediment along the way. The thorium was also deposited onto floodplains during high water periods. The source of the pollution has been controlled so no more thorium is entering the creek.

The sewage treatment plant became contaminated when radioactive thorium residuals from the Kerr-McGee facility were hauled to the treatment facility and used as fill material. Some of the contamination then entered the West Branch DuPage River adjacent to the sewage treatment plant property due to erosion and surface water runoff during rainstorms.

Radioactivity surveys performed in the West Chicago area by the Nuclear Regulatory Commission and EPA resulted in EPA placing the sewage treatment plant and Kress Creek sites on the Agency,s National Priorities List in 1990 and 1991. The National Priorities List is a roster of Superfund sites nationwide. In 1993 EPA began looking at the Kress Creek and sewage treatment plant sites, a process known as a remedial investigation. In 1997, as a result of negotiations between Kerr-McGee and the city of West Chicago, Kerr-McGee began more extensive investigations at the sites. EPA suspended its work at the sites in 1998 at the request of Kerr-McGee and the city. Kerr-McGee continued its extensive site investigation work for several years while continuing to negotiate with the city and other local entities over the cleanups. As a result of the extensive studies and negotiations, Kerr-McGee and the local communities agreed on a cleanup proposal and presented it to EPA. Kerr-McGee then officially took over the remedial investigation and feasibility study from EPA in a written agreement reached in late 2003. The remedial investigation and feasibility study reports prepared by Kerr-McGee include data collected by both EPA and Kerr-McGee.

No cleanup actions have occurred at the Kress Creek site, but some residential properties along the creek were cleaned up in the mid-1990s as part of a separate residential cleanup program. Cleanup actions have also occurred at the upland portion of the sewage treatment plant site. During 1986 and 1987, Kerr-McGee removed about 57,000 cubic yards of contaminated material from the sewage treatment plant as part of a voluntary cleanup action. No cleanup was done along the river banks or in the river, however. In late 2003, Kerr-McGee reached a written agreement with EPA to remove another 4,000 cubic yards of contamination from the sewage treatment plant that was not addressed during the earlier cleanup. This cleanup started in October 2003 and is expected to be completed this spring. When the removal is completed, radiation levels at the upland portion of the sewage treatment plant site will be well within safe levels. Contamination still remains, however, at the river portion of the site.

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