PROBLEM/SITUATION: Develop an accurate, cost-effective method of remediating radioactive contamination in the Kerr-McGee residential area Superfund site.
SOLUTION: Combine GPS, GIS and radiation-detection technologies to provide rapid, accurate identification, analysis, mapping and clean up of site.
JURISDICTION: City of West Chicago, Ill., Dupage County, Ill.
VENDORS: CH2M Hill Inc., Trimble, Sun Microsystems, Oracle, ESRI.
CONTACT: Rebecca Frey, Region 5 project manager, U.S. Environmental Protection Agency, 312/886-4760; Tim Runyon, project manager, Illinois Department of Nuclear Safety, 217/786-6365.
In 1930, the Lindsay Light and Chemical Company Plant in West Chicago began milling naturally occurring radioactive thorium and other rare earths for the manufacture of filament coatings, polishing compounds and other products. In 1958, the plant was purchased by American Potash and Chemical, and in 1957, by Kerr-McGee Corp. When it closed in 1973, wastes from the various milling operations covered much of the 43-acre site. Decades of processing, most predating regulatory control of radioactive materials, left a landscape of thorium tailings (residue from the milling process), sediment piles and leach ponds.
Prior to closure -- and before the dangers of thorium tailings were known -- local residents, contractors and the city of West Chicago were allowed to haul away truckloads of the sandy residue to use as fill material in parks, streets, sidewalks, lawns, swimming pools and septic-tank installations. Runoff from heavy rains carried these wastes into sewers that emptied into a creek running through the surrounding residential area. When the creek flooded, waste from the plant site was deposited in people's yards.
To determine the extent of waste dispersal, aerial radiological surveys were conducted by the Nuclear Regulatory Agency in 1977, and again in 1989 by the U.S. Department of Energy and CH2M Hill, an engineering firm under contract to the federal Environmental Protection Agency (EPA) for remediation of Superfund sites. The surveys indicated that the waste had produced radioactive contamination in a 30-square-mile area around the plant site.
SUPERFUND SITE ESTABLISHED
In 1989, the EPA established the Kerr-McGee residential area as a Superfund site. Today it is the largest and most active of four such sites in West Chicago. In 1992, EPA; its prime contractor, CH2M Hill; Illinois Department of Nuclear Safety (IDNS); and Kerr-McGee Corp., began the actual clean up.
Identifying which of the more than 1,200 properties in the area require clean up is the responsibility of the EPA and the prime contractor. EPA Region 5 project director, Rebecca Frey, described this as the "discovery-characterization phase of the project." It includes surveying 1,200 to 1,400 properties, processing the data, and providing EPA with individual property summaries -- including GIS and GPS information -- and the analytical results from soil sampling.
EPA then passes the information to Kerr-McGee, which is under unilateral order to carry out excavation and property restoration. Following excavation, IDNS conducts soil-sample analysis and gamma radiation tests to determine if the property is "clean." If not, IDNS indicates where further excavation is needed. When the results meet EPA clean-up standards, Kerr-McGee is given authority to back-fill and restore the property.
The EPA requires remediation of properties having five picoCuries-per-gram total radium in the soil above the normally occurring background gamma radiation levels. However, naturally occurring background gamma radiation comes from the content of radium and uranium in the soil, and must be determined by lab analysis of random soil samples from the area. A gamma radiation detector will not do the job because the instrument is unable to distinguish between naturally occurring soil radiation and that "broadcast" by the concentration of thorium tailings at the nearby plant site. A conventional approach would be to measure radium levels by manually analyzing soil samples from hundreds of individual properties. "A slow, costly process," said CH2M Hill Quality Assurance Manager John Fleissner. "It produces insufficient data that