The Rocky Mountain Arsenal (RMA) is nearly 27 square miles. RMA is located at the western edge of the Colorado plains, near the foothills of the Rocky Mountains, ten miles northeast of downtown Denver, Colorado. Characterized by rolling terrain, grasslands, shrublands, wetlands and aquatic habitats, the site supports a variety of plant and wildlife species. To the west and northwest of the site sits Commerce City and the South Platte River. Newer residential developments and the town of Henderson are located to the north, and the neighborhoods of Montbello and Stapleton are to the south. The Denver International Airport is located just to the east.

The U.S. Army established the Rocky Mountain Arsenal (RMA) in 1942 to produce incendiary munitions and chemical warfare agents such as mustard gas used in World War II. Following the war, and through the early 1980s, the Army continued to use these facilities. Private industry was also encouraged to lease facilities at RMA after the war to foster economic growth in the area, offset operational costs and maintain facilities for national security. Under the lease program, Julius Hyman and Company began producing pesticides in 1946.

In 1952, Shell Chemical Company acquired Julius Hyman and Company and continued to produce agricultural pesticides on-site until 1982. These activities over time resulted in widespread and significant environmental contamination across the site. Contamination was detected in soil, ditches, stream and lakebed sediments, sewers, groundwater, surface water, biota, structures, and, to a much lesser extent, air. The most highly contaminated sites are concentrated in the central manufacturing, transport and waste disposal areas. The buffer zone along the boundaries or the site proved to be relatively uncontaminated. The principal contaminants included organochlorine pesticides, heavy metals, agent-degradation products and manufacturing by-products, and chlorinated and aromatic solvents.