The 4.5-square-mile Vasquez Boulevard and I-70 site is located in Denver, Colorado. The site includes several smelting companies, including the former Omaha & Grant Smelter, the Argo Smelter and the ASARCO Globe Plant. Smelting operations to produce gold, silver, copper and lead from mining ore began as early as 1878. Operators left process wastes in unlined dumps on the northern edge of the property. The Omaha & Grant Company began on-site trash incineration in 1944. Improper waste disposal and handling contaminated groundwater with heavy metals. Remedy construction for residential soils has finished. Investigations are underway at the Omaha and Grant Smelter and the Argo Smelter.