The Department of the Army, Army Corps of Engineers, South Pacific Division, Los Angeles District, has a requirement for remedial action construction (RAC) at the Iron King Mine–Humboldt Smelter (IKM-HS) Superfund Site in Dewey-Humboldt, AZ.

• The RAC will be completed in compliance with the ROD and supplemental design information. The ROD selected remedy is Alternative 3B: On-Site Consolidation/Containment at Two Repositories with Waste Remaining East and West of the Highway. The highway is State Route 69 that serves as the main road to Prescott, Arizona, from Arizona Interstate 17. The Construction Contractor will be expected to perform the work described in the ROD Alternative 3B, including the dam removal noted below, retaining wall construction, creating a cap for the two repositories, and other construction activities as described and/or as needed for the site.
• Alternative 3B removes mine and smelter wastes, and contaminated soils and moving them to two waste repositories. Mine wastes and contaminated soils from the former mine and surrounding areas west of Highway 69 would be moved into a repository on the existing mine tailings pile west of the highway. Mine wastes at the former smelter and in the Chaparral Gulch east of Highway 69 would be moved into a second waste repository east of the highway.
• Additionally, the Lower Chaparral Gulch Dam east of the highway shall be removed to allow access to waste in the Lower Chaparral Gulch and restore the natural hydraulics and vegetation of the drainage. This shall include watershed and habitat restoration. A specific plan for removal of the dam will be provided to the dam removal contractor.
• Additional notable details concerning the site are associated with the former pyrometallurgical operations and the wall of solid slag hanging on a cliff above the Agua Fria River. The former pyrometallurgical operations of the Humboldt Smelter, (former blast furnaces, metal-purifying converters, coal and coke heating, sintering, power generation, etc.) were situated on the north end of a high plateau surrounded by steep slopes and lower terrain.  This area contains soils contaminated with metals including arsenic and lead and the area is covered by dross waste. South of the former pyrometallurgical operations area, the smelter plateau also contains arsenic lead contaminated soils.
• On the eastern edge of the smelter plateau, a wall of solid slag hangs on the cliff above the Agua Fria River about 80 feet high. It contains roughly 280,000 cubic yards of material. The slag is similar to solidified lava rock. It is inert and does not pose a chemical health risk unless it is pulverized into soil-like material or sediments. Data indicates that pulverized slag is leachable and slag falling into the river and being pulverized could release metals to the river over time
• The Contractor performing this work shall comply with all applicable Federal, State, and local laws, and regulations including, but not limited to the 1968 National Oil and Hazardous Substances Pollution Contingency Plan, as amended, and the 1980 Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), as amended.