EPA Superfund Site

IRON KING MINE - HUMBOLDT SMELTER

AZ | EPA ID AZ0000309013

About this site’s exposure pathways: As of December 2024, the Iron King Mine Humboldt Smelter is currently designated as "Human Exposure Not Under Control". EPA has completed the RI/FS and the ROD was issued in October 2023. The site is now in the remedial design phase. EPA has performed removal actions in 2006, 2011, and 2017 that have greatly reduced human exposures to contaminated residential soils. However, because the ROD reduced cleanup levels for arsenic and lead, extensive additional sampling and cleanup of residential properties is underway. There are still residences with soils contaminated above the new cleanup levels. The remedial design to carry out actions selected in the ROD to address the mine tailings in tailings piles, drainages, flood plains, behind the dam, and on the former smelter property, is ongoing. These are not areas of usual human contact in these waste-bearing areas. EPA has posted numerous danger signs near contaminated areas. EPA and the Arizona Department of Environmental Quality have taken actions to place an effective seal on waste dross material at the smelter to prevent aerial entrainment of dust, and to install a fence with warning signs, cutting off an access path children may have used to access the smelter plateau and dross. EPA has also reinforced gates to prevent casual access. At the separate massive mine tailings pile at the former mine, thousands of feet of new fencing has been installed in an attempt to limit or eliminate human access to the pile. EPA communicates to Dewey-Humboldt residents and the Town government on a regular basis. While human exposure is not certain, there could be casual/short-term human contact with these tailings and occasional inhalation hazards in the immediate vicinity of tailings areas during high winds. Some tailings areas cannot be effectively sealed off from all human access in all situations. Such conditions will likely persist until such time as mine tailings and wastes are removed and capped as selected by the ROD. The primary chemicals of concern at the site are arsenic and lead. Sampling results indicate the presence of elevated levels of arsenic and lead that could present health risks if a person is exposed to these metals over an extended period of time.