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U.S EPA proposes Iron King Mine - Humboldt Smelter to Superfund site list

Release Date: 03/19/2008
Contact Information: Margot Perez-Sullivan,, 415.947.4149 or 415.760.9161 (mobile)

SAN FRANCISCO – Today, the U.S. Environmental Protection Agency announced it is proposing the Iron King Mine - Humboldt Smelter facility in Dewey-Humboldt, Ariz. to the federal National Priorities List or Superfund list.

The Arizona facility is one of six sites nationwide that were proposed to the National Priorities List today.

“We are mobilizing to collect the data that will help us address the sources of contamination which have been an ongoing concern for many residents,” said Keith Takata, Superfund division director for the EPA’s Pacific Southwest region. “The Superfund program is an appropriate solution where no other viable regulatory options for cleaning up the sources of contamination from these historical operations exist”

The 153-acre Iron King Mine was intermittently active from 1906 until 1969. Ore from that mine and other mines was processed at the 189-acre Humboldt Smelter, which operated from the late 1800s until the early 1960s. Mine operations and processing have contaminated soil, sediments, surface water and groundwater with arsenic, lead and other metals.

A significant residential area of the Dewey-Humboldt site sits between the mine and the smelter. Arsenic and lead have been detected at levels considerably above health based standards in soil of several residential yards. Listing the site on the NPL will enable the EPA to investigate the sources of contamination and determine the best cleanup approach to protect human health and the environment. An interim removal of soil from yards has been conducted to date.

The Arizona Department of Environmental Quality supports the Superfund listing, along with the Mayor and City Council of Dewey-Humboldt who voted in support of listing. Sites are proposed or added to the National Priorities List as part of the periodic review and update of the Superfund program. The U.S. EPA identifies and ranks these sites according to threats to nearby populations through actual or potential contamination of soils, groundwater, surface water or air.

In order to address site conditions as soon as possible, the EPA is proceeding with a remedial investigation/feasibility study (RI/FS), which involves the collection of environmental data necessary to select a cleanup method. The EPA plans will begin field sampling for the RI/FS in this summer. In the coming months, EPA will hold a community meeting to discuss the Superfund program, upcoming site activities, and opportunities for community involvement.

With today’s decision, there are now 8 final and 1 proposed National Priorities List sites in Arizona. Nationwide, the agency is adding 12 new hazardous waste sites to the Superfund National Priorities List and is proposing to add six other sites to the list.

Superfund is the federal program that investigates and cleans up the most complex uncontrolled or abandoned hazardous waste sites in the country posing the greatest long-term threat to public health and the environment.
To date, there have been 1,581 sites listed to the National Priorities List. Of these sites, 324 sites have been deleted resulting in 1,257 final sites on the list. With the proposal of the six new sites, there are 60 proposed sites awaiting final agency action: 55 in the general Superfund section and five in the federal facilities section. There are a total 1,317 final and proposed sites on the National Priorities List.

For Federal Register notices and supporting documents for these final and proposed sites, please visit