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U.S. EPA adds the Iron King Mine - Humboldt Smelter site to national Superfund list

Release Date: 09/03/2008
Contact Information: Francisco Arcaute, (213) 244-1815, cell (213) 798-1404,

Agency will address contaminated soil and groundwater

SAN FRANCISCO - Today, the U.S. Environmental Protection Agency added the Iron King Mine - Humboldt Smelter site in Dewey-Humboldt, Ariz., to the federal National Priorities List, or Superfund list, after its initial proposal in March.

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

“Today’s action of placing this site on the National Priorities List allows us to comprehensively investigate and respond to environmental concerns,” said Keith Takata, Superfund director of the EPA’s Pacific Southwest region. “Our site team is already in the field taking water and soil samples that will help us determine what should be done to move this site toward cleanup.”

The site encompasses areas of contamination from two facilities: the Iron King Mine property and the Humboldt Smelter property. The Iron King Mine was an active mine from 1904 until 1969. The majority of this area is covered by tailings and waste rock piles.

The Humboldt Smelter is situated less than one mile east of the Iron King Mine property. The smelter operated from the late 1800s until the early 1960s. This area is covered in yellow-orange tailings, grey smelter ash, and slag. Mining 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 above health based standards in soil at the site. Today’s listing 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 already been conducted.

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 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 identify and address site conditions as soon as possible, EPA initiated a remedial investigation and feasibility study (RI/FS) in August 2008. The primary objectives of the RI/FS are to determine the nature and extent of contamination and to gather sufficient information so that EPA can select a remedy that eliminates, reduces, or controls risks to human health and the environment. The investigation will include the collection of airborne particulates, groundwater, surface water, surface soils, subsurface soils, and sediment data.

On August 20, EPA held a community meeting in Dewey-Humboldt, Ariz., to discuss the Superfund program, opportunities for community involvement, and upcoming site activities.

With today’s decision, there are now nine National Priorities List sites in Arizona. Nationwide, the agency is proposing to add eleven other sites.

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 1,587 sites listed to the NPL. Of these sites, 329 sites have been deleted resulting in 1,258 sites currently on the NPL.

For Federal Register notices and supporting documents for today’s final and proposed sites, please visit

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