IRON KING MINE AND HUMBOLDT SMELTER

Description and History

The Site encompasses areas of contamination from two separate facilities: the Iron King Mine property and the Humboldt Smelter property. The smelter is situated less than one mile east of the Iron King Mine property. The Humboldt Smelter property is bordered by the Town of Humboldt to the west and north, the Agua Fria River to the east, and the Chaparral Gulch to the south.

The Iron King Mine area covers approximately 153 acres. The majority of this area is covered by tailings and waste rock piles. There are five retention ponds, at least five mine shafts, a collapsed mine shaft (glory hole), and areas of stained soil.

The Iron King Mine was an active mine from 1904 until 1969. The mine was expanded in 1936 to remove lead, gold, silver, zinc, and copper from underground. A 140-ton mill was erected to crush ore and was expanded to 225-ton capacity in 1938. A cyanide processing plant was added to the site in 1940 to treat the mill tailings to enhance precious metal recovery. Waste rock and tailings were deposited in large piles adjacent to actual mine property boundaries. More recently, the mine tailings from the site have been used to create fertilizer.

The Humboldt Smelter occupies approximately 182 acres. This area is covered in approximately 763,800 square feet of yellow-orange tailings, over 1 million square feet of grey smelter ash, and 456,000 square feet of slag.

The Humboldt Smelter operated from the late 1800s until the early 1960s. The original smelter burned down in 1904 and a smelter that processed 1,000-tons of ore per day was rebuilt in 1906. This smelter operated until 1918 and then intermittently between 1922 and 1927. The smelter reopened in 1930.

Presently, the full extent of soil contamination and possible groundwater contamination is being assessed. The EPA has identified five Areas of Interest at the Site:

• Iron King Mine – The Iron King Mine Proper Area, Iron King Operations Area, Former Fertilizer Plant Area, and ancillary associated properties
• Humboldt Smelter and ancillary associated properties
• Off-site Soil in the vicinity of the Site
• Waterways - Including the Chaparral Gulch, Galena Gulch, Aqua Fria River, and
adjoining drainage channels and outfalls
• Groundwater, both shallow alluvial and deep bedrock groundwater

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Contaminants and Risks

The Site is a combination of sources and releases from two separate facilities: the Iron King Mine property and the Humboldt Smelter property. Due to past mining and smelting operations, arsenic, lead and other metals have contaminated soil, sediments, surface water and ground water on-site at levels above background.

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Who is Involved

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Investigation and Cleanup Activities

A PRP lead removal action was initiated in 2006 to remove contaminated soil from four off-site residential properties. Staff from EPA’s Office of Emergency Response supervised the sampling and removal of the contaminated soil conducted by the PRP’s contractor.

Portions of this Site were regulated under the Arizona Department of Environmental Quality (ADEQ)’s Voluntary Remediation Program. In September 2007, EPA received a response from Arizona Governor Napolitano consenting to the placement of the Site on the National Priorities List (NPL). On 19 March 2008, EPA formally proposed the Site to the NPL, commonly called the Superfund List.

Placing the site on the NPL allows EPA to use federal resources to conduct cleanup activities at the site, including investigating the sources of contamination and determining what measures may be necessary to protect human health and the environment.

EPA received comments from the community on EPA’s NPL proposal for this Site. EPA will review and consider each comment received and announce its final decision in the Federal Register.

During summer 2008, EPA initiated the field investigation portion of the Remedial Investigation and Feasibility Study (“RI/FS”). 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. The investigation will include the collection of airborne particulates, groundwater, surface water, surface soils, subsurface soils, and sediment data. Specifically, the field investigation involved the following tasks:

• Collection of meteorological data for ambient air sampling
• Ambient air sampling for inorganic constituents to evaluate potential off-site migration of airborne contamination
• Surface and subsurface soil sampling to characterize the nature and extent of contamination
• Groundwater sampling from 1 deep (bedrock) and 5 shallow (alluvial) newly-installed monitoring wells
• Preliminary radiological screen of contaminated areas
• Tap water sampling from private and municipal wells
• Sediment and surface water sampling from the Site waterways, washes, and the dam,
• Sediment and surface water sampling from five on-site impoundments at Iron King Mine and the retention pond at Humboldt Smelter
• Volumetric estimates of the mine tailings
• Storm water evaluation of Iron King Mine drainage pathways
• Collection of geotechnical testing data from soil borings
• National Historic Preservation Act, Section 106 review to determine if any historical or cultural resources will be affected by this project
• Ecological habitat survey

EPA is currently working on the human health risk assessment and ecological risk assessment. The human health risk assessment will evaluate commercial/industrial, residential, construction worker, recreational, and trespasser exposure scenarios for the areas identified during the investigation, as appropriate. The ecological risk assessment will characterize and quantify, where appropriate, the current and potential ecological risks that would prevail if no further cleanup action is taken.

All of this information will be compiled and presented in a Remedial Investigation Report (RI Report). The RI Report is an in-depth document that compiles the data needed to determine the nature and extent of contamination at a Superfund site and establishes site cleanup criteria. The RI Report will be followed by an analysis of ways to address the contamination.

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Cleanup Results to Date

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Potentially Responsible Parties

Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.

Under CERCLA, EPA identifies those parties that are responsible for the contamination, and then may require them to perform cleanup activities with EPA oversight. EPA may use Superfund monies to perform the cleanup itself and then seek to recover the cleanup costs from the responsible parties. EPA is currently conducting a PRP search for the Site.

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Documents and Reports

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Community Involvement

Public Meetings:

The Superfund investigation work continues at the Site. EPA completed most of the sample collection during summer and fall 2008. We conducted additional sampling during April 2009. The additional sampling focused on the following areas: additional water sampling of residential wells, semi-annual groundwater sampling of the six newly installed monitoring wells, characterization of air quality during high-wind events, additional soil sampling in residential yards and on-site areas, and conducting a wetlands assessment. The wetlands assessment will occur in July 2009. We are compiling the sampling results which will be included and described in the forthcoming Remedial Investigation Report. We initiated a long-term ambient air sampling program in January 2009. The ambient air sampling program consists of four air monitoring stations across the site that measure meteorological data (wind direction and speed), suspended particulates data, and metals data.

EPA also conducted an Aerial Photographic Analysis of the Site. The analysis was performed using 14 dates of historical black-and-white, color, and color infrared aerial photographs that cover the period from 1940 to 2003. The analysis reveals the locations of different operations and processes, and how tailings and waste piles transformed over time. Through the analysis, we gained information about the locations of significant Site features (for example: areas of historic surface water flow and impoundments) that we can now incorporate into the Site investigation.

The University of Arizona (UA) Superfund Basic Research Program is working on a pilot study to determine the amount of compost needed for successful plant establishment in Iron King Mine tailings pile. The UA initiated the greenhouse portion of the study in early February 2009. This is the first step in analyzing if and how phytostabilization could be used to reduce wind-blown dust from the large tailings pile. The UA’s research results will add to the information EPA is collecting as part of the Remedial Investigation.

If you would like to be added to the site mailing list or would like more information about the Site, please call the toll free hot-line (800) 231-3075 and leave a message with your name and address.

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Public Information Repositories

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Additional Links

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Contacts

	Name	Phone Number	Email	Address
EPA Site Manager	Leah Butler	415-972-3199	Butler.Leah@epa.gov	Mail Code SFD62 75 Hawthorne Street San Francisco, CA 94105
EPA Community Involvement Coordinator	David Cooper	415-972-3245 1-800-231-3075	Cooper.David@epa.gov	Mail Code SFD63 75 Hawthorne Street San Francisco, CA 94105
EPA Public Information Center		415-947-8701	r9.info@epa.gov
State Contact	Brian Stonebrink	602-771-4197	Stonebrink.brian@azdeq.gov	1110 West Washington St. Phoenix, AZ 85007
PRP Contact
Community Contact
Other Contacts
After Hours (Emergency Response)	US EPA	(800) 424-8802

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