Gay Mine Superfund Site

The Gay Mine is located on the Fort Hall Indian Reservation, about 16 miles east of Fort Hall, Idaho. It was the only phosphate mine in the Southeastern Idaho phosphate field to be located on the Shoshone-Bannock Indian land, and was the first open pit mine in Southeast Idaho to extract Federally-owned phosphate. The mine eventually consisted of about 7,000 acres of leased Tribal and allottee lands within the Fort Hall Indian Reservation.

Remedial Investigation and Feasibility Study

The Environmental Protection Agency, and the Shoshone-Bannock Tribes have an agreement with JR Simplot Company and FMC Corporation (the Companies) to study the Gay Mine Superfund site and to determine if clean up is needed for contamination that may be found there. If clean up is needed, then the study will prepare several clean up alternatives.

P Phosphate mining in southeast Idaho over the last 100 years has left waste rock dumps and open pits. If not managed properly, selenium and other hazardous substances can potentially pollute the nearby water, soil, sediments or plants. The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) provides the framework to address these issues.

G Government to Government Meetings: EPA will consult with the Shoshone-Bannock Tribes throughout the Gay Mine Investigation in accordance with
the EPA Policy on Consultation and Coordination with Indian Tribes and the EPA Region 10 Tribal Consultation and Coordination Procedures.

R The Remedial Investigation identifies if contamination is present and, if so, the extent of the contamination. It looks at whether this contamination is currently, or will later become, a threat to the environment and/or the people nearby. From this information the EPA, in consultation with the Tribes, will determine if the site requires cleanup. If EPA determines that the site must be cleaned up, the Feasibility Study investigates and presents cleanup options which will protect human health and the environment.

United States Environmental Protection Agency

EWMP Participates in Old Mine Cleanup

Southeast Idaho is a major phosphate-producing region. Mining phosphate ore generates open pits and piles of overburden materials which are naturally elevated in selenium and other trace metals. When exposed to the precipitation, these overburden piles can release selenium and other trace metals to the environment. The EWMP is a participant in the cleanup of old mines.

The mining process has created releases of high levels of metals contamination, notably selenium, which have resulted in livestock deaths, surface and groundwater contamination, and other environmental effects.

Program Background

JR Simplot Company and FMC Corporation mined phosphate ore at the Gay Mine on the Fort Hall Indian Reservation from 1946 to 1993. Mining activities resulted in the creation of waste rock dumps, ore stockpiles, and open pits at hundreds of locations across the nearly 8,500 acre mine site. EPA is concerned that these mining activities may have caused the release of selenium and other metals such as cadmium, vanadium, and nickel into the soil, ground water, streams, animals, plants, and air (in the form of dust).

HH Pit

Exposed rock walls and erosion at the HH pit


Tipple at the Gay Mine Headquarters


A12 pit at the Gay Mine

Mine Pits

A total of 158 mine pits were excavated at the Gay Mine. Most pits were partially or completely backfilled with over-burden generated from nearby pits, although several pits were not backfilled.

Mine Pit Lakes

Several pits, usually the last pits in the mining sequence in each area, were not backfilled or were partially backfilled. Some of these pits contain or have intermit-tently contained water that forms lakes.

Mill Shale Stock Piles

There are 57 mill shale piles at the Gay Mine containing approximately 30 mil-lion tons of mill shale. Mill shale generally contained 15% to 19% phosphate and may have future economic value.

Overburden Piles

Overburden consists of all the mined geologic materials that were not shipped as ore or segregated in mill shale piles. When overburden was not used as pit backfill, the overburden material was placed in external piles. Some of the piles were contoured to resemble naturally-occurring rolling and undulating slopes of the surrounding terrain.

Project Resources

Public Records Database

EWMP maintains all project files on an internal database that is accessible to the public on request.

For help obtaining a document or report please contact, Julie Taylor, Environmental Field / Records Technician, (208)478-3904

Shoshone-Bannock Tribal Contacts

Location of Documents

  • Environmental Waste Management Program Office
    4 Mission Road
    Fort Hall, ID 83203
  • EPA Region 10 Superfund Record Center
    1200 6th Avenue, Suite 155
    Mail Stop OMP-161
    Seattle, WA 98101
    Phone: 206-553-4494



PO Box 306, Pima Drive
Fort Hall, Idaho 83203
Located in Building #245

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