Eastern Michaud Flats

The Eastern Michaud Flats Superfund Site is located on the Fort Hall Indian Reservation, about 10 miles south of Fort Hall, Idaho. The 2,530-acre Eastern Michaud Flats Contamination site is located near Pocatello, Idaho. Two on-site phosphate ore processing facilities, the FMC Corporation and the JR Simplot Company, began operations in the 1940s.

Record of Decision (ROD) Issued by the EPA

The 1998 Record of Decision is being amended to add phosphorus as a major contaminant of concern and to require additional pollution source controls. The original ROD identified a number of contaminants of concern found in the groundwater were discharging through springs to the Portneuf River. The action to amend the ROD is needed because it has been found that these springs fed by groundwater from the Superfund site discharge more phosphorous to the Portneuf River than any other single known source.Information gained over time led to the 2010 Interim ROD amendment (IRODA) for the Simplot OU, and the 2012 IRODA for the FMC OU.

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

What is the Current Site Status?

EPA divided the site into three separate cleanup areas called operable units (OUs): the former FMC Plant OU, the Simplot Don Plant OU and the Off Plant OU. Cleanup measures include capping contaminated soils; lining the gypsum stack; extracting, treating, or reusing contaminated groundwater; groundwater monitoring; and land/water use restrictions to protect people while response actions continue. Interim remedy construction began in 2010 at the Simplot OU, and in 2014 at the FMC OU.

The greatest potential health risk to people is through drinking contaminated groundwater or through direct contact with contaminated soil. Institutional controls prevent using contaminated groundwater for drinking, and contaminated soils have been covered (capped) with clean soil. In the short term exposure pathways that could result in unacceptable risks are being controlled.

Program Background

The Eastern Michaud Flats was placed on the NPL List in 1990. The J.R. Simplot facility produces solid and liquid fertilizers using phosphate ore, sulfur, air and natural gas. The FMC plant produced elemental phosphorus for use in a variety of products from cleaning compounds to foods, until ceasing operations in 2001. Operations at both plants contaminated groundwater and soil with hazardous chemicals. Site cleanup is underway.

HH Pit

Simplot part of the Eastern Michaud Flats


Continuous Leak onto Federal Land


Groundwater and surface water contamination from FMC / Simplot

Groundwater Migration Not Under Control

EPA has reviewed all information on known and reasonably expected groundwater contamination, and the migration of contaminated groundwater is not stabilized.

Construction Not Complete

Either physical construction is not complete or actions are still needed to address contamination.

Sitewide Not Ready for Anticipated Use

All cleanup goals not affecting current and reasonably anticipated future land uses of the entire site have been achieved, so there are some unacceptable risks. Not all required land-use restrictions or other controls have been put in place. The site has not achieved Construction Complete status.

Human Exposure Under Control

There are currently no unacceptable human exposure pathways; andEPA has determined the site is under control for human exposure.

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

Contact us.

Phone: (208)236-1048
Fax: (208)236-1064

Email Us