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NPL Site Narrative for Eastern Michaud Flats Contamination

Pocatello, Idaho

Federal Register Notice:  August 30, 1990

Conditions at proposal (May 5, 1989): The Eastern Michaud Flats Contamination Site covers 2,530 acres in Power County, Idaho, near Pocatello. The Michaud Flats are on the Snake River Plain and are bounded on the north by American Falls Reservoir, on the east by the Portneuf River, on the west by the Rock Creek, and on the south by foothills of the Deep Creek Mountains and Bannock Range. Within the eastern part of the flats are two adjacent phosphate processing facilities. FMC Corp. has produced elemental phosphorus from phosphate shale ore on 1,400 acres since 1949. J.R. Simplot Co. has produced a variety of fertilizer products from phosphate ore on 1,130 acres since 1944.

Waste water from both facilities has been stored or disposed of in unlined ponds. FMC is phasing out the use of unlined ponds, and J.R. Simplot has implemented a waste water treatment system. In the summer of 1987, EPA detected elevated levels of heavy metals in sediments of the unlined ponds at both facilities and in waste water at J.R. Simplot. In addition, arsenic, cadmium, and selenium were detected in monitoring wells in the deep confined aquifer.

Public and private wells within 3 miles of the area provide drinking water to an estimated 55,000 people and are also used to irrigate over 2,100 acres of forage crops. A private well is 800 feet from an on-site lagoon. In 1976, the State of Idaho closed a drinking water well downgradient of FMC due to elevated arsenic levels. Currently, no other private or public water supply wells are known to be contaminated, although elevated levels of arsenic were detected in a downgradient spring used for drinking.

Status (August 30, 1990): EPA will soon be sending out general notice letters and requests for additional information to FMC, J.R. Simplot, and other parties potentially responsible for wastes associated with the site. EPA will then investigate the possibility of those responsible performing a remedial investigation/feasibility study to fully define the nature and extent of contamination at the site.

For more information about the hazardous substances identified in this narrative summary, including general information regarding the effects of exposure to these substances on human health, please see the Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs. ATSDR ToxFAQs can be found on the Internet at ATSDR - ToxFAQs (http://www.atsdr.cdc.gov/toxfaqs/index.asp) or by telephone at 1-888-42-ATSDR or 1-888-422-8737.

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