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NPL Site Narrative for Monsanto Chemical Co. (Soda Springs Plant)

Soda Springs, Idaho

Federal Register Notice:  August 30, 1990

Conditions at proposal (May 5, 1989): Monsanto Chemical Co. has produced elemental phosphorus in southeastern Idaho 1 mile north of Soda Springs, Caribou County, since 1952. The 530-acre site is in a broad, flat valley near the western base of the Aspen Range. Significant agricultural crops in the area include wheat and hay. A number of large industrial complexes are in the valley, including Kerr-McGee Chemical Corp., directly across State Highway 34 from Monsanto. The Kerr-McGee plant is also being proposed for the NPL at this time.

Monsanto's Soda Springs plant generates a number of process waste streams containing inorganic compounds. Most liquid and solid wastes are stored or treated in on-site ponds or piles. Slag constitutes the greatest quantity of waste. Molten slag is tapped from the base of the electric air furnaces and poured out to cool in piles. The piles cover a large portion of the site and are more than 150 feet high.

As part of a hydrogeological investigation conducted by a Monsanto contractor in 1984, 31 monitoring wells were installed around the facility in support of existing wells, and pump tests were performed on numerous monitoring wells and three on-site wells supplying water to the plant. Ground water contamination was detected at the site. The contractor identified the sources as a leaky hydroclarifier and several unlined ponds. Monsanto has discontinued use of the old ponds, installed new lined ponds, and replaced the old clarifier.

On-site monitoring wells and sediments in an old unlined pond that received process waste water contain arsenic, cadmium, and chromium, according to tests conducted as part of a November 1987 EPA site inspection. Within 3 miles of the site are public springs and private wells that provide drinking water to an estimated 3,000 people.

Water discharging from an on-site pond to Soda Creek 2,000 feet away is contaminated with cadmium, according to EPA analyses conducted in 1985. Water withdrawn from Soda Canal 1.2 miles downstream is used to irrigate 4,040 acres.

Status (August 30, 1990): EPA will soon be sending out a general notice letter and a request for additional information to Monsanto. EPA will then investigate the possibility of Monsanto 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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