An unfinished cleanup of a federal Superfund site in southeastern Idaho already has led to reduced water pollution, officials say.
Phosphorus leaking from the Eastern Michaud Flats Superfund Site has dropped from 1.6 milligrams per liter of water five years ago to less than half a milligram today, said Jannine Jennings, the U.S. Environmental Protection Agency’s project manager for the Simplot area of the site.
“They still have some work to do,” Jennings said. “But the phosphorus going into the river is dropping.”
The site includes the Boise-based J.R. Simplot Co.’s Don fertilizer plant, which is still operating, and the acreage where FMC Corp. operated a phosphorus plant until December 2001. The FMC plant was removed in 2002.
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Both plant sites were sources for phosphorus contamination in the groundwater, though the processes that led to the problem differ. Simplot uses a liquid process to produce fertilizer. FMC used massive furnaces and a dry heat process to produce elemental phosphorus.
From 1949 until 2001, FMC operated the world’s largest elemental phosphorus plant in Power County just west of Pocatello. The physical plant and all structures were removed within two years of closure, but soil at the site and massive piles of radioactive slag — a byproduct of phosphate ore processing — remain. The soil in and around the old furnace area is saturated with elemental phosphorus.
To monitor and eventually treat runoff from the FMC site that contains phosphorus and arsenic, three test wells have been drilled on the northeast corner of that property. Preliminary data indicate that it may take up to 11 treatment wells along the border of the FMC property to treat runoff before it enters the Portneuf River drainage, the EPA says. Twelve treatment wells are already in operation on the Simplot property.
Work also continues on a gypsum pile behind the Simplot plant. Portions of the pile are being lined to collect and control runoff water. Water on the hill will go into lined cells and then to a decant pond before being processed for reuse inside the plant. About 75 percent of the area has been lined. The project will continue through 2017.
EPA’s responsibility will go on for decades, said Jonathan Williams, the agency’s project manager for the FMC area.