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Simplot Superfund Cleanup Plan Strengthened

Release Date: 01/26/2010
Contact Information: Kira Lynch/EPA Seattle 206-553-2144,, Mark MacIntyre /EPA Seattle 206-553-7302,

Simplot Superfund Cleanup Plan Strengthened
Officials: “More required pollution controls and better accounting for phosphorous from Simplot’s ‘Don Plant’ will help protect the Portneuf River.”

(Seattle, Washington – January 26, 2010) - The U.S. Environmental Protection Agency has modified the Record of Decision (ROD) for the Simplot Plant Operable Unit (Simplot OU) of the Eastern Michaud Flats Superfund site. The ROD is the legal document that guides the cleanup of property or facilities that have been added to the National Priorities List or federal “Superfund” site list.

According to Lori Cohen, acting Director of EPA’s Superfund cleanup office in Seattle, today’s action will reduce phosphorous pollution from entering the Portneuf River and better protect local groundwater.

“As a result of this action, Simplot will make a major investment in reducing phosphorous leaving both the gypstack and the phosphoric acid production plant,” said EPA’s Cohen. “This is a big deal for protecting local health, the Portneuf river and area groundwater.”

Under the amended ROD, Simplot must now make some fundamental changes at their plant:

  • Identifying phosphorus in groundwater as a “contaminant of concern”;
  • Characterizing all contamination sources at or near the phosphoric acid plant;
  • Control of all phosphorus contamination sources to the extent
  • practicable;
  • Installation of a high-density polyethylene (HDPE) liner on top of the phosgypsum pile, which is known as the “gypstack,” to minimize process water infiltration through the gypstack and into groundwater;
  • Continued development, operation, and maintenance of the groundwater extraction system to address those areas where arsenic and phosphorus concentrations remain above cleanup standards or levels of concern.

Reducing the amount of phosphorous entering the Portneuf River is critically important because it acts as a fertilizer, causing explosive weed growth and choking algae during the warmer months. This runaway plant growth robs the water of life-supporting oxygen needed by fish, insects and other aquatic life.

Recent studies have revealed that more than 80% of the phosphorus entering the Portneuf River downstream of Batiste Road comes from the Simplot facility. And unfortunately, high levels of phosphorous continue downstream to the American Falls Reservoir and further along the Snake River system.

Cleaning up the groundwater underneath the Simplot facility is expected to improve water quality in the Portneuf River, the Reservoir and the Snake River, as well as help the Portneuf meet Idaho water quality standards for nutrients.

The changes to the Simplot ROD become effective immediately upon publication in the federal register.

For more about the site, and to download a copy of the modified Simplot ROD, visit EPA’s Eastern Michaud Flats Superfund Site Web page: