The U.S. Environmental Protection Agency (EPA) said Jan 26 that it has modified a Record of Decision (ROD) with the J.R. Simplot Co. to reduce phosphorus pollution entering the Portneuf River near Simplot’s Don phosphate fertilizer plant west of Pocatello, to better protect groundwater. EPA estimates 1,200 pounds of phosphorus per day enter the river from the plant.
“As a result of this action, Simplot will make a major investment in reducing phosphorus leaving both the gypstack and the phosphoric acid production plant,” said Lori Cohen, acting director of EPA’s Superfund cleanup office in Seattle. “This is a big deal for protecting local health, the Portneuf River, and area groundwater.”
The ROD is a legal document that guides the cleanup of property or facilities that have been added to the federal Superfund site list or the National Priorities List. Under the amended ROD, Simplot must now make fundamental changes at its plant:
- Identify phosphorus in groundwater as a “contaminant of concern.”
- Characterize all contamination sources at or near the phosphoric acid plant.
- Control all phosphorus contamination sources to the extent practical.
- Install a high-density polyethylene (HDPE) liner atop the phosgypsum pile, known as the “gypstack,” to minimize process water infiltration through the gypstack and into groundwater.
- Continue to develop, operate, and maintain a groundwater extraction system to address those areas where arsenic and phosphorus concentrations remain above cleanup standards or levels of concern.
Reducing the amount of phosphorus entering the Portneuf River is critically important because it acts as a fertilizer, causing rampant weed and algae growth during the warmer months, EPA says, adding that it robs the water of life-supporting oxygen needed by fish, insects, and other aquatic life.
Recent studies have revealed that more than 80 percent of the phosphorus entering the Portneuf River downstream of Batiste Road comes from the Simplot plant. High levels of phosphorus continue downstream to the American Falls Reservoir and along the Snake River.
Last summer, Simplot constructed a large decant pond to capture and store process water to block it from penetrating the gypsum stack. Simplot officials estimate the company has spent more than $6 million in the past four years on the project.
Cleaning up the groundwater beneath the Simplot plant 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. A consent decree, a formal legal document between Simplot and EPA, should be finalized in federal court in the next two or three months, officials said.
The Simplot plant is on the Eastern Michaud Flats Superfund site, encompassing 2,475 acres. The adjacent FMC elemental phosphorus plant that closed in December 2001 and was later demolished was also located there. Both plants were constructed in the 1940s. The FMC property was 1,450 acres. Simplot’s acreage totals 1,025. EPA anticipates a similar plan for the FMC site by this summer.
While the Simplot plant is not located on the Fort Hall Reservation, the Portneuf River flows through the property’s northeast section and north into “the Bottoms,” where most Shoshone-Bannock conduct traditional and ceremonial activities, including fishing and the gathering of native plants.