The J.R. Simplot Co. and the Idaho Department of Environmental Quality (DEQ) have entered into a voluntary consent order/compliance agreement in which Simplot agrees to reduce phosphorus discharges into the Portneuf River from its Don phosphate fertilizer plant near Pocatello by 50 percent in 2013, 75 percent in 2015, and 94 percent in 2021.
In the April 11 agreement, Simplot also agrees to financially support the Portneuf Watershed Partnership. Beginning in 2008 and payable by Aug. 31, Simplot will pay $15,000 annually for 10 years to operate a monitoring station and provide $25,000 annually for four years to ensure water quality improvements on the Upper Portneuf River, assessing the most beneficial, cost-effective projects through local agencies.
In April 1999 the DEQ submitted to the Environmental Protection Agency a Total Maximum Daily Load (TMDL) for the Portneuf River, listing nutrients among pollutants that needed to be addressed in the Lower Portneuf. The phased target for total phosphorus was set at 75 micrograms per liter at Siphon Road near the Don Plant.
In January 2004, DEQ completed a water quality study evaluating the impacts associated with the adjacent Simplot and FMC phosphate ore processing plants, which are included in the Eastern Michaud Flats Superfund site. It concluded groundwater beneath the plants was contaminated with nitrate, ammonia, and orthophosphate from a gypsum stack and a phosphoric acid/liquid plant area.
It was determined that groundwater beneath the Don Plant discharged into springs and the Portneuf River. Samplings showed the measured annual median value for total phosphorus at Siphon Road from 2004 through 2007 was about 1,250 micrograms per liter, far exceeding the TMDL maximum target, and possibly causing or contributing to violations of the state water quality standard for dissolved oxygen.
In accordance with a Comprehensive Response Compensation and Liability Act (CERCLA) consent decree with EPA, Simplot operates a groundwater extraction system of wells at the site to contain the migration of contaminants of concern, especially arsenic, from a phosphogypsum stack, and reduce the extent of resulting shallow groundwater contamination.
About 250 to 300 gallons per minute (gpm) of groundwater were extracted under the first phase, which is now being expanded into the second phase that consists of a more extensive field program to obtain chemistry and hydrogeologic information needed to fill major data gaps. About 600 gpm of groundwater will be extracted under the second phase. A third phase will include the system’s design and startup, with up to 1,100 gpm expected to be extracted.
To measure compliance, DEQ will collect water samples at Siphon Road to determine the concentration of total phosphorus in the Portneuf River on a monthly basis. Simplot also will conduct monthly samplings at Batiste Road and up to 400 meters north of Batiste Road.
By April 2009, Simplot will submit a technical report that specifies a groundwater and surface water monitoring program plan and a description of the last two years of past releases, tank inspections, and maintenance activities in the Don Plant’s production area. It also must submit a remedial action plan within that time frame that includes short- and long-term actions to prevent phosphorus releases to soil and groundwater and/or reduce contaminated water entering the Portneuf River.
Simplot has agreed to pay $1,000 a day for each day it is late in meeting stipulated deadlines.