SODA SPRINGS — J.R. Simplot Co. has rerouted a stream away from tainted waste rock and built a $30 million water treatment plant in its efforts to keep selenium out of the water supply near its Smoky Canyon Mine east of Soda Springs.

Nonetheless, members of a Montana-based conservation group point to recent data showing selenium concentrations remain as high as ever in tissue samples of trout removed from a few nearby streams.

Officials with Montana-based Earthworks and Crow Creek Conservation Alliance, which comprises property owners near Smoky Canyon, object that Simplot is in the final stages of getting an expansion of the mine approved, though historic pollution still lingers.

“We think there should be further progress by now because these are important public resources,” said Bonnie Gestring, northwest program director for Earthworks. “We think more needs to be done by Simplot, both in terms of pollution control and treatment.”

Selenium, which is present in some of the waste rock removed from Caribou County phosphate mines, is a naturally occurring element essential for life in small amounts but toxic in larger quantities. In 1996, livestock deaths attributed to excessive selenium consumption in the phosphate patch triggered concerns about mining-related contamination.

Today, there are 13 historic mining sites within the phosphate patch, including Smoky Canyon, in which companies have consented to work with federal and state agencies to investigate and clean up selenium and other contaminants.

About five years ago, Earthworks took over Greater Yellowstone Coalition’s program of testing native Yellowstone cutthroat tissue samples from streams within the phosphate patch. Their test results have been consistent with Simplot’s own data: trout tissue in surrounding streams often contains selenium concentrations well above the EPA’s acceptable limit of 8.2 mg/kg.

According to Simplot’s testing, levels in fish tissue from Crow Creek reached 23 mg/kg in 2018, compared with 10 mg/kg during the prior year.

Lower Sage Creek samples tested at 34 mg/kg in 2018, down from 46 mg/kg in 2017 but significantly up from under 20 mg/kg in 2010. Earthworks found Smoky Creek tissue samples dropped from 12 mg/kg in 2018 to 6 mg/kg in 2017.

Simplot spokesman Josh Jordan said the company worked in 2006 with federal and state agencies to install a pipeline to route Pole Canyon Creek around overburden from past mining. The company also built an infiltration basin upstream to direct water away from the overburden area. The company added a cap and cover system over overburden in 2013 to further reduce selenium leaching, he said.

The water treatment plant on Hoopes Springs, which flows into Sage Creek, became operational in December 2017.

“We’ve been in the area for a long time and plan to be there for a long time and will continue those cleanup efforts and to use the latest technology to correct issues of the past,” Jordan said.

Jordan said Simplot has made its best effort in the cleanup thus far, but he acknowledged the job is far from over. He also emphasized that maintaining a dependable fertilizer supply is vital to growing crops and feeding the world’s population.

Jeff Cundick, minerals branch chief with the Bureau of Land Management in Pocatello, said a draft environmental impact statement for Simplot’s planned East Smoky Canyon Mine expansion was released last fall, and a final EIS will be issued this fall. Cundick said Earthworks made the most extensive comments, which are helping to shape the final document. He said it will take about 2.5 years to extract the additional phosphate ore from the new mining panel.

Cundick said waste rock from the planned mining panel is low in selenium, and conservative modeling shows it will take 80 years for the slightest trace of the contaminant to surface in the water supply at Hoopes Springs.

“There would be virtually zero impacts,” Cundick said of the proposed mine expansion. “We’re still working with the (Idaho Department of Environmental Quality) to get their judgement call.”

Gestring, however, is concerned, based on the track record at Smoky Canyon. She’d like to see the mine plans include a more robust cover. She also emphasized that the water treatment system doesn’t treat all of the water flowing from Hoopes Springs.

“We have streams that really can’t take any more selenium, even a small amount,” she said.