Soda Springs, Idaho-Agrium Inc. will spend at least $446,000 to remove hazardous sediment from the defunct North Maybe Mine nearly 20 miles east of Soda Springs near the Idaho/Wyoming border in Caribou County. The U.S. Forest Service on Sept. 8 approved a plan to eliminate the sediment from the 43-year-old phosphate mine, which has been blamed for sending selenium-tainted water into the Blackfoot River, wiping out Yellowstone cutthroat trout in the East Mill Creek tributary. Levels in the creek measured more than 100 times above state standards for selenium, according to John Hart of the Greater Yellowstone Coalition, a group that unsuccessfully fought the Forest Service’s June 2008 approval of a 1,400-acre expansion of Simplot’s Smoky Canyon Mine near Afton, Wyo., on grounds the region’s old mines should be cleaned up before new projects should proceed. In addition to selenium, other elements at the site include cadmium, chromium, nickel, vanadium, and zinc, which could potentially affect the area’s ground water. Agrium will restore sediment retention ponds, contain and isolate sediment with high concentrations of selenium, and bolster erosion control at a dump left over from a mine closed in 1993. Jeff Jones, a Caribou-Targhee National Forest geologist in Pocatello, said that it’s likely that Agrium will need to construct an entirely new dam that will last longer and need to be maintained. Two existing ponds are nearly filled to capacity, allowing sediment to migrate during normal runoffs. Once the work is completed, the Forest Service and Agrium will turn to longer-term measures aimed at reducing high levels of dissolved selenium in East Mill Creek’s water, which will mean additional undetermined costs for Agrium, Jones said. At least 17 old mines are now under federal Superfund authority, including North Maybe, which is entirely within the Caribou-Targhee National Forest.
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