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Study: Toxin from Caribou County mines likely moving through groundwater

Updated: Jun 4, 2019

by Idaho State Journal Staff and Wire Reports



In this March 26, 2014 photo provided by the U.S. Geological Survey, a U.S. Geological Survey hydrologic technician measures streamflow in the Blackfoot River at the site of USGS stream gaging station in the Blackfoot River above Blackfoot Reservoir near Henry, Idaho. An 11-year state and federal study of selenium pollution in the southeastern Idaho watershed where some 700 sheep, cattle and horses have died over the last several decades after grazing in contaminated areas has found the toxin is likely moving through groundwater. AP Photo/USGS

A government study of selenium pollution in a Southeastern Idaho watershed where hundreds of grazing animals have died has found that the toxin is likely moving through groundwater.


The 11-year study on the Upper Blackfoot River Watershed was released earlier this month by the U.S. Geological Survey. It found that selenium levels spiked in the river during spring thaw and exceeded healthy limits for aquatic species, such as the native Yellowstone cutthroat trout.


“That’s where the Blackfoot is at,” said Chris Mebane, a water quality specialist with the USGS and one of the study’s authors. “It’s over that threshold of concern.”


The selenium pollution stems from the mining that has taken place in the Caribou County area for decades. While the newest mines have safeguards, the companies that own the mines are paying the price for the older, non-active mines that, in some cases, they have inherited.


Center Waste Shales


Phosphate mining in the Caribou County area started around 1920. Over the years, numerous mining companies have operated in the region, but only three — J.R. Simplot Co., Monsanto Co. and Agrium Inc. — operate active mines now.


The upper watershed has 12 phosphate mines, three of them active. Phosphate ore is used in farm-based fertilizers and other products.


The USGS report says the selenium is highly concentrated within the center waste shales, which is found between layers of phosphate ore.


Over time, the selenium has seeped into local vegetation and the Upper Blackfoot River watershed in Caribou County area.


Though selenium is an essential nutrient, it can be toxic in larger quantities.


The Ecological Impact


Waste rock from the mines contains selenium that has been blamed for killing livestock and harming trout populations in some the Upper Blackfoot River and its tributaries. The watershed is a key area for Yellowstone cutthroat trout and wildlife, and it’s also a popular recreation area for humans.


The issues with selenium contamination first attracted attention in 1996 when the deaths of sheep, cattle and horses started occurring. As of today, about 700 deaths have been attributed to livestock entering mine land and consuming selenium.


The most recent livestock losses happened in October 2012 when 95 sheep died after grazing at a re-vegetated inactive mine site.


Elk and deer, the USGS report said, appear to be more tolerant of elevated selenium.


The animals ingest selenium by eating contaminated plants and vegetation.


“The plants get it — the roots pick up moisture from the soil,” Mebane said.


Twelve sites in the upper watershed are under Superfund authorities for cleanup. The USGS study, conducted with the Idaho Department of Environmental Quality, provides insights on results of the remediation efforts.


“I think the overall data set would suggest that we haven’t started to successfully manage our selenium source yet,” said Lynn Van Every, a water quality manager with the Idaho Department of Environmental Quality and a co-author of the study.


The U.S. Environmental Protection Agency lists two segments of the Blackfoot River and 15 tributary segments as impaired. If the watershed consistently fails to meet safe standards, opening new phosphate mines could be more difficult.


“The expectation for mitigation and control and better engineering (of mines), those expectations will remain very high,” said Dave Tomten, a Boise-based geologist with the EPA whose duties include compliance and enforcement.


Fixing the Problem


Mitch Hart, manager of mining projects and remediation at Agrium, says that when his company acquired its series mines in the Upper Blackfoot River watershed in 1995 from Nu-West Industries, it inherited the selenium pollution problems that were already in place.


In the 19 years since the purchase, Hart says Agrium has spent tens of millions of dollars to clean up the mines, some of which have been inactive.


“These are obligations that we have,” he said. “The important thing is to continue to be economically viable in Idaho but also be viable enough to take care of these historic issues.”


Simplot and Monsanto also have worked to clean up the contamination and prevent further pollution.


Simplot has been working to reduce selenium discharge from one its mines in the watershed by capping waste rock.


“This cover and new drainage systems are expected to significantly reduce the potential for selenium releases from this overburden area,” Simplot spokesman Ken Dey.


The most recent mine in the watershed, the Blackfoot Bridge, is run by Monsanto, the maker of Roundup weed killer. Authorities said Blackfoot Bridge is designed to avoid selenium problems of the kind attributed to older mines.


“The good news is that the new mines that have come on line, these are a lot tighter operating than what happened back in the ’70s and ’80s,” Mebane said. “The proof will be when we come back and look in a few years.”


In 2012, the Upper Blackfoot Confluence was formed consisting of Monsanto, Simplot, Agrium, Trout Unlimited and the Idaho Conservation League. The organization seeks to help restore the native Yellowstone cutthroat trout population and improve the quality of the water in the Upper Blackfoot River watershed.


However, despite efforts from conservation groups, governmental agencies and the companies that own the mines, clean-up efforts, especially issues involving the groundwater, could take generations.


“It could be decades or even centuries,” Mebane said.


Originally published in the Idaho State Journal

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