A version of this article originally appeared in Green Markets.
The Bureau of Land Management has given Monsanto until the end of May to submit a corrective action report in regards to an earthen holding pond leaking three million gallons of water onto a meadow near its new Blackfoot Bridge Mine in southeastern Idaho’s phosphate-rich Caribou County.
The March 29 breach along a spillway conduit in a catch basin created a 150-foot-long sediment plume on the wetland, but recent testing of the water showed no elevated selenium levels, said Randy Vranes, Monsanto’s mineral operations manager. State and federal regulatory agencies were alerted to the pond failure.
Selenium is a toxic byproduct created when water reacts with phosphate waste rock or overburden. The catch basin is designed to allow for the controlled release of natural runoff and snow melt water into the meadow.
The Blackfoot Bridge Mine is expected to start operating later this year with a 17-year life expectancy. In June 2011, the BLM approved the 1,469-acre mine, which will disturb about 740 mostly private acres not far from the Blackfoot River.
About 10 percent of it would be on BLM land. Monsanto’s South Rasmussen Mine is expected to be exhausted this year.
Monsanto uses the phosphate from its mines to manufacture elemental phosphorus and Roundup weed killer at its three-furnace plant near Soda Springs.
An engineering design investigation is under way to ensure the new mine’s advanced water management system functions reliably, Monsanto spokesman Trent Clark said, noting the mine’s comprehensive design incorporates many environmental protections.
Jeff Cundick, the BLM’s minerals branch chief in Pocatello, said the failed settling pond is part of a network of ponds controlling surface water runoff. Initial reports indicate as the pond was filling the buoyant force of a 60-inch pipe caused it to float enough to separate its joint and allow water to flow around the outside of the pipe, washing away the dam’s center part.
BLM is working with other federal and state agencies to assess if any statutory violations occurred and to review Monsanto’s reports and revised designs to ensure similar failures do not recur, Cundick said, adding no waterways or wetlands were adversely impacted.
The company has constructed a temporary berm so the pond is able to function consistent with the approved water management plan.
Marv Hoyt, Idaho director for the Greater Yellowstone Coalition, said he toured the pond failure site with Monsanto managers. He said there was not a lot of sediment that flowed into and covered some of the wetlands downstream.
“On the other hand, it is somewhat troubling that one of the simplest and least complex pieces of a highly complex mine failed,” Hoyt said. “It certainly gives us reason to scrutinize future mine proposals in the region.”
Fifteen phosphate mine sites in Southeast Idaho are listed as Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) or Superfund sites, encompassing 15,000 acres, mostly in Caribou County.