The company reported the March 29 leak to regulators, Oregon Live reports. The water system failure drained some 3 million gallons of water from the pond, which holds stormwater and snowmelt that collects at the Blackfoot Bridge Mine near Soda Springs. The leak also caused a 100-foot sediment plume, the news site says.
Phosphate is a key ingredient in Monsanto’s Roundup weed killer.
Monsanto now has 60 days to investigate what went wrong and submit a corrective action plan to the US Bureau of Land Management. The plan must include a redesign for the holding pond and assessment of other on-site water holding structures.
The mine, which has a 17-year life expectancy, is slated to begin operations this year, Oregon Live reports.
The news site says selenium, a byproduct created when water interacts with mine waste, is the biggest environmental threat from phosphate mining. To prevent the two from mixing, the Blackfoot Bridge Mine has a waste pit that will be capped by a geosynthetic cap, a plumbing system designed to capture any tainted water and several treatment ponds for water that test positive for selenium or other toxins.
The pond that failed is separate from these treatment ponds, Oregon Live says.
Earlier this year, Monsanto joined the World Business Council for Sustainable Development and said it would offer the organization’s Business Ecosystems Training course globally for employees. Monsanto says the BET course will enhance employees’ understanding of the links between ecosystems and business.