The U.S. Environmental Protection Agency (EPA) has reversed its 2014 decision to halt the permitting process for the Pebble Mine, a proposed copper mine project at the headwaters of the world’s largest salmon fishery.
Research suggests that dissolved copper is hazardous to salmon at concentrations measured in millionths of a gram per liter. The EPA’s previous analysis determined that the Pebble project posed unacceptable levels of risk to the Bristol Bay salmon population, in large part due to the potential for toxic levels of copper in stream water as a result of mine activity.
Additional risks that the agency identified included habitat degradition from sediment and streamflow alterations across the 8,000-acre development site, and – in a worst case scenario – the possibility of a containment failure at the mine’s waste tailings pit. A similar large-scale waste containment failure occured at the Mount Polley mine in British Columbia in 2014, releasing 24 million cubic meters of waste into the Fraser River watershed.