Platinum Creek Mine former general manager Robert Pate of Washington has pleaded guilty to three felony violations of the federal Clean Water Act in federal court in Anchorage, Alaska, US.
The announcement was made by US Department of Justice Environment and Natural Resources Division assistant attorney general John Cruden and District of Alaska US attorney Karen Loeffler.
Pate admitted that he discharged wastewater from the Platinum Creek mine into Platinum/Squirrel Creek knowingly, without a Clean Water Act Permit.
He also admitted that he violated the conditions of XS Platinum's Clean Water Act permit for discharges to the Salmon River.
Further Pate falsely reported to the Alaska Department of Environmental Conservation in the 2010 Annual Report for placer mining at the Platinum Creek Mine that there was 'no discharge'.
Pate worked with XS Platinum in Seattle, Washington, from February 2010 to June 2012.
According to the plea agreement, Pate documented unpermitted discharges of turbid effluent process water from the placer mining at the Platinum Creek Mine into the Salmon River beginning on 3 July 2010.
The water contained pollutants such as suspended particles and sediments and may have also included waste such as dissolved metals that posed a potential threat to aquatic life.
Assistant attorney general Cruden said: "The defendant had a responsibility to ensure the wastewater at the Platinum Creek Mine was handled safely and responsibly but instead took specific actions that posed serious risks to the environment.
"By pleading guilty, the defendant has admitted responsibility and will be held accountable under our nation's environmental laws."
Acting special agent in charge of the EPA's Criminal Enforcement Program in Alaska Jay Green said: "The wastewater produced at Platinum Creek Mine contained pollutants that posed a potential threat to both aquatic life and human health.
"As general manager of XS Platinum, the defendant knew firsthand about the discharges of mine wastewater into the Salmon River."
According to the agreement, the US will recommend a sentence that will include imprisonment, as well as home confinement, in addition Pate also agreed to pay a $10,000 fine.
The US Department of Interior Bureau of Land Management Office of Law Enforcement and Security and the US Environmental Protection Agency Criminal Investigation Division are conducting the investigation.