Under the settlement, ARC will treat acid mine drainage for 5 years -- at a cost the EPA estimates at $5.6 million. In addition, the company will reimburse the EPA for $1.7 million in past cleanup costs, pay $90,000 in penalties for failing to comply with an EPA order issued in 2000, and spend $400,000 on a riparian restoration project at the River Fork Ranch on the Carson River, near Genoa, Nev.
“Today’s agreement addresses the most significant pollution from the mine and protects Leviathan Creek until a long-term cleanup strategy is in place,” said Keith Takata, the Superfund Division director the EPA’s Pacific Southwest region. “This settlement makes sure that the company that caused the pollution pays for the cleanup and restores vital habitat downstream from the site.”
Until a final cleanup plan is developed, seasonal treatment of acid mine drainage is necessary to prevent untreated releases of elevated concentrations of metals and metalloids, most notably arsenic, as well as iron, aluminum, chromium, cobalt, copper, nickel and zinc. There are several releases of acid mine drainage at the site that have the potential to impact Leviathan Creek. When a release from the site occurs, it can flow into the Leviathan Creek/Bryant Creek watershed, which drains into the East Fork of the Carson River -- a major source of water and a habitat for fish.
Under EPA oversight, the company will treat acid mine drainage from several sources at the mine from June 1 to September 30. The treatment season will be extended before the final cleanup is selected, if conditions at this remote mountain site allow safe access and operation. Because the site lacks paved roads and power lines, winter treatment of most seeps will not be accomplished through interim actions, although cutting edge biological treatment technology will continue to treat one of the seeps at the site through the winter.
Today’s settlement complements a separate EPA order issued in June 2008 requiring ARC to investigate long-term cleanup methods for the site, which the EPA will select. Afterwards, the agency anticipates that ARC, the state of California, the Washoe Tribe of Nevada and California, and other stakeholders will enter into negotiations to implement final cleanup by 2013 and address other outstanding issues at the site.
The settlement also resolves the EPA’s claims that ARC violated a 2000 order when it released untreated acid mine drainage for nine days in the summer of 2006 and failed to build a year-round treatment system that the EPA had required for treatability studies. The EPA subsequently decided to proceed with seasonal interim treatment for most of the site, while the investigation for long-term cleanup explores options for year-round treatment.
The site, which was listed on the EPA’s National Priorities List in 2000, was initially developed as an underground mine for gold, copper and copper sulfate, starting in 1863. From 1954 through 1962, Anaconda Copper Mining Company, which later was acquired by ARC, conducted open pit mining. The open-pit mining of sulfur from the site left wastes and underground conduits that result in acid mine drainage. The low pH and high metals content of the acid mine drainage historically limited most aquatic life in Leviathan Creek and portions of Bryant Creek downstream of the mine.
In 1984, the state of California acquired approximately 495 acres of the mine to clean up and abate water quality problems associated with historic mining. The Lahontan Regional Water Quality Control Board, which was delegated authority over the mine property, constructed evaporation ponds in an attempt to reduce the impact from some of the mine releases. Since 1999, the water board has treated drainage collected in these ponds, to prevent overflow into Leviathan Creek. This work, together with seasonal treatment conducted by ARC since 2001, has improved conditions for aquatic life when the systems are operating.