Asarco and Newmont Mining have agreed to pay federal and state agencies $138.5 million--including the second largest state settlement for natural resource damages in Colorado history--to help remediate the California Gulch Superfund site in and around Leadville, Colorado.

The consent decree stipulating the terms of the settlement was filed Tuesday in U.S. District Court and is now undergoing a 30-day public comment period.

The former Asarco/Resurrection Mining Joint Venture has already constructed a water treatment plant to reduce contaminants flowing from the Yak Tunnel near Leadville, Colorado, eventually winding up in the Arkansas River. Prior to construction of the Yak Water Treatment Plant, the tunnel discharged about 210 tons of metals each year into California Gulch, which drains into the Arkansas River.

The Superfund site includes about 18 square miles in Lake County, Colorado including Leadville. Mining, mineral processing and smelting activities in the area have produced gold, silver lead and zinc for more than 130 years.  The site includes an 11-mile portion of the upper Arkansas River, as well as more than 2,000 slag piles, tailings and waste rock piles, and abandoned mine structures.

The Asarco/Resurrection Mining JV was created in the mid-1950s to explore and develop mineral resources in the Leadville area.

The settlement also resolves the last of seven natural resource damage lawsuits brought by Colorado in 1993. Work is expected to begin on the restoration projects next summer, according to California Attorney General John W. Suthers.  Asarco will provide $10 million natural resource damages money while Resurrection/Newmont USA will provide $10.5 million to the state.

The two mining companies also agreed to pay for, or perform, $118 million of additional remediation and maintenance of the area, to be supervised by state regulators and the EPA.

The Attorney General's Office said the settlement will help resolve outstanding issues at the California Gulch Superfund site, provide for restoration of important aquatic and terrestrial habitat along the 11-mile section of the Arkansas River south of Leadville and guarantee the final reclamation of the Black Rock Mine.

The issue began in December 1983 when the State of Colorado filed a complaint against the Resurrection JV and others for injury, destruction, or loss of natural resources associated with the release of hazardous substances from the Yak Tunnel and associated mine working. By August 1986 the U.S. EPA also filed a complaint against Newmont Mining, Resurrection Mining, and others.

Colorado Gov. Bill Ritter said in a news release that through negotiation rather than litigation, this settlement was achieved as a result of strong inter-agency collaboration and with invaluable advice and counsel from local land owners.

Last week EPA announced it has begun pumping and transporting water from the Leadville Mine Drainage Tunnel, which is located above the town of Leadville. Water is currently being pumped at a rate of approximately 1,000 gallons per minute and is being sent via a 4,700-foot long pipeline to a water treatment plant operated by the Bureau of Reclamation. The water, which contains elevated concentrations of dissolved metals, is being safely treated before being sent to the Arkansas River.

The 70-year old Leadville Mine tunnel is located 350-feet underground and contains an estimated 500 million to 1 billion gallons of water that has become trapped behind various blockages. Pressure has been building in the tunnel since 2001 due to rising water levels. Efforts to remove this water have included securing access from property owners, constructing a drill pad, drilling the relief well, and clearing, trenching and installing nearly one mile of pipeline from the well site to the water treatment plant.