Milltown Reservoir Superfund Site - Superfund Designation and Study

Superfund Designation and Study

In 1981, through a routine Missoula County water quality study, four wells in Bonner that served 35 households, were found to be contaminated with heavy metals. The Environmental Protection Agency and the Montana Department of Environmental Quality closed the wells and began to look into the cause of the contamination of Milltown area groundwater. Two years later, in September 1983, it was determined that the contamination was the result of a buildup of heavy metal laden sediment from years of intensive mining upstream by the Anaconda Copper Mining Company. That finding resulted in the addition of the Milltown Dam Site to the initial National Priorities List. Review began immediately by the EPA to determine the Potentially Responsible Party (PRP) and to develop a plan to fix the groundwater contamination problem. In 1977 Anaconda Copper was purchased by the Atlantic Richfield Corporation (ARCO), which assumed liability for the damages. In 2000, ARCO was purchased by British Petroleum.

In 1992, through the action of committed citizens in the Deer Lodge Valley, the EPA designated the Clark Fork River upstream from the Milltown Dam to the Warm Springs Ponds part of the Superfund Site. In 1995, the study of the extent of site contamination was completed by the EPA and ARCO. A subsequent feasibility study attempted to determine how to restore the Milltown groundwater. That study was halted, however, as the unusually wet winter of 1996 sent a large ice jam down the Blackfoot River and into the Milltown Reservoir, causing a severe scouring of the contaminated sediment in the reservoir bed and caused a fish kill downstream. Fearful of a major uncontrolled release of water (and sediment), officials quickly drew down the level of the reservoir, stranding the ice pack before it could cause any more damage. The EPA immediately began to examine the extent of the damage, and after a contentious public discussion, it became clear that the threats of continued releases of contaminated sediments into the downstream fishery must be addressed in the final remediation plan.

In 2003 the State of Montana, through its Natural Resource Damage Program, drafted a conceptual plan for the restoration of the Milltown Dam site. In December 2004, the final remediation plan was released by the EPA, calling for the removal of more than two million cubic yards of contaminated sediment and the removal of the Milltown Dam. In August 2005, a consent decree was signed by the parties, allowing the project to move out of the planning phase and onto the ground. After over 20 years of study and litigation, work finally began on the Milltown Site on June 1, 2006 with a drawdown of the Milltown Reservoir. Contaminated reservoir sediments were hauled to an upstream repository near the town of Opportunity, a move opposed by some local residents.