The Clark Fork River Operable Unit of the greater Milltown Superfund Site, shown in relation to Butte and Anaconda area Superfund sites, including subarea Reaches of the river. Map from the 2004 EPA Record of Decision for the site.

Mine wastes washed down the Clark Fork River from Butte and Anaconda were spread throughout the floodplain, settling in deposits called “slickens.” Slickens can be easily observed throughout the Deer Lodge Valley today; typically, they are dry, sandy areas with no vegetation near the river or in the floodplain. In 1992, EPA designated the mainstem river, from the outlet of the Warm Springs Ponds near Anaconda downstream to the Milltown Dam near Missoula, as a separate unit from the Milltown Dam sites.

This graph from 1998 shows sources of copper, which can be very toxic to aquatic life, in the Clark Fork River. Many efforts have since been undertaken basin-wide to reduce contamination in the river. Graph from the 2004 EPA Record of Decision for the site.

An investigation into the nature and extent of contamination on the Clark Fork began in 1995. EPA notified the Potentially Responsible Party (PRP), BP-ARCO, known at the time as Atlantic Richfield, of its liability and entered into a Consent Order with BP-ARCO to conduct a Remedial Investigation and Feasibility Study. In 2000, EPA ordered ARCO to conduct a time-critical removal action to address immediate human health risks for residents of Eastside Road in Deer Lodge.

Studies are ongoing to determine the exact location and extent of tailings deposits along the river near the town of Deer Lodge. Removal and/or in-place remedy will likely begin in the next few years.

EPA released a proposed plan for cleanup in August 2002. The cleanup proposal included a combination of removal and in-place treatment of toxic mine tailings and contaminated soil, followed by revegetation. Stabilization of eroding streambanks is an important part of the remedy, because they contribute approximately 60 percent of the pollutants to the river.

EPA invited public comment on the proposed plan for 120 days and received nearly 2,000 comments. A Record of Decision or ROD was signed in April of 2004. You can download the ROD for the Clark Fork via the Superfund Library or the links below:

• EPA Record of Decision for the Clark Fork River Operable Unit (April 2004)
  • ROD Summary Fact Sheet
  • Part 1: Declaration
  • Part 2: Decision Summary
  • Part 3: Responsiveness Summary
  • Part 4: Acronyms and Abbreviations, and References
    • Appendix A: Identification and Description of Applicable or Relevant and Appropriate Requirements (ARARs)
    • Appendix B: Clark Fork River OU Streambank Stabilization Design Consideration and Examples
    • Appendix C: Clark Fork River OU BMPs and Riparian Management Plan Considerations
    • Appendix D: Clark Fork River OU Weed Prevention and Management Planning Information and Weed Species Fact Sheets
    • Appendix E: Grant-Kohrs Ranch National Historic Site
    • Appendix F: Concurrence Letter from State of Montana

EPA concluded settlement discussions with ARCO and the State of Montana in 2008 in an effort to settle cleanup responsibilities and costs associated with the remedy proposed in the ROD. The settlement also involves the state’s natural resource damage plan, which is being implemented along with EPA’s selected remedy. The Department of Interior’s federal restoration plan, which addresses the Grant-Kohrs Ranch National Historic Site and BLM land, will also be implemented.

On February 7, 2008, a Consent Decree for the Clark Fork River Operable Unit Site was lodged with the Federal District Court in Montana. Public comments were received on the Consent Decree during a 60-day public comment period. The Consent Decree provides the structure for how BP-ARCO “cashed out” its cleanup responsibilities by providing over $168 million to the State of Montana, which is performing the remedy and restoration activities with EPA and National Park Service oversight. The Consent Decree and Montana/EPA Memorandum of Agreement (2007) provide the details of how the project will be performed. For more, refer to the Fact Sheet on the ARCO Settlement.

In this 2007 photo, a slicken, or a deposit of mine waste (tailings) washed downstream from the Butte and Anaconda areas, is clearly visible near the Clark Fork River at Grant-Kohrs Ranch near Deer Lodge, Montana. Ongoing cleanup is removing or capping such waste deposits.

Further Exploration

• Complete details on the Clark Fork River Mainstem cleanup can be viewed through the EPA links below, and current information about the site is available at the Clark Fork River Technical Assistance Committee (CFRTAC) Website.
• Click here to view or download the EPA Consent Decree for the Milltown / Clark Fork Site from 2008.
• Click here to view the EPA Press Release for the Consent Decree for the Milltown / Clark Fork Site from 2008.
• Click here to view or download the ARCO Settlement Fact Sheet from EPA.
• Additional documents can be found on the EPA Superfund Website.
• A list of cleanup activities for the Milltown / Clark Fork Site can be found at the EPA Superfund Information System.
• Additional site details can be found on the EPA Superfund Information System Site Profile.