Montana Pole & Treating Site

The boundaries of the Montana Pole & Treatment Superfund site in Butte, Montana. Map from the EPA Five Year Review Report for the site (2011).

The boundaries of the Montana Pole & Treatment Superfund site in Butte, Montana. Map from the EPA Five Year Review Report for the site (2011). Click on the map to view a larger version.

The Montana Pole and Treating site is an abandoned 40-acre wood treatment facility in Butte, Montana. From 1946 to 1983, the facility preserved utility poles, posts and bridge timbers with pentachlorophenol (PCP). Hazardous substances from the pole-treating operations were discharged into a ditch next to the plant that ran towards Silver Bow Creek.

The site is in a residential and industrial area. The nearest residence is 100 yards away. The nearest private well is located one fifth mile down gradient from the site. Federal and state agencies are addressing soil and groundwater contamination, as well as waste products on site. Contaminated soil currently is being treated with bioremediation in an on-site land treatment unit.

About 16,000 gallons of PCP contaminated waste oil were sent to a licensed disposal facility in Utah for incineration in the 1980s. In spring 1998, forty drums of PCP contaminated sludge were shipped to Utah. The state of Montana signed an agreement with a contractor in March 1999 to dispose of all remaining site debris.


Recent News

The third five-year review for the Montana Pole and Treating Plant was completed in 2010-2011. The purpose of the review was to determine whether the remedy at the site, as selected and implemented subsequent to the Record of Decision (ROD), is protective of human health and the environment. The methods, findings and conclusions of the review are documented in the five-year review report. Both the Five Year Review Report and the ROD for the Montana Pole site are available via the links below, or in the Superfund Library.

 Montana Pole 5-Year Review (2001)
489.7 KiB
Montana Pole & Treatment Site Record of Decision (1993)
156.7 KiB

The Montana Department of Transportation (MDT) construction activities associated with the Interstate 15/90 bridge replacement near the site that commenced in spring 2010 are continuing and will be completed soon. In March 2009, consultants from Tetra Tech submitted a report on the Final Treatability Study Workplan, Montana Pole and Treating Plant Site – Phase 5. The report and appendices from the report are available in the Superfund Library.

Based on the results of these evaluations, the Montana Department of Environmental Quality (DEQ) concluded that it is not economically or technically reasonable to pursue excavation of these soils during MDT’s interstate bridge removal project. The treatability study will be revisited and the contaminated soils remaining beneath the interstate remediated beginning in 2012, after MDT’s construction activities have been completed.

Recent dewatering efforts associated with upgrades to Butte/Silver Bow’s wastewater treatment plant have resulted in concentrations of PCPs above the ROD cleanup level migrating to the north of Silver Bow Creek. A November 2010 report, Information Summary, Conceptual Model, and Groundwater Modeling Report: Butte Metro Sewer Treatment Plant Dewatering, provides additional details. Report Appendices, Figures, and Tables are available on the Superfund Library page.

This report includes key observations and conclusions associated with this dewatering effort as well as a summary of groundwater modeling performed to better understand the impacts dewatering has on the site. Based on these efforts, plans were made to excavate remaining sources of PCP beneath several power poles located between the Near Creek Recovery Trench and Silver Bow Creek in summer 2011. The site treatment plant will also be upgraded to allow for treatment of additional water to be pumped from the Recovery Tench during future site dewatering, as a mitigation strategy.

The final phase of cleanup at the site, Phase 6, will consist of removal of all soils and drainage once it meets specified performance standards and their use as fill material above historic high-groundwater levels in the excavated areas within the site as specified in the ROD. It also calls for the disposal of the soil treatment facilities on the south side of the site and final reconfiguration of all disturbed areas.

At that time, DEQ expects to turn the site over to Butte-Silver Bow local government. It is expected that the final land use at the site will be determined in conjunction with Butte-Silver Bow, with certain constraints on land use as specified by DEQ and EPA that are consistent with the ROD. A timeline has not yet been set for this final phase.



The ground water and soils at the Montana Pole site are contaminated with PCPs, dioxins, furans (flammable liquids from wood oils), volatile organic compounds (VOCs) and metals. The sludge also is contaminated with PCPs, dioxins and furans. PCP has been detected in Silver Bow Creek.

Accidentally swallowing or having direct contact with ground water, surface water, soil or sludge can be hazardous to human health. Contaminants may enter the air naturally or during cleanup operations, presenting another potential source of exposure. The site was proposed for addition to the EPA’s Superfund National Priorities List (NPL) in June 1986. The final date of its addition to the NPL was July 1987.


Cleanup Approach

The site is being addressed in two stages: an immediate action and a long-term remedial phase. EPA completed a cleanup action in late 1988 to halt the seepage of PCP and diesel oil into Silver Bow Creek. Contaminated soils were excavated and stored on the site, which has been fenced. Monitoring wells and oil recovery trenches have been installed. A temporary groundwater/ soil separation treatment system was put into operation to separate PCP-contaminated oil from the ground water. The treated water is pumped up gradient to infiltration galleries.

In January 1990, Special Notice Letters were sent to three Potentially Responsible Parties (PRPs). A Consent Order to conduct an investigation of site contamination was negotiated with the Atlantic Richfield Company (ARCO). An additional notice letter was sent to Burlington Northern Railroad Company in October 1991.

In early 1991, EPA conducted a cleanup of oil-contaminated soil, following the release of 3,000 gallons of contaminated oil from a holding tank. Approximately 21,000 gallons of polluted oil have been intercepted and are stored on the site. In the summer of 1992, EPA conducted another removal action.

During this action, a plastic liner was inserted into the ground to prevent PCP contaminated fuel in the ground water from entering Silver Bow Creek. Groundwater recovery wells were installed to recover free phase PCP contaminated fuel from site ground water. A water treatment plant was built to clean contaminated ground water. After treatment, the water is discharged to Silver Bow Creek.

In 1993 ARCO completed site studies to determine the nature and extent of contamination. A remedy was selected in the fall of 1993. The remedy includes:

  • Bioremediation of the soil and ground water, including excavation of approximately 200,000 cubic yards of contaminated soil
  • Construction of a land treatment unit to biologically treat the soil
  • Construction of a carbon water treatment plant with extraction of the ground water, treatment of the ground water with nutrients
  • Reinjection of the treated ground water

Currently, the water treatment plant is operating, and excavation of the contaminated soil is under way.


Financial Considerations

EPA sued ARCO for recovery of past removal costs in September 1991. ARCO countersued EPA contractors in October 1991. A settlement was reached in 1996. The PRPs are providing $38 million for a state led cleanup under a cash out, where the PRPs provide funding and the agencies conduct the cleanup. Through its Technical Assistance Grant (TAG) program, EPA funds CTEC to hire a technical expert to review EPA studies and cleanup work, and to convey the findings to the community.


Environmental Progress

EPA has taken measures to prevent further contamination of Silver Bow Creek. Additional actions were taken to remove the immediate sources of soil contamination, treat ground water and restrict access to the site. These measures have reduced the potential for exposure to hazardous substances while further cleanup activities are under way.


Further Exploration


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