HELENA – The Montana Department of Environmental Quality on Wednesday released a Five-Year Review report assessing the progress and effectiveness of the Superfund cleanup at the former Montana Pole and Treating Plant (Montana Pole) in Butte.
Montana Pole operated from 1946 to 1984, treating wood for industrial uses such as telephone poles and bridge timbers. For most of the plant’s lifetime pentachlorophenol (PCP) mixed with petroleum oil was added to the wood products to slow decay. PCP and petroleum are both known carcinogens.
An emergency cleanup in 1985, led by the federal Environmental Protection Agency (EPA), excavated much of the contaminated soil to prevent the pollutants from spreading. To treat the groundwater and remaining soil, a water treatment plant and soil treatment area were built on the 40-acre Site. DEQ has excavated more than 200,000 cubic yards of contaminated soil, which was moved to the on-site soil treatment area – a lined area where the soil was spread out and contaminants were broken down via oxidation and other natural processes. Once treated, the soil was backfilled into the area from which it was removed. The water treatment plant will operate until the groundwater contamination reaches water quality standards and treatment is no longer needed.
The newly released Five-Year Review report, the fourth such report on the Site, shows that the cleanup project is successfully reducing PCP and petroleum contamination in the soil and groundwater.
“While much work remains, there has been cleanup progress at the Site,” said Jenny Chambers, DEQ Waste Management and Remediation Division Administrator. “Concentrations of PCPs and petroleum are below the risk levels set in the original cleanup plan. DEQ is appreciative of the community’s support and input as we continue work to make the site safe and look toward returning the land to the community.”
While most aspects of the cleanup have been successful, the report found that one soil contaminant – dioxin – did not break down as expected. When the Superfund cleanup plan for the Site – the Record of Decision (ROD) – was approved in 1993, scientists believed dioxins in the soil would break down over time in the on-Site soil treatment area. However, dioxin levels remain well above the limit determined to be protective for human health and the environment in some areas of the Site.
As a result, DEQ proposed to revise the cleanup plan in a separate document called an Explanation of Significant Difference (ESD), as required by the Superfund process. The proposed change to the cleanup plan includes the installation of a protective cap over the treated soil. The soil has been effectively treated for PCP and petroleum, but still contains unsafe levels of dioxin. The cap would consist of a waterproof barrier and at least one foot of clean soil covered with vegetation. The cap would prevent moisture from reaching the dioxin-contaminated soil below, and would prevent visitors to the Site from being exposed to dioxin, a known carcinogen. The Agencies will also implement long-term site controls (institutional controls), such as zoning to maintain protectiveness.
DEQ will submit the ESD, which will describe the proposed change to the cleanup plan, to the Environmental Protection Agency (EPA) this fall and a public comment period will be announced.