The St. Regis Paper Co. Superfund Site is in Cass Lake, Minnesota, on the Leech Lake Indian Reservation adjacent to the Chippewa National Forest. The property was used as a wood treating operation from approximately 1958 until 1985. On Sept. 21, 1984, the site was placed on the Superfund National Priorities List because of contamination of the soil and ground water with dioxin; pentachlorophenol, or PCP; and polycyclic aromatic hydrocarbons, or PAHs. A 1984 study showed these contaminants posed a potential risk to people and the environment.
In 1985, the Minnesota Pollution Control Agency and the former owner/operator of the wood treating facility, Champion International Corp., agreed to clean up the site. The state agency oversaw Champion’s cleanup of the soil and ground water, as well as monitoring the remaining contamination. Specifically, the cleanup involved:
- Digging up more than 40,000 cubic yards of visibly contaminated soil and the sludge from the site, including excavated ponds and the city dump pit, and placing the material in a newly constructed on-site hazardous waste cell, commonly referred to as the “containment vault.”
- Installing contaminated ground water extraction wells at Operable Unit (OU) 1 and OU3, and a groundwater treatment system.
- Long-term operation and maintenance of the ground water extraction and treatment system.
- Long-term operation and maintenance of the containment vault.
- Long-term monitoring of the ground water.
In 1995, EPA became the lead agency. Concerns were raised during regular five-year site reviews about possible remaining contamination. As a result, EPA conducted additional sampling in 2001 and found that OU1 and OU2 needed to be further evaluated for possible additional soil removal. EPA also found that a risk assessment was needed to evaluate how well the cleanup protected residents, workers and the environment. During 2003 and 2004, samples of soil, sediment, surface water, house dust, ground water, plants and animals were collected and evaluated.
EPA issued an interim cleanup plan in 2005 and ordered International Paper Co. to clean the inside of nearby residences, apply a three-inch layer of clean soil and grass on yards and apply dust suppressant to unpaved roads. Based on soil sampling results, EPA oversaw the excavation and disposal of more than 3,900 tons of contaminated soil by the responsible parties.
IP did a study called a Human Health and Ecological Risk Assessment to determine how contaminants from the wood treating operations affect people and the environment. In August 2008, the conclusion was that there were still risks to residents, workers, and the environment in portions of the site. Based on these results, IP and BNSF Railway Co. agreed in September 2008 to conduct a Feasibility Study to evaluate how best to deal with these risks. Several cleanup options were developed, and in June, 2011, EPA proposed to select a remedy to address contaminated soil with a combination of excavation and off-site disposal and clean soil cover. EPA subsequently decided to collect additional soil data to further refine and evaluate the cleanup options before selecting a final soil remedy. If a different remedy is preferred, EPA will issue a new Proposed Plan, hold a public meeting, accept public comments, and review and respond to all comments received before selecting a final soil remedy.
Site Groundwater Contamination
EPA also continues to evaluate ground water contamination, which is being treated by the system put in place in the late 1980s. Since the original cleanup, over 25 years of monitoring data show a measurable reduction in the contaminant concentration, but the system still continues to pump elevated PCP concentrations near old operations and disposal areas. The pump-and-treat system has also been effectively reducing the amount of contaminants in the ground water. As of the end of 2013, more than 31,000 pounds of PCP and 16,000 pounds of PAHs have been removed from the ground water.