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The 125-acre St. Regis Paper Company site is located within the external boundaries of the Leech Lake Band of Ojibwe Indian Reservation in Cass Lake, Minnesota. The wood-treatment facility operated from the 1950s to the 1980s using creosote and pentachlorophenol. The facility’s operations contaminated soil and groundwater with hazardous chemicals. The contaminants of concern include pentachlorophenol, dioxin and polycyclic aromatic hydrocarbons, or PAHs.

Operable Units

During cleanup, a site can be divided into a number of distinct areas depending on its complexity. These areas, called operable units (OUs), may address geographic areas, specific problems, or areas where a specific action is required. The St. Regis site has four geographic OUs:

  • OU1 is where the wood treatment and storage facility was placed.
  • OU2 is where sludge was dumped and where the containment vault is located.
  • OU3 is within the City Dump where sludge was deposited and burned.
  • OU7 is those residential properties adjacent to the former operations area.



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What Has Been Done to Clean Up the Site?

In 1986, the Minnesota Pollution Control Agency (MPCA) signed two Minnesota Enforcement Decision documents which outlined the response actions for contaminated soil, sludge and groundwater at the site. Beginning in 1987, then-owner Champion International Corporation (Champion) extended the Cass Lake municipal water system to nearby residences, excavated 37,500 cubic yards of contaminated soil and sludge from the wastewater lagoons and 4,500 cubic yards of contaminated soil and sludge from the city dump pit, and constructed groundwater extraction wells at both the treatment facility area and the city dump area. The contaminated groundwater is extracted, treated onsite to remove contaminants, and then discharged into a channel between Pike Bay and Cass Lake. Champion constructed an onsite containment vault to hold the excavated soil and sludge. Champion and subsequent owner International Paper (IP) has monitored and maintained the treatment system and soil containment unit since the late 1980s.

In 2001 EPA collected data from the site to evaluate whether the response actions remain protective of human health and the environment. Dioxin was encountered in shallow soils on the site property at levels above the Superfund Removal Action Level of 1 parts per billion toxic equivalency (ppb TEQ). In 2003 EPA issued an administrative order (PDF) (106 pp, 4.63 MB) that directed the potentially responsible party (PRP) to conduct a Removal Site Evaluation and Supplemental Assessment to delineate the extent of soil contamination. Based on additional confirmatory and delineation sampling performed by IP in 2003, removal actions for shallow soil were performed between 2003 and 2005 by International Paper and BNSF Railway Co. under EPA oversight.

In 2004 EPA issued a Unilateral Administrative Order (PDF) (20 pp, 713.29 KB) to IP to conduct a Human Health and Ecological Risk Assessment. Samples of soil, sediment, groundwater, surface water, indoor dust, fish, and other plants and animals were analyzed. The report was finalized in 2011 and concluded that contaminated surface soil on one residential property could pose unacceptable noncancer risks to a potential future child resident, that the contaminated groundwater plumes could pose unacceptable noncancer risks to future utility workers, and that contaminated soil in the southwestern corner of the containment unit area is acutely toxic to invertebrates.

Since 2005 IP has performed a number of investigations and activities to determine whether the groundwater remedial actions are effectively capturing and removing contaminated groundwater. IP drilled several new soil borings and monitoring wells between 2006 and 2017 east of the former treatment area and the city dump area. The groundwater samples from these borings showed that a tarry liquid was present in the city dump area plume and that the plumes in the operational area and the city dump area are not fully captured by the groundwater extraction system. IP also performed aquifer tests to better understand the hydrogeology of the site, and developed a new ground water model to evaluate the overall effectiveness of the groundwater extraction system.

Soil remedy

EPA issued an Interim Record of Decision (PDF) (97 pp, 22.23 MB) in 2005 based on samples of dioxin-contaminated indoor dust in nearby homes that showed unacceptable risks to residents. Necessary interim cleanup actions included an initial comprehensive cleaning of all area residences with carpet replacement, HEPA vacuum cleaning, wet wiping, steam cleaning soft furniture, and cleaning of draperies and rugs. In addition, supplemental periodic cleaning of homes, clean soil yard cover, and dust suppression to the unpaved roads was required. In 2006, under EPA oversight, International Paper conducted all initial cleanings, the yard work, and dust suppression. The house cleanings and dust suppression will continue until a final remedy for surface soil is completed.

 In September 2008, based on unacceptable potential risks from surface soil and groundwater identified in the risk assessment, IP and BNSF signed an Administrative Order on Consent (PDF) (58 pp, 4.3 MB) with EPA to conduct a feasibility study  to evaluate final remedial alternatives. EPA issued a Proposed Plan (PDF) (19 pp, 1.15 MB) outlining EPA’s preferred remedial alternative in 2011, but at the request of LLBO and MPCA, EPA agreed to defer issuing a Record of Decision until additional soil sampling was conducted. Additional soil samples collected in 2013 and 2014 largely confirmed the distribution of soil contamination.

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What Is the Current Site Status?

EPA proposed a cleanup plan (8 pp, 261.82 KB) in March 2016 to address soil contamination in the residential areas. The following steps are proposed as part of the cleanup plan:

  • Removing contaminated soil from affected residential areas and replacing it with clean soil and vegetation.
  • Storing most of the removed soil on-site below the ground surface with long-term monitoring.
  • Disposing of heavily contaminated soil at an off-site facility.

EPA is considering the comments received on the proposed plan before issuing a Record of Decision that will finalize the cleanup plan.

Groundwater remedy

The ongoing groundwater cleanup includes removing contaminated groundwater from the ground and treating it to remove the hazardous chemicals. As of the end of 2016, the groundwater treatment remedy has removed an estimated 15,018 kilograms of pentachlorophenol and an estimated 7,027 kilograms of polycyclic aromatic hydrocarbons from groundwater.

EPA has conducted several five-year reviews of the site’s remedy. These reviews ensure that the remedies put in place protect public health and the environment, and function as intended by site decision documents. The most recent five-year review (PDF) (50 pp, 5.4 MB), issued in July 2015, concluded that response actions at the site protect human health in the short term. EPA expects the cleanup to be protective of human health and the environment in the long term after selection and completion of the final soil, attainment of groundwater cleanup goals, and implementation of enforceable land use controls. In the interim, there are no apparent complete human exposure pathways; therefore, there are no unacceptable current human risks.

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Activity and Use Limitations

At this site, activity and use limitations that EPA calls institutional controls are in place. Institutional controls play an important role in site remedies because they reduce exposure to contamination by limiting land or resource use. They also guide human behavior. For instance, zoning restrictions prevent land uses – such as residential uses – that are not consistent with the level of cleanup.

For more background, see Institutional Controls.

 The city of Cass Lake Resolution 14-2006 prohibits the construction and use of private water wells, and require the permanent sealing of a private water well. The city of Cass Lake Zoning Ordinance No. 12282005 limits the use (e.g. small scale industrial, low density residential) of properties in Cass Lake. A Quit Claim Deed on some properties owned by the city of Cass Lake prevents installation of groundwater wells or any use which would disturb the properties.

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Sampling and Monitoring

Numerous investigations as well as routine monitoring have been performed at the site since the early 1980s. Samples of soil, groundwater, surface water, sediment, indoor dust, fish tissue, and plant tissues have been collected and analyzed. Groundwater samples continue to be analyzed on a quarterly basis and treatment plant effluent is analyzed on a monthly basis.


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Emergency Response and Removal

Cleanup has included removal actions, or short-term cleanups, to address immediate threats to human health and the environment. In 2003, EPA issued an administrative order on consent (54 pp, 2.44 MB) that directed IP to excavate surface soil on portions on commercial property owned by the City of Cass Lake with dioxin concentrations exceeding 1 part per billion (ppb). The removal action was completed in 2005 and removed a total of 3,321 tons of contaminated soil. In 2005, EPA and BNSF signed an Administrative Order on Consent (33 pp, 2.98 MB) for a removal action to include excavation of shallow soil containing dioxin levels at or above 5 ppb on BNSF property. The excavation was completed in 2005 and involved the removal of 674 tons of contaminated soil and subsequent revegetation and fencing of all areas above 1 ppb. In 2006, to address the property owned by Cass Forest Products, IP took a voluntary response action to apply geotextile fabric and 4 inches of clean gravel to work areas and fence another area above a surface soil dioxin concentration of 1 ppb.


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Enforcement Information

The site is being addressed through potentially responsible party (PRP) actions under federal oversight, in consultation with EPA’s two support agency partners, the LLBO and the MPCA. During the past 10 to 15 years, the level of effort on this site has been very high from EPA, State and Tribal regulators, the local community, and the potentially responsible parties. Removal actions and interim remedial actions have been taken to reduce health risks to the local residents while work continues on selecting a final cleanup remedy.



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