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Columbia Falls Aluminum Reduction Plant
Site Type: Site Reassessment
Updated May 2014
EPA recently completed a site reassessment at the Columbia Falls Aluminum Company property in Flathead County, Montana. Three sources with high potential to contribute environmental contamination were directly or indirectly sampled: the landfill and sludge pond area, the north percolation pond and the south percolation pond. Analytical results indicate groundwater samples down-gradient of these sources have above-background concentrations of metals, including cyanide, as well as fluoride. Residential wells nearby were sampled and cyanide was detected at concentrations below EPA’s Maximum Contaminant Level (MCL) and Montana Department of Environmental Quality (DEQ)’s Numeric Water Quality Standards. EPA is conducting another sampling event the week of April 7, 2014 to gather data from nearby domestic wells not previously sampled. Flathead River sample results indicated above-background concentrations of cyanide, fluoride and manganese. Cedar Creek sample results indicated elevated levels of metals, including cyanide.
|Media Affected||Contaminants||Source of Contamination|
|Percolation Ponds (pond water and sediment)||fluoride; semi-volatile organic compounds; metals, including aluminum, cyanide, iron, lead, manganese, nickel, vanadium, zinc; pesticides; Arochlor-1254||aerial deposition; ponds received process fluids that have since (partially) evaporated or percolated|
|Groundwater on-site down-gradient of source areas||metals, including arsenic, cyanide, chromium, lead, iron nickel, selenium, vanadium; fluoride; nitrate/nitrite||leaching from landfills and sludge pond complex, percolation ponds, and potentially other unknown sources|
|Cedar Creek and Flathead River||metals, including copper, cyanide, manganese; fluoride||groundwater infiltration; groundwater seeps|
A site reassessment was completed for the Columbia Falls Aluminum Reduction Plant site in April 2014. Results from that report are summarized here. The full report for this investigation is available in Site Documents below. The assessment and report is organized such that potential sources are evaluated to determine potential contaminants and then compared to analytical results for potential receptors, including surface water features and groundwater down gradient of the source areas.
Landfill Sources – Samples were not directly collected from landfills at the site in order to prevent compromising the integrity of the covers. In lieu of direct sampling, EPA sampled monitoring wells previously installed in locations down-gradient of the landfill and sludge pond sources. EPA compared the down-gradient sample results to up-gradient, background concentrations in order to determine if contaminants are significantly elevated compared to background conditions. For the purposes of this investigation, an observed release is documented if the down-gradient concentration for a particular contaminant is at least three times the background concentration.
The following is a list of contaminants that have met the observed release criteria, which document an elevated contaminant concentration above background conditions: metals, such as aluminum, arsenic, chromium, copper, cyanide, iron, lead, nickel, selenium and vanadium, among others; fluoride; and nitrate/nitrite as N.
Percolation Pond Sources – Waste sediment and surface water samples were collected from two percolation ponds for a common hazardous constituent analysis to determine contaminants present in the ponds at the site. The following is a list of contaminants determined to be present in percolation pond sources: semi-volatile organic compounds, such as anthracene, benzo(a)pyrene, chrysene, fluoranthene, and pyrene, among others; metals, including aluminum, arsenic, chromium, copper, cyanide, iron, lead, magnesium, manganese, nickel, sodium, vanadium and zinc, among others; pesticides; and fluoride.
Groundwater Migration Pathway – As discussed previously, landfill sources were indirectly evaluated by comparing down-gradient groundwater samples to up-gradient, background groundwater samples. This evaluation confirms that contaminants discussed previously have been released to groundwater at the site. Five residential wells were evaluated to determine if groundwater near the facility has been impacted. Cyanide was detected in one well southwest of the facility and another well to the north of the facility. The detections of cyanide were below EPA’s Maximum Contaminant Levels (MCL) and the State of Montana’s Numeric Water Quality Standards. When compared to EPA’s Risk Based Screening Levels, however, the concentrations of cyanide in both water samples were higher than the EPA Tapwater Risk Based Screening Level. The screening concentration is a conservative value that EPA considers to be protective for humans over a lifetime. Exceeding these values does not necessarily indicate that a health affect will occur, but that a more detailed assessment may be warranted. No other contaminants were detected above the regulatory or risk-based screening levels.
Surface Water Migration Pathway – Surface water and sediments from the Flathead River and Cedar Creek were collected for a common hazardous constituent analysis. Similar to the groundwater analysis, downstream samples were compared to background samples to determine if there is an observed release of any contaminants. In Cedar Creek, there were observed releases of copper, cyanide and potassium. In Flathead River, there were observed releases of cyanide, manganese, sodium, zinc and fluoride.
This stretch of the Flathead River is believed to be used by anglers. Fish tissue samples were not collected as part of the site reassessment. With the limited amount of data captured as part of this sampling event, it is unknown if bioaccumulation of these contaminants is a concern.
In response to the cyanide detection in a residential well down-gradient of the facility, EPA is conducting a second round of sampling for residential wells located within the neighborhood down-gradient and adjacent to the facility. The purpose of this sampling event is to gather more detailed data about the groundwater quality in the area. The sampling will take place the week of April 7, 2014.
Columbia Falls Site Reassessment Report, April 4, 2014
Site Assessment Manager
U.S. Environmental Protection Agency, Region 8
1595 Wynkoop Street (EPR-B)
Denver, CO 80202-1129
800-227-8917 ext. 312-6664 (toll free Region 8 only)