EPA report details contaminant sources at smelter

More information about the source and pathways of contaminants at the Columbia Falls Aluminum Co. smelter site has been made available in the Environmental Protection Agency’s 271-page site reassessment report released in April.

The Montana Department of Health and Environmental Sciences conducted a preliminary assessment of the smelter site in March 1984 and concluded that hazardous wastes at the site included solvents, spent potliner, basement sweepings and air pollution control dusts.

Consultants for the EPA conducted a site investigation in 1988 that found polycyclic aromatic hydrocarbons in soils and sediments and a release of cyanide to the groundwater. The EPA concluded that no further remedial action was planned.

Last fall, consultants for the EPA took 68 groundwater, surface water, sediment and soil samples at the plant and the surrounding area for a site reassessment. Some monitoring wells were not sampled for a variety of reasons, and some landfills and ponds were not directly sampled to avoid compromising their caps or covers.

Hazardous materials found in the samples include a wide range of metals, fluoride from reduction pot emissions and cyanide from spent potliner. Contaminant levels exceeded background, human health and ecological screening levels.

CFAC’s 3,196-acre property is bordered by Cedar Creek Reservoir to the north, Teakettle Mountain to the east, Flathead River to the south, and Cedar Creek to the west. The smelter site proper covers about 953 acres.

Surface water drains west to Cedar Creek, which runs beneath the city of Columbia Falls before entering the Flathead River. Surface water also drains east to the Cedar Creek Reservoir overflow ditch, which empties into the Flathead River through a pipe near Bad Rock Canyon.

Depth to groundwater at the plant site varies but is typically about 15 feet. Groundwater is recharged by ephemeral streams on the west flank of Teakettle Mountain and by Cedar Creek, and it principally discharges into the Flathead River.

Landfills and waste ponds cover about 72 acres north of the plant. Percolation ponds cover about 70 acres in the center and south end of the property. They include:

• The East Landfill, also known as the Spent Potliner Landfill, was used from 1980 to 1990 prior to spent potliner being declared a hazardous waste by the EPA in 1991. The clay-lined landfill was covered with a synthetic cap and revegetated in 1990.

• The West Landfill is an unlined solid-waste landfill used from 1955 to 1981. General garbage, steel and wood scraps, and spent potliner was dumped there from 1955 to 1970. Solvents and other hazardous wastes were also likely dumped there. The landfill was capped with clay in 1992 and with a synthetic material in 1994.

• The Wet Scrubber Sludge Pond Landfill took sludge from the smelter’s early air pollution control equipment and was closed around 1980. It also took spent potliner from 1994 to 1998. In February 1998, the Montana Department of Environmental Quality ordered CFAC to remove all spent potliner from the landfill.

CFAC sampled pot diggings in the landfill in July 1998 and found cyanide in all samples, but based on EPA criteria, DEQ declared no further cleanup was required for the pot diggings or underlying soil. The landfill has been recontoured, covered with soil and revegetated.

• The Center Landfill, also known as the Carbon Pile, is an unlined landfill used from 1970 to 1980. Solvents and other hazardous wastes were also dumped there. It has been covered and revegetated.

• The Sanitary Landfill is a clay-lined landfill used for plant garbage. Solvents and other hazardous wastes were also likely dumped there. It has been covered with soil and revegetated.

• The Asbestos Landfill was used in the early 2000s. It is now covered with grass.

• The Industrial Landfill is still active and used for nonhazardous waste and debris. It is now covered with gravel and has a 10-foot high fence around it.

• The North and South Leachate Ponds are hypalon-lined ponds built on both sides of the East Landfill in 1980 to collect runoff. The water in the ponds was aerated to allow ultraviolet light to break down cyanide that leached out of the spent potliner in the East Landfill.

In 1990, with DEQ approval, about 150,000 gallons of leachate in the south pond, containing fluoride and cyanide, was drained into the Wet Scrubber Sludge Pond Landfill. The south pond was dried, capped and closed in 1993. Leachate in the north pond, which contained fluoride but not cyanide, was also drained into the Wet Scrubber Sludge Pond Landfill. The north pond was capped and closed in 1994.

• The 8-acre North Percolation Ponds initially received wastewater from the paste plant, wet scrubbers and various industrial shops. It also received effluent from the Cathode Soaking Pits prior to 1978. More recently, the ponds received wastewater from the vehicle maintenance garage, the lab boiler and various sumps and stormwater drainage. A 10-foot high fence surrounds the ponds.

• The Cathode Soaking Pits were not described.

• The West Percolation Pond received boiler blowdown from various shops and stormwater.

• The 62-acre South Percolation Ponds took wastewater from the rectifier building, the sewage treatment plant and the laboratory, noncontact water from the casting facility, and other wastewater. The ponds are now vegetated with grasses, shrubs and trees.

• Five above-ground and 12 underground storage tanks located around the plant were used to store diesel fuel, hydraulic oil, motor oil, gasoline and waste oil. Three of the underground tanks are still in use.