Additional air-quality testing in January by an EPA contractor suggests a chemical contaminant plume in the vicinity of Butte High School and an adjacent apartment building does not pose health hazards for occupants of either building.
The EPA said this week that the agency has no plans to perform additional testing.
The samples examined ambient air or involved drilling a hole in a concrete slab and testing for chemical vapors accumulated beneath the slab.
Joseph Chisholm, a site assessment manager for EPA, said samples taken in the high school and apartment building showed no contaminants of concern above detection levels.
The EPA has not determined the source of the plume but believes it likely originated from one or more defunct dry cleaning businesses that operated nearby.
Chisholm described the testing results from January as “very good news.”
He said the testing was conducted during a time when indoor air is most susceptible to pollution because of attempts to seal off cold air from outside.
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The Montana Department of Environmental Quality first detected the solvent plume in 2009. The EPA contracted for a preliminary investigation of the site over a decade later – raising pointed questions about why the investigation was delayed for so long.
The report was completed this past summer, and shared with Butte-Silver Bow officials this fall.
The report found the site posed a potential risk to human health and recommended that a thorough site inspection be completed to find out for sure.
EPA toxicologist Charlie Partridge has said the chemical concentrations found in 2009 presented a fairly low risk to people, as does the potential exposure pathway.
In 2009, tetrachloroethylene (PCE) was detected in groundwater near Butte High at more than double the state’s standards. The highest concentration was 12 micrograms per liter and the standard is 5 micrograms per liter. The contamination was over 20 feet deep.
PCE is commonly used in dry cleaning solvents, adhesives and degreasing aerosols like brake cleaner. The chemical can cause neurological, kidney and liver damage, and is a probable carcinogen.
Also detected in the plume was trichloroethylene (TCE), another chemical used in a variety of industrial products and by commercial dry cleaners for spot removal. According to the National Cancer Institute, TCE can cause kidney cancer and may be associated with increased risk for other cancers as well.
The contaminated groundwater was first discovered during excavation for the bleachers at Butte High’s Naranche Stadium in 2009, according to the 2021 report to the EPA.
Butte School District No. 1 hired Butte-based engineering firm Water and Environmental Technologies to monitor the area with 10 shallow wells in 2009, according to the report, and the data was provided to the DEQ.
Today, the EPA believes the plume is not a threat.
“The plume has most likely moved, dispersed, been diluted,” Chisholm said.
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