The Montana Department of Environmental Quality is proposing changes to the original cleanup plans for the Montana Pole and Treating Plant that it says will make the site safer for people.
The original plan, laid out in a record of decision in 1993, was to cleanup the soils at the former wood-treating facility to a level safe for recreational use.
Now, the state is proposing to clean it to a level that would make the property safe for industrial use.
The state says that means the 36-acre site near Montana Street and Interstate 15-90 would be safe enough for people to work there daily.
The state has spent more than 20 years treating the property, where a toxic mix of chemicals — such as pentachlorophenol, diesel and dioxins — contaminate the soils. Those chemicals were released onto the land without any controls during the former wood-treating plant’s operations from 1946 to 1984.
“The choice for the remediation was to do a bioremediation biological land treatment of the soils, and there were approximately well over 200 thousand cubic yards of contaminated soils that needed to be treated,” said David Bowers, environmental scientist at DEQ.
The idea was the contaminated soil would be moved to a certain lined area on-site, known as the Land Treatment Unit, where exposure to sunlight and air, plus some tilling and water, would lead to the natural degradation of the chemicals in the soils, namely pentachlorophenol, petroleum and dioxins.
“But that process caused some fairly significant odors, and the people down at the Boulevard neighborhood had some concerns about that,” Bowers explained. “DEQ came in, did some air monitoring, talked to the community, and finally, what was decided was that we would abandon the tilling and the watering ... And that in turn slowed the bioremediation process down.”
However, Bowers added, the odors went away.
While pentachlorophenol and petroleum degraded, the dioxin was not breaking down as expected. Dioxins are a byproduct of PCP production, Bowers said, and are highly toxic.
“It was envisioned in the ROD that it might be possible to meet the cleanup levels for the dioxins, but they were just degrading too slowly and everything else was done,” Bowers said. “The challenge with dioxins is there's so few things that you can do with it.”
Bowers listed the treatment options available with dioxins. One would be to ship the contaminated soil away to a licensed waste facility. Another method would be to incinerate the dioxin-laced soil on site. But due to the volume of dirty soil at Montana Pole, Bowers said, those treatments are not feasible.
“What's important to remember about all of that is that wood-treating waste chemicals, pentachlorophenol and the diesel are listed hazardous waste and that's important for what we can and cannot do out on the site,” Bowers explained. “Even though we met the ROD cleanup levels, they still have to be kept on site and managed on site. And that also means that the dioxins that come with those chemicals also have to stay on our site.”
That’s why the DEQ has decided to keep the roughly 200,000 cubic yards of treated dirty soil on site and to cap it with a plastic liner. “The treated soils, plus other soils not meeting new cleanup levels, will be capped,” according to Bowers. “The placement of treated soils back into excavated areas is part of the original ROD remedy, not a departure.”
As part of that change, the DEQ is proposing to modify parts of the original cleanup plan issued in 1993, including the soil cleanup standards for dioxins, the final treatment and future land use plan.
The DEQ outlined these changes in a report, called “Explanation of Significant Differences,” which was made available Monday for a 30-day public comment.
One of the most significant changes, Bowers said, is “we're taking two of the contaminants [pentachlorophenol and dioxins] and reducing the cleanup levels down to more protective cleanup levels.”
Setting more protective cleanup levels for pentachlorophenol, Bowers said, helps keep the dioxin from moving in the soil.
By setting those cleanup standards for the two chemicals, Bowers said, the contaminated soils can be stored and capped in one location. He said the reason for capping the soils is to prevent rain water from getting to the pentachlorophenol, which can act as a carrier fluid for dioxins.
Another significant change, Bowers said, is that all the soils that do not meet the new cleanup levels for pentachlorophenol and dioxins will be stored on-site in a 9-acre landfill, known as a “Corrective Action Management Unit.”
Bowers said the goal of this new cleanup plan is to make the remaining 27 acres on Montana Pole’s property “absolutely protective as possible to the industrial/commercial” use.
When asked why the DEQ and EPA didn’t implement more protective pentachlorophenol cleanup levels in the original cleanup plan, Bowers said, scientists at the time didn’t fully understand the fate and transport of contaminants into the groundwater and that “protection to groundwater as part of a remedy wasn’t considered like it is today.”
The DEQ is hosting a public meeting to discuss the proposed changes at 6:30 p.m. next Tuesday, Feb. 18, at the Butte Brewing Company, 465 E. Galena Street.
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