Drilling begins to measure ground water treatment success

A contractor for International Paper Co. began to drill wells last Thursday under direction of the Environmental Protection Agency to better delineate the boundaries of contamination within the Libby Ground Water Contamination Superfund Site.

“We’re drilling a series of wells on the west and north of the site to define the areal and vertical boundaries of the upper aquifer,” explained David Cosgriff of Arrowhead Engineering Inc., a contractor for International Paper.

The work is part of a list of follow-up actions outlined in the Superfund site’s most recent five-year review, which determined that the current remedy is not protective of human health due to revised standards, the potential for use of better technology and a newly identified exposure pathway.

The drilling “is to see how effective the treatment of the ground water has been,” according to Lisa DeWitt of the Montana Department of Environmental Quality, a supporting agency in the cleanup.

“A lot of it is just confirmatory work,” she added.

International Paper is the corporate successor to wood-treating facilities that leaked creosote and other toxins into the soil at the former mill site. The chemicals seeped into the upper and lower aquifers beneath the city, which led to it being designated a Superfund site in 1983. A city ordinance that passed in 1986 currently bans the drilling of new wells and the use of well water.

Workers are in the process of drilling 30 wells of varying depth at 10 locations to help determine if the plume has shifted or shrunk since the process of removing contaminants began over 20 years ago.

“They are completed at a different depth to get a good vertical view of the groundwater,” Cosgriff said.

Drillers estimate finishing the work by Aug. 6, but if testing reveals contamination, workers will have to drill additional wells further out to determine how far the plume has shifted.

“If they all came back clean, that would show that we found the boundary around the plume,” Cosgriff said, “and that would really help us define the size of the plume.”

EPA’s fourth five-year review, which was released this spring, stated that follow-up actions to address new issues raised would “in all likelihood” lead to either an amendment to the record of decision or a major explanation of significant differences – a document that explains major changes in the remedial action but that does not have to go through the same process as a ROD amendment.

Once the EPA and Montana DEQ learn where the contamination is and isn’t located, they can re-examine the best technology to remove the toxins. It has been more than a decade since technologies were last evaluated, according to DeWitt.

“A lot of the reason for the work is to gain updated information so you’re not using information from 20 years ago,” DeWitt said. “As you do cleanup, the conditions change. I think going out to re-evaluate that is a very positive thing.”

The EPA is scheduled to evaluate several aspects of the ROD over the next year. The five-year review calls for looking into adjusting the risk-based cleanup levels for the soil and ground water due to changes in the factors that are used to calculate it. More stringent standards concerning arsenic will also have to be considered.

In addition, the EPA will evaluate the mill site to determine if contamination is spread into the air through vapor. The review cited a 2008 preliminary study that detected the presence of compounds that had evaporated from contaminated soil and water. Vapor intrusion was not detected anywhere outside the site, the review read, but the new exposure pathway would have to be evaluated further as the mill site may be redeveloped in the future. 

The review also suggested that the city ordinance banning the use of wells should be expanded to include the former mill site.