BROOKSVILLE, Maine — The U.S. Environmental Protection Agency on Wednesday signed the record of decision for the cleanup of the former Callahan Mine site, ending the investigative phase of the SuperFund process at the site.
The record of decision formally lays out the scope of the cleanup, including the contaminants and the physical areas involved, according to project manager Ed Hathaway. The formal comment period on the cleanup proposal ended Sept. 10.
The decision, Hathaway said Thursday, is essentially the same plan the EPA presented at a public hearing in August. The only substantial change, he said, was the addition of Dyer Cove and Goose Cove. The investigations at the mine site, which began in 2004, discovered deposits of mine waste in those two areas and the initial plan had identified them for further study.
Although there was just a “modest level” of comment on the plan, Hathaway said those who did comment urged the agency to include those sites in the cleanup.
“There was very strong support for adding them to the cleanup,” he said.
Callahan Mining Co. did extensive mining at the site in the late 1960s and early 1970s, extracting an estimated 800,000 tons of rock containing copper, zinc, lead and traces of silver from the open pit site. About 5 million tons of waste rock containing contaminants also was removed from the mine and deposited on the site.
The mine site was listed as a SuperFund site in 2002 and investigations into the extent of contamination began in 2004. EPA officials have described the site as “heavily contaminated,” with studies over the years showing high levels of lead, zinc and arsenic on the mine site, along with polychlorinated biphenyl, or PCB, contamination in isolated areas of the site. In addition, they found lead and arsenic contamination on private, residential properties adjacent to the mine site.
The cleanup plan calls for much of the contaminated materials — at the ore pad, the mine operations area and one of the waste rock piles, as well as contaminated sediment — to be disposed of in the former mine pit, which was flooded when mine operations ceased in 1972 and is now underwater. It also calls for an impermeable cap over the tailings impoundment.
PCBs, petroleum-contaminated sediment, and the deposits of lead and arsenic will be excavated and disposed of at an approved disposal facility.
The plan also places strict regulations on the future use of the property and the groundwater under it.
While the signing of the record of decision ends one phase of the SuperFund process, Hathaway said it could be years before any work is done at the site.
The EPA still needs to determine who will pay for the cleanup. The agency has identified several potentially liable parties, including the state of Maine, the Smith Cove Preservation Trust, which is the current owner of the property, and the Coeur d’Alene Mining Co. of Coeur d’Alene, Idaho, which purchased the Callahan Min-ing Co. after the mine closed in 1972. They all will be “invited” to participate in the cleanup, Hathaway said.
It appears likely that the EPA and the state of Maine will be the only parties paying for the cleanup. In that event, Hathaway said, the state will be responsible for developing the detailed engineering plans necessary, a process that could take as long as two years, and the EPA will oversee the implementation of those plans. Under SuperFund regulations, the cost of the cleanup would be split 90-10 with the state paying 10 percent of the total cleanup costs. The state also will be responsible for 100 percent of the cost of maintaining the site once the cleanup is completed.
A completed design will be forwarded to EPA headquarters in Washington, D.C., where it will be ranked by priority with other SuperFund projects from around the country.
It is possible that a portion of the cleanup — the removal of the PCBs and the arsenic and lead on adjacent residential properties — could be designed and implemented separately, and be done more quickly.
“Those are smaller projects and would cost less money,” he said.
The EPA has estimated the total cost of the cleanup at $25 million.
The record of decision, including a summary of formal comments on the plan and EPA’s responses to those comments, will be posted on the agency’s Web site within a week or two. That site is www.epa.gov/superfund.