BROOKSVILLE, Maine — The Environmental Protection Agency will present a preliminary cleanup plan next week that calls for spending an estimated $23 million to deposit contaminated sediment and waste rock underwater in the former mine pit at the site.

Representatives from the EPA will review the draft feasibility study for the mine when they meet with residents at 7 p.m. Tuesday, June 9, at the Brooksville Public Service Building.

The feasibility study is still in draft form and has not been released yet, according to Ed Hathaway, the EPA project manager for the mine site. But it is far enough along for the EPA to discuss the likely cleanup option for the site, he said.

Last month, the EPA along with the state Department of Environmental Protection and the Maine Department of Transportation reviewed the results of the remedial investigation, which has been under way since the mine site was placed on the National Priorities List as a SuperFund site.

During the mining operations on the 150-acre site, about 5 million tons of waste rock containing contaminants also were removed from the mine and deposited on the site. Metals leaching from the waste rock have contaminated areas around the site, including areas in Goose Pond.

The plan calls for the contaminated sediment in Goose Pond to be dredged and deposited in the former mine pit, which is now underwater. Material from waste rock pile No. 3 and the former ore pad also will be deposited in the mine pit.

Mining operations in the late 1960s and early ’70s created an open pit mine that was approximately 320 feet deep. When mining operations ended in 1972, dams that kept water out of the mine pit were opened, flooding the mine pit.

The cleanup plan would fill between 30 to 40 percent of the pit, but according to Hathaway, that would still leave at least 100 feet of water over the deposited materials.

“That is below the depth of mixing, so materials will not be scoured up,” Hathaway said Friday. “This is a standard way to dispose of these materials. It’s a very stable environment and a very effective long-term solution.”

Not all of the materials will be placed in the mine pit. Some areas of PCB contamination and deposits of lead and arsenic will have to be removed from the site, he said. They will be disposed of at an approved site, he said. The plan also calls for a cap on the former tailings pile at the site.

According to Hathaway, the EPA also will develop restrictions that will prevent residential development of groundwater resources at the site.

The cost of the cleanup is estimated at $23 million. That is within the range of earlier estimates, and, Hathaway said, slightly lower than anticipated.

Work on the cleanup will not begin right away.

Because the former mine is a SuperFund site, there are still steps in the process to be completed. Once the feasibility study is completed, it will be published and there will be a period for public comment. After the comments have been reviewed, the EPA will make a final record of decision on the project. Until that happens, Hathaway said, the cleanup plans are only proposals.

The record of decision will start a new phase in the process. The next step will be to develop a detailed design for the cleanup. With a large project such as this one, Hathaway said, the design phase easily could take one to two years.

The project then would go into a pool where funding will be allocated, with the most serious problems being funded first.

“We could have to wait some time for funding to kick in,” he said.

Although it is possible that the cleanup of the PCBs, lead and arsenic could be done separately beforehand, it could be two to three years before the major cleanup of the site begins.