BROOKSVILLE — The U.S. Army Corps of Engineers, New England District recently issued a contract not to exceed $45 million with a five-year period for remediation work at the Callahan Mine Superfund Site in Brooksville, according to a press release from the Corps of Engineers.
The contract was awarded on May 18 to Environmental Quality Management Inc. of Cincinnati, Ohio.
The former Callahan Mine site was an open-pit mine developed in Goose Pond, a shallow tidal estuary of approximately 75 acres in the town of Brooksville.
From 1968 through 1972, approximately 5 million tons of waste rock and 800,000 tons of ore-bearing rock were mined from the open pit. The waste rock was disposed on-site in three large piles. The outside footprint of the tailings impoundment encompasses approximately 17 acres and contains 725,000 cubic yards of mining-related waste (tailings), the press release stated.
Erosion of mine waste (tailings and waste rock) and precipitation of metals in the discharge from the tailings impoundment and waste rock piles has contaminated the soil in the salt marsh and sediment in Goose Pond.
Concentrations of copper, lead and zinc may represent a threat to insectivorous and piscivorous birds, fish and other aquatic organisms.
The ongoing acid rock drainage from the waste rock piles and tailings act as a continuing source of copper, lead and zinc to groundwater, surface water and sediment, according to the Army Corps.
A tailings impoundment dam must be stabilized to prevent a failure of the dam and the subsequent release of tailings into the estuary and Penobscot Bay.
The major work elements include the following:
- Remediation of the tailings impoundment.
- Remediation of a waste rock pile.
- Slope stabilization of a tailings impoundment
- Consolidation and capping of the tailings impoundment.
- Sediment excavation and disposal.
- Remediation of residual contamination at a second waste rock pile and the ore processing area.
- Site restoration and mitigation and monitoring.