Fort Hartford

Remediation of Underground EPA Superfund Site

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Copyright© Geo/Environmental Associates, Inc. 1995 through 2008

Using a combination of modern computerized design technology and longtime underground mining techniques, Geo/Environmental Associates, Inc. assisted Commonwealth Aluminum Concast, Inc. in successfully converting an EPA Superfund site into an environmentally acceptable monitored waste storage facility. The Fort Hartford Mine Superfund Site, in a rural area of Ohio County, Kentucky, is about 645 acres in size. Included within the site are about 120 acres of abandoned underground limestone mine workings where the previous owner had stored an estimated 1.4 million tons of salt cake fines, a by-product of an aluminum recycling operation. Contaminants in salt cake fines react with water to form several gases, the most prominent of which is ammonia.

Barmet Aluminum Corporation, the previous owner of the Fort Hartford Mine Site, entered into an Administrative Order on Consent with the EPA in 1989. Actions were taken to reduce the contact between the salt cake fines and water. These actions included the diversion of surface water runoff, closure of existing mine collapses and sinkholes, and removal of water within the mine by pumping.

A comprehensive mine roof stability study was conducted to delineate areas of the mine that were suitable for long-term waste storage based on the presence of factors known to cause mine roof failures. Finite element modeling was used to delineate zones of relative stability and potential for water intrusion. It was found that several parts of the mine were suitable for safe long-term storage of salt cake fines. In the spring of 1995, the EPA selected a final cleanup remedy that included continued diversion of intruding mine water and monitoring.

Commonwealth Aluminum Concast, Inc. assumed responsibility for the site in 1996 through acquisition of the previous owner. Upon review of the proposed remedial design plans, Commonwealth Aluminum made worker safety the primary consideration in the execution of the work. They undertook a comprehensive 2-year project to make the workplace safe. To limit the frequency of underground exposure for workers, Commonwealth Aluminum elected to install an automated pumping system for the removal of mine water. However, even with the automated pumping system, periodic entry into the mine would still be required for maintenance of the pumping equipment. Under the guidance of GA engineers, loose and unstable roof rock along the required travelways was removed by both manual and mechanical scaling methods. Areas in the mine with obvious high risk of roof spalling and rock falls were delineated. These identified high risk areas along the travelways were repaired by several methods including roof bolting, timber cribs, concrete column supports, and the construction of portal canopies. GA engineers designed these mine roof support systems and monitored their installation. Due to the poor underground air quality, much of the work had to be accomplished using full-face respirators and supplied air.

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