Interim covering of waste pit 4 at the feed materials production center

The Feed Materials Production Center (FMPC) is a Department of Energy (DOE) owned facility operated by Westinghouse Materials Company of Ohio (WMCO) for the purpose of producing metallic uranium fuel elements, target cores, and other uranium compounds. These materials are used at other DOE facilities in support of the US defense program. In the past, disposal of waste generated from production operations at the FMPC was accomplished by constructing waste disposal pits and landfilling the waste. As a result of this practice, the FMPC has six waste disposal pits which contain many different types of waste including uranium, thorium, construction rubble, fly ash and various other wastes unique to the FMPC. None of the waste disposal pits are currently operated for the disposal of waste and all six pits are being investigated under a sitewide Remedial Investigation/Feasibility Study to determine what effect the pits are having on the environment. Waste Pit 4 is unique among the six pits in that it contains an amount of mixed (hazardous/radioactive) waste and has been classified under the Resource Conservation and Recovery Act as a hazardous waste landfill. For this reason the US Environmental Protection Agency requested that the US DOE consider interim closure of Waste Pit 4 to prevent surface water infiltration. To meet this request, WMCO developed the Cover for Pit 4 project which involves placing subgrade fill onto the existing pit surface to form a domed cap over the pit, covering the cap with 0.6 meters of clay compacted to 10-7 cm/sec permeability, and installing a 1.1 millimeter reinforced Hypalon cover over the clay. This paper will detail the design process with the associated problems and solutions and the projected construction sequence