Monroe, Michigan
The DTE Monroe, Michigan power plant bottom ash impoundment area was constructed in the late 1960s. A perimeter dike was built to surround a low area of Lake Erie. Coal Combustion Residual (CCR) materials had been placed and allowed to drain into the pond until 2015. The area defined for closure was approximately 86 acres. The primary contaminant of concern is CCR.
Sevenson performed remediation of CCR contaminated sediments via hydraulic and mechanical dredging. Crews utilized two dewatering methods designed to operate in series to dewater dredged material. The first step in this series was a Terrex screening device and the Total Clean System (TCS) with the ability to remove sand materials above the API #200 screen. The TCS removed approximately 65% to 75% of the material, and the desanded material was then dropped onto radial stacked conveyors and stockpiled for disposal. The second step was the use of Geotubes® for the remaining 25% to 35% of material. The Geotubes® were 90-ft. in circumference and ranged in length from 200-ft. to 243-ft. long. The Geotubes® were stacked three tubes high and had a drying period of two to three weeks. Upon completion of the drying process, the Geotubes® were cut open and the contaminated sediments were removed and transported to the disposal location. Sevenson dewatered approximately 161,000 CY via Geotubes® and 343,600 CY of sediments through the TCS.