Coulee Frac Sand, based in La Crosse, Wis., recently took delivery of a 10-in. Wolverine Class cutter suction dredge by DSC Dredge LLC. The dredge, which was designed and manufactured at DSC Dredge’s Greenbush, Mich., facility, is mining sand at the PineCrest Mine on the site of Doc’s Bunkhouse campground, near the town of Merrillan in central Wisconsin.
As groundwater was encountered 6 ft. below ground level, the company proposed mining the material through the use of a hydraulic dredge, with an onsite processing plant. The operation has been designed to return all dredged water back to a man-made lake. Coulee Frac Sand anticipates the dredging of approximately 1.6 million tons of sand will be complete in two to three years, at which time the site will be reclaimed as a manmade lake for recreational use by Doc’s Bunkhouse campground patrons.
This dredge project is unique in that it started at a site that has no natural flowing source of water. All of the water used by the operation is sourced from groundwater and precipitation. The two main components to the mine include the Wolverine dredge and an onsite wet processing plant with screens, separators, hydrocyclones, and a hydrosizer to separate and dewater oversize, coarse and fine sand from unusable ultrafines.
The company readied the site for the Wolverine dredge by excavating a quarter-acre starting pit 12 ft. deep (4 ft. below the water table) into which the Wolverine has been placed. The initial job for the dredge is to enlarge this area to include 2.7 acres, at a depth of approximately 24 ft. deep (16 ft. below the water table), and then excavate an artificial river bending toward the processing plant. The processing plant is currently being built, so the initial dredged material is being placed in a temporary spoil site at this time, with the return water flowing back through stand pipes to the lake.
Once the processing plant is up and running, the dredge will pump material and water directly to the plant, where the material (comprising medium-grade, non-compacted brown sand) will be separated and readied for transport offsite. The mine is designed so that return water, stockpile drainage and stormwater will flow into the artificial river and back to the lake in a closed loop, thus not drawing any water from surrounding sources other than on the premises.
This mine is a win-win for Coulee Frac Sand and for the region in that it is yielding a valuable natural resource, which is being harvested in an environmentally friendly manner. At the end of the mine’s life, reclaimed land totaling approximately 21 acres will become a recreational lake that will be enjoyed by current and future generations.
The DSC Wolverine dredge is powered by a 440-hp Caterpillar C13 ACERT diesel engine. The cutterhead, designed with six cast-steel smooth blades, is attached to a variable-speed, reversible, hydraulic cutter motor manufactured by Kawasaki. The dredge pump, a J30 Metso Minerals/Thomas Simplicity series, is rated for 200 ft. of total discharge head at 4,200 gal.-per-minute. Five hydraulic winches, rated with a 4,500-lb. line pull capacity, are used to swing the dredge, lift the spuds and lift the ladder.