County crushes road materials and costs
Wibaux County (Mont.) Road Supervisor Gary Lawrence used to contract out his crushing jobs. However, that was costly and inefficient. So Lawrence, who manages 500 miles of county road, convinced county commissioners that they could do better.
“We had a contractor come in and crush 20,000 yards for us (about one-third of the material needed per year),” Lawrence says. “That cost $33,000. It took only six weeks of road surfacing to exhaust that material.”
On Lawrence’s recommendation, the county commissioners approved the purchase of a portable horizontal shaft impactor (HSI). The road supervisor assured commissioners that, by eliminating the need for an outside crushing contractor, the new equipment would pay for itself in less than three years.
Consequently, the county replaced its 42-year-old jaw/roll plant with a Pioneer 4233 HSI manufactured by Yankton, S.D.-based Kolberg-Pioneer. A 50-foot radial stacking conveyor accompanies the impactor and allows access to small pits and moves easily in and around hilly terrain.
“Primarily, we are crushing scorrio and gravel,” Lawrence says. “Scorrio is millions-of-years-old burnt coal, a softer, red-colored rock that we crush to two-inch minus and use for road surfaces. We can pull the impactor behind our tractor and go from one pit to another, cutting the costs of trucking material over long distances.”
Wibaux County gets 200 tons-per-hour of scorrio from the impactor and considerably more gravel per hour. Material is screened with two-inch-minus material bypassing the impactor and traveling directly to a stockpile. “Larger material is crushed in one pass and is ready to go out on the road,” Lawrence says. “With our new crushing operation, we get enough fines in our scorrio that we don’t have to add as much dirt to the final surface mix as we had in the past. The fines and dirt prevent road surface materials from shifting back and forth over time.”