Stability is key

County State Aid Highway 25 was typical of Cass County’s other 377 miles of gravel-surfaced roads. The costs associated with keeping and maintaining a gravel surface was rising faster than the allocated revenues. With an average daily traffic approaching 200 vehicles and increasing routine maintenance, the decision was made to place a thin Otta Seal gravel-oil-emulsion surface on
the road.

“We selected the surface due to its relative cost savings. The surface costs approximately 50% less than a hot-mix bituminous surface,” David Enblom, county engineer for the Cass County Highway Department, said. “The main difference is the surface provides minimal structure strength to the road. As a measure to add strength to the surface, it was decided to treat the underlying aggregate base with Team Laboratory Chemical Corp.’s Base One aggregate base stabilizer.

“This project was constructed in 2001 and is performing very well with no maintenance needed to date. We have constructed other gravel-oil-emulsion surface roadway sections since this original project. These later projects varied—some having stabilizer added to the base aggregates and some without. The projects are all performing well. Those that did not include the base stabilizer have had to have routine maintenance performed, such as pothole patching as well as bituminous overlays.

“When considering future projects, an aggregate base stabilizer will be included in the project.”