Montana Department of Transportation — I-15 Rockfall Mitigation

Constructed in the 1960s with steep to near-vertical cut slopes, Interstate 15 between Sieben and Hardy Creek had a history of rock fall activity and required a high level of maintenance. I-15 spans the length of Montana to the Canadian border and midway on the route between Yellowstone and Glacier National Parks. The challenge for Montana DOT: find a way to remove massive amounts of unstable rock and failing branches, while installing safety measures with minimal disruption to travelers. The solution: a three-phase $19 million project that involved 17 sites that stretched over 25 miles. Rather than phase out the work by the sites, the agency conducted it by work type and traffic logistics. This allowed Montana DOT to hire specialized contractors for earthwork and blasting activities, versus scaling and drilling. Temporary safety features allow traffic to flow more smoothly when work came close to the roadway. Helicopters were also used to hoist materials and prevented additional or longer closures. Road closures were down to 20-minute intervals during construction activities, such as blasting, and only limited to perform closures six days a week, helping to save money and complete the project on time. The agency also deployed a number of safety measures, including crack meters, to monitor future rock movement. Travelers now have a safer route to access national parks, free from the hazards of rock falls.