Geotechnical projects - Rock Slopes and Tunnels - Rockfall Hazard Rating System
High Hazard Rock Slope, I-15, Montana

The Montana Department of Transportation (MDT) selected Landslide Technology, a division of Cornforth Consultants, Inc., to assist them in implementing the Rockfall Hazard Rating System (RHRS) as a tool to manage rock slope assets along MDT highways. The RHRS provides a relative ranking of rock slopes and allows sites to be prioritized for capital expenditures for mitigation. The system takes maintenance history, slope geometry, highway characteristics, traffic data, and geology into account and yields a unique numerical rating for each slope.

The RHRS implementation was performed in a phased approach over two years. The first phase involved reviewing MDT digital photograph inventory for every mile of highway in the MDT system. The photo review resulted in an inventory of approximately 2,500 rock slope locations and general site descriptions. Site visits and field preliminary ratings were made at each rock slope identified in the image inventory. Landslide Technology developed a database to store all rock slope data and rating information.

Based on the preliminary ratings, detailed ratings were completed on approximately 850 of the higher hazard A-rated sites. The top 100 rated sites were identified and conceptual designs and construction cost estimates were developed.