I-15 (D3) Rock Slope Mitigation Design and Construction
Helena to Great Falls, Montana
Along I-15 between Helena and Great Falls, Montana, there are numerous existing rock cuts and natural rock slopes that have a history of hazardous rockfall activity and require a high-level of maintenance by Montana DOT (MDT). LT was retained by MDT to assist with the assessment and design of rock slope stabilization measures for 15 high-hazard slope segments along a 27-mile corridor.
LT performed field reconnaissance and geologic mapping using advanced photogrammetry to collect relevant rockfall and structural data and evaluate rockfall hazards associated with each site. Mitigation measures included trim blasting, scaling, draped-mesh, attenuator systems, rock bolting, concrete barriers, and expanding fallout areas.
LT provided technical guidance during construction and provided on- site construction observation services for the more difficult access elements like trim blasting, rock bolting, and attenuator system installations.
LT worked closely with MDT geotechnical and maintenance personnel to develop a realistic rockfall retention and mitigation design goal that met the Agency’s needs of improving the safety of the traveling public, while addressing as many slope segments as possible given the available funds. LT developed temporary protection and traffic control measures that allowed nearly all of the 2,500 scaling-hours to be performed while allowing interstate traffic to flow.