Central Zone Geotechnical Investigations and Preliminary Designs

The United States Forest Service (USFS) identified 10 sites on forest service roads in the Nez Perce – Clearwater National Forest in northern Idaho that failed and required rehabilitation. AESI was contracted to conduct geotechnical investigations and provide preliminary designs to stabilize the failed road sites. Site visits, topographic surveys, and subsurface geotechnical explorations were undertaken, and typical slope treatment options were developed for the 10 sites. The typical slope treatment options include a geotextile reinforced wall, a mechanically stabilized earth wall (with proprietary facing), a reinforced soil slope (with naturally vegetated facing), a reinforced rock edge fill, and an unreinforced rock edge fill. These options encompass the most feasible and cost-effective remediation techniques for these forest roads. Three of the typical slope treatment options were selected and analyzed for each site. Based upon site observations, drainage, road geometry, failure geometry, subsurface soil characteristics, cost, constructability, and the analysis and discussion amongst senior AESI and USFS civil and geotechnical engineers, a preferred option was selected for each site.