DJ&A was tasked with completing scoping and design to improve two connecting segments (21 miles total) of road in eastern Idaho with a goal of enhancing safety and drainage along the corridor, which is heavily used by both recreationalists accessing the Caribou-Targhee National Forest and commercial traffic.

On one segment in Clark County, efforts included rehabilitation design to pave and widen 7.9 miles of gravel roadway; minor drainage improvements; repairs to soft spots; and additional base. The other segment included design for a 27-foot wide, 3.5” thick asphalt overlay on a pulverized base, with sight distance, clear zone, and approach improvements; design of two large culverts; and shoulder improvements. A portion of this project also evaluated the feasibility of constructing a proposed trail.

Final design included 3.3 miles of 10-foot wide aggregate-surfaced trail running parallel to the road, 16 feet of clearing to accommodate a snow grooming machine, and a 210-foot-long trail bridge. Given the length of this project, it was challenging to provide an appropriate surfacing design that satisfied the roadway’s future loading conditions while also minimizing overall project costs. DJ&A fine-tuned the surfacing design to an appropriate low-volume and budget-sensitive solution, which included full depth emulsified asphalt reclamation.

This project is in rural Idaho in an area required environmental services including wetland and stream delineation, preparation of Wetlands and Waters of the US Report, and development of a Biological Assessment.

Key Services

• Roadway design to improve approaches, drainage systems, sight distance, and clear zones
• Hydraulic study/inventory of existing culverts and designed two large culverts to improve drainage and facilitate fish passage
• Oversaw geotechnical services including subsurface exploration for pavement and bridge design and recommendations for pavement and structures
• Bridge rehabilitation and retrofit
• R/W determination and utility conflict identification and coordination
• Topographic survey and mapping
• Environmental services including wetland and stream delineation, preparation of Wetlands and Waters of the US Report, and development of a Biological Assessment
• Extensive public involvement services
• Coordination with project stakeholders Fremont County, Clark County, Bureau of Land Management, and U.S. Forest Service