Western Federal Lands Highway Division

What is the project, and where is the work taking place?

This project concerns reconstruction of approximately 2.5 miles of Forest Highway 26, better known as State Highway 75 (SH 75). SH 75 gives travelers access to the heart of south-central Idaho, noted for its rugged and historic scenery and recreational activities. The roadway also provides one of a few east-west links across central Idaho. The Ketchum-Challis Highway runs along the Salmon River in the Sawtooth National Recreation Area (Sawtooth NRA), just south of the border between Sawtooth NRA and the Salmon-Challis National Forest. The project follows the existing alignment from approximately milepost (MP) 205.5 to approximately MP 208. The project area includes a reach of the Salmon River known locally as the Narrows.

Why is reconstruction needed?

Frequent rockfall from steep and unstable cut slopes above the roadway poses a safety hazard to motorists. Fill slope instabilities below the road have undermined and narrowed the roadway, creating variable and substandard pavement widths. These conditions create safety concerns for the users of SH 75, a key state highway that provides access between communities in Custer County and Blaine County. As a roadway administered under the Forest Highways Program, SH 75 must provide safe and adequate transportation access to and through National Forest System lands for visitors, recreationists, resource users, and others.

What reconstruction is occurring?

Road reconstruction includes widening the existing road, stabilizing slopes prone to rockfall, installing cross-drain culverts with riprap outlet protection, constructing fill-side retaining walls, and performing the secondary activities needed to support these actions. FHWA is constructing two 11-foot lanes with 2-foot shoulders. Guardrails will be installed towards the Salmon River to protect motorists from the steep fill and the walls. The frequent and dangerous rockfall will be addressed through methods such as scaling, bolting, attenuator fencing, and both pinned and contoured rockfall mesh.

When is construction occurring?

This project is being constructed in two phases, divided between the western (Phase 1) and eastern (Phase 2) portions of the project area. Phase 1, covering the area between the project’s western terminus (approximately MP 205.5) and the end of the Narrows (approximately MP 206.5), will be constructed under two separate contracts. To minimize traffic delays, the first contract issued for Phase 1 includes rock scaling only and took place in the fall of 2012 and will be completed in the spring of 2013. The second contract for Phase 1 will involve the work needed to reconstruct the road and will take place in 2013 and 2014. Phase 2 will involve road reconstruction in the area between approximately MP 206.5 and the project’s eastern terminus near MP 208. Work timing on Phase 2 is dependent on available funding, which to date is not secured. Phase 2 will not likely require more than one construction season, assuming that the work could begin in the spring when the weather would be suitable for construction.