Bernard Suspension Bridge, 2001

Middle Fork Salmon River

River of No Return Wilderness, Salmon & Challis National Forests, ID


Satellite view of bridge. View Larger Map

USE:  Pack & Saddle Stock/Pedestrian

SPAN:  270'

TRAVEL WIDTH:  6'

TOWERS:  ASTM A7-50,W8x31 & W8x17 Steel Wide Flange Beams

ANCHORS:  1 1/2" grouted in place loop rock anchors

MAINLINES:  1-1/2" Bridge Strand

 

 

 

 

 

Bernard Suspension Bridge crosses the middle fork of the Salmon River, deep in the heart of the River of No Return Wilderness in central Idaho.  Originally constructed in 1956/57, the bridge is accessible only by trail, air, and via the river itself. The nine mile trail begins at Middle Fork Peak, located about 50 miles by dirt road west of Salmon, ID. Floaters frequently pass under the bridge, enroute on what is typically a five day Wildernss float trip. For construction access we travelled by air, using fixed wing aircraft provided by Salmon Air and landing at the nearby Bernard Air Strip, one of central Idaho's famous mountain/wilderness airfields. The bridge and airfield are closely associated with the Flying B Ranch, a private ranch in-holding located in the heart of this roadless area. the Ranch is owned and operated by an Owner Association, that manages the Ranch for recreational purposes, including hunting, fishing, horseback riding, etc., see wwwflyingresortranches.com . The bridge is owned and maintained by U.S. Forest Service, who called on Sahale to assess the damaged bridge, develop a repair methodology, and implement recommended engineering upgrades.  

Bernard Bridge was damaged during the extensive wildfires that ocurred throughout the West in 2000, most notably in central Idaho. The bridge was damaged, not by fire directly, but by a thundering fire-generated windstorm whipped up as the fires converged on the nearby ranch. Ranch occupants escaped with their lives by evacuating to the river and immersing themselves in the cool water, just upstream of the bridge. While in the water, winds estimated by Sahale engineers to have exceeded 150 mile per hour roared through the canyon and over their heads, deflecting the bridge sideways up to 12 feet and pulling the ends of the bridge superstructure off its bearing pads at the abutments. Witnesses in the river reported wrenching metal twisting and clanging sounds emanating from the bridge during the wind storm and they were convinced that entire span was near collapse. When the winds died down the deflected mainspan relaxed back into the abutments, but not in the orginal bearing seats. Jammed between the abutments the mainspan buckled as the 270' long superstructure settled into a space shorter by about four feet.

Repair of the bridge involved returning the superstructure to the original beam seat locations and replacement of damaged stringer and floor beam sections. Additionally, the bridge was upgraded to included a new sway brace system to prevent future superstructure dislocation, and the deck and railing timbers and suspenders were replaced. The field work was completed by Sahale in late spring/early summer, 2001.

Mobilization to this remote site was accomplished using fixed wing aircraft.  Altogether, more than 30,000 pounds of steel, timber, tools and camp equipment was mobilized by air for the bridge reconstruction.  The crew were housed at the Flying B Ranch during their four week stay.