Engineer warns of rot, recommends posting and temporary decking for Knockley Bridge

Adam, a consulting engineer who called into the meeting, told Treasure County commissioners the Knockley Bridge shows significant end-rot and "crushed bearings" on several girders that are signs of progressive deterioration. He said the observed condition (about eight of 14 girders exhibiting crushing at the bearing) can lead to sudden splitting failures and advised the county to limit heavy loads on the span.

"The girders, they're crushing their bearings," Adam said, noting that "a crushed bearing is usually a red flag of deterioration" and that these failures "can lead to other issues." He recommended installing long, threaded screws at the beam ends as an interim strengthening measure and said, based on his limited field checks, the span could be posted for roughly 4 tons if that work and monitoring are implemented.

Commissioners discussed low-cost temporary options, including setting two railroad boxcars or flatcars across the existing abutments as a temporary superstructure and adding a moisture barrier to protect anything in contact with saturated soil. Adam cautioned that the county lacks definitive internal testing of the beams and that the screws are intended both to strengthen the ends and to help gauge how deep rot extends into the timber.

"I initially was sitting back there going, man, my recommendation is to be, like, ultimately, I think we should probably close this bridge," Adam said, adding that after running numbers he believed a 5-to-10 ton posting might be defensible but that the county must decide its acceptable risk level.

The board directed staff to pursue immediate measures to reduce heavy loads using signage and community outreach, to investigate sourcing usable boxcars or steel beams, and to report back with procurement options and cost estimates. Commissioners suggested staff be authorized to search for available railcars and to return with recommendations rather than wait on lengthy state schedules.

Provenance: topicintro SEG 1456, topfinish SEG 1927.