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US-93 Pahsimeroi River Bridge Replacement

The purpose of the project is to provide an improved and safe crossing of US-93 over Pahsimeroi River.

The Idaho Transportation Department (ITD) is evaluating feasibility of replacing the Pahsimeroi River Bridge on the border of Custer and Lemhi counties in Idaho. The purpose of the project is to provide an improved and safe crossing of US-93 over Pahsimeroi River.

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Why does the bridge need replaced? The existing bridge structure crossing the Pahsimeroi River was built in 1938 and is structurally deficient and requires replacement. The current bridge does not meet current design standards for highways or bridges, and the bridge is showing significant erosion at the abutment and pier spread footings. Additionally, the turning space is inadequate at the existing intersection of US-93 and Pahsimeroi River Road resulting in the need for commercial trucks heading northbound to cross into oncoming US-93 southbound traffic in order to make the turn.

What options have been evaluated? ITD is considering the following three alternatives for the new US-93 bridge: Alternative 1 – Replace the existing bridge in the current location; Alternative 2 – Realign the Pahsimeroi River; and Alternative 3 – A no-build option. Alternative 2 was developed out of a hydraulic risk assessment that investigated four different alignments to address increased safety, avoid impacts to culturally sensitive areas, reduced construction costs and long-term maintenance costs. Alternative 2 considers rerouting the Pahsimeroi River to just south of the post office creating a single bridge on US-93 instead of the two existing crossings.

What happens next? In the coming months, ITD will consult with the Shoshone-Bannock Tribe and conduct several stakeholder interviews to solicit feedback on the three alternatives. ITD will take feedback in to consideration and then select a preferred alternative. ITD will then continue refining the design of the project.

Summer/Fall 2021
Conduct field research including environmental, cultural, and geoarchaeological investigations. Preliminary alternatives evaluations.
Spring/Summer 2022
Develop Hydraulic Risk Assessment Memorandum that evaluates the environmental, archaeological, and cultural risks for each alternative.
Fall/Winter 2022/23
Conduct stakeholder outreach and meetings with individual property owners. Provide public comment period and select preferred alternative.
Spring/Summer 2023
Conduct geotechnical investigation. Develop preliminary/final design. Conduct Environmental Evaluation. Refine Right of Way plans for impacted properties.
Fall 2023-2024
Stake and appraise properties to be acquired.
Tentative Construction (dependent on funding)
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