Projects

SH-21 Lowman Bridge

The old bridge over the South Fork of the Payette River is at the end of its life cycle and is being rebuilt.

SH-21 Lowman Bridge

The old bridge over the South Fork of the Payette River is at the end of its life cycle and is being rebuilt.

Overview

The bridge will be replaced with a new structure designed to blend in to the natural surroundings while safely accommodating vehicle and pedestrian traffic. Construction is currently scheduled for spring through Fall in both 2025 and 2026 with minor additional work in 2027.

Bridge crosses the river

Background

The original late 1800s timber truss bridge at this location was replaced by a new timber truss bridge in 1925. This bridge used a timber crib center pier and two concrete piers, both still in use today, to support the deck. The truss bridge was determined unsafe in 1946 and soon replaced with the existing steel girder bridge.

The new weathering steel girder bridge will feature 11-foot travel lanes and seven-foot shoulders, with red-toned, three-tube galvanized steel railings.

Black and white historical photo of the 1920s bridge
The timber truss bridge from the 1920s

Construction

To protect critical bull trout spawning habitat and avoid winter weather delays, construction will span two seasons.

Construction began in May 2025. Crews reconstructed the roadway adjacent to the bridge followed by demolition of the north half of the current bridge in July. Traffic alternated using one lane of the existing bridge and a traffic signal, while the new north section of bridge was constructed.

Between July and November 2026, traffic will shift to one alternating lane on the new bridge with signal control, while crews demolish the remaining old bridge and construct the south half of the new structure.

The new bridge is scheduled to open to traffic in both directions in Fall 2026. 

Engineering drawing of the typical cross section of the new bridge
The new bridge will have two lanes each 12 feet wide for traffic and shoulders that are 6 feet wide
Engineering drawing showing the side view of the bridge
The new bridge will be 250 feet long and about 10 feet tall

Timeline

Construction will take two years.

  • Spring – Fall 2025

    Crews to reconstruct the roadway adjacent to the bridge and start demolition of the current bridge

  • Spring – November 2026

    Work begins in May. In July crews are scheduled to move traffic to the completed section of the new bridge and demolish the remaining old bridge.

  • Fall 2026

    Both sections of the new bridge complete and two-way traffic returns.

Contact the project team

If you have questions or comments about this project, please contact Bryant Keuchle at bk@langdongroupinc.com or 208-739-3048.

Construction starts

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