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.

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. Crews will reconstruct the roadway adjacent to the bridge followed by demolition of the north half of the current bridge in July. Traffic will alternate using one lane of the existing bridge and a traffic signal through November, while the new north section of bridge is constructed.

November 2025 through June 2026, both lanes will be open. Southbound traffic will use the new structure and northbound traffic will use the old structure.

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 for completion 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

  • November 2025 – June 2026

    Work will pause, and both lanes will be open

  • July – November 2026

    Crews to demolish remaining bridge, and new structure to start construction

  • Fall 2026

    Completion

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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