Eagle Road Bridge Replacement

The Eagle Road Bridge Replacement project replaced an existing single-span, two-lane bridge that was nearing the end of its service life. The new bridge spans 45 feet and includes two 11-foot-wide travel lanes, a future center turn-lane, two five-foot-wide bicycle lanes, and two seven-foot-wide sidewalks, in addition to curbs, gutters, and parapets. The new bridge was designed using Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) technology, only the second bridge in Idaho to use this technology. By utilizing GRS-IBS for the Eagle Road Bridge, Lochner shortened the construction time to three months.

GRS-IBS bridge design and construction provides an innovative, economical, and accelerated way to construct bridge abutments using local contractors, commonly available materials, and ordinary construction equipment. GRS-IBS structures accommodate a variety of different superstructure types, offering a proven alternative to deep foundations on loose granular soils. In addition, GRS abutments are less costly than conventional reinforced concrete abutments, take less time to construct, and reduce maintenance costs by eliminating joints at the bridge ends. The reduced construction schedule translates into less exposure around work zones, ultimately improving safety.

In addition to structural design, Lochner developed a maintenance-of traffic (MOT) plan that involved closing Eagle Road. By closing the roadway, construction was accelerated and the road was open to traffic within 90 calendar days. Lochner also assisted the Ada County Highway District (ACHD) in completing the right of way acquisition from four adjacent property owners. Lochner’s design incorporated driveway changes and field access approaches to aid the land owners in the acquisition process.

Eagle Road Bridge crosses Dry Creek, a FEMA flood zone. To satisfy the requirements for the “no-rise” certificate from the Flood Plan administrator, Lochner completed the hydraulic analysis for the bridge to determine the scour design that would protect the GRS abutments. Lochner prepared the Idaho Department of Water Resources Stream Alteration Permit and the Corps of Engineers 404 Permit, and assessed the project for impacts to wetlands, waters of the US, and cultural resources.

Lochner worked closely with ACHD and property owners to ensure that various construction activities would not impact the traveling public, adjacent property owners, and Dry Creek operators. Lochner communicated frequently with ACHD Public Involvement staff to provide updates on project process.