Project Info:

Location: Ada County, Idaho

Role: Prime

Owner: Idaho Transportation Department

Client: Idaho Transportation Department

Construction Cost: $12,200,000


  • Stormwater/Pavement Drainage Design
  • Structural Load Rating Analysis
  • Intelligent Transportation System Planning/Design
  • Substructure Design
  • Benefit/Cost Analysis
  • Construction Support Services
  • Superstructure Design
  • Retaining Wall Design
  • Interchange Design
  • Alternatives Development and Analysis
  • Bridge Replacement
  • Specification Development
  • Right of Way Plan Development
  • Maintenance‐of‐Traffic (MOT) Plan Development
  • Shop Drawing Review
  • Accelerated Schedule
  • Structural Design


2021 American Council of Engineering Companies (ACEC) of Idaho First Place Engineering Excellence Award, Structural Systems


Roughly ten miles west of Boise in eastern Ada County, two three‐span, two‐lane bridges carry I‐84 over Blacks Creek Road. Because these bridges were nearing the end of their service life, the Idaho Department of Transportation initiated a project to replace both structures using bridge slides, a first for Idaho’s interstate system. Lochner was lead design engineer and produced all design plans and construction documentation within the eight‐month accelerated design schedule.

Lochner’s design included two new single‐span structures that extended 112 feet. The design also upgraded the loop ramp exiting I‐84 westbound with an added 14‐foot‐wide deceleration lane and reconfigured all on/off ramps to better accommodate the new 80 mile‐per‐hour (MPH) speed on I‐84. Additionally, the Lochner team redesigned Blacks Creek Road to include two 12‐foot‐wide travel lanes and eight‐foot shoulders, providing better level of service for corridor users.

During the design, Lochner prepared temporary falsework plans and developed comprehensive construction staging and maintenance‐of‐traffic plans. Construction required a series of shoulder and lane closures on I‐84 as well as complete nighttime closures with detours. To limit the impacts to I‐84 traffic, paving limits on the interstate were substantially reduced with minimal time given to the contractor.