I-84 ITD Highway Improvements

I-84 is the primary east-west route through southern Idaho and a major freight route—making it an important resource to the state’s economy. Congestion is already an issue along the busy stretch of interstate between Caldwell and Boise, and Canyon County is expected to continue its rapid growth. The Idaho Transportation Department (ITD) has invested more than $500 million in improvements to the interstate over the past decade just to make sure the region’s transportation infrastructure can keep up.

As geotechnical subconsultant to Parametrix and David Evans and Associates for several phases of this work for ITD, GeoEngineers planned and oversaw the geotechnical investigation, analyzed groundwater infiltration and mounding, tested for lead and asbestos contamination and delivered recommendations for bridges, culverts, retaining walls and reinforced soil slopes. Improvements included two expanded travel lanes along with new ramps bridges and other structures along I-84 between Caldwell and Nampa.

Approach

• Fast-Paced Schedule: ITD’s schedule was the number one challenge for GeoEngineers’ team. The design team had 8 months to develop a final package of plans, specifications and estimates for the initial phase, leaving just two months to complete the initial geotechnical scope. To meet these deadlines, our field team completed necessary geotechnical investigations in just 6 weeks to keep things moving. To meet this aggressive deadline, GeoEngineers organized five drilling crews, streamlined the design schedule and (safely) scheduled work during night shifts to reduce impact to travelers. More than 70 GeoEngineers staff completed 350 explorations and worked more than 6,800 hours, most them night shifts, to finish the geotechnical investigation in time.
• Traffic Management: Traffic control was critical to safely working along busy I-84. GeoEngineers identified a highly qualified Disadvantaged Business Enterprise (DBE) traffic control subcontractor to keep workers and the public safe while GeoEngineers performed services next to active travel lanes.
• Cost Savings Through Pile Setup Testing: The team took every opportunity to think about the project from ITD’s perspective. During the design phase, GeoEngineers’ experts were also interested in taking advantage of potential pile setup (progressively increasing resistance after installation), which could result in construction cost savings. GeoEngineers installed two test piles during design and performed PDA testing and CAPWAP analysis. The team used this additional data to select the most appropriate type of pile, more accurately estimate the pile setup factor, and optimize the design. The tests showed a pile setup factor of two times the side resistance from initial drive, which meant significantly higher pile capacity. Higher capacity meant fewer piles could do the same job, saving ITD construction costs.
• Pavement Design Recommendations: The GeoEngineers team also stepped up their pavement design recommendations by using AASHTOWare Pavement ME software—a more sophisticated way to analyze the performance of rigid concrete pavement and completing lifecycle cost analysis for paving alternatives.
• Value Engineering Approach: Always looking for opportunities to improve efficiency and performance, the design team and ITD held a value engineering (VE) session to seek additional professional opinions. For a fresh perspective, the team looked to in-house experts from their own firms who had no previous involvement with the project, including a senior GeoEngineers employee who attended the VE session and worked closely with other diverse experts to provide an “outsiders” review on the design.

Results

The completed I-84 improvements are giving the greater Boise community a robust interstate corridor. GeoEngineers was able to reduce costs for ITD and the taxpaying public by thinking creatively and always looking at the project from the client’s point of view. The success of these I-84 projects has allowed ITD to start tackling additional infrastructure problems in the growing Boise community.