Twin Bridge study prescribes design, construction ideas

In an effort to incorporate new construction techniques in an ITD project, a Cost Risk Assessment/Value Engineering (CRAVE) study was completed for the reconstruction of the I-84/Snake River Twin Bridges project near Declo.

Four days of brainstorming, developing and compiling of nine project recommendations resulted from the first District 4 value engineering study in more than a decade. The group was composed of both ITD and individuals from the private sector to bring unique perspectives to the study.

“Each person had their strong points and they were brought in to focus on different areas of design and construction,” D-4 project manager Brock Dille said. “The whole idea was to have separation from the design team to bring these new ideas. Some members were there to bring background and continuity, but everyone else had an open mind.”

With consultants from HDR Inc. overseeing the study, the group developed a plan to help not only cut costs but increase the value of the project. The final recommendations had specific focus around the constraints of the project – the nearby Declo Interchange, the on- off-ramps, recreational needs of the river and the river itself.

The recommendations included:

  • Eliminating a full-span third lane
  • Improved accommodations for the on- off-ramps
  • Lowered speeds during construction to allow for safety and keeping interchange open
  • Utilize schedule savings through single contract and contract requirements
  • Optimize design features to maintain recreational clearances
  • Lengthening bridge spans, and
  • Accelerate construction by incorporating precast elements and alternative construction scenarios

Only one recommendation potentially increased costs – lengthening bridge spans – but if all were incorporated there is a potential to save as much as $4 million.

Without the increased bridge spans, savings could reach almost $6 million.

The consultant is compiling information and will produce a final report by the end of April. The D-4 decision team will consider the recommendations when moving forward with planning and design. Construction of the first bridge is scheduled to begin in 2015.

Published 3-23-2012