Short Takes: I-15 NOW

September/October 2009

Road to Innovation

I-15 NOW used design-build to save time and money

By J.T. Long

Construction of additional lanes on I-15 in Ogden required demolition and replacement of 24 precast concrete and steel girder bridges. (Photo Courtesy of Granite Construction Inc.)

AGC of Utah members Granite Construction Inc. and Ralph Wadsworth Construction Co. Inc. teamed up to form Weber County Constructors for a design-build project that added new lanes to 9.5 miles of Interstate 15 in booming Ogden.

The joint venture delivered I-15 NOW, a $238-million project that replaced 24 precast-concrete and steel-girder bridges, added two new bridges and embedded an Automated Traffic Management System. The project broke ground in February 2006 and was completed by August 2008, seven weeks ahead of schedule.

“We were able to keep work and traffic flowing with minimal temporary work by working inside out,” says Con Wadsworth, general manager of Draper, Utah-based Wadsworth Construction. Crews began by constructing the additional lanes within the existing median with live traffic flowing on both sides. When that was complete, they directed traffic to the new lanes and began demolition of the old roadway and bridges, with crews following each other up the freeway in stages.

The contractors used stone columns to anchor the overpass of the 24th Street bridge structure as a means of remediating soil-liquefaction-induced settlement. The presence of a retired landfill threatened the stability at a major interchange on 31st Street, which was mitigated by deep dynamic compaction for bridge foundations.

Two bridges over the Weaver River also impacted trout-spawning wetlands, so contractors took fish runs into consideration in designing construction timelines. “We stopped construction during spawning season and prevented silt from flowing into the river,” says Brent DeYoung, UDOT project director.

Despite the roadblocks, the team found ways to save an estimated $5.4 million for the owner by working creatively. Savings included use of thinner pavement sections in passing lanes, elimination of retaining walls in some areas and rubbling concrete pavement as a base-course material.

In one case, engineers coordinated construction of a replacement bridge over a railroad crossing to coincide with improvements to a Union Pacific Railroad project. The strategy created a more direct route for the 12th Street overpass and accommodated a new rail line. Shortening the overpass’s length allowed the contractor to used concrete girders instead of steel reinforcements, which saved money.

To save time on the construction of bridge abutments, contractors used 8-ft x 30-ft concrete panels instead of piecing together standard 8-ft x 5-ft sections. “Handling the panels was a difficult task, but once they were in place, they were welded temporarily to the piling for stability, and the backfill operation could start immediately,” says Abby Albrecht, Granite Construction public affairs manager. “This process saved time on the overall schedule.”

An inside-out construction schedule that had crews working in shifts to minimize road closures delivered the I-15 project seven weeks ahead of time. Cost savings included use of thinner pavement sections in passing lanes, elimination of retaining walls in some areas and rubbling concrete pavement as a base-course material. (Photo Courtesy of Granite Construction Inc.)

In addition to working collaboratively in the field, the team focused on opening lines of communication with the public by creating a Citizen Review Board, staffing a 24-hour hotline, using highway billboards and going to county fairs to let people know about progress and planned road closures. Construction on the urban artery impacted an estimated 90,000 cars daily.

The project won a 2009 Aon Build America award.