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Aging Snake River Bridge Replaced in Wyoming

Thu December 30, 2010 - West Edition
Mary Reed


Rock excavation begins for the newbridge’s footing.
Rock excavation begins for the newbridge’s footing.
Rock excavation begins for the newbridge’s footing. A Kobelco 2500 crane sets the precast anchor blocks into place. A Kobelco 2500 crane unloads precast anchor blocks. New bridge footing reinforcements begin to take form on the bank of the Snake River.

Wadsworth Brothers Construction Company Inc., of Draper, Utah, is acting as general contractor for a $25 million project to replace an aging bridge on Wyoming’s Snake River, southwest of Hoback Junction, near the confluence of the Hoback and Snake Rivers.

The existing steel and concrete bridge was built in the 1950s and is not only in an area vulnerable to landslides but also does not meet current seismic standards in an area known to have earthquakes. In addition, the bridge is exhibiting serious signs of deterioration, exacerbated by increased use as residents of nearby Jackson move out into dormitory communities, precipitating a rise in commuter traffic.

The Snake River project, work on which began in June 2010, involves reconstruction of Hoback Junction Bridge as well as a retaining wall, landslide stabilization, a roundabout at the intersection of U.S. Routes 189-191 and 26-89, roadway, pathways, a bus shelter and a park-and-ride lot.

The steel girder arch span will be 780 ft. (237.7 m) long downstream from, and parallel to, the existing bridge, which will continue to carry traffic until its replacement is completed. The new bridge will feature safety shoulders, three lanes, and a separate pathway for bikes and pedestrians. It also will be fitted with a webcam so drivers can view road conditions both during construction and when the bridge is in use.

“We are currently performing landslide stabilization activities. It is crucial to stabilize the slope before we move forward with the structures. The hillside is very unstable; the road has been lost to a landslide before,” Wadsworth Brothers’ Project Manager Shawn Hadfield said in December.

“We are literally holding the mountain back by installing 111 45,000-lb. concrete blocks along the face of the slope. These 10-foot by 10-foot by 3-foot blocks are being tied into the underlying bedrock with a series of 100 to 120 foot long steel anchors.”

“We have poured two skewback footings on the opposite side of the river. These will be utilized for the installation of the new arch bridge that will be erected next summer,” he went on, “and we are also working on some repairs to the existing bridge so that it can function adequately until the new bridge is completed.”

With five to 10 Wadsworth employees on the job, equipment in use on site includes Kobelco 300 and Caterpillar 365 excavators as well as a Kobelco 2500 crawler crane and a Grove 80-ton (72.5 t) RT crane, along with Klemm and Hutte drill rigs.

By early December the company had installed half of the anchor blocks and excavated and poured two of the four skewback footings. The majority of the bridge structure will be done next year.

Work still to be completed includes all the roadwork, installation of a complex retaining wall system, placing sidewalks and pathways, construction of the park-and-ride lot, and demolition of the existing bridge.

The project has not been without challenges.

“The gravel/rock/soil layers combined in such a way that difficulties were encountered during the drilling operations. As a result, we lost a substantial amount of casing. drill bits, etc. in the hillside,” Hadfield recalled. “Specialized tooling was secured, various equipment and techniques were utilized, and specialists consulted in order to come to a workable solution to the problems.”

He went on to praise the company’s subcontractors for their flexibility and willingness to increase personnel, bring in additional equipment, and work an additional shift to complete the job.

Despite these difficulties, the project is on schedule for completion in October 2012.

Wadsworth’s subcontractors for this job include Schnabel Foundation Company of Aurora, Colo., (ground anchors), Kilroy LLC of Afton, Wyo., (excavation), and Evans Construction Company of Jackson, Wyo. (asphalt paving and concrete supplier)

Another company project, the mammoth 392-ft. (119.4 m) Hurricane Arch Bridge spanning the Virgin River near Hurricane, Utah, is very similar to the Hoback Junction Bridge. The former was the first steel arch bridge to be constructed in Utah since 1985 and a particularly challenging project for the company.

This new structure included the complete renovation of the existing steel arch bridge originally constructed back in 1937 and providing the only access across the Virgin River between the towns of LaVerkin and Hurricane, necessitating continued traffic and utilities across the existing structure while the new bridge was constructed.

Construction of arch bridges of large canyons is as challenging as bridge construction gets and for the Virgin River job the sides of the canyon walls were first pre-split and blasted in order to excavate a place for the footings.

Once the anchor bolts were installed and the footings poured, Wadsworth Brothers then had to provide access for the huge cranes required to erect the bridge.

In order to support the arch until assembly was completed, tie-back towers were installed behind the abutments, and these towers were guyed to rock anchors drilled into the sandstone behind them. The bridge was then erected from each side and supported from the towers with large steel cables.

The towers were hinged at the base to allow longitudinal rotation with temperature fluctuations. The pennant cable that supported the arch segments from the tie-back towers were attached with load cells and reverse frame jacks which could monitor and adjust the individual loads to within 500 lbs. (226.7 kg)

Once the steel bridge was erected, the challenge then was forming and pouring a concrete deck 120 ft. (36.5 m) in the air above the river. Every aspect of this project was difficult and dangerous and required equipment and techniques seldom used in ordinary bridge construction.

In the final stages, the renovation of the existing structure required Wadsworth to remove the original lead point paint and reinforce existing columns and cross braces by welding additional structural steel members in place. The company determined that this work could be done more effectively by disassembling the existing steel bridge down to the arches, flying each piece up to a temporary shop on the canyon bank, and performing this work on the ground rather than in the air.

Wadsworth Brothers and its team members were able to overcome each of the challenges and successfully complete one of the most difficult and aesthetically renowned bridges in the state without any injuries, accidents, or lost time. The Virgin River bridge received the Engineering Challenge Award at the 2004 UDOT Engineer’s Conference, as well as Best Heavy Project and Best Steel Project in the Best of 2005 awards from Intermountain Contractor.

Wadsworth Brothers Construction Company Inc., has won a number of other awards, including being honored by the Utah Department of Transportation (UDOT) for the 2009 Rural Construction Project of the Year, recognizing replacement of four bridge decks in 16 hours a piece using self-propelled modular transports, as well as UDOT’s 2009 Urban Construction Project of the Year for work on the Southern Parkway Project. The latter also earned the company and UDOT a joint award for the 2009 Best Partnered Project of the Year from the Associated General Contractors of Utah (AGCU).

The AGCU also presented Wadsworth Brothers with their 2009 Bridge Construction Project of the Year Award for the I-84 Weber Canyon Road Asphalt Pavement Rehabilitation Project, a pre-cast full deck panel job carried out in a narrow canyon with limited access.

Founded in 1990, Wadsworth Brothers Construction is a heavy-highway and building contractor based in Draper, Utah. The Heavy-Highway Division, the historic base of the company, focuses on traditional projects such as bridges and overpasses.

The company has completed several very high profile projects such as the 2002 Legacy Bridge at the University of Utah and the “Lego” bridges on east I-215. Today the highway division has also branched into concrete paving, water tanks, pile-driving and steel erection.