Bridge Description

The third stage of this project was a lateral slide over a weekend to connect the north and south sides of Oak Creek Canyon, visited by an estimated two million tourists each year.

On US 89A at milepost 381.32 south of the city of Flagstaff

Tier 2 (within 3 days)

ABC: Weekend closure

Conventional: Four months of traffic impacts

Reduced traffic impacts; minimized environmental impacts

190-ft long and 41.17-ft wide single-span post-tensioned concrete box girder bridge slide-in

50000

Traffic management alternative, if constructed conventionally: 80-mile detour

The existing 23.33-ft-wide steel deck truss bridge had two 10-ft-wide lanes. It connected the north and south side of Oak Creek Canyon. Built in 1933, the 20-ft-wide bridge was too narrow to safely accommodate current traffic needs and had to be replaced.

The two-lane replacement bridge has two 4-ft-wide shoulders and a 5-ft-wide sidewalk. The cross-section consists of two 11-ft-wide post-tensioned concrete box girder cells that vary in depth from 8.5 ft to 16.0 ft, with a 9-inch-thick deck that cantilevers approximately 9.5 ft on each side. It was designed to resemble the old Luten Arch bridge with the use of architectural effects and rock wall facing on the new abutments. In order to avoid closing the highway and forcing motorists on an excessively long detour, ADOT drew on a design from the past and coupled it with an innovative technology from today. The result was a permanent concrete bridge that was built at one location and moved laterally into place.

The project was done in three phases. Stage one called for keeping traffic on the old bridge, excavation, removing the existing southwest wing wall and replacing with temporary shoring. Also, new abutments were built about three feet west of the existing bridge and the new box girder superstructure was built along with a new northwest retaining wall. In stage two, traffic was detoured onto the new bridge while the existing southeast retaining wall and wingwall and the old bridge were demolished. All debris was contained and none was allowed to fall into the creek. Sections of the approach slab were also built in stage two.

Stage three involved moving the new bridge laterally 26.33 ft into position using bearings coated with Teflon, finishing the approaches, and demolishing the temporary abutments.