The widening of Interstate 5 through downtown Tacoma required the removal of three overpasses near the Tacoma Dome. Two of the bridges are being rebuilt: Yakima Avenue and Delin Street.
Stage 1: Building the bridge supports on each end of the freeway requires three primary steps.
Step 1:
Crews use an excavator to dig deep trenches before building the footings and abutment wall for the new Yakima Avenue Bridge.
Step 2:
Next, the footings are installed.
Step 3:
Abutment walls are constructed.
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Stage 2: Inserting the casings
Crews use a vibratory hammer to drive a 10-foot- diameter casing into the ground. A crane is used to place the vibratory hammer on the top of the casing. The casings serve as a ground-stabilizing force. Once the casings are in the ground, crews will dig a shaft, insert a shaft cage, then pour concrete into the shaft. The shafts are the foundation for the columns that are the center supports for the two new bridges. Each bridge gets four center columns.
After the casings are pushed underground, crews will hollow out a shaft before inserting a shaft cage, a cylindrical cage that will serve as the skeletal system for the subsurface concrete column. A similar cage, called a column cage, will serve the same purpose - only above ground.
Stage 3: Footings, Columns and Abutment Walls
Crews pour the concrete footings for the new Yakima Avenue bridge abutment wall. More than 300 yards of concrete will be used to build the wall.
Wooden form for Yakima abutment wall. An abutment wall supports the bridge deck.
Column cages for the Yakima Avenue bridge are now in place. Each of the two new bridges will supported in the center by four columns.
The first concrete column is complete. A crane is used to lift the form off the finished column.
Phase 3 - Girder Setting
A 300-ton hydraulic crane lifts steel girders into place for the new Yakima Ave overpass. Each bridge will be built with 12 girders. Individual girders weigh as much as 75 tons and are as long as 159 feet. Watch time-lapse video of girder-setting.
Crews weave 4-by-6 carrier beams and stringers across the bridge girders before laying out the plywood sheets that serve as the floor for the concrete deck.
Installing the green epoxy-coated re-bar is one of the final steps before the decks are paved.
On Nov. 20, 2007, crews began paving the deck of the new Yakima Avenue overpass. The yellow machine in the background is a Bidwell finisher, which is used to create a smooth, consistent surface.
The new Yakima Avenue overpass (left) opened to traffic on Feb. 29, 2008. The Delin Street overpass (right) opened March 17, 2008, following a ribbon-cutting ceremony.
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