SR 99 Puyallup River Bridge Replacement
The Atkinson team will design then demolish and replace the existing bridge (spans F-16A & B and F22) with a new precast concrete girder bridge that is four lanes wide and includes two 5’ bike lanes and two 5’ sidewalks on either side. The new bridge crosses over six sets of railroad tracks and ties into the existing roadway at the intersection of Puyallup St. and Portland St. at the west end and the existing Puyallup River Bridge over the water on the east end. We proposed an undulating weathering steel paraboloid to create a “Gateway to Tacoma” feature that will frame the City when heading west into town, and frame the trees and water of the Puyallup River when heading east. The new gateway structure comprises 17 naturally weathered steel “ribs” that span the width of the bridge span over the railroad mainline, which allows us to seamlessly integrate the railroad safety fence.
We solved the difficult geotechnical soil conditions by designing drilled shaft bridge foundations founded in the underlying glacial till. We eliminated the need for ground improvements by designing three drilled shafts to support the Pier 1 abutment and backfilling the pier with lightweight fill. We planned our construction sequence and access to avoid adjacent wetlands, Puyallup Tribal land, and overhead high voltage power lines—all while maintaining local roads, access to adjacent businesses, and railroad train schedules.
We also eliminated the greatest risk to railroad schedules by developing a reverse launch demolition scheme to remove the existing steel truss bridge over the railroad tracks intact without any railroad mainline closures. We accomplish this by jacking the truss up, installing a launching nose, and skidding the bridge to the west using a combination of Hillman rollers and skid beams. Once the truss is secured atop the existing bridge on the west side of the tracks, we can demolish it in place—safely, away from the tracks. This allows us to reduce the bridge closure duration to 8.9 months—a significant benefit to the community and Port of Tacoma freight mobility.