This project replaced 832 feet of the west end of this 1902 rail bridge, BNSF’s only east-west crossing from Seattle to Chicago. The new structure was built on the same alignment as the existing track. This required all work activities that had the potential of “fouling” the track to be performed during “train free” windows, which was based on each day’s track schedule. Construction began with AAC installing a temporary sheet pile bulkhead and work trestle. The trestle was key to the success of the project by creating access to the full length of the project and staging for construction materials. To accommodate the demanding schedule AAC worked double shifts during the summer months. The new structure consisted of 16 each bridge piers constructed from 6 each 24-inch x 155-foot closed ended pipe piling. The piling had reinforcing steel placed in them followed by concrete. Precast concrete pier caps were delivered to the project, removed from rail cars and set on modular barges for later installation. The new bridge came into service when AAC worked jointly with BNSF crews to remove existing spans and install new. All removal and installation, including installing new structural steel spans, rail, ballast and aligning the track, was completed within six hours. The completed 832 feet of bridge was in service within three months of beginning work onsite.
Once the new structure was in service AAC began removal of the existing concrete bridge piers. AAC used diamond wire saws to section the piers for hoisting and removal. All removal work was completed without any delay to train traffic utilizing a custom lift barge with hydraulic jacking frame. Permitting required for piers to be removed at the lake bed; therefore divers were needed to assist the wire saw operators, which was all self performed by AAC crews.