Boeing North Bridge Replacement
This project replaced the 1969 Boeing North Bridge located at the mouth of the Cedar River where it enters Lake Washington. Boeing uses the bridge to tow 737 airplanes—more than 40 per month—from the Renton assembly plant to the flight line at Renton Airport where they are prepared for their first flight. Work included constructing a temporary bridge south of the existing bridge, demolishing the existing bridge, and constructing the new permanent bridge within the original footprint to provide continuous access for plane deliveries and maintain production schedules.
Most of work occurred during the summer salmon spawning in-water work windows between June 1 and August 15 each year—including driving temporary bridge pilings and cofferdam installation. The in-water work also included demolishing the existing bridge piers and approach aprons to below the planned dredge elevation, removing bulkheads, restoring channel grading, installing channel bank armoring, and restoring channel habitat.
The temporary bridge was founded on 24-inch diameter, 90-foot-long steel pipe pile—four each at nine temporary piers—with steel pile caps, steel plate girders, and precast bridge deck. The new permanent bridge was a three-span, 48-foot-wide by 245-foot-long steel plate girder bridge with precast bridge deck and 134-foot main span. Two 6.5-foot diameter, 90-foot-long drilled shafts—two at each intermediate pier (Piers 2 and 3)—and 2-foot diameter 100-foot-long concrete pile—five at each abutment (Piers 1 and 4)—support the bridge. The superstructure also included precast concrete crossbeams, 4-foot diameter columns, LED guidance, and channel lighting.
Atkinson worked with Boeing, the Seattle Airports District office, and the Renton Airport to minimize airport impacts and comply with FAA regulations. This included scheduling work to reduce the duration and frequency of displaced landing thresholds, monitoring airport operations using special aviation radios, and clearing the runway of foreign object debris.