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May 31, 2018
Interstate 405 shoulder/toll-lane improvements
Location: King and Snohomish counties
General contractor: Graham Contracting
Owner/developer: Washington State Department of Transportation
Primary designer: David Evans and Associates
The Interstate 405 northbound shoulder lane design-build project constructed a new peak-use shoulder lane for additional traffic capacity.
This new capacity accommodates larger traffic volumes entering I-405 from state Route 527 and reduces congestion near the state Route 522 interchange. Additional scope included a 1,700-foot-long noise wall, modification of toll-rate signs at Northeast Sixth Street, striping and signal work at the Northeast 128th Street overpass, a merge lane between Northeast 195th Street and SR 527, and toll lane markings between Bellevue and Interstate 5 in both directions of I-405.
To achieve project goals set by the Washington State Department of Transportation and open the shoulder lane to traffic within a 120-day schedule, Graham developed an innovative maintenance-of-traffic strategy, negotiated an exclusive agreement with a key subcontractor, and partnered with WSDOT to verify the quality of completed work at end of each shift.
The construction of the 1.8-mile peak-use shoulder lane required a 3-foot shift of all existing I-405 northbound lanes toward the median. To minimize impacts to the tolling operation, WSDOT required all the work for this lane shift to be completed in one weekend. Also, the existing shoulder and rumble strip had to be demolished and repaved.
Graham's maintenance-of-traffic strategy involved re-striping the existing lanes and widening the right shoulder by 1 foot. This innovation created the necessary space to accommodate the peak-use shoulder lane.