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Project Title & Location
SR 520 W Lake Sammamish Parkway to SR 202 - Redmond
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Project Description
This project will widen State Route 520 to eight lanes between the West Lake Sammamish Parkway Interchange and the State Route 202 Interchange. The widening includes auxiliary lanes, ramps and high occupancy vehicle (HOV) lanes.
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Contractor/Consultant
CH2M-HILL was selected as the prime design consultant for this project (both Stages 3A and 3B). Tri-State Construction has been selected as the prime construction contractor for the Flyover portion (Stage 3A).
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Recent Progress
The construction contract for stage 3A (the flyover ramp) has been awarded to Tri-State Construction. Construction of stage 3A will start in May.
We are working with Region and Headquarter to obtain approval for the Design Decision Package, Deviations, and channelization plans for stage 3B. Revisions are being made to stormwater treatment plan to comply with new City of Redmond codes. This will also feed into the completion of the Biological Assessment (BA) for Stage 3B of the project.
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Design Construction Impacts
The Flyover ramp project will require closure of SR 202 for several nights in the vicinity of SR 520 to set bridge girders across SR 202. A detour agreement have been worked out with the City for these operations.
Stage 3B will require lane closures on SR 520 and ramp closures. The design team is looking into ways to minimize impact to the traveling public during the construction of stage 3B.
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Environmental Impacts / Compliance
WSDOT is working closely with City of Redmond and the MAP Team to provide water quality treatment and detention for the project. The right of way constraints of Bear Creek and Marymoor Park and the low roadway elevations on SR 520 relative to the Sammamish River make other methods to achieve water quality impractical.
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Impacts to Traffic
The construction of the flyover ramp (stage 3A) is starting in May. The will be intermitten lane closure on SR 202. Closure of SR 202 between 11 PM and 4 AM will also be needed to set the flyover bridge girders across SR 202. This work will occur during the summer of 2007.
Mitigation efforts will include a comprehensive public awareness campaign and implementing a detour route.
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