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Project Title & Location
I-90 - Snoqualmie Pass East - Hyak to Keechelus Dam
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Project Description
This project will improve I-90 to provide a safer, more efficient six-lane freeway from Hyak to Keechelus Dam. This project is the first of several projects that will address concerns along I-90 from Hyak to Easton. Tunnels and/or mitigation measures will minimize avalanche closures and hazards due to rockfall. Aging pavement will be replaced to provide a smoother ride. Expanded bridges and culverts will minimize wildlife collisions by providing safer crossings.
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Contractor/Consultant
General Engineering Consultant: URS Corporation - Headquartered in San Francisco, CA
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Recent Progress
Geotechnical analysis and recommendations from 2007 exploration to be completed this quarter. Road alignment is final. Preliminary design complete and foundation recommendations submitted for Gold Creek & Rocky Run bridges. Preliminary design is in progress for the balance of bridges, walls, snowshed, culverts, drainage systems, stormwater treatment best managment practice, guardrail, signing, lighting and landscaping. Initial design is in progress for off-site stormwater mitigation.
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Design Construction Impacts
Road alignments adjusted to minimize cuts into unstable rock at Slide Curve requiring an added retaining wall. Changes to national standards for seismic design critieria resulted in additional analysis and engineering for bridges and walls. Wall design is now to be based on a 1,000 year seismic event, rather than a 500 year event.
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Environmental Impacts / Compliance
SAC concurrence was obtained in Jan. 2008. ESA Biological Assessment was submitted in Jan. 2008. Wetland mitigation is under development, in collaboration with Ecology, Corps of Engineers and other agencies.
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Impacts to Traffic
No impacts to traffic this quarter.
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