|
Project Title & Location
I-90 - Snoqualmie Pass East - Hyak to Keechelus Dam
|
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.
|
|
Contractor/Consultant
General Engineering Consultant: URS Corporation - Headquartered in San Francisco, CA
|
|
Recent Progress
Wall options along Keechelus Lake have been evaluated and design work has begun. Large-scale geotechnical exploration is proceeding. Bridge foundation recommendations are expected this fall. Gravel sampling to assess aggregate quality from the proposed Rocky Run pit site is nearly complete. Design work continues for bridges in the Gold Creek and Rocky Run Creek areas . The use of snow retention fences above the snowshed has been ruled out, although they are still planned at Slide Curve.
|
|
Design Construction Impacts
Geotechnical investigations have confirmed the presence of scarps (tension cracks) upslope of I-90 on Slide Curve. This necessitated redesign of the roadway geometry to minimize the cut into the rock slope below the scarps. An initial redesign has been completed based on a worst case scenario, but final design is pending the outcome of field investigations. Activities associated with the design of structural walls near Slide Curve will be delayed until final design is complete.
|
|
Environmental Impacts / Compliance
Signatory Agency Committee (SAC) concurrence is anticipated by Feb-08. ESA Biological Assessment submitted in Nov-07. FEIS will be completed with ROD on or before scheduled. Wetland mitigation is under review with Ecology and Corps of Engineers.
|
Impacts to Traffic
Lane closures are planned to occur regularly on weekday mornings through October for helicopter support of drilling operations on the slopes above the highway. Limited use of rolling slowdowns can still be expected.
|