I-90 - Eastgate to SR 900 - Corridor Improvements

Project news

  • Beginning mid-July, crews working for WSDOT will close the eastbound lane of NW Sammamish Road for 90 continuous days. Westbound lanes will be open for one-way local access only.  This closure will allow crews to build noise walls between the interstate and NW Sammamish Rd. 
  • As of May 7, 2020, this project has resumed as part of the governor's "Safe Start Washington" (pdf 502 kb) recovery plan. Contractor crews will adhere to a list of 30 safety protocols (pdf 138 kb) and will be required to have site specific safety plans and regular pre-activity meetings to ensure compliance with these standards. 
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Over the next two years, WSDOT contractor crews will add capacity on both directions of I-90 between the Eastgate and West Lake Sammamish Parkway interchanges, by restriping the existing roadway and creating auxiliary lanes. Crews will also build sound walls in strategic locations within the project area to minimize traffic noise.

What's an auxiliary lane?
An auxiliary lane is a supplemental or extra lane that’s added between closely spaced interchanges. They are frequently used to give drivers more time to safely enter or exit the highway, depending on if they need to merge over, speed up or slow down. These new lanes will be located on the outside of the existing lanes in both directions of I-90, adding capacity and accessibility to all travelers 24 hours a day, seven days a week.

Auxiliary lane diagram for the I-90 Eastgate to SR 900 Corridor Improvements project.

Work details

Travelers should plan ahead for the following throughout this two-year project:

  • Overnight lane and ramp closures between the hours of 8 p.m. and 5 a.m.
  • Single lane closures during daytime hours.
  • Around-the-clock shoulder closures.
  • Narrowed and shifted lanes on both directions of I-90.

Temporary I-90 traffic changes
Before the new auxiliary lanes can be added, contractor crews have to reinforce catch basins, drainage pipes and utility covers along the shoulders so they can withstand the weight of everyday traffic. To safely perform this work, crews will temporarily restripe both directions of I-90 and shift traffic so they can install concrete barriers.

Travelers should expect a lane shift to the right between 150th Avenue Southeast near Eastgate and State Route 900 in Issaquah starting on Monday, Aug. 5, while crews work in the center median. Once the median work is finished, the contractor will restripe the lanes and shift traffic to the left to complete work along the right shoulder. This second shift is currently scheduled to begin in spring 2020, weather-dependent.


  • 2016 - 2019: Design phase.
  • March 2019: Project was advertised for competitive bidding.
  • May 2019: Project was awarded to Atkinson Construction, LLC.
  • August 2019: Construction began.
  • Nov. 25, 2019 - Spring 2020: Project in winter suspension.
  • Fall 2021: Construction is scheduled to be complete.


Financial Data for PIN 109052P
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $0
CWA $73,035
Total $73,035


Jordan Longacre
WSDOT Communications


Map for the I-90 Eastgate to SR 900 Corridor Improvements project.