Work on two major roadways, including Interstate 90, is expected to have a ripple effect for traffic on both sides of Lake Washington starting next Friday, March 27, and continuing until Monday morning, March 30.

Drivers heading across Lake Washington from the Eastside will see westbound Interstate 90 detoured to the express lanes as crews upgrade tunnel operations systems inside the westbound Mount Baker and Mercer Island tunnels.

In addition, in Seattle, the State Route 99 Alaskan Way Viaduct will be closed during daylight hours Saturday and Sunday for a semiannual inspection. Contractor crews working on the SR 99 Tunnel Project, the Mercer Corridor Project and Seattle Public Utilities (SPU) will take advantage of the closure to complete utility and sign bridge installation work.

Westbound I-90 detour info

11 p.m. Friday, March 27, until 5 a.m. Monday, March 30

Contractor crews will shift all westbound I-90 traffic between Bellevue Way and Rainier Avenue South to the express lanes from 11 p.m. Friday to 5 a.m. Monday.

Drivers wishing to access Mercer Island will need to exit westbound I-90 at East Mercer Way. There are no westbound exits to Mercer Island from the express lanes.

Those wishing to travel from Mercer Island to Seattle should enter the express lanes at 77th Avenue Southeast or Island Crest Way.

Westbound I-90 drivers will be unable to exit to Rainier Avenue South and should follow the signed detour via Fourth Avenue South and South Dearborn Street.

Drivers needing to transport flammable materials westbound across Lake Washington must use alternate routes such as Interstate 405 or state routes 520 or 522.

SR 99 closure details

7 p.m. Friday, March 27, until 5 a.m. Monday, March 30

SPU crews will close two northbound lanes and one southbound lane of SR 99 between Ward Street and Highland Drive from 7 p.m. Friday to 5 a.m. Monday.

WSDOT and SDOT contractor crews will close SR 99 between the Battery Street Tunnel and Valley Street from 10 p.m. Friday to 5 a.m. Monday.

6 a.m. to 6 p.m. on Saturday, March 28

WSDOT crews will close lanes on the SR 99 Aurora Bridge for maintenance work. Crews will close up to two lanes in either the northbound or southbound direction from 6 a.m. to 6 p.m. on Saturday, March 28.

6 a.m. to 6 p.m. Saturday, March 28, and Sunday, March 29

WSDOT bridge inspection crews will conduct a scheduled inspection of the Alaskan Way Viaduct between Spokane Street and the Battery Street Tunnel.