Major construction for the Interstate 90/State Route 18 interchange improvement project will begin in late spring.

Residents traveling near the I-90 and SR 18 interchange should plan for increased congestion in the coming weeks as contractor crews install work zone signs and clear trees throughout the project area.

The project will build a new diverging diamond interchange. According to the Washington State Department of Transportation, this will improve traffic flow and safety for residents who use this busy corridor.

Improvements to SR 18 include widening the highway to two lanes in each direction from the interchange to about two miles south.

Additionally, crews will build three new bridges to improve habitat for native fish species and area wildlife. The project is expected to be complete in 2025.

Crews will continue to clear trees along SR 18 through March to make room to widen the highway. When construction is finished, they will plant 14,000 new trees in the project area and 3,040 trees along I-90 between Issaquah and North Bend.

At least 382 of the felled trees will remain onsite and will be used to improve fish and wildlife habitat. Six culverts that are now barriers to fish passage will be removed, opening up access to 13 miles of fish habitat that is essential for salmon and steelhead.

A separate project still in design will finish widening SR 18 where the last project left off, creating two lanes in each direction to Issaquah-Hobart Road. Crews are conducting drilling along SR 18 as well to collect information for the design process. This project could begin as early as 2025.

From 5 a.m. Monday, Feb. 13, through 5 a.m. Thursday, Feb. 16, crews will close the truck climbing lane just two miles south of the interchange on westbound SR 18 to clear trees for highway widening