After a delay last month, the Washington State Department of Transportation (WSDOT) has announced that the I-90/SR 18 Interchange Improvements project will reach a major milestone the week of September 9 when the first ramps of the new diverging diamond interchange open to traffic near Snoqualmie.

First up is the SR 18/Snoqualmie Parkway on-ramp to westbound I-90, which will switch to the new ramp configuration overnight Monday, Sept. 9. Next will be the eastbound I-90 off-ramp to SR 18, which will change to the new configuration overnight on Thursday, Sept. 12.

Once the new ramps open at 5 a.m. the following morning, people should remain distraction free and pay attention to the new striping and signs. The new on- and off-ramps are the first pieces of the new diverging diamond interchange to open to traffic. The full interchange is expected to open in early 2025.

Busy Week of Nighttime Work
In addition to the two ramp switches, contractors working for WSDOT will install overhead structures to hold new signs that will help direct drivers through the new interchange. These will be placed above the eastbound and westbound I-90 off-ramps to SR 18 and Snoqualmie Parkway north of I-90.

People traveling through the I-90/SR 18 interchange at night the week of Sept. 9 should expect the following closures:

Overnight Monday, Sept. 9 

• The SR 18/Snoqualmie Parkway on-ramp to westbound I-90 will close from 9 p.m. Monday, Sept. 9, through 5 a.m. Tuesday, Sept. 10, to switch to the new ramps. A signed detour will use eastbound I-90 and loop around to westbound I-90 at Winery Road/North Bend Way (exit 27).
• SR 18 will be reduced to a single lane with flaggers alternating traffic near the I-90 interchange from 9 p.m. Monday, Sept. 9, through 5 a.m. Tuesday, Sept. 10, to unload and set up a concrete barrier.

Overnight Tuesday, Sept. 10 

• The westbound I-90 off-ramp to SR 18/Snoqualmie Parkway will close from 9 to 11:59 p.m. Tuesday, Sept. 10, to install an overhead sign structure. A signed detour will continue on westbound I-90, loop around at Preston/Fall City (exit 22) and use the eastbound I-90 off-ramp to SR 18.
• Snoqualmie Parkway will be reduced to a single lane with flaggers alternating traffic from 12:01 to 5 a.m. Wednesday, Sept. 11, to install an overhead sign structure. All northbound and southbound lanes will close intermittently for 15 minutes as the structure is lifted into position.

Overnight Wednesday, Sept. 11 

• The eastbound I-90 off-ramp to SR 18/Snoqualmie Parkway will close from 9 p.m. to 11:59 p.m. Wednesday, Sept. 11, to install an overhead sign structure. A signed detour will continue on eastbound I-90, loop around to westbound I-90 at Winery Road/North Bend Way (exit 27) and use the westbound I-90 off-ramp to SR 18.
• The SR 18 on-ramp to eastbound I-90 will close from 12:01 to 5 a.m. Thursday, Sept. 12, to remove light poles. A signed detour will use westbound I-90 and loop around to eastbound I-90 at Preston/Fall City (exit 22).

Overnight Thursday, Sept. 12

• The eastbound I-90 off-ramp to SR 18/Snoqualmie Parkway will close from 9 p.m. Thursday, Sept. 12, to 5 a.m. Friday, Sept. 13, to switch to the new ramp. A signed detour will use westbound I-90 and loop around to eastbound I-90 at Preston/Fall City (exit 22).

Real-time travel information is available via the WSDOT mobile app, the WSDOT Travel Center map or by signing up for WSDOT's email updates.