Mercer Street on-ramp to northbound I-5 in Seattle closing for back-to-back weekends starting Aug. 18

A map showing the SR 520 and I-5 interchange in Seattle. The portion of I-5 from 520 to Mercer Street is highlighted by an orange line showing the project area.

Travelers in Seattle’s South Lake Union neighborhoods will need to prepare for planned back-to-back weekend closures of the Mercer Street on-ramp to northbound Interstate 5 beginning at 9 p.m. Friday, Aug. 18.

Contractor crews working for the Washington State Department of Transportation will close the on-ramp, which includes the entrance to the I-5 Express Lanes, until 4 a.m. Monday, Aug. 21.

Crews will do some utility and paving work and continue work on new retaining walls between the northbound and southbound ramps.

Detours will be in place during the closure.

The Mercer Street on-ramp to northbound I-5 will close again the following weekend, Aug. 25-28, with the same detour and schedule. The closure begins at 9 p.m. Friday, Aug. 25 and continues until 4 a.m. Monday, Aug. 28.

Construction schedules can change at anytime and any delays or changes to this planned weekend closure will be shared on the project website and on social media.

People can get real-time traffic information from the WSDOT app and learn more by visiting the SR 520 Construction Corner webpage.

People can also call or text the 24-hour hotline at 206-316-2559.

  1. Definitely was not marked as closed as of 8:3 tonight heading from South Lake Union east on Mercer to I-5. Had to do a pretty obnoxious turnaround on I-5. No demarcations until the closure and certainly no detour.

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