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Mercer Corridor Project – Where We’ve been and what’s next

The Mercer neighborhood
Whether you’ve attended a concert at Seattle Center, watched the Fourth of July Fireworks around Lake Union, or dined at one of the many area restaurants, you’ve probably traveled along Mercer Street at some point. For more than 40 years, the Mercer Corridor has been a sticky transportation challenge. A priority for SDOT is addressing the needs of all users in the area which includes the 80,000 vehicles using the I-5 interchange daily, in addition to the growing number of pedestrians and bicyclists as people and businesses move into South Lake Union. SDOT is dedicated to keeping people, goods, and services moving on this major corridor in our city. Together with WSDOT’s North Portal project, the two projects will rebuild the street grid across Aurora Ave. N to connect South Lake Union, Uptown, and Seattle Center.

Mercer construction – nearly complete!
In early 2010, SDOT began the first phase of construction, Mercer East, and in August 2012 Mercer St. opened to two-way traffic between I-5 and 9th Ave. N. The next phase of construction, Mercer West, began in 2013, and focused on the corridor between Dexter Ave. N and 5th Ave. W. SDOT is pleased to announce that substantial completion for Mercer West is anticipated to occur later this summer.

In June, final lane striping along Mercer St. was completed and the intersection of Mercer St. and Dexter Ave. N was changed into its final configuration. This means that all turns are now legal – but please be sure to obey the signals to protect other vehicles, pedestrians, and bicyclists! Crews are currently working to complete sidewalks and landscaping along Mercer St. as well as a median between 8th and 9th avenues. The intersection of 5th Ave. N and Thomas St. will also be completed with final striping, crosswalks, and signal timing in August. At this point, Mercer Street and 5th Ave. North will be in their final configurations. This means that all signals, turn lanes, crosswalks, and sidewalks will be open and in their final configurations.

While construction on Mercer Street is nearly complete, the Project will be adding work for WSDOT’s North Portal Area Projects to our contract. The Mercer West Project will install a large storm water detention pipe in Roy Street between Fourth Ave N and Fifth Ave N this fall. This will provide storm water detention to meet code requirements for WSDOT’s North Portal Area Projects. SDOT and WSDOT have coordinated with Seattle Public Utilities and determined that this new facility is the most cost-effective way for WSDOT to meet the storm water detention requirements under the Seattle Municipal Code. It is also the preferred approach for Seattle Public Utilities who will own and maintain the detention system.











Keep in touch

Even though Mercer Corridor construction only has a few months left, we are always happy to answer any and all questions about its construction and your travels through the area. The best way to reach us is via email at or via the 24-hour construction hotline at 206-419-5818. To receive up-to-minute construction updates, visit our website and join our project email list at always, SDOT thanks you for your patience while project construction nears completion.