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On The Move

Advisories from the Seattle Department of Transportation

Mercer Corridor Project: Weekend closures of southbound SR 99, eastbound Mercer Street, and the I-5 on-ramps at Mercer Street

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The Seattle Department of Transportation (SDOT) advises travelers of the upcoming weekend closures of southbound SR 99, eastbound Mercer Street, and the I-5 on-ramps at Mercer Street during March 21-23 for construction activities associated with the Mercer Corridor Project. These separate closures will accommodate completion of critical Mercer Street widening and SR 99 bridge replacement work and roadway improvements on the I-5 on-ramps.

Closure of southbound SR 99 and eastbound Mercer Street begins at 11 p.m. Friday, March 21

Southbound SR 99 and eastbound Mercer Street will be fully closed to traffic beginning the evening of Friday, March 21 at 11 p.m. for the setting of the SR 99 bridge girders over Mercer Street. During the closure:

  • Southbound SR 99 will be fully closed to traffic between Valley Street and the southern end of the Battery Street Tunnel. Traffic traveling through      Seattle via SR 99 will be directed to I-5 in northern Seattle at 85th Street. More information about alternate routes during construction may be found at: http://www.seattle.gov/transportation/mercercorridor.htm.
  • Eastbound Mercer Street will be fully closed to traffic between Fifth Avenue N and Dexter Avenue N. Traffic heading east towards I-5 from Queen Anne will be detoured to Fifth Avenue N to either Denny Way to access southbound I-5 at Yale Avenue or through downtown on Fifth Avenue N to access northbound or southbound I-5.
  • The sidewalk on Mercer Street will also be closed between Fifth Avenue N and Dexter Avenue N. Pedestrians will be detoured to Broad Street.
  • The I-5 off-ramps at Mercer Street, westbound Mercer Street, and Broad Street will remain open during this work.

Early warning signs will be available in advance of the SR 99 lane restrictions and Mercer Street detours. Travelers can expect significant traffic and delays and should plan ahead and use alternate routes.

Access to Seattle Center from I-5 via westbound Mercer and Broad streets and from southbound SR 99 at Valley Street will be open through the weekend, but travelers should expect delays.

Southbound SR 99 re-opens midday Saturday, March 22; eastbound Mercer Street between Fifth Avenue N and Dexter Avenue N remains closed until approximately 6 p.m. on Saturday, March 22 

After crews complete the setting of the SR 99 bridge girders over Mercer Street, southbound SR 99 will re-open to traffic at approximately 12 p.m. on Saturday, March 22. Eastbound Mercer Street will remain closed between Fifth Avenue N and Dexter Avenue N through approximately 6:00 p.m. on Saturday, March 22

Please note that SR 99 will remain closed south of Denny Way for Alaskan Way Viaduct-related work from 4:30 a.m. through 7 p.m. on Saturday, March 22.

Daytime closures of the I-5 on-ramps at Mercer Street scheduled for Saturday, March 22 and Sunday, March 23 from 8 a.m. to 6 p.m.

The I-5 on-ramps at Mercer Street will be fully closed to traffic on Saturday, March 22 and Sunday, March 23 between the hours of 8 a.m. and 6 p.m. each day. During the closures:

  • Eastbound traffic on Mercer Street will be detoured south on Fairview Avenue N to  either Denny Way for access to southbound I-5 at Yale Avenue, or to Boren Avenue and Olive Way for access to northbound I-5.
  • The I-5 off-ramps at Mercer Street, westbound Mercer Street, and Broad Street will remain open throughout the weekend.
  • The on-ramps will reopen Saturday evening at 6 p.m. and will remain open until Sunday morning at 8 a.m., at which time the on-ramps will close again until work is completed at approximately 6 p.m. Sunday evening.
  • Uniformed police officers will be positioned at various intersections along the detour route to facilitate traffic flow.

Please note that all South Lake Union businesses will remain open and accessible via alternate routes. The on-ramps work is weather dependent and may be rescheduled in the event of inclement weather.

Early warning signs will be available in advance of all detours. More information about alternate routes during construction may be found at: http://www.seattle.gov/transportation/mercercorridor.htm.

Contact:  Richard Sheridan, 206.684.8540