A significant amount of construction continues at the SR 99 tunnel’s future north portal. The 80-foot-deep pit is where Bertha, the SR 99 tunneling machine, will emerge at the end of her two-mile journey beneath downtown Seattle.
Crews are also building the connection between the tunnel and Aurora Avenue North, and new on- and off-ramps at Republican Street. Our interactive simulation shows you how this area will change during construction.
When construction is complete, drivers, pedestrians and bicyclists will be able to travel between South Lake Union and Seattle Center via three improved east-west streets across the new Aurora Avenue North.
Long-term traffic impacts on SR 99: Lane closures begin March 7 through late-May
Beginning as soon as March 7, crews building the future north portal of the SR 99 tunnel will close a single lane in both directions of SR 99/Aurora Avenue North between Valley Street and the Aurora Bridge. Two lanes will be open in each direction while crews install foundations for four large sign structures in the median and curb areas.
Closure details and schedule
Phase 1 (approximately 8 weeks): one lane closed in both directions for median work
- One lane in the northbound and southbound directions will be closed around-the-clock while crews install four sign foundations in the median
Phase 2 (approximately 4 weeks): one lane closed in southbound direction for curb work
One southbound lane will be closed around-the-clock while crews install two sign foundations in the southbound curb area
WSDOT understands that these closures will be inconvenient for those who use SR 99 on a regular basis. As such, this work is being completed in winter and early spring to take advantage of typically lower traffic volumes and to avoid conflicts with the recent football season and upcoming major summer events.
Construction schedules are inherently unpredictable due to weather and other factors. Durations shown for each phase are approximate and may change. We will keep the public informed as we prepare for Phase 2 work.
Bus rider information
Because northbound and southbound buses will travel – and stop – in the outside lanes with other vehicle traffic, trips may take longer than normal. During both phases the southbound bus-only lane restriction will be lifted.
Nighttime and weekend work
In an effort to balance the needs of drivers and residents, some work will occur during nighttime and weekend hours. An additional lane may close at night and during some weekend days.
The long-term lane closures are expected to cause additional backups on SR 99 for vehicles and buses, particularly during peak commute times. WSDOT is encouraging drivers and bus riders to:
- Allow plenty of extra time and expect additional congestion, especially during peak commute times, on SR 99 between the Aurora Bridge and downtown.
- If possible, consider leaving early, delaying your trip or telecommuting to avoid traveling during peak commute times in the morning and afternoon.
- If you must drive, know before you go and use WSDOT's travel tools or visit SDOT’s travelers information page.
Current construction near Dexter Avenue North
To make room for SR 99 tunnel construction, crews are relocating utilities along Dexter Avenue North and Republican Street.
During this work, Dexter Avenue North will be reduced to one lane in each direction between Harrison and Mercer streets.
Other construction in the area
As you've likely noticed, the north end is bustling with construction activity. In addition to tunnel construction, our partners at the City of Seattle are making great progress on the Mercer Corridor Project. We’re coordinating closely with their construction, and will continue to do so as we move forward.