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Seattle City Light Continues Support for SR 530 Slide Communities with Detour Access

Seattle City Light continues its support for the communities affected by the SR 530 landslide by allowing drivers to use the utility's access road as an occasional detour while WSDOT rebuilds the highway.

Seattle City Light continues its support for the communities affected by the SR 530 landslide by allowing drivers to use the utility’s access road as an occasional detour while WSDOT rebuilds the highway.

Some upcoming construction work will require use of the detour. Below is WSDOT’s announcement.


Midweek detours from SR 530 near Oso to start in August
Traffic will return to the Seattle City Light access road on a one-way, piloted basis 9 p.m. Tuesdays through 4 a.m. Thursdays

OSO – Drivers traveling through the section of State Route 530 near the site of this spring’s tragic landslide should allow extra time for their trips on certain midweek dates during August.

Contractor crews from Guy F. Atkinson Construction have been making progress since June on building the new, elevated SR 530 just south of the existing roadway. To advance to the next phases of construction they will need to divert traffic from the existing roadway for 31-hour periods each week in August.

During those times, traffic will return on a one-way, piloted basis to a neighboring single-lane gravel road, known as the Seattle City Light access road. Pilot cars will escort westbound traffic at the top of the hour and eastbound traffic on the half hour, around the clock. Drivers are encouraged to arrive early.

“The detours for this project are scheduled during the middle of the week to minimize traffic impacts to the community, and avoid conflicts with major summer events,” said Washington State Department of Transportation Regional Administrator Lorena Eng. “We appreciate the continuing patience and support from the communities of Arlington, Oso and Darrington, as well as their many visitors this summer.”

Detour details

The first set of detours to the Seattle City Light access road are currently scheduled for:

  • 9 p.m. Tuesday, August 12 to 4 a.m. Thursday, August 14
  • 9 p.m. Tuesday, August 19 to 4 a.m. Thursday, August 21
  • 9 p.m. Tuesday, August 26 to 4 a.m. Thursday, August 28 (contingency date if needed)

The detours are subject to cancellation based on construction progress. During these detours, crews will install two new culverts under the roadway for improved fish passage and complete paving, guardrail and restriping work to connect the new, elevated eastern section of the roadway with the existing SR 530.

At all other times during August, traffic will continue to operate on a two-way basis on the existing SR 530. Drivers should continue to add about 10 minutes to their trips, as they will experience intermittent flagging 6 a.m. to 6 p.m. Monday through Saturday to allow safe movement of construction vehicles and equipment.

WSDOT will announce any detour schedule changes in advance through a variety of means, including the project website, the SR 530 email list, project hotline, social media channels, traffic advisories and roadway signage.  

Rules of the Seattle City Light access road

  • This road will be open for local access only 24/7.
  • Pilot cars will escort drivers westbound at the top of each hour and eastbound on the half hour around the clock.
  • The speed limit is 10 mph.
  • Stops along the road are not permitted.
  • Drivers are encouraged to arrive early.
  • Local access will be provided to residents within the work zone.

Larger Vehicles

  • Vehicles over 105,500 pounds are not permitted.
  • Trailers up to 24 feet, including horse trailers, and dump pup trucks are allowed. 
  • School buses and RVs are allowed.
  • Logging trucks are allowed around the clock.
  • Semi-trucks up to WB 40 are allowed.
  • Drivers should be able to negotiate their vehicles over steep grades of up to 18%.
  • Drivers should also be skilled and familiar with the area and road due to a tight corner on the west side.

Next steps for the permanent road

Crews will continue working throughout the summer to build a permanent new section of SR 530 south of the existing roadway, moving next toward the west side of the slide area. Substantial completion of the new alignment is expected in early October.

The March 22 landslide changed the geography of the valley floor and the Stillaguamish River North Fork, increasing the chance of flooding along the corridor. As a result, the roadway must be rebuilt and elevated.

The SR 530 reconstruction project is funded with $28.1 million of Federal EmergencyRelief funding.