SR 530 Emergency Roadway Reconstruction
Repairing SR 530 after the Oso landslide
Washington State Department of Transportation
Roadways & Bridges
Atkinson reconstructed SR 530, which was impacted by the catastrophic Oso landslide on March 22, 2014. The scope of work included raising the grade of the roadway as much as 20 feet, constructing drainage and stormwater treatment facilities, replacing six fish passage culverts, wetland mitigation, and roadside restoration and erosion control.
Atkinson and designer Jacobs Engineering, together with our earthwork subcontractor and design consultants, developed a design and made commitments that led to winning the project. The team's design allowed us to build a significant amount of the new roadway offline, outside the footprint of the existing road. This allowed the team to repair and reopen the existing SR 530 roadway within 19 days to two-way traffic and suspend the one-way piloted traffic operation at that time.
Additionally, when constructing the tie-in between the new and old roadways, the team committed to placing crushed rock surfacing so that traffic never drove on gravel borrow, which reduced the risk of third party damage. Also, the team developed a design at the 'knoll' (approximate center of the project) that allowed the workers to increase the slope to 2:1 by installing horizontal slope drains and reduced the amount of excavation on site by 50%.
Finally, instead of paying over $2 million to buy wetland mitigation credits at an existing WSDOT wetland bank, the Atkinson-led team proposed to buy a local property in the Oso area, permit, design, and install a wetland mitigation site. Once complete, Atkinson will donate the property to the Snohomish County Parks Department as a set-aside land trust, which creates open space, species habitat, and room for additional wetland mitigation development.
All of these approaches and innovations led to the successful completion of the project on September 24, 2014, seven days ahead of WSDOT's October 1 completion date and six months to the day after the landslide.
I want to thank you and your staff for all the cooperation and coordination in assisting us in our endeavor.
Robert Morrison, PE, Construction Supervisor, Snohomish County Public Works