If you drive, walk or ride a bike along Rainier Avenue you may have seen the recently completed retaining wall project that protects a portion of the 9700 block Rainier Avenue South. Like many Seattle Department of Transportation (SDOT) projects, the photos of the finished product are impressive, but do not tell the whole story!
During heavy rains last spring, a slide occurred at this location on March 22 and again on April 7. After the two slides temporarily closed the sidewalk and the major arterial street, SDOT had to determine what action should be taken to cost effectively address the long term problem. This area along Rainier Avenue S has a long history of landslides and the 9700 block is one of most significant segments in the slide area.
To permanently address the problem, our SDOT Roadway Structure crew built the wall. During the design phase, our staff realized that a sewer main line under the sidewalk could potentially be impacted by the proposed retaining wall. SDOT had to negotiate with the Seattle Public Utilities department and the property owner to get a permanent easement for the wall. During construction, difficult soil was encountered and the project team had to decide to use a different construction method which required a redesign of the wall to some degree.
Ultimately the wall took a month to build at a cost of approximately $190,000. The 78 foot long and 11 foot high soldier pile wall is stoutly built to withstand any future slides. Kudos for the excellent work for SDOT’s Roadway Structure crew!