Oso Slide Memorial

Snohomish County, WA

On March 22, 2014, a major landslide occurred approximately four miles east of Oso, Washington. The slide covered a rural neighborhood, caused catastrophic damage, and claimed the lives of 43 people. Perteet and the Snohomish County Parks and Recreation Department have recently completed final design on the Oso Slide Memorial Park which will be constructed as a memorial to honor those that died, the community response, the community that was lost, and the geological event. Entrance to the memorial is via the original Steelhead Drive which used to lead into the residential neighborhood that was buried during the landslide. The 2.26 acre memorial site includes a small parking lot, a bus turnaround, an entry gateway welcoming visitors with a timeline, a community gathering space complete with an obelisk, and an interpretive trail that circumnavigates the site and tells the story of the geological event, the response, the rescue, the community lost, the survivors, and a reflection of nature’s resilience.

Perteet donated our services for this project as part of our commitment to helping our community.



  • Transportation
  • Emergency Preparedness
  • Site/Utilities

Perteet was responsible for all civil and site related design including erosion and sediment control, site grading, horizontal control, parking lot and trail design and stormwater design. Site grading was performed such that ADA accessibility was achieved throughout the memorial site. Stormwater design includes a meandering streambed cobble swale in the middle of the site, a 12” storm drain collection system and a StormFilter vault for treating polluted runoff from the parking lot. Runoff from the memorial site is conveyed directly to the North Fork Stillaguamish River, a flow control exempt water body, so the County was not required to provide any detention.