Oso, Wash. - Newly released documents from Snohomish County planners show the homes destroyed in the Oso mudslide were built between 1940 and 2012. The newest was a replacement mobile home.
The neighborhood is called Steelhead Haven in county documents. The plat was recorded in 1960.
KIRO 7 found evidence relating to landslides in the neighborhood in a document written in 1969. The most recent big slide in the area was in 2006. The county said no homes were damaged in that slide, and seven homes were later issued permits outside the slide zone under stricter building standards. Those standards required the floors of houses and all electrical systems to be at least a foot above what's called "base flood elevation."
Flooding from the Stillaguamish River has long been the primary concern in the neighborhood. The file includes a handwritten document describing many parcels as "flooded out."
County records also paint a picture of a riverfront community with affordable homes. Most had assessed values well below $200,000. One 1974 home had a recorded value of $7,300.