Thank you Google Maps ...
A satellite view of the nasty intersection: Route 9 and 240th St. SE., Snohomish County WA
• Three "X's" mark the locations of ground slumpage.
• I've circled the location of a retention pond located behind the concrete block wall!
• On the right of the photo is the boundary line for Wellington Hills Park - located above a vertical cliff behind the Primus building.
• Check out the last version of the Department of Park's "Master Plan" for Wellington Hills Park.