Soos Creek Trail, Phases 5 and 6
Huitt-Zollars, King County
Over many years Hart Crowser has provided geotechnical engineering for design and construction of more than six miles of paved bicycle and equestrian trail, related facilities, and parking areas along Big Soos Creek for King County. Phases 5 and 6 included design of 25,000 feet of pedestrian and bicycle trail. The trails will also be used by maintenance and emergency vehicles. Hart Crowser provided recommendations for subgrade preparation of at-grade trail sections, and pin pile supported boardwalk segments across wetland areas to minimize land disturbance.
Where the north end of the trail traverses across geologically complex and steep terrain, the trail is supported by retaining walls, rockeries, open cuts, and embankment fills. Slope-W stability analysis was performed on the existing steep slopes to establish appropriate trail set-back criteria from the slope top and bottom. Hart Crowser also completed extensive geological field reconnaissance to assess the stability of previous landslide areas and oversteepened bluff areas along the proposed trail alignment. Near the north end of the project alignment, where Soos Creek enters into the Cedar River, the trail is routed across existing perimeter berms (dikes) around old stormwater detention ponds, which are proposed to be reused for the current trail development project. To evaluate the feasibility of routing new trail segments across the detention pond areas, a stability assessment of the existing pond dikes was performed.