Sinnema Quaale Trail Protection and Habitat Enhancement

Flood-induced erosion led to loss of an old revetment and adjacent hill slope slumping through a 1,000-foot section of the Snoqualmie River bank. To protect the Snoqualmie Valley Regional Trail and a buried fiber-optic line immediately adjacent to SR 203, the County needed to reinforce the slope in ways that enhance habitat for salmonids and maintain the trail through this area. We led analysis, design, permitting and construction support for this large-scale bank stabilization project. We analyzed hydraulic and geomorphic conditions for several project alternatives with a 2D hydraulic model, leading to selection of a preferred alternative featuring large logs secured by timber piles at the toe of the bank, two steel sheet-pile walls on the slope above the log structures, and an upper structural earthen wall supporting the reconstructed trail and embankment. As part of this complex project, we managed a multidisciplinary team that include geotechnical engineers, structural engineers, and trail design experts.