SW via a 5-foot diameter aluminum culvert. The existing culvert was last surveyed by the Washington Department of Fish and Wildlife in 2015 and was identified as a 67% passable barrier due to velocity. The culvert is oriented in an alignment that is perpendicular to the roadway, even though the stream alignment is skewed on either side of the road. This reach of Percival Creek is located within a confined ravine, which limits channel movement. The existing culvert directs flows directly at the right bank of the ravine, immediately downstream of the culvert outlet. This has resulted in excessive erosion and instability along the right bank of the ravine and stream channel, which appears to be undercutting and jeopardizing the stability of a very large fir tree. City staff believe that if the tree were to fall it would break the 8-inch sewer line that runs from the neighborhood to the north to the main sewer line along Somerset Hill Drive. Initial analysis and pre-planning were completed to secure funding grants and determine the general project direction. This preliminary work is presented as the Type, Size, and Location (TSL) Study in Exhibit B, the Percival Creek Tree Assessment in Exhibit C, and the Preliminary Slope Stability Assessment in Exhibit D. This RFQ is for selection of the final design Consultant for this site, and the selected Consultant will be based solely on qualifications to complete the work as described herein.
