1410 SEINER DR FISHERMAN JACKS 2025-08-21

WATERFRONT PLACE CENTRAL HYDROLOGIC AND HYDRAULIC REPORT PORT OF EVERETT — PSA 1-2015-005 PND No. 154016 — 005.01 • Should overtopping occurs for the 100 year storm, the additional flow over the ground surface shall not extend beyond half the lane width of the outside lane of the traveled way and shall not exceed 4 inches in depth at its deepest point. • Conveyance systems and hydraulic structures will use uniform flow analysis method to check pipe capacities per Chapter 6 of WSDOT Hydraulic Manual. • Minimum pipe slopes have been set in accordance with figure 6-2 of the WSDOT Hydraulics Manual to provide a minimum clearing velocity of 2.5 fps. However, during a design treatment event, much of the system will be in a backwater condition upstream of the Modular Wetland flow control weir. As such reported velocities for the backwater analysis will not reflect this minimum flow velocity. A summary of the backwater conditions for each system is provided in Tables 2 and 3. Detailed analysis and results are for the designs are provided in Appendix D of this report. Table 2: Peak Backwater Conditions Downstream of Flow Control Weir Table 3: Peak Backwater Conditions Upstream of Control Weir 8.8. MAINTENANCE AND OPERATION PLAN Stormwater treatment facility maintenance will include: Proper disposal of any standing water removed during maintenance operations. Prior to any discharge to a sanitary sewer the City of Everett will be contacted for approval. Any residuals will be disposed of in accordance with current Snohomish County Health Department and Department of Ecology requirements. Runoff control facilities (including catch basins and associated structures) shall be inspected annually, at a minimum. A"V