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SYSTEM EVALUATION, CAPACITY ASSURANCE, CAPITAL IMPROVEMENTS © 2025 Fischer Compliance, LLC. All rights reserved. Sewer System Management Plan licensed for Redwood City use only Page 46 of 59 8.2. Capacity Assessment and Design Criteria WDR REQUIREMENTS Attachment D-8.2 (pgs. D-8/D-9) “The Plan must include procedures to identify system components that are experiencing or contributing to spills caused by hydraulic deficiency and/or limited capacity, including procedures to identify the appropriate hydraulic capacity of key system elements for: • Dry-weather peak flow conditions that cause or contributes to spill events; • The appropriate design storm(s) or wet weather events that causes or contributes to spill events. • The capacity of key system components; and • Identify the major sources that contribute to the peak flows associated with sewer spills. The capacity assessment must consider: • Data from existing system condition assessments, system inspections, system audits, spill history, and other available information; • Capacity of flood-prone systems subject to increased infiltration and inflow, under normal local and regional storm conditions; • Capacity of systems subject to increased infiltration and inflow due to larger and/or higher- intensity storm events as a result of climate change; • Increases of erosive forces in canyons and streams near underground and above-ground system components due to larger and/or higher-intensity storm events; • Capacity of major system elements to accommodate dry weather peak flow conditions, and updated design storm and wet weather events; and • Necessary redundancy in pumping and storage capacities.” COMPLIANCE The City completed a Sanitary Sewer Capacity Master Plan in November 2023 (“2023 Master Plan”), which is found in Appendix 8 to this SSMP. The 2023 Master Plan identifies and prioritizes capacity and rehabilitation improvement projects and recommends a phased capital improvement program, including budget estimates, for implementing the needed capacity improvements to the wastewater collection system. The 2023 Master Plan includes an updated hydraulic analysis with flow monitoring information and land use data. The update resulted in revisions to the City’s future capital improvement program for both existing and future capacity enhancement requirements. The recommended capacity improvement program is designed to provide adequate sewer system capacity for the City’s existing and anticipated future development. Most of the recommended projects are in the Main City collection system. For the most part, the sewer capacity improvement projects involve replacing existing deficient sewers with larger diameter pipes. Eight of the 25 gravity sewer capacity improvement projects were also identified as being needed in the City’s previous master plans. The other projects are primarily on small diameter sewers that were not previously included in the trunk system model used in the previous studies. The 2023 Master Plan includes information collected from the flow monitoring program in the 2018/19 wet weather period. Information collected from the flow monitoring program which is typically performed annually during the wet weather period is used to identify capacity deficiencies within the sanitary sewer system network and calibrate the City’s hydraulic model of the sewer system. A 10-year return period for design storms is assumed for hydraulic modelling of peak wet weather flows. ATTY/RESO.0077/CC RESO SEWER SYSTEM MANAGEMENT PLAN - EXHIBIT A REV: 07-14-25 LF Page 53 of 317