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SYSTEM EVALUATION, CAPACITY ASSURANCE, CAPITAL IMPROVEMENTS © 2025 Fischer Compliance, LLC. All rights reserved. Sewer System Management Plan licensed for San Leandro use only. Page 45 of 57 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 has periodically completed flow monitoring and hydraulic modeling analyses to anticipate future growth or increased demand on the system. The City’s most recent Sanitary Sewer Capacity Study and Master Plan was completed in 2015 to confirm existing flows in the collection system and anticipate capital needs for capacity improvement. The project used a systematic process that incorporated land use planning information, water use and flow monitoring data, and design criteria for estimating wastewater flows, and applied in a computer hydraulic model of the trunk sewer system. The model was used to assess how the system would perform under various planning and flow scenarios and identify pipes and/or pump stations that may not have sufficient capacity to convey the predicted flows under existing or future conditions. Improvement projects were developed to provide the required capacity, the capitals costs of the required projects were estimated, and the projects were prioritized based on the model results. Two planning scenarios, defined based on planning information and discussions with the City’s Community Development Department staff, were evaluated for Master Plan. The existing scenario examined the current capacity of the sewer system based on existing development, with flows defined based on winter water use data and calibrated to flow monitoring data collected in 2013 and 2014. The future scenario incorporated information on planned development provided by the City. Planned development represents approximately 3,600 new residential dwelling units and 2.8 million square feet of commercial and industrial building floor space, which are estimated to increase current base wastewater flows by about 30 percent. Model results were examined to determine trunk system capacity needs, as indicated by areas where flow in the pipes would exceed their capacity and cause surcharge conditions (water levels higher than the