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Executive Summary City of Redwood City (0011239.02)16 Woodard & Curran, Inc. Sanitary Sewer Capacity Master Plan November 2023 model results indicated surcharging that has not been visually observed in the system (confirmation level 2). In these cases, the City may wish to conduct additional investigation to further verify the project need and sizing. Verification could be conducted by temporary flow or surcharge monitoring during wet weather periods. •Assessment of rehabilitation effectiveness. If the City conducts extensive repairs and rehabilitation within a relatively small area with a well-defined drainage area, conducting flow monitoring both before and after the rehabilitation efforts could provide valuable insight into how effective the rehabilitation has been in reducing RDI/I. If rehabilitation efforts are less concentrated, however, with work in various areas around the City, or if the drainage area is not well defined, with potential flow splits affecting flow coming into the basin, limited monitoring to try to assess rehabilitation effectiveness is not likely to be informative. In this scenario, the City would be better served by conducting periodic system-wide flow monitoring (perhaps every five years) in conjunction with a model calibration update to update RDI/I parameters. •Confirmation of flow prior to major developments. On occasion, it may be appropriate for the City to conduct temporary monitoring to verify flows in a pipe that is expected to be affected by a major development. Such monitoring is typically brief (2 to 3 weeks) and focused on dry weather capacity. •Model calibration update. The City will be relying on the new, all-pipe model developed for this Master Plan for a number of purposes. Periodically updating the model loads and the model calibration as development changes and as the City’s sewer rehabilitation efforts continue will be important for the model to continue to be useful in the future. For the purpose of keeping the model up-to-date, periodic system-wide flow monitoring is far more effective and provides a much sounder basis for updating the model calibration than limited annual monitoring. Selecting appropriate, hydraulically suitable flow monitoring locations is critical for obtaining accurate data. An effective approach to select sites with the best hydraulics possible is to first identify where sites are needed to serve the intended purpose of monitoring. Then review the sewer network data in the vicinity to identify what appears to be the best specific manhole for metering, but also determine how far upstream or downstream of this site the meter could be installed and still capture the flow intended. This way, if the selected site does not look ideal upon site investigation, the flow monitoring contractor can further investigate upstream or downstream to identify a manhole that would provide more suitable hydraulic conditions. Any flow monitoring conducted during wet weather needs reliable rainfall data to be useful. If there are no local, reliable rain gauges available, temporary rain gauge(s) should be installed as part of the flow monitoring program. ATTY/RESO.0077/CC RESO SEWER SYSTEM MANAGEMENT PLAN - EXHIBIT A REV: 07-14-25 LF Page 105 of 317