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City of Redwood City (0011239.02)2-1 Woodard & Curran, Inc. Sanitary Sewer Capacity Master Plan November 2023 2.HYDRAULIC MODEL DEVELOPMENT AND CALIBRATION This chapter documents the development of the hydraulic model that was used to assess the capacity of the City’s sewer system. The chapter provides an overview of the model development process, including descriptions of the modeled sewer network, the flow monitoring program conducted for this study and the basis for estimating wastewater flows, and the calibration of the model. A detailed description of how the model was developed is provided in the Model Development Technical Memorandum (TM) in Appendix A. This chapter summarizes the information presented in the TM. Woodard & Curran developed the model in InfoWorks™ ICM, a fully dynamic hydraulic modeling software supported by a GIS-based modeling interface. 2.1 MODELED SYSTEM The City’s sanitary sewer model is divided into three separate networks: the Main City Area, Seaport/Pacific Shores, and Redwood Shores. The model networks include all City pipes but exclude private, Port of Redwood City, and County- owned facilities (except a few cases where County pipes are connected both upstream and downstream with the City’s system). In total, the networks include about 194 miles of pipelines (183 miles of City gravity mains and 11 miles of force mains) and 31 pump stations and lift stations (both types are referred to as pump stations in this report). The model networks comprise all City-owned sewers, as described in Chapter 1 and shown in Figure 1-2 and Figure 1-3. Schematic diagrams of the pump stations in the Seaport/Pacific Shores and Redwood Shores networks are presented in Figure 2-1 and Figure 2-2, respectively. The data used to create the model networks were provided by the City as GIS files of sewer system pipes, manholes and other structures. The model construction and validation process included the following: •The modeled network was checked for connectivity, i.e., verifying that the correct upstream/downstream manholes were identified for each pipe and that there were no missing links in the network. •Manhole and pipeline network data, including rim and invert elevations and pipeline sizes and lengths, were verified and refined where needed based on information from record drawings, previous master plan models, field verification of flow split locations provided by the City, and County LiDAR ground model data. Note that the Main City Area model network includes over 200 potential flow split locations (manholes that have more than one outlet pipe, creating alternate downstream flow paths depending on hydraulic conditions and physical configuration). Verification of outlet pipe invert elevations at key flow splits was important for model accuracy. •The model software was used to generate profiles of pipe reaches to visually check for missing or suspect data. These profiles were also used to identify potential datum differences in source data. Adjustments were made to bring all model data to a common datum. In the Main City Area, the datum used for this study was Redwood City’s “old” (pre-2008) datum (represented as being equal to NGVD29 – 2.56 feet), since most of the GIS data are based on that datum. However, in the future the City plans to convert the model to the City’s current official datum, NAVD88. •All pipelines were initially assigned a Manning’s n of 0.013, which is standard practice for master planning-level modeling analyses. •The sources of model data (e.g., GIS, record drawings, field verification, datum adjustment, inference, etc.) were documented using “flags” in the model database. ATTY/RESO.0077/CC RESO SEWER SYSTEM MANAGEMENT PLAN - EXHIBIT A REV: 07-14-25 LF Page 117 of 317