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River Islands Development at Lathrop January 2021 Final River Islands Potable Water Technical Report—Rev 3 #6520 4 River Islands Potable Water Distribution System and Model 4.1 WaterGEMS Model Bentley's WaterGEMS for AutoCad 2019 water distribution analysis and design software, was used to conduct a steady state analysis of the River Islands PW distribution system under ADD, MDD, and PHDs. A steady-state analysis determines the operating behavior of the system at a specific point in time under steady-state conditions (flow rates and hydraulic grades remain constant over time). The results of the steady-state analysis helped determine the following performance criteria as required by the City's Standards and Water Master Plans. • Distribution System Pressures under ADD, MDD, and PHDs • Pipeline Velocities under ADD, MDD, and PHDs • Pipeline Headloss Gradients under ADD, MDD, and PHDs 4.1.1 WaterGems Model Basis and Assumptions The River Islands WaterGEMs model was created from a combination of as built drawings, issued for construction improvement plans, or preliminary PW utility exhibits. The AutoCad drawings were imported into WaterGEMS for AutoCad 2019 and the PW lines were converted into a hydraulic model. If improvement plans or as built drawings were available, the elevation of the PW lines, location and size of valves, and the location and size of fire hydrants were imported into the hydraulic model. As recommended in Section 7 of the City's Water Master Plan, the following baseline assumptions were used in the steady- state analysis. • All valves were assumed to have a minor loss coefficient equal to K=0.4. • All pipes were assigned a Hazen-Williams friction loss coefficient of 140. • The location of PW demands were assigned to the nearest applicable junction based on the location of the parcel's service lateral. No pipe laterals were modeled in this analysis. 4.1.1.1 Areas Without Finalized Improvement Plans Assumptions In locations where improvement plans or as built drawings were not available, the following was assumed in order to conduct a steady-state analysis. • The location of all PW lines were assumed to match the preliminary PW utility exhibits • The elevation of all PW lines were assumed to be 4 feet below the finished grade • Valves or fire hydrants were placed into the distribution model in accordance with the City Standards. • All unknowns needed to run a steady-state analysis, such as minimum pipe sizes, were assumed to the minimum requirements listed in the City Standards or Water Master Plan. 15