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River Islands Development at Lathrop January 2021 FINAL River Islands Non-Potable Water Technical Report Rev 2 #6520 4 River Islands Non-Potable Water Distribution Model — Basis of Design, Assumptions, & Analysis Parameters 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 NPW distribution system under PMIDs (see Section 3.3.1). 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. • Pipeline Velocities under PMIDs over a daily 8-hour irrigation window. • Pipeline Headloss Gradients under PMIDs over a daily 8-hour irrigation window. • Distribution System Pressures under PMIDs over a daily 8-hour irrigation window. 4.2 WaterGEMS Model Basis and Assumptions The River Islands WaterGEMs NPW distribution model was created from a combination of as built drawings, issued for construction improvement plans,or preliminary NPW utility exhibits. The AutoCad drawings were imported into WaterGEMS for AutoCad 2019 and the NPW lines were converted into a hydraulic model. If improvement plans or as built drawings were available, the elevation of the NPW lines and the location and size of valves were imported into the hydraulic model. 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 NPW demands was assigned to the nearest applicable junction based on the location of the parcel's service lateral. No pipe laterals or service meters were model in this analysis. 4.2.1 Hydraulic Model Assumptions -Areas Without Finalized Improvement Plans In locations were 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 NPW lines was assumed to match the preliminary NPW utility exhibits. • The elevation of all NPW lines was assumed to be 4 feet below the finished grade. • Valves were placed into the distribution model in accordance with the City's requirements. • All unknowns needed to run a steady-state analysis, such as minimum pipe sizes, were assumed to be the minimum requirements listed in the City Standards. 15