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River Islands Development at Lathrop January 2021 FINAL River Islands Non-Potable Water Technical Report Rev 2 #6520 5 River Islands Non-Potable Water Distribution System Model - Results 5.1 Steady State Analysis Results— Peak Month Irrigation Demands - Recommendations As shown in Appendix F, the preliminary NPW utility exhibit showed a 16-inch, and an 8-inch NPW line connecting the Phase II NPW PS to the distribution system. The hydraulic model results determined that both the 16-inch and 8-inch mains under P-Street would operate with a velocity range of 6.5-8 feet per second (ft/s) under PMID. While this does not exceed the City's operational requirements, operating with a high velocity range is not recommended for the following reasons. • The distribution pressures in the system will decrease from 80 psi (see Figure 5-1) at the pump stations down to 58-60 psi at the ends of the system. This pressure drop is in result to approximately 10 psi of head losses from the Phase II NPW PS to the respective connections along River Islands Parkway. This will result in additional electrical power usage as well as wear on the irrigation pumps from having to overcome the high friction losses. • The pressures shown in the model results are for the distribution system and are not the pressures at the individual meters/service laterals. Therefore, the expected pressure at the actual irrigation service can be expected to be lower due to line and meter losses. The lower distribution pressure may result in decreased performance of the connected irrigation systems under PMIDs. Therefore, it is recommended that the 8-inch NPW main under P-Street be upsized to a 16-inch main to account for the proposed location of the Phase II NPW PS. Furthermore,the existing 8-inch NPW stub out connection under River Islands Parkway is recommended to be upsized to 16-inches as well. 20