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MEMORANDUM Rice Creek Commons Water Distribution System Modeling Results Update January, 2025 Page 8 H:\KIMLEYHO_PR\0T4133552000\2_Preliminary\C_Reports\Preliminary Design Report Update\Report Update\Water Preliminary Engineering Analysis\Memo-Rice Creek Commons Water Distrib Sys Modeling Results Update Final Draft 01.24.2025.docx that the south tower cycles between 40% and 60% full and is unable to recover as the east booster station is pumping on a nearly continuous basis. It is best practice to not require running of the pumps continuously. Figure 7 shows that the north tower is nearly emptied from the simulated 3-hour fire. These simulations show that additional infrastructure of a water tower and/or a booster station is necessary for the system to operate and supply adequate fire protection. Furthermore, additional storage volume is recommended so that each pressure zone has sufficient storage to meet or exceed the average daily demand of that pressure zone. The addition of demands from TCAAP/RCC development area results in the existing storage being insufficient. Scenario No. 3 – TCAAP/RCC with New West Booster Station and No New Water Tower Next, the TCAAP/RCC development site was simulated with a new west booster station and no new water tower within the proposed development area. This scenario performed well, even with the fire simulation during MDD conditions. See Figures 8, 9, and 10 in Appendix A. With the addition of a new west booster station, the south tower can cycle between 60% and 75% full under MDD conditions. This is because the west booster station receives its water supply from Roseville’s interconnections, while the east booster station receives its water supply from the south tower. This shows that the system may function without a new water tower in the north zone and still provide sufficient fire flow at 3,500 gpm for 3-hours. However, the distribution system and the north pressure zone in particular would not have sufficient storage to meet ADD. It is recommended that municipalities have sufficient storage to meet average daily demands and that water towers turn-over their storage volume in one to two days. This turn-over keeps water fresh and prevents freezing issues in winter. Scenario No. 4 – TCAAP/RCC with New West Booster Station and New Water Tower Finally, the TCAAP/RCC development site was simulated with a new west booster station and a new water tower. This scenario performed well during ADD conditions, MDD conditions, and the fire simulation, except for the west booster station continuously running during MDD conditions. This is due to hydraulic differences between the two towers in the north pressure zone, which results in the system experiencing a water level imbalance between the existing north tower and the proposed TCAAP/RCC Tower. See Figures 11, 12, and 13 in Appendix A. The imbalance between the two water towers in the north pressure zone is due to headloss between the tower locations. The existing north tower is closer to the booster stations, which act as the source water for the north pressure zone. Immediately downstream of the booster stations is where the water will have the highest hydraulic grade (potential water elevation). The proposed TCAAP tower is further from the source and is at a lower hydraulic grade. This means that the proposed water tower will not be able to fill to the same high-water level as the existing north tower when it is full. Also, while the proposed west booster station is controlled to fill the TCAAP/RCC tower, it is also filling the existing north tower while it is running. An altitude valve may be installed at the north tower as suggested in the 2017 TCAAP Development – Water System Model Review by WSB to prevent continual filling of the existing water tower after it is filled while filling the proposed TCAAP/RCC tower. The 2018 Water Model Review by AE2S modeled Arden Hills and Roseville together and demonstrated additional controls at the Roseville water tower which improved tower performance in Arden Hills. The proposed TCAAP/RCC tower will also meet the best practice of providing the amount of water storage equal to the ADD. When the tower project is authorized for development of plans and specifications, it is recommended to study the water level imbalance between the existing north tower and proposed TCAAP/RCC tower and