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MEMORANDUM Rice Creek Commons Water Distribution System Modeling Results Update January, 2025 Page 7 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 operations, the system’s pressure and flow rate changes and pump station operations under varying demand conditions. For the purposed of this model, the maximum day demand was used as the basis for the EPS analysis. A diurnal curve was developed to provide the demand multipliers in a stepwise manor with a different multiplier for each hour over a period of 24 hours, with the highest multiplier equal to two times the maximum day demand (as noted previously). This method essentially predicts tank levels, pump function, pipe flows and resulting system pressures at each hour of a single maximum water usage day. The results of several EPS simulations were evaluated and used to determine several key system requirements to adequately provide water and firefighting supplies. Initially it was assumed that the target requirement for the system would be to meet target fire flows in the proposed development and that if the fire flows were able to be satisfied, the consumptive water use would also be met. Since the development plan includes the potential for industrial sites along much of the Spine Road and through Outlot A (the “thumb”), in essence from north to south, an industrial fire flow has been targeted through much of the development. For initial modeling purposes, the selected target for industrial development was a 3-hour, 5,000 gpm fire flow, which is also consistent with the prior (1990) water plan. This fire flow criteria will be evaluated during final design, and may potentially be reduced. To determine the required system components to meet the fire flow, a worst case scenario was developed. To develop the worst case scenario, an EPS simulation was performed. Assuming that a fire would place the largest burden on the system at a point when the storage volumes within the system were at their lowest levels, the period of time in which the total stored volume was at its lowest became the start time for the fire flow simulation. This corresponded to starting a fire flow EPS when the storage tanks were approximately half full. Results The following is a summary of results for the scenarios that were examined. As stated above, these scenarios assume the 2024 development plan shown in Appendix B, and allows for both some background growth in other areas of Arden Hills and some intensification of development within TCAAP/RCC. Each scenario was examined at ADD and MDD. ADD starts with the water towers 2-ft from full, and MDD starts with the water towers at half-full to simulate a stressed condition. Scenario No. 1 – Existing System (No TCAAP/RCC) The existing system was analyzed to establish a baseline of tower cycling rates, see Figures 3 and 4 in Appendix A. The system performs well with regular cycles for both ADD and MDD. Note that during ADD conditions, both towers cycle above 80% full. During MDD conditions, the towers overcome the initial stressed condition of being half-full, and cycle above 70% full for the south tower and 80% full for the north tower by the end of the simulation period. Scenario No. 2 – TCAAP/RCC with No West Booster Station and No New Water Tower The TCAAP/RCC development area was added to the existing distribution system without the addition of a new water tower or new booster station to see if the existing infrastructure could supply adequate fire flow capacities. This scenario performed well during ADD conditions but failed during MDD conditions and during the fire simulation (see Figures 5, 6, and 7, respectively, in Appendix A.) Figures 6 and 7 show