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MEMORANDUM Rice Creek Commons Water Distribution System Modeling Results Update January, 2025 Page 9 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 provide recommendations solution to solve this issue. A couple of options may be installation of an altitude valve at the north tower and/or implementation of additional controls with the Roseville tower. Tower Sizing: The water model results above suggest that the TCAAP/RCC development may be constructed and function without a new water tower, as shown in Scenario No. 3; however, it is recommended that each pressure zone have sufficient storage to meet average daily demands (ADD), and that turnover rates are kept under two days to prevent freezing in winter. The existing demand of the north pressure zone, according to the model, is 0.445 MGD, and the full development of the TCAAP/RCC site is expected to add 0.565 MGD, for a total of 1.010 MGD. It is recommended that the tower be sized to allow for background growth within Arden Hills outside of the TCAAP and also allow for some development intensification. The existing storage capacity of the north pressure zone is 0.5 MG with the north tower, which covers existing ADD; however, it is recommended that a new 0.75 MG water tower be built in the development area due to the additional demand of the planned TCAAP/RCC development area. A 0.75 MGD tower provides for the discussed background growth and potential RCC development intensity. The results of the fire flow simulation discussed above were used to determine what facilities and improvements are needed to satisfy the water demands. To evaluate this, the system was required to satisfy the 3-hour, 5,000 gpm fire flows while maintaining a minimum residual pressure of 20 psi everywhere within the system at a point in time when the modeled available storage was the lowest. This fire flow criteria will be evaluated during final design, and may potentially be reduced. The initial analysis was performed without additional storage or pumping facilities, and then these facilities were added until the fire flow demand and pressure requirements were met. The results of these analyses indicate that a 1.0 to 1.5 MG storage facility in the TCAAP development is required, as well as an additional pumping facility within the existing Arden Hills system. The most logical location for a storage tank was at the highest ground elevation within the TCAAP redevelopment area, which is located near the southeastern part thereof, near the border with the Arden Hills Army Training Site (AHATS). A suitable pump station location was determined to be on the existing 12” water main crossing I-694 near Snelling Avenue, which is also a location that provides additional benefits to the higher pressure zone within Arden Hills, including redundancy of critical infrastructure. Adding these two facilities, the system was capable of supplying the target fire flow while maintaining the residualpressure requirement. After the fire flow duration, the proposed tank’s storage volume was nearly depleted but then rebounded to approximately 55% of its available capacity by the end of the 24-hour EPS simulation. After determining the tank and pumping facility requirements, the EPS simulation was performed on the system to determine the resulting pressures for the system. Figure 1 shows the pressure contours resulting from this analysis. The highest resulting pressure in the system occurred at the lowest lying area near Rice Creek in the TCAAP development at approximately 108 psi. Although this pressure is near the high end of a desirable range, creating a separate pressure zone in this area would create a closed distribution system and is not recommended. Also, it should be noted that the pressures near Rice Creek will be fairly close to those currently observed in the Round Lake vicinity. Operating the separate pressure zone would add considerably complexity versus the minimal benefitachieved.