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MEMORANDUM Rice Creek Commons Water Distribution System Modeling Results Update January, 2025 Page 6 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 the required infrastructure to serve the area and develop a phasing plan time reference to construct the required infrastructure. The updated model has three watermains supplying flow to the TCAAP/RCC site, two crossing County Road 96 W on the southeast side of the development area, and the other crossing Hwy 10 on the west side of the development area, see Figures 1 & 2 in Appendix A. The model assumes looping of all trunk watermain; therefore, Outlot A “the Thumb” on the north side has two watermains supplying that area, both running parallel in the Thumb Rd roundabout, then diverging to the east and west sides of Outlot A. Similarly, the 122-unit residential area on the northeast end of the development area was given two watermains to allow looping. Looping is recommended to provide redundant supply routes in the event that one breaks, and looping provides higher fire flow capacities. Previous reports concerning the development of the TCAAP/RCC site suggest that a new water tower and booster station be constructed to supply the north pressure zone with the addition of the TCAAP/RCC development site. The previous studies assumed the development site would have higher demand than the latest land use planning does and recommended the construction of a 1.0 MG water tower. This analysis allows for some background growth within Arden Hills, the current TCAAP RCC development plan as shown in Appendix B, and some intensification of development beyond this development plan. With these assumptions, we are recommending that a 0.75 MGD tower be constructed within the TCAAP site. The original report recommended 1.0 MGD tower. The reduction in size is primarily due to the reduced intensity/water supply need of development within the TCAAP site when compared to the maximum AUAR development plan from 2015. As previously stated, the 0.75 MGD allows for some background growth in other parts of Arden Hills and additional development within TCAAP if proposed and approved. Multiple scenarios were examined to determine what infrastructure is needed to provide fire protection to the north zone and particularly the TCAAP/RCC development site. Scenarios examined 1) the existing system to establish a baseline of water tower cycling rates (the rate water levels fall and rise based on demand and pumping rates.) 2) the TCAAP/RCC site without a new tower or new west booster station, 3) the TCAAP/RCC site with a new west booster station, but not a new tower, and 4) the TCAAP/RCC site with both a new water tower and new booster station. A scenario with a new tower but not a new booster station was not considered because a new west booster station is considered an essential, redundant supply route for the north pressure zone if the existing east booster station is down or experiences a watermain break that would prevent it from functioning. Extended period simulations lasting for a 5-day period were conducted for each scenario. During some scenarios, a 3-hour, 3,500 gpm fire is simulated on the northeastern end of the Thumb, as this location is furthest from the proposed tower site and is a commercial area that would necessitate higher fire flow capacities. The 3-hour, 3,500 gpd fire flow is standard for the types of land uses proposed and is used in the latest model studies provided by the City. Additional controls were added to the model to allow the second booster pump of the existing east booster station to turn on if the water level in the north tower continues to fall while the primary booster pump is running. To evaluate the system’s ability to provide water under several different conditions, the extended period simulation (EPS) function of WaterCad was used. This type of allows the modeling of tank level