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MEMORANDUM Rice Creek Commons Water Distribution System Modeling Results Update January, 2025 Page 10 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 To help define minimum system pressures, a 5,000 gpm demand was imposed at the north end of the TCAAP development and was modeled for a duration of 3 hours to simulate a fire. Pressure contours were generated to display the system’s pressures immediately following the 3 hour fire and are shown on Figure 2. The fire flow EPS simulation was also used to verify the appropriate pipe sizing for the new development. Original plans included the installation of a 16” and two 12” diameter pipes connections to the existing system to service TCAAP. During the simulation, it was determined that downsizing the 16” to a 12” would result in adequate flows and allow a 3-hour, 5,000 gpm fire flow while maintaining a minimum residual pressure of about 40 psi. Results of the available fire flow throughout the system are shown in Figure 3. Additional Analyses No additional analyses were completed with this engineering study update. An additional analysis was performed to estimate the level of fire protection that could be provided for a situation in which a single 12” pipe is initially installed to service the Outlot A area of the development for a short period of time before the full expansion is constructed. The results of this analysis indicate that this pipe, connecting to the Arden Hills system near Prior Avenue and Highway 10 at the north end of Arden Hills, would produce a 3-hour, 2,200 gpm fire flow. Also, additional fire flow could be obtained with an emergency connection to Mound View (a normally-closed gate valve “interconnection” between the Arden Hills and Mounds View systems that would only be opened in the event of a water emergency). Information provided by Mounds View was analyzed, and it is expected that by opening this emergency connection, a target fire flow of 5,000 gpm will be attainable throughout most of the Outlot A area. Only the very northernmost portion of Outlot A may be slightly reduced, providing fire flows in the 4,000 to 5,000 gpmrange. Another analysis was performed to determine the full-development system’s service ability in the event that one of the supply lines into TCAAP would be out of service. The results of this analysis indicate that additional pumping could overcome the loss of flow through the out of service transmission pipe; hence, it does not appear that an emergency connection to Mounds View or AHATS is required. However, for Mounds View, if there is an early development in the Outlot A area, the interconnection will be beneficial both in terms of improved fire flow and also simply to provide an alternate water supply in the event water service via the single 12” pipe from the south is inadvertently interrupted. These results also indicate that adequate water supply would still be available if the 12” connection on the southeast side of TCAAP were omitted. However, without knowing the sequencing of the planned construction, and given the possibility that one of the other connecting pipelines could be out of service, it would be beneficial to construct the southeast 12” pipe (going south from the water tower) in order to loop the water tower location. This is particularly true given that complete construction of the 12” pipe going north from the water tower is not likely until some of the later phases of TCAAP redevelopment have been completed, making the completely-connected pipe unavailable for some time.