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Ms. Sue Polka June 2, 2017 Page 4 The total projected calculated storage need for the future North Pressure Zone, including the proposed TCAAP development, is approximately 1.5 MG. Adding 1.0 MG of additional storage capacity is needed to meet this requirement. The existing storage capacity of the North pressure zone is significantly less (approximately 500,000 gallons) than recommended even without the demands from TCAAP development included. In fact, the existing storage capacity is not even sufficient to supply the Year 2017 average day demand of the North pressure zone. After the proposed west side booster station is constructed, the firm supply pumping capacity to the North pressure zone will increase to 4,500 gallons per minute (one pump out of service) and the storage deficit will be decreased to approximately 30,000 gallons in 2019 and increase to approximately 1.0 MG with full development of the TCAAP site. - Water Pressures: The modeling results for maximum day static pressures on the distribution system are depicted with pressure contours in Figure 2. The future system pressures for the maximum day demand range from 48 psi at the high elevations to approximately 104 psi in the low-lying areas. In Ten State Standards, it is recommended that the normal working pressure in the distribution system be approximately 60 to 80 psi, and not less than 35 psi in any location. During emergency conditions, such as high fire demands, pressure should remain above 20 psi. The current and future system pressures are within the margins of industry standard at most locations. The highest pressures in the system occur at the lowest lying areas near Rice Creek in the TCAAP site and Round Lake, at approximately 100 psi. While this pressure exceeds the maximum recommended pressure, creating a separate pressure zones in these small areas would require separate individual pressure zones to be created with pressure reducing valves to reduce the pressures to below 80 psi as recommended by Ten States Standards and the Minnesota Plumbing Code. Therefore, individual pressure reducing valves on individual buildings may be preferred by the City. - Available Instantaneous Fire Flow: According to the American Water Works Association (AWWA), the minimum fire flow available at any given point in a system should not be less than 500 gpm at a residential pressure of 20 psi. For commercial and industrial buildings, the needed fire flow varies considerably, and are based on several characteristics of individual buildings as previously mentioned above. The computed available fire flows for the current distribution system are represented in Figure 3. They are shown as fire flow contours in gpm, and represent the available fire flows at a residual pressure of 20 psi during a maximum day demand. The required fire flows in a residential area are usually less than1,500 gpm and in a commercial or industrial areas are 3,500 gpm or higher. The available fire flows throughout the north pressure zone appear to meet the minimum recommended flows for the TCAAP site. It can be seen in Figure 3 that the TCAAP site can be connected to the existing north pressure zone from the south (across Highway 96 at the Spine Road) and from the west (across U.S. Highway 10) with a 12-inch diameter main. - System Improvements: Additionally, an extended period simulation (EPS) was conducted using the updated model to analyze system operations during maximum day demands. The primary purpose of this simulation was to check for cumulative system imbalances between the existing North Tower and the proposed TCAAP tower in the north pressure zone since these imbalances are not observed with a steady state model. A 24-hour period was simulated with maximum day conditions to view the interaction between the existing North Tower and the proposed TCAAP tower. Following the simulation, it was concluded that to maintain balanced water levels within the existing North tower and the proposed TCAAP tower an altitude valve will be required at the North tower. This valve will prevent the North water tower from overfilling and allow the proposed TCAAP water tower to be filled to its full capacity.