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Lk" 46 $; ' 4 -� �Y , • A Community Interconnections The City of Hugo currently also has two water system interconnections with the City of Lino Lakes. Each interconnection has a capacity of 5,000 gallons per minute or 7.2 million gallons per day. The City has and will continue to explore additional interconnections with neighboring communities. In the short term, this includes Lino Lakes and White Bear Township. In the medium term, Forest Lake, and in the long term, Grant and May Township. The Metropolitan Council recently completed a study which included analysis demonstrating that the City of Hugo can connect to five neighboring water systems. These existing and potential interconnections not only serve as a water source in the event of an emergency, but also create capacity for the sale and purchase of water supply between communities should the need arise in the future. Computer Model A computer model of the City of Hugo's water system was prepared to reflect the existing and 2040 water demands and network configurations. The model was used to evaluate the capacity of the existing system and to verify the improvements that will need to be made through the year 2040. 1-1UG0 2040 COMPREHENSIVE PLAN UPDATE --how System Pressures and Velocities The Ten State Standards for water distribution system design recommend working pressures of 60 to 80 psi, with a minimum normal working pressure of 35 psi and a minimum at all times at all ground level points of 20 psi. A design target of 50 to 70 psi for working pressures is often used as well. The Minnesota Department of Health requires a minimum pressure of 20 psi during any fire or other emergency water use. Pressures above 100 psi are not recommended. The City of Hugo's water distribution network has two pressure zones, south and north. A map of the existing steady state system pressures calculated by the model, with the tower levels set to the lowest level seen during maximum day demand, is shown in Map 9-2. • The overflow elevation of the south Tower 2 is 1,055.5 feet. Ground elevations within this pressure zone vary between 906 to 950 feet. Therefore, static pressures at ground elevations in this zone when Tower 2 is full vary from 46 to 65 psi. • The overflow elevation of the north Tower 3 is 1,084.0 feet. Ground elevations within this pressure zone vary between 906 to 962 feet. Therefore, static pressures at ground elevations in this zone when Tower 3 is full vary from 53 to 77 psi. DRAFT Dec14-17 for review only It is recommended that velocities in long watermain segments be less than five feet per second (fps) to avoid excessive energy loss and pressure reduction. Under maximum day demand, none of the pipes in the model indicate velocities greater than 5 fps. The greatest calculated velocities, from 3-5 fps, occur primarily in the watermain connecting the production wells and water towers to the network. Fire Flow Capacities The Insurance Services Office (ISO) provides fire flow requirements for individual structures within a community. These requirements, which specify both the quantity and duration of fire flows, are typically focused on large commercial, industrial, and public buildings. The fire flows required for these structures usually fall between 2,500-3,500 gpm. A map of the existing available fire flows throughout Hugo's water distribution system, with the tower levels set to the lowest level seen during maximum day demand, is shown in Map 9-3. The areas that exhibit lower available fire flows in the model are the low density residential areas in the east -central part of the system near Goodview Avenue North; the available flows still satisfy ISO requirements for low density residential development. COMPREHENSIVE WATER SUPPLY 211 AND DISTRIBUITION PLAN