11-19-2018 Planning Commission Packet

Home Browse Search

CMP Part 4C. Water Supply Existing Available Fire Flow The modeled fire flows were run up to a maximum of 5,000 gpm. The minimum fire flow available at any given point in a system should not be less than 500 gpm at a residual pressure of 20 psi. This represents the amount of water required to provide for two standard hose streams on a fire in a typical residential area for residential dwellings with spacing of 100 feet. The distance between buildings and the corresponding fire flow is summarized in Table 4C-13 Distance Between Buildings Required Fire Flow (feet) (gpm) More Than 100 500 31-100 750 30-11 1,000 Less Than 11 1,500 The computed fire flows for the current distribution system are represented in s .. Generally, available fire flows are adequate throughout the water distribution system. Areas with less than 500 gpm mostly include residential properties with limited water main looping due to locations along cul-de-sacs or dead end roads. The majority of these locations are in the Navarre system and the Wayzata System Extension. Pipe Velocities and Friction Losses Pipe segments are considered potentially deficient, or most-limiting, if they have the following conditions: • Velocities greater than 5 ft/s; and • Head losses greater than 10 ft/1000 ft. Velocities in pipe segments are acceptable up to about 10 ft/s during emergency or extreme demand conditions of short duration. As velocities increase, pipe friction increases and problems with water hammer occur. This is especially true in systems with higher pressures. The system has been checked for locations where velocities and head losses meet the above stated conditions.There are several locations where pipe velocities exceed 5 ft/s during emergency or peak demand flows. During normal operating conditions, no segments with high velocities or high head loss were observed. City of Orono Community Management Plan 2020-2040 Part 4C, Page 16