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TO: Mayor Richard C. Irvin
FROM: Mark Phipps, Professional Engineer
DATE: February 26, 2018
SUBJECT:
Resolution to approve a professional services agreement with Crawford, Murphy & Tilly, Inc. in the amount of $343,900.00 for the 2018 Water Main Flushing Program.
PURPOSE:
To continue providing high quality water to the City's water customers.
BACKGROUND:
Regular maintenance of the water distribution system is necessary to keep the system working well. One standard maintenance activity is a system-wide water main flushing program.
Because water mains are sized to handle fire-fighting flows, which may be several times larger than domestic and commercial water use needs, the velocity of flow through water mains is normally fairly low. Low velocity flow allows solids to settle on the bottom of pipes. These deposits can be a source of color, taste, or odor when they are stirred up by short-term increases in flow, such as water main breaks or hydrant flow testing by the Fire Department. Implementing a City-wide, planned and organized flushing program allows the deposits that settle in the bottom of a pipe to be removed from the water distribution network systematically.
Crawford, Murphy & Tilly, Inc. (CMT) developed a computer model of the City's Water Production Plant and water distribution system in the 1990's. They have updated the model periodically and are nearly finished with an update that began in 2017. CMT uses the model to determine which valves need to be closed in sequence to produce flow velocities high enough to flush deposits from the water distribution network. Each summer, in a designated section of the City's water distribution system, CMT staff operates valves and hydrants, tests water quality, adjusts the computer model, posts informational signage, and works around the schedules of critical water users. The City began planning its system-wide water main flushing program in 2012. Flushing began with Area 1 in 2013. By 2016 th...
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