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TO: Mayor Thomas J. Weisner
FROM: David E. Schumacher, P.E; Superintendent of Water Production
DATE: February 19, 2015
SUBJECT:
A resolution authorizing the conditional purchase of a PAX model PWM600 water mixing unit for the Water Production Division.
PURPOSE:
To obtain City Council approval for the potential purchase of the PAX Water Technologies, Inc. PWM600 water mixing unit from Utility Service Company, Inc. (USCI) Perry, GA. The purchase is contingent upon completion of a successful trial and testing period.
BACKGROUND:
The subject purchase is contingent upon completion of a successful trial and testing period of the PAX model PWM600 water mixing unit (see attached data sheet) at the City of Aurora's Southeast Standpipe. The standpipe is a 5 million gallon finished water storage vessel located at 1718 Normantown Road. The standpipe was constructed and placed in service in 1988 to provide water distribution storage and pressure to the far southeast area of Aurora.
A standpipe is defined as a ground-level water storage tank for which the height is greater than the diameter. The overflow height of the Southeast Standpipe is 134 feet. By nature, water movement and mixing within this type of tank is less than ideal; essentially water movement inside the tank is similar to that of liquid moving up and down in a straw. Because of poor mixing within the standpipe, the water temperature does not remain uniform within the entire water column. This is referred to as stratification, or in other words, the water temperature greatly varies throughout the 134 feet of water with warmer temperatures occurring at the top and colder temperatures at the bottom where fresh, new water enters the tank. Stratification within the water column can result in water quality degradation which is most evident in the loss of total chlorine residual as shown by data collected from the chlorine residual analyzer currently located at the standpipe. The c...
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