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TO: Mayor Thomas J. Weisner
FROM: David E. Schumacher, P.E.; Superintendent of Water Production
DATE: February 9, 2015
SUBJECT:
Resolution to Authorize a Professional Services Agreement to perform water main flushing and design work for several areas of the City-Wide Water Main Distribution System Flushing Program for the Water Production Division
PURPOSE:
To obtain City Council approval to attain a professional engineering services agreement with Crawford, Murphy & Tilly, Inc., Aurora, IL (CMT) to perform water main flushing for Areas 3 & 4 (which were designed in 2014), and to design a water main distribution system flushing program for the remainder of the city designated as Area 5 and Area 6 as shown on the attached Exhibit B.
BACKGROUND:
The City of Aurora's water main distribution system is a large, robust, web of interlinked piping ranging in size from 4-inch to 20-inch diameters with a total length of more than 740 miles. This system provides potable water in adequate quantities and pressures for commercial, industrial, residential, and fire-fighting uses. As with all complicated systems, regular maintenance and repairs are required to keep the system working acceptably and efficiently. One type of standard maintenance activity for sustaining the performance of the water distribution system is a system-wide water main flushing program.
Because water mains are sized to handle required firefighting flows, which may be several times larger than domestic and commercial water use needs, the velocity of flow through the pipes is normally fairly low. Due to this, solids may settle on the bottom of pipes. Over time, these deposits reduce the "carrying capacity" of the pipe, and they can also be a source of color, taste, and odor if the deposits are stirred up by short-term increases in flow (i.e. Aurora Fire Department hydrant flow testing, water main breaks, etc.).
DISCUSSION:
The City's Water & Sewer Maintenance Division (W&SMD) is responsible for the operation and maintenance of the water main distribution system, while the Water Production Division (WPD) is responsible for the treatment and water quality experienced by customers. Thus, when water quality is adversely affected by the water main distribution system, the WPD receives those complaints and must react. Historically, the WPD only performed reactionary spot-flushing in areas where water quality complaints were received. A system-wide, planned, organized program, instead of reactionary spot-flushes, will selectively open and close hydrants and valves to a precise schedule. This engineered approach will significantly increase flow velocities in pipes such that sediments and deposits are removed from the pipes via opened hydrants in a proficient manner.
The goals of a routine system-wide water main flushing program are to achieve the following key performance indicators:
• Significantly reduce customer complaints
• Improve water quality delivered to consumers - reduce turbidity, taste and odors, discoloration
• Remove solids, deposits, and biofilm growth from pipes
• Potentially reduce water pumping costs, disinfectant demand, and disinfection by-product formation
• Discover additional problems (i.e. inoperable valves and hydrants, closed valves, etc.)
Overall, flushing programs must strike a balance between water quality improvements, demand for operation and maintenance resources, impacts to customers, and water conservation. A system-wide planned preventative maintenance program can dramatically reduce ineffective and inefficient "band-aid" reactive actions.
A computer hydraulic model of the City's water main distribution system was developed by CMT in 2005 in response to the Stage 2 Disinfectants/Disinfectant By-Products federal rule. This same model, after some updating, was used to design the previous year's flushing programs. The model assesses and improves flushing effectiveness by estimating system pressures and water age. Model outputs include target flushing velocities in all pipes to insure effectiveness, the means to achieve them via hydrant and valve operating combinations, predictions of minimum system pressures during flushing to insure adequate pressures are maintained, and optimized flushing routes/patterns. This current funding request will permit CMT to generate flushing sequences for Area 5 and Area 6 as well as actually perform the water main flushing work for Area 3 and Area 4 in calendar year 2015.
Funding for the professional services work is provided in the 2015 City Budget account No. 510-4063-511-38-68.
IMPACT STATEMENT:
The work will be visible to the public but should not impact travel on city roadways.
RECOMMENDATIONS:
That the Mayor and City Council approve the attached resolution authorizing the Purchasing Director to execute an agreement with Crawford, Murphy & Tilly, Inc. for a not-to-exceed amount of $298,000.00 to perform water main flushing for Areas 3 & 4 (which were designed in 2014) and to design a water main distribution system flushing program for the remainder of the city designated as Area 5 and Area 6. It is further recommended that this matter be forwarded to the Buildings, Grounds, and Infrastructure Committee for review and recommendation.
cc: Alderman Peters, Chairman
Alderman Garza
Alderman Bugg
Alderman Saville, Alternate
CITY OF AURORA, ILLINOIS
RESOLUTION NO. _________
DATE OF PASSAGE ________________
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A Resolution to Authorize a Professional Services Agreement to perform water main flushing and design work for several areas of the City-Wide Water Main Distribution System Flushing Program for the Water Production Division
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WHEREAS, the City of Aurora has a population of more than 25,000 persons and is, therefore, a home rule unit under subsection (a) of Section 6 of Article VII of the Illinois Constitution of 1970; and
WHEREAS, subject to said Section, a home rule unit may exercise any power and perform any function pertaining to its government and affairs for the protection of the public health, safety, morals, and welfare; and
WHEREAS, the City's water main distribution system has never experienced a system-wide flushing program; and
WHEREAS, the Water Production Division seeks to administer an organized and engineered system-wide water main flushing program, thereby requiring professional services for use of a hydraulic model for design purposes and manpower to assist in the performance of the detailed flushing sequences; and
WHEREAS, a proposal has been received from Crawford, Murphy & Tilly, Inc., to provide the necessary modeling, program development services, and manpower to assist in the performance of the flushing work; and
WHEREAS, budgetary authority is granted and funds are available in the 2015 City Budget account No. 510-4063-511-38-68;
NOW, THEREFORE, BE IT RESOLVED by the City Council of the City of Aurora, Illinois, as follows: that the Purchasing Director is hereby authorized to execute a professional services agreement with Crawford, Murphy & Tilly, Inc. for professional services to assist in the performance of the water main flushing for Areas 3 & 4 and to design a water main distribution system flushing program for the remainder of the city designated as Area 5 and Area 6 in an amount not to exceed $298,000.00.
PASSED AND APPROVED on ______________.
AYES ____ NAYS ____ NOT VOTING ____ ABSENT ____
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Alderman Bohman, Ward 1 Alderman Garza, Ward 2
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Alderman Mesiacos, Ward 3 Alderman Donnell, Ward 4
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Alderman Peters, Ward 5 Alderman Saville, Ward 6
____________________________ __________________________
Alderman Hart-Burns, Ward 7 Alderman Mervine, Ward 8
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Alderman Bugg, Ward 9 Alderman Johnson, Ward 10
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Alderman Irvin, At Large Alderman O'Connor, At Large
ATTEST:
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City Clerk Mayor