cover
TO: Mayor Robert J. O’Connor
FROM: Jason Bauer, P.E. Engineering Construction Coordinator
DATE: January 13, 2017
SUBJECT:
Resolution to authorize a Professional Services Agreement to assist with water main flushing for the City-Wide Water Main Distribution System Flushing Program.
PURPOSE:
To obtain City Council approval to execute a professional engineering services agreement with Crawford, Murphy & Tilly, Inc., Aurora, IL (CMT) to assist with water main flushing for Area 1, as shown on Exhibit B of the attached agreement.
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:
Historically, the City of Aurora 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, is used to design the flushing program sequences. 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 assist with the completion of the water main flushing work for Area 1 in calendar year 2017.
Funding for the professional services work is provided in the 2017 City Budget in 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 $253,200 to assist with the water main flushing for Areas 1.
cc: Alderman Garza, Chairman
Alderman Johnson
Alderman Mesiacos
Alderman Bohman, Alternate
CITY OF AURORA, ILLINOIS
RESOLUTION NO. _________
DATE OF PASSAGE ________________
title
A Resolution Authorizing a Professional Services Agreement with Crawford, Murphy and Tilly to assist with the City-Wide Water Main Distribution System Flushing Program.
body
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, system wide flushing is required in order to properly maintain the City’s water main distribution system; and
WHEREAS, professional services are needed in order to administer an organized and engineered system-wide water main flushing program; and
WHEREAS, a proposal has been received from Crawford, Murphy & Tilly, Inc., to provide the necessary services, to assist with the performance of the flushing work; and
WHEREAS, funding for this work is included in the 2017 budget in account 510-4063-511-38-68 within the Water and Sewer Fund; and
NOW, THEREFORE, BE IT RESOLVED by the City Council of the City of Aurora, Illinois, as follows: the professional services agreement with Crawford, Murphy & Tilly, Inc. to assist in the performance of water main flushing for Area 1 of the city-wide water main flushing program in an amount not to exceed $253,200.00 is hereby authorized, and further, the Purchasing Director is authorized to execute all necessary documents in connection therewith.