WA9302-CS 941201 SHIMEK, JACOBS & FINKLEA
CONSULTING ENGINEERS
8333 Douglas Avenue, #820 Dallas, Texas 75225 (214) 361-7900
ROSS L. IACOBS, P.E.
JAMES E. LAUGHLIN, P.E.
RONALD V. CONWAY, P.E.
JOHN W. BIRKHOFF, RE.
MATT ARMSTRONG, P.E.
JOE R. CARTER, P.E.
GARY C. HENDRICKS, P.E. December 1, 1994
C. L. SHIMEK, P.E.
I. C. FINKLEA, RE.
Mr. Howard Pafford
Water Utilit' s Superintendent
Coppetl/,,Texas 75019
Re: Village Parkway Pump Station Improvement
Pump Selection
Dear Mr. Pafford:
As you directed, we have reviewed the Water Distribution System Master Plan Report for the City of Coppeli,
prepared by Rady & Associates. Our review included that portion of the KY pipe model input and output data
for the planning year 2004, which pertains to the proposed Village Parkway Pump Station expansion. The
tabulation below summarizes the data contained in the output files provided for our use in selection of the
proposed pumps. It was assumed by Rady, that one of the existing 450 horsepower pumps would be used as a
standby. Therefore, the results tabulated below are for 3 - 450 horsepower pumps and 2 - 250 horsepower
pumps running simultaneously.
VILLAGE PARK'vVAY PUMP STATION EXPANSION
PROPOSED PUMPS NO. 5 & 6
OPERATING POINTS BASED ON DESIGN YEAR 2004
(Source: Rady & Associates, Water System Master Plan Report, October, 1994)
Total System Elevated Total
Demand Design Storage Flow Rate Flow Rate Dynamic
Demand Condition (mgd) Year Level (mgd) __(gillILL Head
Average Day Demand 10.05 2004 652 3.84 2669.01 247.10
Maximum Daily Demand 30.15 2004 652 3.96 2749.09 239.90
Maximum Hourly Demand 60.38 2004 652 4.19 2912.61 226.43
Average Day Demand 10.05 2004 667 3.82 2650.19 248.85
Maximum Daily Demand 30.15 2004 667 3.90 2705.86 243.73
Maximum Hourly Demand 60.38 2004 667 4.06 2836.86 232.48
Mr. Howard Pafford
City of Coppell
December 1, 1994
Page No. 2
Based on the above flow and head conditions, it appears that a pump with the characteristics of a Worthington
horizontally split centrifugal pump, Type 8-LR-20 will provide the most efficient operation. Using the
maximum daily demand point and an elevated storage level of 652, the anticipated pump and motor efficiency
combined is expected to be in the range of 73% to 74%.
As you are aware, our engineering design contract for this project provides for the pump selection to be
provided by the City, since the City was under contract with Rady & Associates to evaluate the City's water
distribution system. Although we have evaluated the data provided by Rady, and have made a determination
of a pump that would operate best under the single point condition provided, we normally make pump
selections based on a system curve rather than on single operating point. With a system curve established for
each anticipated operation condition, an evaluation can be made as to the effectiveness of each pump running
on either an individual basis or in parallel with other pumps in the system. With the data currently provided to
us, we can only select a pump based on the model year 2004, with three 450 horsepower pumps running and
two 250 horsepower pumps. We are enclosing an example of a typical system curve and pump curve chart we
normally provide with the design of a pump station when we have developed the water distribution system
analysis.
We believe it is in the best interest of City of Coppell and for the operation of the Village Parkway Pump
Station, to evaluate the anticipated operation of the proposed pumps under conditions that exist today and
under conditions other than with all the pumps running. It is our understanding that one goal of the proposed
pump station expansion, other than providing additional capacity, is to provide additional flexibility in pump
selection in order to meet various demand conditions within the distribution system. With the information we
have at this time, we cannot be certain that the pumps selected will provide the flexibility the City desires.
Developing a series of system curves will assist us in evaluating the effectiveness of the proposed pumps, both
under varying conditions.
Further, it appears from our review of the data provided, that the pump station suction header, discharge
header, ground storage tanks, surge valve and fittings such as tees, valves and bends were not included in the
hydraulic model. Although not necessary, including these items in model generates higher heads at the pump
station, which may more accurately reflect actual conditions at the station. Modeling the surge valve at the
station allows a determination to be made if the selected pumps have in fact exceeded the maximum allowable
pressure set at the valve. We are enclosing an example of a pump station layout we have included in a recent
hydraulic model using the Cyberuet software.
We recommend the City consider having our firm convert the recent Rady water distribution system data to the
Cybernet hydraulic model, so that we may develop system curves for the maximum day condition for both the
1994 model, the 2004 model, and the buildout model. The Cybemet software is designed such that this
process and evaluation could be completed in a very efficient manner. Our firm is very familiar with the
Cybemet program and has been using it since it first came onto the engineering software market. We have
successfully completed numerous water system analysis for our various municipal clients in the area. We
believe we can complete this work in a timely manner and recommend it be included in the scope of our
existing Engineering Services Agreement. In order to complete this work, we would require the Rady KY
Pipe data input files in electronic format and an electronic file of the AutoCAD water system master plan map.
This conversion would also assist the City in setting up and operating the hydraulic model.
Mr. Howard Pafford
City of Coppell
December i, 1994
Page No. 3
As an alternative, we request that Rady undertake the task of providing system curves for the City's use in
selecting the appropriate pumps.
We believe this decision is critical to the proper design of the proposed improvements at the Village Parkway
Pump Station and recommend we schedule a meeting to discuss this proposal further.
Sincerely yours,
Gary C. Hendricks, P.E.
Enclosure
co: Mr. Kenneth M. Griffin, P.E.
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