Coppell Ind 2-CS040408 (2)BIRKHOFF, HENDRICKS & CONWAY, L.L.P.
CONSULTING ENGINEERS
7502 Greenville Ave., #220
JOHN W BIRKIIOFF, P E
RONALD V CONWAY, PE
GARY C IIENDRICKS, P.E
JOE R CARTER, P.E
PAUl A CARLINE, P.E
MATT HICKEY, P.E
DOUGLAS K SDOWERS, PE..
Mr. Kenneth M. Griffin, P.E.
Director of Engineering & Public Works
City of Coppell
P. O. Box 478
Coppell, Texas 75019
Dallas, Texas 75231
Fax (214) 361-0204
April 8, 2004
Phone (214) 361-7900
Re: Existing Water Distribution System Hydraulic Model
Potential New Demand at Junction Node 501
Dear Mr. Griffin:
As you requested, we have analyzed the existing water distribution system to determine the City's ability to
accommodate a potential new demand of 1.4 MGD at or near Junction Node 501. The enclosed exhibit shows
our understanding of the location of this potential new demand.
in our opinion, the most critical demand period for the City, and the scenario that should be evaluated for this
new demand, is during the maximum hour demand period with the water distribution system as it exists today.
No system improvements or enhancements were modeled.
The basic hydraulic model assumptions:
· 1.4 MGD at Junction Node 501 in addition to normal system demands in this area. Based on our
telephone discussion, we understand this potential new customer will consume potable water at this
rate over a 24-hour period and have modeled the hydraulic simulation as such.
· Existing System Maximum Hour Demand scenario 51.6 MGD system demand.
· Elevated Storage Tanks are 1/3 down
· Ground Storage Tanks are 1/3 down
· Pumps I, 2, 3 and 4 are on at the Village Parkway Pump Station (the smaller Pumps 5 and 6 are oft)
Hydraulic Model Results:
The hydraulic model results show that the City can deliver the 1.4 mgd additional demand at Junction Node
501 while maintaining a residual pressure of 60.7psi under the assumptions listed above. This compares to a
residual pressure of 61.7 psi at Junction Node 501 under the normal existing system model demands.
Pressures elsewhere in the system remain generally unchanged with the largest pressure drop (other than the
subject node) being at Junction Node 252, near Bethel Road and Royal Lane, with a pressure drop of less than
1 psi.
Mr. Kenneth M. Griffin, P.E.
Director of Engineering & Public Works
April 13, 2004
Page 2 of 2
The higher demand scenario does result in some water line velocities exceeding 5-feet per second in isolated
areas, mainly around the Village Parkway Pump Station. Although this generally is an indicator of an
undersized water line, by itself it does not necessarily prompt system improvements. Because system
pressures and friction head-losses are within reason, ~ve suggest no system improvements at this time to
accommodate this proposed demand.
Other factors to consider:
The proposed demand could trigger a rate of flow increase from Dallas Water Utilities. Due to the City's
wholesale water rate contract with Dallas Water Utilities, this could result in an annual demand charge
increase in the range of $175,000 per year (based on a $125,875 per mgd demand charge).
Other factors to consider include longer and more frequent run-times on the large pumps at the Village
Parkway Pump Station and a possible acceleration of water system capital improvements necessary to
accommodate other new growth (i.e. accelerated construction schedule for the Star Leaf Pump Station).
Conclusion:
Based on the hydraulic model results, it is our opinion the existing system is adequate to support this proposed
1.4 MGD demand during the Maximum Hour demand condition. The schedule for planned future system
improvements may need to be accelerated to accommodate this new demand, depending on growth elsewhere
in the system. Finally, rate of flow settings with Dallas Water Utilities may need to be adjusted up to
accommodate this new demand resulting in additional annual demand charges. We are available to discuss
this analysis further at your convenience.
Enclosures
]0
PJORIZONTAL
201-12"
NoF~THPoINT
GATE"/
EXISTING
WAGON WHEEL
2,0 MG
ELEVATED
STORAGE TANK
OAKB£NB
£EKVIE
4--12' 125-12# ~'~
BETHEL
251-16"
RD,
JUNCTION NODE 501
1.4- M.O.D. DEMAND
(ALL DEMAND PERIODS)
~ EXISTING SOUTHWESTERN
~ >-- 1.5 MG ELEVATED
0
~ STORAGE TANK
OART
1000
SCALE IN FEB
2000
CITY OF COPPELL, TEXAS
EXISTINg WATER DIST. SYSTEM
JUNCTION NODE 501 ANALYSIS
BIRI(HOFF. HENI)RICKS a,. CON,fAY LLP. APR., 2004-
CONSULTING ENGINEERS