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DRAFT :`
MEMORANDUME :S►E
4055 international Plaza,Suite 200 • Fort Worth,Texas 76109 • 817-735-7300 « fax 817-735-7491
TO: Ken Griffin, P.E., City of Coppell
FROM: Jessica Brown, P.E., Freese and Nichols, Inc.
Jessica Bradley, E.I.T., Freese and Nichols, Inc.
SUBJECT: Analysis of Water and Wastewater Systems for Interim Service to Cypress Waters
Development
DATE: April 5, 2011
INTRODUCTION
Freese and Nichols, Inc. (FNI) was contracted by the City of Coppell to evaluate the ability of the water
and wastewater systems to provide temporary wastewater service and construction water to the
Cypress Waters development. The development is located east of the intersection of Beltline Road and
Lakeshore Drive. The size and types of land use for the development were provided by the City.
WASTEWATER FLOWS
Figure 1 displays the existing wastewater system with the Cypress Waters development highlighted.
The Cypress Waters development has combination of flats and townhomes. For townhomes with three
bedrooms, a density of 3 people per unit was assumed. For one and two bedroom townhomes or flats,
a density of 2.3 people per unit was assumed. There are 59 three bedroom townhomes and 594 two
bedroom townhomes or flats. A residential per capita of 80 gpcd was used to calculate the average daily
flows. A peaking factor of four was used for wet weather conditions. The projected flows for Cypress
Waters and the total flows for the existing system are shown in Table 1.
WATER DEMANDS
Cypress Waters will require water supply during construction from the fire hydrants being installed in
the development. These demands will be temporary until the development is complete and only for
construction water, not service to individual customers. Coppell's existing water system has an average
day demand of 10.5 MGD, a maximum day demand of 23.5 MGD, and a peak hour demand of 47.1
MGD.
Table 1: Estimated Wastewater Flows
Average Peak Wet
Annual Weather
Commercial Daily Flow Flow
Population Acres (MGD) (MGD)
City of Coppell 39,192 2,379 5.0 19.9
Cypress Waters 1,543 - 0.12 0.49
Total 40,735 2,379 5.12 20.39
OREEsE
Analysis of Water and Wastewater Systems for Interim Service to .� t
Cypress Waters Development
4/5/2011
Page 2 of 2
EXISTING WASTEWATER SYSTEM CAPACITY ANALYSIS
The existing wastewater system was analyzed using the existing model in the H2OMap Sewer modeling
software. Loads were distributed using 2008 land use assumptions, and the wastewater system was
analyzed under peak wet weather flows for a 5-year 6-hour design storm of 4.2 inches. A few of the
lines along Beltline Road and Denton Tap Road that the study area flows into experienced surcharging
under the peak wet weather flows. The surcharging in the manholes is at least three feet away from the
rim. Figure 2 shows the areas where the wastewater system is deficient. The red lines show where the
actual flow divided by the capacity of the pipe (q/Q) is greater than 0.90. Having the pipes flow at
greater than 90% full indicates a potential need to upgrade these lines; however, since the flows for
Cypress Waters are temporary,some surcharging in the pipes may be acceptable.
ANALYSIS OF WATER SUPPLY FOR CONSTRUCTION
The existing water system model in H2OMap Water was used to analyze the available capacity for
supplying construction water to Cypress Waters. The water lines proposed by the developer were
added to the water model. Nodes were added at the fire hydrant locations along with the estimated
ground elevations. The model was run for maximum day demand conditions to analyze the available
capacity at each fire hydrant while maintaining a pressure of 40 psi. The model results show that all of
the fire hydrants in the development are able to supply at least 1,560 gpm (2.24 MGD) while
maintaining a residual pressure of 40 psi based on the ground elevations. Figure 3 shows the fire
hydrants and elevations in the Cypress Waters development. There were no pipes with excessive
velocity or headloss during the analysis.
CONCLUSIONS
The wastewater system experiences surcharging with the projected Cypress Waters peak wet weather
flow of 0.49 MGD; however, the amount of surcharging is limited and acceptable within 3 feet of the rim
elevation of the manhole. Unless the City experiences growth, additional improvements are not
necessary.
The water system is capable of supplying up to 1,560 gpm or 2.24 MGD to the Cypress Waters
Development for construction. This demand does not include any additional demand for fireflow at
Cypress Waters.
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