Freeport NIP(8.1)-CS060123TELECOMMUNICATIONS COVER LETTER
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PKNo: 7. 0 ~'2-0_4'-,
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CompJny /~ /
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nl '2:~ 200d 0~;:4:~ I ~.\ [~002 008
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LOCATION MAP
A=145,364 ~j~__
A=133~979 S F",.~
A=122~721 SF ~
A=111,587 SF ~ ~
A=100,579 SF ~ .~
A=95,122 SF ~ /
PROPOSED DRAINAGE CA[
DRAINAGE AREA I . Tc 12
AREA (ocres) C ,(minutes) (inch/hour)
CHAMP. 101.8 0.,30 4,3 2.55
1 11.77 o. go 10 5.04
* 2 7.51 0.90 10 5.04
5 10.72 0.90 10 5.04
,3b 1.28 0.90 10 5.04
4 7.19 0.90 10 5.04.
6 8.34 0.90 10 5.04
*-DENOTES THAT DA 2 IN THE TABLE IS THE COMBINATION
dl 23 200ti o8:44 I \X [~]004/008
U U
EL=512.00
V=139,633 CF
EL=511.00
TOTAL VOLUk4[
V=540~006 CF
V=400,573 CF
- V=128,309 CF
EL=510. O0 v=272,064 CF
V=117,110 CF
EL=509.O0
v=154,954 CF
EL=508,00 V=I06,055 CF V=48,919 CF
'£L=507.50 V=48,919 CF V=O CF
rlON TABLE
15 Q5 hoo Q~oo
:h/hour), (cfs) (inch/hour) (cfs)
3.09 94.4 5.0 152.7
5.88 62.3 8,88 94.0
,5,88 39.7 8.88 60.0
5,88 56,7 8,88 85.7
5.88 6,8 8,88 10,2
5.88 38.0 8.88 57.5
5.88 44.1 8.88 66.7
EAST AND WEST DETENTION PONDS.
0 50 100 200 3O0
GRAPHIC SCALE IN FEET
DETENTION (WES:
C,JE C, JE 1"-100' AUG 2000 2052-00.127
Z~H'G IVO: 2052--26
01 23 2()0~ 08:45 [ \X ~]005/008
pond does not overtop. This basin was design much in the same way as the truck dock areas were
developed, but with one minor change. Where each truck dock was tested at various storm
durations to detemUne the required orifice opening, the detention basin took both DA 7 as weI1 as
DA 8 at the same Storm Duration. What this means is that even though a 20 minute may have
controlled in the truck dock area, a longer storm may and did control the required outlet size of
the detention basin. During tile course of this design it was determined that a 40 minute 100 year
required an orifice opening of ! 1.4 square feet. This opening would then generate a maximum
flow of 118.25 cfs at the peak of this storm. The inflow as well as the outflow hydrographs
generated for this area can be seen in Appendix A2-16.
Champions
In this report the land described as being "Champions" can be more particularly
described as being a 100-Acre Tract located West of the 140-Acre Tract. The Champions tract
drainage currently sheet flows onto the 140-Acre Tract at which point most of the storm water
generated is concentrated to a conunon discharge point located in the southeast comer of the 140-
Acre Tract. Part of the reason the southern detention pond was designed to span the width of the
140-Acre Tract, was to allow Champions a point of discharge onto this tract. Being that
Champions discharges directly into this system, it was prudent for this study to take their
discharge patterns into considerations. Through various conversations with Mr. Chuck Stark,
Vice President w/th Graham Associates, Inc. (Champions' Civil Engineer) Pacheco Koch was
able to obtain the exact acreage of their tract as well as the size of their detention pond. From this
informahon Pacheco Koch took Champions data and inputted their expected outflow hydrograph
into the southern watershed. To achieve a hydrograph consistent with the hydrographs generated
on the 140-Acre site, Pacheco Koch had to modify the design storm so that the methodology was
consistent throughout this analysis. Hydrographs generated for the Champions' site can be seen
in Appendix A2-19.
Southern Detention Basin
The last stage of this design was to determine the amount of volume that would be
required of the main detention pond as well as the size of the outlet structure. The sole purpose of
5
promding detention prior to reaching the main pond was in eftbrts to decrease the amount of
volume required. The analysis performed on the whole system varied from the design of the
individual truck dock areas in the following way. Previously each drainage area utilized the
methodology of the Modified Rational Method as is shown in the City of Dallas "Drainage and
Design Manuel". This method was acceptable for modeling the individual drainage areas due to
the fact that small dra/nage areas were being analyzed. Now that the system was being designed
as a whole, a better method was needed. Pacheco Koch took the approach of using a unit
hydrograph. The advantage of the unit hydrograph was that the same input variables could be
used, all that was changed was the rainfall distribution. This was achieved by taking a ratio of the
peak rainfall, which is based on the storm duration, from time index zero increasing the amount
of rainfall as to reach the peak, time index 1.0, then lagging the storm out five times the peak
time. The ratio used in this exercise can be seen in Table 1-2. As was done for the
O06 ~ (108
TABLE 1.2 - Unit Hydrograph Ratios
Time Discharge Time Discharge
Ratio Ratio Ratio Ratio
(tJtp) {q/qp) (tJtp) (q/qp)
0.0 0.000 t .7 0.460
0.1 0.030 1.8 0.390
0.2 0.100 1.9 0.330
0.3 0,190 2.0 0,280
0.4 0.310 2.2 0.207
0.5 0.470 2.4 0.147
0.6 0.660 2.6 0.107
0.7 0.820 28 0.077
0.8 0.930 3.0 0.055
0.9 0.990 3.2 0.040
1.0 1.000 3.4 0.029
1.1 0.990 3.6 0.021
1.2 0.930 3.8 0.015
1.3 0.860 4.0 0.011
1.4 0.780 4.5 0.005
1.5 0.680 5.0 0.000
1.6 0.560
detention basin located in Drainage Area 8, the watershed was then analyzed as a whole. This
model was tested at various storm durations in order to determme which would control the
design. It was determined that an 80-minute, 100-year event would control the volume required.
01 23 2006 (~8:46 t:~,X [~]007/008
Now that the controlling storm was determined, the next part of this design entailed sizing the
outfall structure as well as the size of the detention pond.
The £mal part of this design was to determme the configuration of the outlet structure as
well as to determine the volume required. The results of this analysis can be seen in Table 1.3
below. First, an estimated volume as well as an estimated outlet opening ,,vas inputted into Pond
TABLE 1.3 - Southern Detention Pond Outtall Design
Design Storm Orifice Invert Height Allowable Expected
Event Opening Elevation Discharge Discharge
(fl2) ft above NWSE (ft) (cfs) (cfs)
2 Year Event 16.0 0.00 1.0 121.5 121.68
5 Year Event 4.0 2.13 0.5 154.5 155.91
100 Year Evenl 6.0 2.78 0.5 250 247.51
Pack as well as the unit hydrograph for a 2-year storm event. The resulting data would show thc
maximum elevation that the pond would reach as well as the maximum flow that would leave the
site. By keeping the volume of the pond constant, the size of the outfall structure was varied in a
traiI an error method until only the aIIowable discharge was leaving the site at any given time
(121.5 cfs). This was achieved by providing a sixteen square foot (16 sf) opening, one foot (1 fi)
in height. Now that the 2-year event was designed for the next item was to take into account the
5-year storm event. From the first part of this analysis it was determined that dunng a 2*year
rainfall event the maximum elevation the water ever reached was two feet, one and a half inches
(2.13 ft) above the normal water surface elevation. With this in mind, another opening with an
estimated opening size and an invert elevation just above the 2-year water surface elevation was
inputted into Pond Pack. From this point the S-year unit hydrograph was inpulted in to the
program m the same manner as the 2-year event was done. Once again, by keeping the volume of
the detention basin equal to that of the 2-year event, a trail an error approach was taken until it
was determined that a four square feet (4 sf) opening at a height ofhalfa foot (0.5') would only
allow 154.5 cfs to pass. The last storm taken into account was the 100-year event. Finally a third
opening was provided to account for the 100-year storm. This analysis was consistent with the
design of the other two openings in that the third open/ngs invert elevation was placed just above
the 5-year storm water elevation, the volume used in the calculations stayed constant for each
evaluation, and that by varying the size of the opening the amount of water released could be
changed. The resulting data shows that ifa six square foot (6 sf) opening that is halfa foot (0.5')
in height the maximum discharge to leave this site is two hundred and forty seven cubic feet of
water per second (247 cfs) and a maximum height of four and a half feet (4.5') above normal
water surface elevation. Based on tNs final evaluation the stage storage data for the main
detention pond can be seen in Appendix Al-7 and Al-8. The resulting inflow and outflow
hydrographs are located in Appendix A2-22.