Oakbend Addn-CS 901113MEMORANDUM
DATE:
TO:
FROM:
November 13, 1990
~~ C~C~L~OdC~,;
NOV 161990 ~~I i~
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Shohre Daneshmand, P.E., Acting City Engineer
Coppell, Texas
Jean Hansen, A. H. Halff Associates, Ina ; ~,~
RE: Oak Bend Subdivision
X ~ ~, ~ ~
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As per your request we have reviewed the drainage plans for the above referenced
project in the area of Stream Cl. There are several alternatives available in this area which
would not require a channel or box culvert through a residential front yard. The following
is a list of the alternatives we feel would be feasible.
1) Retaining Open Channel -
Separate the lots containing the open channel from the subdivision and rezone
as commercial or multi-family fronting on State Road (Future Freeport Parkway). Tne
channel could then be routed along the edge and through the back of apartments or light
commercial. The main drawback to this alternative is the size of the lots. Development
would take careful planning and the lots should definitely be re-platted with an easement
maintenance clause. These lots could also be combined with adjacent property for
commercial development.
2) Box Culvert -
A box culvert could be installed on the west side of State Road going south
and outfalling to Cottonwood Branch at the State Road crossing. This option would
eliminate the existing Stream Ci/State Road culvert which has been experiencing severe
erosion problems. An easement maybe required along the west side of existing State Road.
The storm sewer line (C) could then be routed along lot property lines either to Stream Cl
at the south property line or to the proposed box culvert.
3) Box Culvert -
A box culvert could be installed on the east side of State Road flowing south
along the back of the property, then east to Stream Cl.
These options are shown schematically on the attached drawing. Halff
Associates does not recommend an open channel through the front yard of a private
residence. We also do not feel that Line C should be installed to outfall into this channel
even temporarily. Temporary installations often have a tendency to become permanent.
If the developer wishes to proceed with Line C in its current configuration it could be routed
along the east property line of Lot 52, then west to Stream Cl.
a .-
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DRAINAGE RUN-OFE' Cel ~`l11 a r~nuc •
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D ~t~GE IN ACRES Tc (mins) ~- --- - ~ro (in/hr)
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OFFSfTE
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A
B 2.76
1
09 10
10 0.9 11.7 29.06
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2.82
10 0.9
0.9 11.7
11.7 11.48
29
89
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E 2.51
13
43 10
10 0.9 11.7 .
26.43
F .
74.10
27 0.9
0.9 11.7
7.2 141.42
480
17
G1
G2 0.61
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30 10
10 0.9 11.7 .
6,41
H .
2.62
10 0.9
0.9 11.7
11.7 3.16
27.59
ONSffE
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1
2 1.32
2
71 10
10 0.45 11.7 6.95
3 .
2.36
10 0.45
0.45 11.7
11.7 14.27
12
43
4
5A 2.87
0.49 10
10 0.45
0
45 11.7
11
7 .
15.11
5B
8
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10 .
0.45 .
11.7 2.58
10.69
7 0.75
3
74 10
10 0.45 11.7 3.95
8 .
1.71
10 0.45
0.45 11.7
11.7 19.69
9
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9
10 1.34
1
55 10
10 0.45 11.7 .
7.06
11 .
1.15
10 0.45
0.45 11.7
11.7 8.16
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05
12
13 2.35
1
22 10
10 0.45 11.7 .
12.37
14 .
1.58
10 0.45
0.45 11.7
11.7 642
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32
15
16 2.71
2
18 10
10 0.45 11.7 .
f 4.27
17 .
0.52
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0.45 11.7
11.7 11.48
2
74
18
19 1.84
2
36 10
10 0.45 11.7 .
9,69
20 .
0.92
10 0.45
0.45 11.7
11.7 12.43
4.84
DISCHARGES ARE FOR 100 YEAR STORM BASED ON T.P.-40
USING THE RATIONAL METHOD WHERE:
C=.45 FOR RESIDENTIAL
C=.90 FOR INDUSTRIAL
1=1 1.70 In/hr.
JO =DRAINAGE AREA #
- =DRAINAGE DIVIDES
--- =FLOW DIRECTION
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