HomeMy WebLinkAboutDrainage ReportDrainage Report
for
Saddle Creek Subdivision, Phase 9
Brazos County, Texas
October, 2011
Engineer.-
Schultz Engineering, LLC
TBPE Firm No. 12327
P.O. Box 11995
College Station, TX 77842
2730 Longmire Drive, Suite A
College Station, Texas 77845
(979) 764 -3900
Developer.
Saddle Creek Partners, Ltd.
4440 Bentwood Drive
College Station, Texas 77845
Phone: (979) 690 -2642
Saddle Creek Subdivision, Phase 9
Drainage Report
ENGINEER
SCHULTZ ENGINEERING, LLC.
P.O. Box 11995
College Station, Texas 77842
Phone: (979) 764 -3900
Fax: (979) 764
OWNERIDEV
Saddle Creek Partners, Ltd.
4440 Bentwood Drive
College Station, Texas 77845
Phone: (979) 690 -2642
GENERAL DESCRIPTION AND LOCATION
Location: Saddle Creek Subdivision, Phase 9, is located on the south west side of FM 2154, off of
Stousland Rd.
Description:
• Area:
• Proposed Land Use
• # of Lots:
• Existing Land Use:
• Land Description:
Primary Drainage Facility:
Flood Hazard Information:
FEW FIRM:
Floodplain:
32.032 acres
Single Family Residential
24 lots
Vacant
The terrain slopes towards the south.
Boggy Creek
# 48041C200 -C & # 48041C215 -C (July 2, 1992)
Un- shaded Zone X
HYDROLOGIC CHARACTERISTICS
The existing site is predominately wooded. The elevations range from 256 to 283, sloping generally in a southerly
direction. The runnoff enters tributaries of Boggy Creek.
GENERAL STORMWATER PLAN
The drainage plan for this development will involve the construction of ditches and the installation of culverts.
DRAINAGE DESIGN
General Information: Stormwater runoff from Phase 9 of the subdivision will be collected in the ditches along
Martingale Court and will discharge into Channel No. 1 and then into an existing drainage
channel. Also water will be collected in the ditches along Ranch House Road an then into
an existing drainage channel. Eventually all runoff will flow into the tributaries of Boggy
Creek.
Page 1 of 2
T, Methodology:
T, Minimum
Design Storm Event
Pipe Materials:
Manning's n Value:
Runoff Coefficient:
Design Results
Applicable Exhibits:
CONCLUSION
CERTIFICATION
TR 55
10 minutes
25 -year & 100 -year - residential street & culvert, drainage channel
Corrugated HDPE w /smooth interior
0.012
0.45
Culvert No. 1
Top of Road = 273.17'
Q25 =
HW 270.54'
Q 100 =4.03
HW 1 00= 270.65'
Culvert No. 2
Channel No. 1
Top of Road= 274.05'
Min. 2' Depth
Q =11.13
Q25 = 20 . 29
HW 273.04'
D25 =
Q 100 =13.26
Qioo = 24 . 09
HW 273.56'
D100=0.68'
The data presented above and in the Appendices indicates the culvert sizes are in
accordance with the requirements. The head water elevation for each of the culverts is less
than the top of road elevation for the 100 -yr storm runoff. The velocities in the channels
downstream of the culverts are low enough that grass -lined channels are appropriate. The
proposed drainage channel will be lined with rock riprap where the slope and velocity are
greater than 5 fps, and where erosion is likely to occur.
Exhibit A — Drainage Area Map
Appendix A — Drainage Area Summary
Appendix B — Culvert No. 1, 2 and Channel No. 1 Design Summaries
The culverts, roadside ditches and drainage channels for this subdivision were designed in
accordance with appropriate engineering standards.
I, Joseph P. Schultz, Licensed Professional Engineer No. 65889, State of Texas, certify that this report for the drainage design
for Saddle Creek Subdivision, Phase 9, was prepared by me in accordance with the requirements of the Brazos County Road
and Bridge Department.
OF
A .....................i
JOSEPH P. SCHULTZ
...........................
658 .
F -12327
SCHULTZ ENGINEERING, LLC.
Page 2 of 2
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Saddle Creek Subdivision - Phase 9
Appendix B
Pipe Design Summary
Pipe
Pi
Pipe
Length
Slope
Contributing
Contributing
cin
V26
QI"
Vim
NO.
size
Drainage
Pipes
(in)
(ft)
N
Areas
(cfs)
(fps)
Mai
(fps)
1
18
67
0 .80
305, 306
Riprap
3.42
4.17
4. 03
4.40
2
58
0.80
308
0.6
11.13
6.51
13.26
18
7.63
Appendix B
Channel Design Summary
Channel
No,
Material
Slope
N
Contributing
Drainage Areas
Contributing
Pipes
Q10
(cfs)
VIO
f a
V'*
Depth
(ft)
Qw
(c
VIM
(fps)
Depth,
(ft)
1
Grass
1.50
301,302
20.29
3.29
0.70
24.09
3.51
----0.76--
1
Riprap
1.50
301.302
20.29
4.30
0.57
24.09
4.58
0.6
I
Riprap
5.69
301, 302
20.29
6.88
_ _--I
0.39
---
24.09
f
7.26
0.43
I----
----
_ ..........
_ _ —
CHANNEL No. 1 - 6' Bottom Width, Sides Slopes - 4:1
.. n" value = 0.035 grass, 0.024 riprap
Saddle Creek Subdivision - Phase 9
Appendix A Drainage Area Summary
Area #
Area, A
(acres)
C
tc
(min)
26 year storm
1100 year storm
1 25
(in/hr)
Q25
(cfs)
1 100
(in/hr)
Q100
(cfs)
301
302
303
1.200
6.090
4.540
0.45
0.45
0.45
10.0
32.0
10.0
10.0
10.0
10.0
9.861
5.33
14.97
20.15
11.639
6.498
-1-1-.639-----23.78-
6.29
17.81
4.71 --
3.35
---0.68-,-
0.84
1 13.26 j
5.462
9.861
304
0.900
0.45
0.45
9.861
3.99
2.84
0.58
11.639
11.639
11.639
11.639
305
306
0.640
9.861
9.861
0.130
0.45
0.45
0.45
307
0.160
4.780
10.0
35.0
9.861
1 5.176
0.71
308
1 11.13
6.164
The Rational Method:
Q = CIA I = b I (tc+d)e t, = L/(V*60)
Q = Flow (cfs) t = Time of concentration (min) L = Length (ft
A = Area (acres) V = Velocity (ft/sec)
C = Runoff Coeff.
I = Rainfall Intensity (in/hr)
Brazos County:
25 year sto 100 ne ar storm
b =89 b = 96
d = 8.5 d = 8.0
e = 0.754 e = 0.730