HomeMy WebLinkAboutDrainage ReportG ALIND O E N GINEERS AND PLANNERS, INC.
3833 South Texas Ave., Suite 213 Bryan, Texas 77802 (979) 846-8868
1. TRACT DESCRIPTION
HOLLEMAN VILLAGE ADDITION, SECTION TWO
DRAINAGE REPORT
18-01
This subdivision covers approximately 4. 5 acres of land located at the southwest corner of the intersection
of Holleman Drive and the proposed south extension of Jones-Butler Road. Upon development and deeding
of additional right of way to the City the net subdivision area will be about 4.3 acres. The tract is
currently vacant and it is traversed by an unlined dirt channel that conveys runoff water from upstream
lands as shown on Exhibit 1. These upstream lands are defined as Drainage Area 1 covering approximately
9. 76 acres . Drainage areas 2, 3, 4 and 5 are area within the confines of the subdivision.
Exhibit 2, in a larger scale, shows the total drainage basin, of which this subdivision is a part. The basin
covers a total area of 69.5 acres.
The construction design drawings submitted together with this report constitute a reference document
where appropriate.
The adopted Flood Insurance Study does not identify the existence of a 100-flood plain affecting this tract
(Map # 48041 C 0182 C, July 2, 1992). Exhibit 3 shows the outline of the 100-yr flood plain boundary
interpreted by City Staff.
2. STORMWATER RUNOFF
Exhibit 4, in two pages, shows the runoff calculations for 5, 10, 25, 50 and 100-year rainfalls for the
project area and for the other areas in the basin as shown on Exhibits 1 and 2 before and after
development. Five sections are identified in this exhibit:
Section 1 is the area that contributes the offsite runoff that traverses through the subject subdivision.
Sections 2, 3, 4 and 5 are part of the subdivision itself.
In addition, Exhibit 4 shows the overall basin area less Drainage Sections 1, 2, 3, 4 and 5 or an area of
55.47 acres. Runoff form this area remains unchanged when this subdivision goes from pre to post
development conditions.
3. ON -SITE DETENTION
No onsite detention has been provided for this project due to the proximity of the existing pond across
from the extension of Jones-Butler Rd. shown on Exhibit 1. Currently this pond stores runoff from post
developed Section 1 and pre developed Sections 2 through 5.
Page 1
•
4. STORMWATER SYSTEM
The following analysis was made using Qs for a 100-yr storm.
4.1. Runoff from Section 1 currently will drain through an unlined channel traversing the tract subject of
this report. The characteristics and capacity of this channel are shown on Exhibit 5. This channel,
with a maximum capacity of 78.18 cfs, is capable of handling the 100-yr runoff for Section 1
calculated at 68.16 cfs .
4.2. Runoff from Section 1 will be conveyed into a 33" RCP through a controlled inlet at the entrance of
Holleman Village Addition, Section Two. The characteristics of this pipe are given in Exhibit 6. This
pipe has a full flow capacity of 89 . 95 cfs , greater than the required 68. 16 cfs .
4.3 A curb inlet at the end of the 33" RCP will connect this pipe with a 42" RCP that will extend to the
east side of Jones-Butler Rd. The characteristics of this pipe are given in Exhibit 7. The Q flowing
into this pipe comes from Sections 1, 2, 4 and one half 3, or a total of 85.03 cfs. The full flow
capacity of this pipe is calculated 92.47 cfs.
4.4. An unlined channel, trapezoidal section, will be cut at the end of this pipe and will be extended to
connect with the existing channel that currently drains all runoff to the pond discussed in Paragraph 3
above. The characteristics of this channel are given in Exhibit 9.
4. 5. All runoff from the whole basin accumulates in the pond highlighted in Exhibit 10. This runoff is
estimated at 193. 55+68.16+12.45 = 274.16 cfs (Exhibit 4). After development this figure increases to
193.55+68.16+28.59 = 290.30 cfs, or 5.89%. Exhibit 10 indicates the pond level will rise 0.85', to
about 31 O', due to the additional run off, a figure which is still within the maximum pond elevation
of 311 '.
5. GRIDIRON DRIVE
The following analysis was made using Qs for a 10-yr storm.
Runoff flow on Gridiron Dr. is calculated in Exhibits 11 and 12. Exhibit 11 shows the performance of the
right lane of showing a water depth of 0.41' at the location of a 3-section (15' long) curb inlet. The left
lane at this location, Exhibit 12, will have water to a depth of 0.22'. That is, at the location of the
proposed curb inlet there will be a strip of dry asphalt nearly 10' wide.
The 10-yr flow on the right side of Gridiron Lane (Section 2), at the south end of Section 2, is calculated at
8. 96 cfs. A3-section , 4" depressed, curb inlet installed at this location, with a capacity of 10. 56 cfs,
Exhibit 13, will remove all this runoff.
Page 2
6. CERTIFICATION
This report and design meets the City of College Station Drainage Policy and Design Standards.
~#4473
November 14, 2000
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Page 3
EXHIBIT 1
"1 \ I ) \//
EXHIBIT 2
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I-m :::c >< w
Job:
Date:
Section
18--01
09-Nov-01
Soil
Type
A
Acres
Pre-development of thhis Project
c
RUNOFF CALCULATIONS -RATIONAL METHOD
HOLLEMAN VILLAGE ADDITION, SCTION TWO
COLLEGE STATION, TEXAS
(County: Brazos)
Veloc. Length T cone. in min.
fps ft Cale. Used 5 yrs 10 yrs
OFF-SITE RUN-OFF
Tc = 10.0
25 yrs 50yrs 100yrs
when the calculated value is less than 10.0
Q
5yrs
Q
10 yrs
Q
25 yrs
Q
50yrs
Page 1
Q
100yrs
·----------------------------------------------------------- ---------------------------------------
Nat. Woodlands
Post-development of this Project
Residential
Pre-development
2
3
4
5
Total
Nat. Woodlands
Nat. Woodlands
Nat. Woodlands
Nat. Woodlands
Post-development
2
3
4
5
Total
Residential
Residential
Residential
Residential
County:
Brazos
9.760
9.760
1.730
0.820
0.310
1.420
4.280
1.730
0.820
0.310
1.420
4.280
0.600
0.600
0.250
0.250
0.250
0.250
0.600
0.550
0.600
0.550
5.000
5.000
1.000
1.000
1.000
1.000
4.000
2.500
5.000
2.500
1,600
1,600
500
250
550
550
600
250
520
550
5.3 10.0
5.3 10.0
ON-SITE RUN-OFF
8.3
4.2
9.2
9.2
2.5
1.7
1.7
3.7
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
7.693
7.693
7.693
7.693
7.693
7.693
7.693
7.693
7.693
7.693
Constants for use in formula: l=b/(t+d)Ae
b
e
d
2-yr 5-yr 10-yr 25-yr
65.000 76.000
0.806 0.785
8.000 8.500
80.000
0.763
8.500
89.000
0.754
8.500
8.635
8.635
8.635
8.635
8.635
8.635
8.635
8.635
8.635
8.635
50-yr
98.000
0.745
8.500
9.861
9.861
9.861
9.861
9.861
9.861
9.861
9.861
9.861
9.861
100-yr
96.000
0.730
8.000
11 .148
11 .148
11 .148
11 .148
11 .148
11 .148
11 .148
11.148
11 .148
11 .148
11.639
11.639
11.639
11.639
11 .639
11 .639
11.639
11 .639
11 .639
11 .639
45.05
45.05
3.33
1.58
0.60
2.73
8.23
7.99
3.47
1.43
6.01
18.89
50.56
50.56
3.73
1.77
0.67
3.07
9.24
8.96
3.89
1.61
6.74
21.21
57.75
57.75
4.27
2.02
0.76
3.50
10.55
10.24
4.45
1.83
7.70
24.22
65.28
65.28
4.82
2.29
0.86
3.96
11 .93
11 .57
5.03
2.07
8.71
27.38
68.16
68.16
5.03
2.39
0.90
4.13
12.45
12.08
5.25 .
2.16
9.09
28.59
Job:
Date:
Section
18--01
09-Nov-01
Soil
Type
Pre-development of this project
Rem. Residential
Total
A
Acres
55.470
55.470
Post-development of this Project
Rem. Residential 55.470
Total 55.470
County:
Brazos
c
0.550
0.550
RUNOFF CALCULATIONS -RATIONAL METHOD
HOLLEMAN VILLAGE ADDITION, SCTION TWO
COLLEGE STATION, TEXAS
(County: Brazos)
Veloc. Length T cone. in min.
fps ft Cale. Used 5 yrs 10 yrs
TOTAL BASIN LESS SECTIONS 1, 2, 3, 4 AND 5
2.500 5,000 33.3 33.3 4.054 4.633
2.500 5,000 33.3 33.3 4.054 4.633
Constants for use in formula: l=b/(t+d)Ae
2-yr 5-yr 10-yr 25-yr 50-yr
----------------------------------------------
b 65.000 76.000 80.000 89.000 98.000
e 0.806 0.785 0.763 0.754 0.745
d 8.000 8.500 8.500 8.500 8.500
Tc= 10.0
25 yrs 50yrs 100yrs
5.330 6.070 6.344
5.330 6.070 6.344
100-yr
-------------
96.000
0.730
8.000
when the calculated value is less than 10.0
Q
5yrs
123.69
123.69
123.69
123.69
Q
10 yrs
141.35
141 .35
141 .35
141.35
a
25 yrs
162.62
162.62
162.62
162.62
a
50yrs
185.19
185.19
185.19
185.19
Page 2
Q
100yrs
193.55
193.55
193.55
193.55
Trapezoidal Channel Analysis & Design
Open Channel -Uniform flow
Worksheet Name: HOLLEMAN VILLAGE
Comment: DOUBLETREE CONDOS CHANNEL CAPACITY
Solve For Discharge
Given Input Data:
Bottom Width .....
Left Side Slope ..
Right Side Slope.
Manning's n ..... .
Channel Slope ... .
Depth ........... .
Computed Results:
Discharge ....... .
Velocity ........ .
Flow Area ....... .
Flow Top Width .. .
Wetted Perimeter.
Critical Depth .. .
Critical Slope .. .
Froude Number ... .
2.00 ft
3.00:1 (H:V)
3.00:1 (H:V)
0.060
0.0050 ft/ft
3.00 ft
78.18 cfs
2.37 fps
33.00 sf
20.00 ft
20.97 ft
1.81 ft
0.0549 ft/ft
FULL
Open Channel Flow Module, Version 3.21 (c) 1990
EXHIBIT .5
Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708
Circular Channel Analysis & Design
Solved with Manning's Equation
Open Channel -Uniform flow
Worksheet Name: HOLLEMAN VILLAGE
Comment: 33" RCP FROM DOUBLETREE TO GRIDIRON LANE
Solve For Full Flow Capacity
Given Input Data:
Diameter ......... .
Slope ............ .
Manning's n ...... .
Discharge ........ .
Computed Results:
Full Flow Capacity .... .
Full Flow Depth ....... .
Velocity ......... .
Flow Area ........ .
Critical Depth ... .
Critical Slope ... .
Percent Full ..... .
Full Capacity .... .
QMAX @.94D ....... .
Froude Number .... .
2.75 ft
0.0250 ft/ft
0.013
83.62 cfs
83.62 cfs
2.75 ft
14.08 fps
5.94 sf
2.67 ft
0.0220 ft/ft
100.00 %
83.62 cfs
89.95 cfs
FULL
Open Channel Flow Module, Version 3.21 (c) 1990
EXHIBIT 6
Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708
Circular Channel Analysis & Design
Solved with Manning's Equation
Open Channel -Uniform flow
Worksheet Name: HOLLEMAN VILLAGE
Comment: 42 11 RCP FROM GRIDIRON LANE TO JONES BUTLER
Solve For Full Flow Capacity
Given Input Data:
Diameter ......... .
Slope ............ .
Manning's n ...... .
Discharge ........ .
Computed Results:
Full Flow Capacity .... .
Full Flow Depth ....... .
Velocity ......... .
Flow Area ........ .
Critical Depth ... .
Critical Slope ... .
Percent Full ..... .
Full Capacity .... .
QMAX @.94D ....... .
Froude Number .... .
3.50 ft
0.0073 ft/ft
0.013
85.96 cfs
85.96 cfs
3.50 ft
8.93 fps
9.62 sf
2.89 ft
0.0072 ft/ft
100.00 %
85.96 cfs
92.47 cfs
FULL
Open Channel Flow Module, Version 3.21 (c) 1990
EXHIBIT i
Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708
Trapezoidal Channel Analysis & Design
Open Channel -Uniform flow
Worksheet Name: HOLLEMAN VILLAGE
Comment: CHANNEL FROM JONES BUTLER TO PARK POND
Solve For Discharge
Given Input Data:
Bottom Width .....
Left Side Slope ..
Right Side Slope.
Manning's n ..... .
Channel Slope ... .
Depth ........... .
Computed Results:
Discharge ....... .
Velocity ........ .
Flow Area ....... .
Flow Top Width .. .
Wetted Perimeter.
Critical Depth .. .
Critical Slope .. .
Froude Number ... .
3.00 ft
3.00:1 (H:V)
3.00:1 (H:V)
0.050
0.0050 ft/ft
3.00 ft
105.14 cfs
2.92 fps
36.00 sf
21.00 ft
21.97 ft
1.94 ft
0.0366 ft/ft
FULL
Open Channel Flow Module, Version 3.21 (c) 1990
EXHIBIT 8
Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708
316.7 x
WS
309.2
EXHIBIT 9
SCALE:
80'
1no 1
310.1 x
301 x
•
Trapezoidal Channel Analysis & Design
Open Channel -Uniform flow
Worksheet Name: HOLLEMAN VILLAGE
Comment: PARK POND
Solve For Depth
Given Input Data:
Bottom Width .....
Left Side Slope ..
Right Side Slope.
Manning's n ..... .
Channel Slope ... .
Discharge ....... .
Computed Results:
Depth ........... .
Velocity ........ .
Flow Area ....... .
Flow Top Width .. .
Wetted Perimeter.
Critical Depth .. .
Critical Slope .. .
Froude Number ... .
20.00 ft
5.00:1 (H:V)
9.00:1 (H:V)
0.100
0.0040 ft/ft
16.14 cfs
0.85 ft
0.73 fps
22.03 sf
31.89 ft
32.02 ft
0.26 ft
0.2341 ft/ft
0.16 (flow is Subcritical)
Open Channel Flow Module, Version 3.21 (c) 1990
EXHIBIT 10
Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708
•
Triangular Channel Analysis & Design
Op en Cha nnel -Uniform flow
Worksheet Name: HOLLEMAN VILLAGE
Comment: GRIDIRON LANE CAPACITY, QlO -RIGHT SIDE
Solve For Depth
Given Input Data:
Left Side Slope ..
Right Side Slope.
Manning's n ..... .
Channel Slope ... .
Discharge ....... .
Computed Results:
Depth ........... .
Velocity ........ .
Flow Area ....... .
Flow Top Width .. .
Wetted Perimeter.
Critical Depth .. .
Critical Slope .. .
Froude Number ... .
0 .00:1 (H:V)
26.00:1 (H:V)
0.013
0.0112 ft/ft
8.96 cfs
0.41 ft
4.10 fps
2.19 sf
10.66 ft
11.08 ft
0.49 ft
0.0041 ft/ft
1.60 (flow is Supercritical)
Open Channel Flow Module, Version 3.21 (c) 1990
. EXHIBIT 11
Haestad Methods, Inc . * 37 Brookside Rd * Waterbury, Ct 06708
•
Triangular Channel Analysis & Design
Open Channel -Uniform flow
Worksheet Name: HOLLEMAN VILLAGE
Comment: GRIDIRON LANE CAPACITY, QlO -LEFT SIDE
Solve For Depth
Given Input Data:
Left Side Slope ..
Right Side Slope.
Manning's n ..... .
Channel Slope ... .
Discharge ....... .
Computed Results:
Depth ........... .
Velocity ........ .
Flow Area ....... .
Flow Top Width .. .
Wetted Perimeter.
Critical Depth .. .
Critical Slope .. .
Froude Number ... .
0.00:1 (H:V)
26.00:1 (H:V)
0.013
0.0112 ft/ft
1.61 cfs
0.22 ft
2.67 fps
0.60 sf
5.60 ft
5.82 ft
0.25 ft
0.0052 ft/ft
1.43 (flow is Supercritical)
Open Channel Flow Module, Version 3.21 (c) 1990
EXHIBIT 12
Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708
~ .-. 18-01 s E c T I 0 N 2 2 2 3 I 3 3 HOLLEMAN VILLAGE DEPRESSED INLETS QL = 0.7*(1/(H1-H2))*(H1"5/2-H2"5/2) D E I p D N R E L E p E s T T s H H1 H2 ft in ft ft ft . 5 3 0.41 0.66 0.25 5 4 0.41 0.74 0.33 5 5 0.41 0.83 0.42 10 3 0.41 0.66 0.25 10 4 0.41 0.74 0.33 10 5 0.41 0.83 0.42 15 3 0.41 0.66 0.25 15 4 0.41 0.74 0.33 15 5 0.41 0.83 0.42 INLET - 1, 2 OR 3 SECTIONS DEPRESSION -GUTTER DEPPRS. INCHES DEPTH -FLOW IN APPROACH GUTTER QL -FLOW CAPACITY 2.44 2.44 2.44 2.44 2.44 2.44 2.44 2.44 2.44 EXHIBIT 13 11/09/01 Capture QL Capac. cfs cfs 0.32 0.55 2.75 0.41 0.70 3.52 0.51 0.87 4.35 0.32 0.55 5.51 0.41 0.70 7.04 0.51 0.87 8.69 0.32 0.55 8.26 0.41 0.70 10.56 I 0.51 0.87 13.04