HomeMy WebLinkAboutDrainage CalculationsAlan Gibbs
City of College Station Development Services
P.O. Box 1100
College Station, TX 77840
RE: Emerald Forest Park Playground Drainage Calculations
Dear Alan,
MITCHELL
MM
MORGAN
May 2, 2011
We have completed our design work for the Emerald Forest Park Playground project. As
we discussed prior to our commencing this design work given the minimal amount of fill
that was being contemplated for this project we would provide:
• calculations that illustrated that the project fill limits were outside the conveyance
area for Bee Creek, and
• the project was relatively balanced between cut and fill areas.
Attached you will find the overall grading plan for the project showing the areas that are
being filled in order to raise the new playground approximately 2 feet to prevent frequent
inundation during flooding events.
As part of this project, several sidewalks within the park were also raised to meet this
increased playground elevation. As a result of this we installed several cross drainage
structures under the sidewalk to allow for drainage. Also seen on this grading plan are
several swales designed to convey this overland drainage to the creek.
As we completed the design and looked at the new floodway and floodplain locations that
were recently remodeled with the Bee Creek improvements we realized that the entire
park is located within the floodway of Bee Creek, as seen on Figure 1. This fact alone
will not allow us to illustrate that all improvements will be located outside the
conveyance area of Bee Creek.
We can show that we have not reduced any storage volume as we have balanced the
cut /fill on the project as seen below.
Volume Cut = 11,701.8 CF
Volume Fill = 11,698.6 CF
511 UNIVERSITY DRIVE EAST, SUITE 204 • COLLEGE STATION, TX 77840 • 7 979.260.6963 • F 979.260.3564
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info@mitchellandmorgan.com • www.mitchellandmorgan.com
We have also added the fill that we are contemplating on the project to the current FEMA
approved Bee Creek model. The results of this run and the locations of the cross sections
can be seen in Figure 1 and Table 1. The HEC -RAS runs provided are as follows:
new fill
As seen in Table 1, the largest increase in water surface elevation occurred at River
Station 7255.99 upstream of the park. The water surface elevation rise is 0.01 feet and
occurs in the 10 and 100 year events.
Several velocity values decreased at cross section 7255.99 and 6903.48 but increased
slightly ( +0.09fps maximum) at cross section 7063.37. Given the negligible magnitude
of these changes we feel confident in stating these improvements will not increase
floodplain area, will not increase water surface elevation, will not decrease conveyance
and will not increase velocity. Therefore we believe we have met all the requirements of
the No Adverse Impact (NAI) regulations as set forth in Chapter 13 - Flood Hazard
Protection Ordinance.
We hope that the above description of the project and the attached exhibits have indeed
illustrated that we have designed this project to effect No Adverse Impact on the
surrounding properties.
If you have any questions, please feel free to contact me.
Thank you,
1'
ames T. Batenhorst, PE
Project Engineer
Attachments
cc: file
FEMA approved model
— FEMA approved model adjusted with actual field topo in Emerald Forest Park
- FEMA approved model adjusted with actual field topo in Emerald Forest Park &
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EMERALD FOREST PARK PLAYGROUND
Revisions
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Run 1 Unfilled Shade
Run 2 Filled Shade
Run 3 Filled Shade
Sheet 1
TABLE 1 - PROFILE OUTPUT
HEC -RAS RUN OF UPPER BEE CREEK
Page I
W S
Elev
(ft)
244.78
Crit W.S.
(ft)
E.G. Elev
(ft)
244.86
E.G. Slope
(ft/ft)
0.000673
Vel Chnl
(fUs)
3.04
Flow Area
(sq ft)
3415.63
Top
Width
(ft)
999.77
999
Froude#
Channel
0.2
0.2
Reach
River Sta
Profile
Plan
Q Total
Min Ch El
(ft)
232.97
BeeMain
(cfs)
4980
Upper
7255.99
10.00%
BeeMainWOEFP
4980
232.97
244.77
244.86
0.000675
3.04
3411.67
3415.91
999.83
0.2
Upper
7255.99
7255.99
10.00%
10.00% BeeMainW
-EFP
4980
232.97
244.78
244.86
0.000673
3.04
3885.74
1050
0 24
Upper
BeeMain
6720
232.97
245.23
245.35
0.000905
3.67
1049.9
0.24
Upper
7255.99
2.00%
BeeMainWOEFP
6720
232.97
245.23
245.34
0.000908
3.68
3880.53
1050
4
Upper
7255.99
2.00%
2.00%
BeeMainW -EFP
6720
232.97
245.23
1
0.25
Upper
7255.99
BeeMain
7280
232.97
245.36
245.49
0.000978
3.67
4021 .36
1053.6
0.25
Upper
7255.99
1.00%
BeeMainWOEFP
7280
232.97
245.35
245.48
0.000981
3.87
4015.72
4022.02
1053.8
0.25
Upper
Upper
7255.99
7255.99
1.00%
1.00%
BeeMainW -EFP
7280
232.97
245.36
244.73
245.49
244.77
0.000978
0.000294
3.86
1.99
4798.8
4941.92
1262.4
1262.5
0.14
0.13
BeeMain
4980
234.61
Upper
7063.37
10.00°/
BeeMainWOEFP
4980
234.61
244.73
244 76
1.93
1262.4
0.13
Upper
7063.37
7063.37
10.00%
10.00%
BeeMainW -EFP
4980
234.61
244.73
0.000278
2
4946.92
5359.31
1293
0 16
Upper
BeeMain
6720 234.61
245.17
245.22
0.000404
2.43
1293.1
0.16
Upper
7063.37
2.00%
2.00%
BeeMainWOEFP
6720 234.61
245.17
245.22
0.000383
2.37
5503.03
1293
Upper
7063.37
7063.37
2.00%
BeeMainW -EFP
6720 234.61
245.17
55 .3
130 3
0.16
Upper
BeeMain
7280
234.61
245.29
245.22
0.0004
2.44
1300.8
0.16
Upper
7063.37
1.00%
BeeMainWOEFP
7280
234.61
245.29
245.35
0.000417
2.50
5663.71
5467.76
1300.7
0.17
Upper
Upper
7063.37
7063.37
1.00%
1.00%
BeeMainW -EFP
7280
234.61
245.29
245.35
0.000443
2.57
1406.5
0.11
BeeMain
4980
232.51
244.7
244.73
0.000188
1.93
5909.12
1406.8
0.11
Upper
6903.48
10.00%
BeeMainWOEFP
4980
232.51
244.7
244.73
0.000171
1.84
6212.63
1406.8
0.11
Upper
6903.48
6903.48
10.00%
10.00%
BeeMainW -EFP
4980
232.51
244.7
244.73
0.000167
1.82
6271.91
1427.8
0 14
Upper
BeeMain
6720
232.51
245.12
245.17
0.000268
2.37
6512.11
1428.1
0.13
Upper
6903.48
2.00%
2.00%
BeeMainWOEFP
6720
232.51
245.13
245.17
0.000244
2.27
6818.23
6878.01
1428.2
0.13
Upper
Upper
6903.48
6903.48
2.00%
BeeMainW -EFP
6720
232.51
245.13
245.24
245.17
245.29
0.000239
0.000294
2.25
2.51
6683.12
1433.8
1434.1
0 14
0.14
1.00%
BeeMain
7280
232.51
Upper
6903.48
1.00%
BeeMainWOEFP
7280
232.51
245.25
245.29
0.000268
2.40
6990.11
7050.05
1434.2
0.14
Upper
6903.48
1.00%
BeeMainW -EFP
7280
232.51
245.25
245.29
0.000263
2.37
Upper
6903.48
10.00%
BeeMain
4980
232.45
244.68
238.5
244.72
0.000213
1.94
5105.17
1368.4
1368.4
0.12
0.12
Upper
6860.67
BeeMainWOEFP
4980
232.45
244.68
238.5
244.72
0.000213
1.94
5105.17
1368.4
0.12
Upper
6860.67
6860.67
10.00%
10.00%
BeeMainW -EFP
4980
232.45
244.68
238.5
244.72
0.000213
1.94
5105.17
1404.9
0.14
Upper
BeeMain
6720
232.45
245.09
239.25
245.15
0.000305
2.39
5659.3
1404.9
0.14
Upper
6860.67
2.00%
2.00%
BeeMainWOEFP
6720
232.45
245.09
239.25
245.15
0.000305
2.39
5659.3
5659.3
1404.9
0.14
Upper
Upper
6860.67
6860.67
2.00%
BeeMainW -EFP
6720
232.45
245.09
239.25
245.15
0.000305
2.39
245.21
239.46
245.27
0.000335
2.53
5816.92
1415.2
1415.2
0.15
0.15
1.00%
BeeMain
7280
232.45
Upper
6860.67
BeeMainWOEFP
7280
232.45
245.21
239.46
245.27
0.000335
2.53
5816.92
1415.2
0.15
Upper
6860.67
1.00%
BeeMainW - FP
7280
232.45
245.21
239.46
245.27
0.00 335
2.53
5816.92
Upper
6860.67
Upper
6802.96
Culvert
789.27
0.52
BeeMain
4980
232.35
241.19
239.12
241.80
0.004773
6.56
866.27
789.27
0.52
Upper
6746.75
10.00%
10.00%
BeeMainWOEFP
4980
232.35
241.19
239.12
241.8
0.004773
6.56
866.27
789.27
0.52
Upper
6746.75
6746.75
10.00%
BeeMainW -EFP
4980
232.35
241.19
239.12
241.8
0.004773
6.56
866.27
937.12
0.6
Upper
Upper
Upper
Upper
Upper
Upper
6746.75
6746.75
6746.75
6746.75
_ 6746.75
2.00%
2.00%
2.00%
1.00%
1.00% o
1 00
BeeMain
BeeMainWOEFP
BeeMainW -EFP
BeeMain
Bee MainWOEFP
/0 = --
6720
6720
6720
7280
232.35 241.73
232.35 241.73
232.35 241.73
232.35 242.03
2® 242.03
239.93
239.93
239.93
240.16
240.16
242.63
242.63
242.63
242.67
242.67
0.006219 7.94
0.006219 7.94
0.006219 7.94
0.004735 7.17
0.004735 7 17
978.65
978.65 937.12
978.65 937.12
1697 42 9911.822
697.42 991.82
1�
0.6
0.6
0 53 0.53
0.53
Upper
Run 1 Unfilled Shade
Run 2 Filled Shade
Run 3 Filled Shade
Sheet 1
TABLE 1 - PROFILE OUTPUT
HEC -RAS RUN OF UPPER BEE CREEK
Page I
Alan Gibbs - Emerald Forest Park Improvements
From: Alan Gibbs
To: Haeber, Jeff
Date: 6/14/2011 1:37 PM
Subject: Emerald Forest Park Improvements
CC: Norton, Josh
Jeff,
I inadvertently forgot to include that:
9. Fill in SFHA requires a post Certification of Compaction of fill in accordance with FEMA Technical Bulletin 10 -01.
Jeff,
Below are comments I have after reviewing the 6/6 submittal. I wanted to first send the comment to you - let me
know if you want to discuss.
1. Note that no spoils beyond the specified fill are to be stockpiled on site.
2. Depict floodplain and floodway, and limits of construction
as
3. Proposed utilities and structures (in the absense of being intrusion of wat �� and shall reBst the structueal ( l o ads and
flood - proofed meaning watertight and impermeable to the
buoyancy effects from the hydrostatic and hydrodynamic conditions.
4. The slope of the northernmost proposed sidewalk appears backward.
5. The sidewalk detail and general notes appear to conflict - with regard to joints and bedding /compaction.
6. Confirm if the River Stat 7063 Min Chan elev is actually N2 ft higher than the upstream Stat 7255. Is there standing
water in this reach? If not, update the model.
7. Address why Stat 7063 appears to have proposed net fill, but the flow area increases and there is an increase in
velocity.
8. Fyi, a licensed plumber and electrician will be required to install applicable improvements including necessary
permits.
Alan Gibbs, P.E., CFM
City Engineer
Planning and Development Services
City of College Station
P.O. Box 9960
College Station, TX 77842
Office: (979) 764-3570
Fax: (979) 764-3496
Email: a ibb
a0cstx.aov
City of College Station
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