HomeMy WebLinkAboutNationwide Permit Info Letter7607 Eastmark Drive, Ste. 252 <77840>
P.O. Box 9253, College Station, TX 77842
Off/Fax: (979) 764-0704
email: civil@rmengineer.com
October 31, 2011
Josh Norton, P.E.
Assistant City Engineer
City of College Station
Planning & Development Services
1101 Texas Avenue South
College Station, TX 77842
RE: MDW Centre (Detention Facility) — Initial Site Plan Submittal Package
1150 University Drive, College Station, TX
Lot 2, Block One — Wheeler Subdivision, Ph 2, Brazos County
RME No.197-0423
Josh Norton:
Please find below the latest Nationwide Permit information issued by the USACE. The
detention facility improvements for the above referenced project are covered by the general
NWP 43 and the proposed improvements are below the maximum "limits" and outside the
requirements for Pre -Construction Notification (PCN). These "limits" and PCN requirements
are as follows:
NWP 43 — Stormwater Management Facilities:
Limits: The discharge must not cause the loss of greater than 112-acre of non -tidal waters of
the United States, including the loss of no more than 300 linear feet of stream bed, unless for
intermittent and ephemeral stream beds this 300 linear foot limit is waived in writing by the
district engineer. This NWP does not authorize discharges into non -tidal wetlands adjacent
to tidal waters. The detention facility constitutes approximately 0.27 acres.
Notification: The permittee must submit a pre -construction notification to the district
engineer prior to commencing the activity for all activities involving expansion or
construction of SWM facilities. Maintenance does not require PCN if limited to restoring
original design capacities. The detention facility project is maintenance with no increase in
design capacity.
Please do not hesitate to call should you have any questions.
Sincerely,
Rabon A. Metcalf P.E. No. W583
Texas Firm Registration No. F-4695
rabon@rmengineet.com
CD1-197-0423-L02
Page I of I
7607 Eastmark Drive, Ste. 250-F <77840>
P.O. Box 9253, College Station, TX 77842
Off/Fax: (979) 764-0704
email: civil@rmengineer.com
October 31, 2011
Josh Norton, P.E.
Assistant City Engineer
City of College Station
Planning & Development Services
1101 Texas Avenue South
College Station, TX 77842
RE: MDW Centre (Detention Facility) — Acknowledgement of City Standards
1150 University Drive, College Station, TX
Lot 2, Block One — Wheeler Subdivision, Ph 2, Brazos County
RME No.197-0423
Josh Norton:
The purpose of this letter is to acknowledge that the construction plans for the public
infrastructure improvements, for the above referenced project, to the best of my knowledge, do
not deviate from the latest B/CS Design Guideline Manual.
I also acknowledge, to the best of my knowledge that the details provided in the construction
plans are in accordance with the B/CS Standard Details.
Please do not hesitate to call if you have any questions.
Sincerely,
��P(E OF TEA, %I
'CEN:E"
Rabon A. Metcalf, P.E. No. 88583 10
Texas Firm Registration No. F-4695
rabon@rmengmeer.com
rmengmeer.com
C13I-197-0423-1,03 Page 1 of 1
M.D.W. Centre — Detention Facility Modifications
Drainage Study
RNIE Consulting Engineers
October 3, 2011
TABLE #3
Te SUMMARY
Combined
Drainage
Overland Channel Flow
Tc
Area I.D.
Flow Time Time
min
Xl
0.081 1.38
16.2
X2
0.215 10.96
33.9
P1
0.144 3.52
12.2
P2
0.215 11.82
34.7
1) The minimum Tc utilized for any drainage basin
will be ten (10) minutes;
2) A time extension of 10 minutes was added to "X2"
& "P2" to compensate for storage timing through
the detention facility of the Grand Oaks
Subdivision;
3.5 Stormwater Runoff Quantities:
Stormwater runoff quantities were calculated, using the Rational Method with the
assistance of the Hydrologic/Hydraulic stormwater modeling program HydroCAD.
Runoff values for the larger watersheds are summarized below in Table #4 — "Drainage
Basin Runoff Quantities". HydroCAD-Existing & Proposed Conditions Drainage
Calculations and their supporting data are contained the "Attachment — Section 3.0"
appendix of this Drainage Report. These calculated runoff quantities were reviewed and
considered reasonable for the studied watershed. It should be noted that the runoff rates
for Drainage Area "Pl" are noticeable different (higher) than what was computed and
illustrated in Table #4 of the original report (1/23/06) and all others DA values slightly
less. This is due to a computational error with rainfall intensities was present in the
original HydroCAD program. Other variations are primarily due to "better data" used for
the hydrologic modeling of other drainage areas. This is further explained in the
"Explanation ofDA Runoffs" paragraph below.
Also, "benchmark" or target discharge rates for post -development conditions being
metered from the detention facility was discussed earlier in Section 2.1 and 2.2. The
following equation was utilized for calculating these target discharge rates (which will be
the required maximum flow released from the detention pond) and are quantified below
in Table #4.
Target Discharge Equation: P2nErAmEo :5 ('Xl+X2)-Pl
Explanation for DA Runoffs:
Since the original runoff values of DA 'TV have increased then also the required
"benchmark" discharge rates, from the detention facility, have decreased. This is
mathematically illustrated above in the "Target Discharge Equation". If X1 and X2 are
moderately constant with the original runoff numbers, but PI values increase, then the
result will yield lower P2o,,.. values.
Detention volume is then estimated as P2 - P2o.. As mentioned earlier P2 values
reduced from the original figures therefore the detention volume will be less.
M.D.W. Centre - Detention Facility Modifications
Drainage Study
RME Consulting Engineers
October 3, 2011
TABLE #8
STORM DRAINAGE SUMMARY
Pipe Size
US Top of
US Node
DS Node
Diameter
Velocity
Capacity Runoff Q
US HGL
Curb
Diff
ID
ID
(in)
(fps)
(cfs) (cfs
ft
Elev. ft
(ft
]0-YEAR RAINFALL EVENT
At
01
30
10.33
44.51 41.65
289.88
297.50
-7.62
A2
Al
30
9.86
44.34 37.60
290.47
299.02
-8.55
A3
A2
24
11.81
32.85 34.66
293.53
300.60
-7.07
A4
A3
24
5.03
32.39 1.29
294.80
302.54
-7.74
A5
A3
18
27.25
44.77 33.27
297.19
300.60
-3.41
100-YEAR RAINFALL EVENT
Al
OI
30
11.64
44.51 57.12
290.69
297.50
-6.81
A2
At
30
10.50
44.34 51.56
291.53
299.02
-7.49
A3
A2
24
15.12
32.85 47.51
295.62
300.60
-4.98
A4
A3
24
5.48
32.39 1.74
295.63
302.54
-6.91
A5
A3
18
28.85
44.77 45.60
299.51
300.60
-1.09
1) The existing 18" pipe (between A3 & A5) is a private line that drains the detention
facility of the Grand Oaks Subdivision into the public drainage system of Lincoln Avenue;
6.0 CERTIFICATION
"This report for the drainage design of M.D.W. Centre (Detention Facility) - Wheeler
Subdivision, Phase Two - Lot 2, Block One was prepared by me (or under my supervision) in
accordance with provisions of the Bryan/College Station Unified Drainage Design Guidelines for
the owners of the property. All licenses and permits required by any and all state and federal
regulatory agencies for the proposed drainage improvements have been issued."
tF. of TE 74%
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Rabon Metcalf, P.E.
State of Texas P.E. No. 88583
Texas Firm Registration No. F-4695
197-0423 Drainage Report Page -15
stmOutput
WinStorm (STORM DRAIN DESIGN)
PROJECT NAME : 197
JOB NUMBER 0423
PROJECT DESCRIPTION : MDW Centre -System A
DESIGN FREQUENCY 10 Years
ANALYSYS FREQUENCY : 100 Years
MEASUREMENT UNITS: ENGLISH
OUTPUT FOR DESIGN FREQUENCY of: 10 Years
Runoff Computation for Design Frequency.
Version 3.05, Jan. 25, 2002
Run @ 10/20/2011 5:07:44 PM
ID
C Value
Area
Tc Tc Used
Intensity
Supply Q
Total Q
-----------------------------------------------------------------------------
(acre)
(min) (min)
(in/hr)
(cfs)
(cfs)
A-1
0.82
1.12
10.00 10.00
8.63
0.000
7.930
0.96
0.84
Pavement
0.4
0.28
Undeveloped
A-2
0.746
0.89
10.00 10.00
8.63
0.000
5.733
0.96
0.55
Pavement
0.4
0.34
Undeveloped
A-3
0.68
0.24
10.00 10.00
8.63
0.000
1.409
0.96
0.12
Pavement
0.4
0.12
Undeveloped
A-4
0.68
0.22
10.00 10.00
8.63
0.000
1.292
0.96
0.11
Pavement
0.4
0.11
Undeveloped
A-5
0.55
13.45
35.00 35.00
4.50
0.000
33.267
-----------------------------------------------------------------------------
0.55
13.45
Single family
Cumulative Junction Discharge Computations
Node
Node
Weighted
Cumulat.
Cumulat.
Intens.
User
Additional
Total
I.D.
Type
C-Value
Dr.Area
Tc
Supply Q
Q in Node
Disch.
---------------------------------------------------------------------------------
(acres)
(min)
(in/hr)
cfs)
(cfs)
(cfs)
OUT1
CircMh
0.584
15.92
35.19
4.48
0.000
0.00
41.652
A-1
JnctBx
0.584
15.92
35.19
4.48
0.000
0.00
41.652
A-2
JnctBx
0.566
14.80
35.09
4.49
0.000
0.00
37.603
A-3
JnctBx
0.554
13.91
35.01
4.50
0.000
0.00
34.664
A-4
JnctBx
0.680
0.22
10.00
8.63
0.000
0.00
1.292
A-5
---------------------------------------------------------------------------------
JnctBx
0.550
13.45
35.00
4.50
0.000
0.00
33.267
Page 1
stmoutput
Conveyance Configuration Data
Run#
Node
I.D.
Flowline
Elev.
US
DS
US
DS
Shape
#
Span
Rise
Length
Slope
n_value
----------------------------------------------------------------------------------
(ft)
(ft)
(ft)
(ft)
(ft)
M
1
A-1
OUT1
287.97
287.63
Circ
1
0.00
2.50
33.90
1.00
0.012
2
A-2
A-1
288.69
288.07
Circ
1
0.00
2.50
62.30
1.00
0.012
3
A-3
A-2
291.76
290.86
Circ
1
0.00
2.00
50.10
1.80
0.012
4
A-4
A-3
294.53
292.48
Circ
1
0.00
2.00
117.40
1.75
0.012
5
---------------------------------------------------------------------------------
A-5
A-3
296.18
292.48
Circ
1
0.00
1.50
24.20
15.47
0.012
Conveyance Hydraulic Computations. Tailwater = 288.210 (ft)
Hydraulic
Gradeline
Depth
Velocity
Junc
Run#
US Elev
DS Elev
Fr.Slope
Unif.
Actual
Unif.
Actual
Q
Cap
Loss
----------------------------------------------------------------------------------
(ft)
(ft)
M
(ft)
(ft)
Ws)
(f/s)
(cfs)
(cfs)
(ft)
1*
289.88
289.54
0.878
1.91
1.91
10.33
10.33
41.65
44.51
0.000
2*
290.47
289.88
0.716
1.77
1.81
10.13
9.86
37.60
44.34
0.000
3*
293.53
292.63
2.000
1.77
1.77
11.81
11.81
34.66
32.85
0.000
4*
294.80
293.53
0.003
0.27
1.05
5.03
0.78
1.29
32.39
0.000
5*
297.19
293.53
8.544
0.96
1.05
27.75
25.29
33.27
44.77
0.000
OUTPUT FOR ANALYSYS FREQUENCY of: 100 Years
Runoff Computation for Analysis Frequency.
ID
C Value
Area
Tc Tc Used
Intensity
Supply Q
Total Q
-----------------------------------------------------------------------------
(acre)
(min) (min)
(in/hr)
(cfs)
(cfs)
A-1
0.82
1.12
10.00 10.00
11.64
0.000
10.689
0.96
0.84
Pavement
0.4
0.28
Undeveloped
A-2
0.746
0.89
10.00 10.00
11.64
0.000
7.728
0.96
0.55
Pavement
0.4
0.34
Undeveloped
A-3
0.68
0.24
10.00 10.00
11.64
0.000
1.900
0.96
0.12
Pavement
0.4
0.12
Undeveloped
A-4
0.68
0.22
10.00 10.00
11.64
0.000
1.741
0.96
0.11
Pavement
Page 2
stmOutput
0.4 0.11 Undeveloped
A-5 0.55 13.45 35.00 35.00 6.16 0.000 45.596
0.55 13.45 Single family
-----------------------------------------------------------------------------
Cumulative Junction Discharge Computations
Node
Node
Weighted
Cumulat.
Cumulat.
Intens.
User
Additional
Total
I.D.
Type
C-Value
Dr.Area
Tc
Supply Q
Q in Node
Disch.
---------------------------------------------------------------------------------
(acres)
(min)
(in/hr)
cfs)
(cfs)
(cfs)
OUT1
CircMh
0.584
15.92
35.17
6.15
0.000
0.00
57.114
A-1
JnctBx
0.584
15.92
35.17
6.15
0.000
0.00
57.114
A-2
JnctBx
0.566
14.80
35.07
6.16
0.000
0.00
51.556
A-3
JnctBx
0.554
13.91
35.01
6.16
0.000
0.00
47.512
A-4
JnctBx
0.680
0.22
10.00
11.64
0.000
0.00
1.741
A-5
---------------------------------------------------------------------------------
JnctBx
0.550
13.45
35.00
6.16
0.000
0.00
45.596
Conveyance Configuration Data
Run#
Node
I.D.
Flowline
Elev.
US
DS
US
DS
Shape
#
Span
Rise
Length
Slope n_value
----------------------------------------------------------------------------------
(ft)
(ft)
(ft)
(ft)
(ft)
M
1
A-1
OUT1
287.97
287.63
Circ
1
0.00
2.50
33.90
1.00
0.012
2
A-2
A-1
288.69
288.07
Circ
1
0.00
2.50
62.30
1.00
0.012
3
A-3
A-2
291.76
290.86
Circ
1
0.00
2.00
50.10
1.80
0.012
4
A-4
A-3
294.53
292.48
Circ
1
0.00
2.00
117.40
1.75
0.012
5
----------------------------------------------------------------------------------
A-5
A-3
296.18
292.48
Circ
1
0.00
1.50
24.20
15.47
0.012
Conveyance Hydraulic Computations. Tailwater = 288.780 (ft)
Hydraulic
Gradeline
Depth
Velocity
Junc
Run#
US Elev
DS Elev
Fr.Slope
Unif.
Actual
Unif.
Actual
Q
Cap
Loss
----------------------------------------------------------------------------------
(ft)
(ft)
M
(ft)
(ft)
(f/s)
(f/s)
(cfs)
(cfs)
(ft)
1
290.69
290.13
1.652
2.50
2.50
11.64
11.64
57.11
44.51
0.000
2
291.53
290.69
1.346
2.50
2.50
10.50
10.50
51.56
44.34
0.000
3
295.62
292.84
3.757
2.00
2.00
15.12
15.12
47.51
32.85
0.000
4*
295.63
295.62
0.005
0.32
2.00
5.48
0.55
1.74
32.39
0.000
5
299.51
295.62
16.050
1.26
1.50
28.85
25.80
45.60
44.77
0.000
* Super critical flow.
NORMAL TERMINATION OF WINSTORM.
Page 3
stm0utput
Warning Messages for current project:
Runoff Frequency of: 10 Years
Tailwater set to uniform depth elevation = 289.54(ft)
Drop flowline elevation. Downstream HGL set to uniform depth elevation at Run# 3
Run# 3 Insufficient capacity.
Upstream hydraulic gradeline exceeds critical elevation at node Id= A-5
Runoff Frequency of: 100 Years
Tailwater set to uniform depth elevation = 290.13(ft)
Run# 1 Insufficient capacity.
Run# 2 Insufficient capacity.
Run# 3 Insufficient capacity.
Run# 5 Insufficient capacity.
Upstream hydraulic gradeline exceeds critical elevation at node Id= A-5
Page 4