SW6140505_Calculations_20140529

Stormwater and Erosion Control Calculations
for:
Fort Bragg Regional Training Institute
Motor Pool Expansion (Pratt Road)
Fort Bragg, NC
SCO FILE # 110921701
ms consultants project #:
64-26528-00
May 2014
Prepared by:
FED 1 0 2015
Irk —
SEAL
039941
ms consultants, Inc.
engineers, architects, planners
500 Jackson Street
Roanoke Rapids, North Carolina 27870
Phone: [phone]
Fax: [phone]
www.msconsultants.com
(r/LL/W

ms consultants, Inc.
engineers, architects, planners
500 Jackson Street
Roanoke Rapids, NC 27870
[phone]
FAX: [phone]
www.msconsultants.com
DITCH CALCULATIONS
I = 0.2
Project Name:
RTI Motor Pool
SCO FILE # :
110921701
Project Number:
64-26528
Project Location :
Fort Bragg, NC
Designed by:
CAB
Date :
May-14
Inletiditch
s%
n
C
A (Ac)
cfs
total
M
BW
D(ft)
V (fps)
SHEAR
TD1
1.00
0.022
0.40
1.17
0.11
0.11
2.0
0.0
0.20
1.3
0.12
SWALE
0.30
0.022
0.95
1.17
0.25
0.25
5.0
0.0
0.24
0.9
0.04
DITCH
1.00
0.022
0.95
1.33
0.29
0.29
4.0
0.0
0.22
1.5
0.14
SWALE*
0.30
0,022
0.95
1.00
0.22
0.22
5.0
0.0
0.23
0-9
0.04
'Using 10yr-24 hr storm
Summary of Calculations
s% = slope of ditch
In = roughness coefficient
C = runoff coefficient
i = average intensity of rainfall in inches per hour based on a ten year storm
A(sf) =.drainage area in square feet
A(Ac) = drainage area in acres
Q(cfs) = flow in the channel (from channel section runoff only) in cubic feet per second
Qtotal = flow in the channel (from channel section runoff and upstream channel sections) in cubic feet per second
M = horizontal component of sideslope
BW= bottom width of a trapezoidal channel (triangular if BW = 0)
D(ft) = normal flow depth in feet
V (fps) = average velocity in the channel in feet per second
SHEAR = Shear stress at normal depth in pounds per square foot
n = per table 8.05b of the design manual
c = weighted average from table 8.03a of the design manual
A(Ac) = A(sf) / 43560
Q(cfs) = C ' j ` A(Ac)
Qtotal = Q(cfs) + Q(cfs) of all upstream sections
Depth = (( Q(cfs) ` ((2 . sgrt(1 + ( MA2)))A(2/3)) / ( 1.49' agrt(s)' (MA(5/3))))A(3/8)
V(fps) = Qtotal / (( DEPTH , (DEPTH * M)) + ( DEPTH ` BW)
SHEAR = 62.4 ` DEPTH ` a%
'values for depth in trapezoidal channels (BW > 0) are determined using the trapezoidal channel calculator (AutoCa(

ms consultants, Inc.
engineers, architects, planners
500 Jackson Street
®Roanoke Rapids, NC 27870
FAX: ( 52) 515
FAX:[phone]
www.msconsultants.com
Project Name:
RTI Motor Pool
SCO FILE # :
110921701
Project Number :
64-26528
Project Location :
Fort Bragg, NC
Designed by:
CAB
Date :
May-14
PIPE CALCULATIONS
n = 0.013
# of
Upstream S C I A g Q total Pipes Req. Pro. Size Velocity
DRY POND 1 From Ditch Calm => 0.3 2 3.6 15 2.6
Summary of Calculations
s = slope
n = roughness coefficient
Q = flowrate - from ditch calculations or Q=CiA
Req. Size =16'(((Q'n)/(sgrt(s/1Do)))A(3/8))

ms consultants, Inc.
engineers, architects, planners
500 Jackson Street
Roanoke Rapids, NC 27870
[phone]
FAX: [phone]
www.msconsultants.com
DISSIPATOR PAD CALCULATIONS
Type A = no defined Channel
Type B = into defined channel
Project Name :
KI,Motor Pool
SCO FILE # :
110921701
Project Number:
64-26528
Project Location :
Fort Bragg, NC
Designed by:
CAB
Date :
May-14
Type B Type B .Type A Type B
Outlet Dia. Velocity Zone Type sideslope B.W.. Width Death Length Thickness Stone Type
DRY POND 15 2.61 1 B 4 0 3.75 0.4688 5 1 A
Summary of Calculations
Zone = per figure 8.06.b.1 in the Design Manual
Length = per figure 8.06.b.2 in the Design Manual
B.W. = Bottom Width of downstream ditch
Width = 3' pipe diameter
Depth = ( ( width - bottom width) / 2) / sideslope
Thickness = per table on bottom of page 8.06.6 of the Manual
Stone Type = per figure 8.06.b.2 in the Design Manual

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ms consultants, Inc.
engineers, architects, planners
500 Jackson Street
Roanoke Rapids, NC 27870
[phone]
FAX: [phone]
www.msconsultants.com
SEDIMENT TRAP CALCULATIONS
i-10 = 8.0
Project NamP''`RTI Motor Pool
SCO FILE t# :
110921701
Project Number:
64-26528
Project Location :
Fort Bragg, NC
Designed by:
CAB
Date
May-14
At c A (sf) Alec) O (10) SA req L W SA pro V rep D V pro WL
1 0.5 52272 1.20 4.80 2091 65 33 2145 4320 3.0 5607 5
5ummarV of Calculations
C = runoff coefficient
i(10) = average intensity of rainfall in inches per hour based on a ten year storm
A(sf) = drainage area in square feet
A(ac) = drainage area in acres
Q(10) = flow into the trap in cubic feet per second based on a ten year storm
SA req = surface area required at design flow in square feel
L = proposed length of trap in feet
W = proposed width of trap in feet
SA pro = surface area provided in square feet
V req = volume required in cubic feet
D = Depth of the sediment trap from bottom of trap to top of weir in feet
v pro = proposed volume of the trap in cubic feet
WL = Length of weir in feet
c = weighted average from table 8.03a of the design manual
A(ac) = A(sf) 143560
Q(10) = C - i(10) - A(Ac)
SA req = 0.01 . Q(10)
SA pro =L`W
V req = 3600' A(ac)
V pro = (((L'W)+((L-20)'(W-2D)))/2)'D
WL = per table 6.60a of the design manual
BOTTOM EL.
226

r. .
ms consultants, Inc.
engineers, architects, planners ': ;E•
500 Jackson Street
Roanoke Rapids, NC 27870
[phone]
FAX: [phone]
www-msconsultants. com
DRY DETENTION POND CALCULATIONS
Runoff Volume using Simple Method (Section 3.3)
Rainfall Depth
Drainage Area =
50891 SF
Drainage Area =
1.17 Ac
Impervious Area =
35302 SF
Impervious Fraction (IA) =
0.69
Runoff Coefficient (Rv) =
0.67
Rainfall Depth to control =
1 "
Volume =
2859.696 cf
Pre/Post Development Differece
lyr 24 hr Rainfall Depth =
3.06 "
Predev Drainage Area =
50891 sf. .
Predev Impervious Area =
8712
Impervious Fraction =
0.171189
Predev Rv =
0.2
Volume =
6155.228 cf
Outlet Structure
Project Name :
RTI Motor Pool
SCO FILE #:
110921701
Project Number:
64-26528
Project Location :
Fort Bragg, NC
Designed by:
CAB
Date :
May-14
= Drainage Area / Impervious Area
= 0.05 + ( 0.9 * IA)
= 3630 * Depth * Rv * Area
= Drainage Area / Impervious Area
= 0.05 + ( 0.9 * IA )
= 3630 * Depth * ( Rv post - Rv pre) * Area
Release Rate
Predevelopment C = 0.2
1 yr 24 hr Intensity = 0.128 "/hr
Predevelopment Flowrate = 0.03 cfs = C * I * A
Drawdown Time
Control Volume (per depth) = 6155.2 cf
Target drawdown time = 3.5 days
Flowrate = 0.02 cfs = Volume / Time
Circular Orifice
Target Flowrate Q = 0.03 cfs
Discharge Coeff. Cd = 0.6
Storage Depth = 3 ft
Orifice X-sect. Area = 0.006 sf = ( Q / ( Cd * ( SQRT (2 * 322 * ( Depth / 3 )))))
# of orifices = 1
Calculated Orifice Diameter = 1.07 in. = 2 * SQRT (( Area / # of orifices) * Pi ))

ms consultants, Inc.
eng i nee rs,-arch itects,,,pla n n ers
500 Jackson Street
Roanoke Rapids, NC 27870
[phone]
FAX: [phone]
www.msconsultants.com
DRY DETENTION POND CALCULATIONS
Check
Proposed Orifice Diameter = 1.07 in.
Calculated Flowrate = 0.03 cfs
Calculated Drawdown Time = 2.37 days
Project Name:
RTI Motor Pool
SCO FILE # :
110921701
Project Number:
64-26528
Project Location :
Fort Bragg, NC
Designed by;
CAB
Date :
May-14
Anti -Floatation Calculations cf pcf pounds
Weight of Water Displaced = 2.5' x 4' x 4' = 40 x 62.4 = 2496
Weight of Concrete Box=(3x(0.5'x3.5'x3.5'))+(4'x4'x0.5')= 21.125 x150= 3168