SW6221101_Design Calculations_20230327

PN79439.2 SOF Technical Support Training Annex
Fort Bragg, NC
03/22/2023
BIORETENTION CELL
#
REQUIRED VOLUME
DA IA Rd
WQV
Dp
SOIL MEDIA
SAm K
A 1
421,487
237,759
1
19,588
1
19588.12 1
B5 2
57,336
31,155
1
2,576
1
2500 1
B4 3
36,539
24,840
1
2,015
1
2500 1
B3 4
50,100
35,607
1
2,879
1
2500 1
Summary of Calculations
Dm
Q m
FSu
Qu
Su
nu
Dmf
Du
#u
2.5
0.181
10
1.814
0.2
0.011
11.8
6
4
2.5
0.023
10
0.231
0.2
0.011
5.5
4
2
2.5
0.023
10
0.231
0.2
0.011
5.5
4
2
2.5
0.023
10
0.231
0.2
0.011
5.5
4
2
# = Bioretention Basin Number
DA sf)= Drainage Area
IA (sf)= Impervious Area
Rd (in) = Runoff Depth
%I = Percent Impervious = IA / DA
Rv = Runoff Coefficient = = 0.05 + ( 0.9 * %I )
WQV (cf)= Water Quality Volume = 3630 * RD * Rv * DA
Dp t)= Depth of Pond at max stage
S (sf) = Surface Area of Media
K (in/hr) = media permeability
Dm (ft)= Depth of Media
Qm (cfs)= Flowrate thru Media at max stage=((K*2)*SA*Dp)/(Dm*3600*24) = Modified Darcy
FSu = Factor of Safety for underdrains
Qu (cfs)= Design Flowrate of underdrains
Su (%)= Slope of Underdrains
nu = Mannings Roughness Coefficient of Underdrains
Dmf (in)= Diameter of Manifold = 16*(((L7*0.011)/(0.005^0.5))^(3/8)) = Manning
Du (in)= Diameter of Underdrains
#u = Number of Underdrains required = Qud/(((0.005^0.5)/0.011)*((Dud/16)^(8/3)))

Project Name: VLC
Project Number: XXX
Project Location : Butner, NC
Designed by: NSR
Date : 8/30/2018