SW3230301_Calculations_20230919 (2)

Kerns Ridge 4mcKuv PROJECT NO.: 08433-0001 BY: JCB IE. 0 ED
DATE: 09/19/22 T.M.: JCB
REVISED: 09/19/23 P.M.: JCB WET POND#2 CALCULATIONS
DESIGN OBJECTIVE
Awet pond shall be designed to capture the design storm and release it slowly over a period oftwo to five days via a properly designed outlet structure.The first outlet in the structure is
designed to be above the bottom of the pond,thus creating a permanent pool of water.Stormwater shall have an adequate flowpath to bring about removal of TSS through dilution and
settling.The pond shall be designed in a manner that protects the device,the areas around the device and the receiving stream from erosion.The pond also must be maintained properly
to prevent the resuspension of captured sediments.
SITE CHARACIERISTICS
Drainage Area 1,261,062 if
Post-development impervious area 599,990 112
Post-development impervious percentage 48%
Design rainfall depth 1.0 in
DESIGN VOLUME
Mnimum volume required 50,653 113
3630 x rainfall depth x drainage area x(0.05+0.9 x impervious percentage)
Volume provided 60,202 ft3 See Stage-Storage table below
ELEVATIONS
Temporary pool elevation 677.00 finsl
Permanent pool elevation 675.50 finsl
Top of6fl vegetated shelf elevation 676.00 finsl
Bottom of 6ft vegetated she If elevation 675.00 finsl
Sediment cleanout,top elevation(bottom of main pool) 671.50 finsl
Sediment cleanout,bottom elevation 671.00 finsl
Sediment storage provided 0.5 it
SURFACE AREAS
Temporary pool area 43,257 ft2
Nhin pool area REQUIRED 22,573 ft2 SAIDAratio x Drainage Area
Main pool area PROVIDED 30,896 ft2 OK
SAIDAratio 1.79 From SAIDAtable for Piedmont/Nbuntains(50%impervious,3.0 feet average depth)
Bottom of vegetated shelf area 29,623 112
Bottom of main pool area 19,747 ft2
VOLUMES
Temporary pool volume 60,202 ft3 See Stage-Storage table below
Main pool volume 100,396 ft3 See Stage-Storage table below
Forebay volume 15,062 ft3 See Stage-Storage tables below
Forebay%of main pool volume 15.00% OK

Kerns Ridge •
PROJECT NO.: 08433-0001 BY: JCB `v' KNI&CREEL
n� ' l
DATE: 09/19/22 T.M.: JCB v
REVISED: 09/19/23 P.M.: JCB WET POND#2 CALCULATIONS
Im. MAINPOOL STAGE-STORAGE TABLE
Elevation Area Volume Volume
Area(sf)
(i si) (ac) (cu-ff) (act)
671.50 20870 0.4791 0 0.0000
672.00 21792 0.5003 10654 0.2446
673.00 23880 0.5482 33459 0.7681
674.00 26093 0.5990 58413 1.3410
675.00 28357 0.6510 85603 1.9652
675.50 30896 0.7093 100396 2.3048
FOREBAY#1 STAGE-STORAGE TABLE
Elevation Area Volume Volume
Area(sf)
(imp (ac) (cu-ff) (ac$)
672.50 1999 0.0459 0 0.0000
673.00 2144 0.0492 1035 0.0237
674.00 2627 0.0603 3414 0.0784
675.00 3135 0.0720 6288 0.1444
675.50 3399 0.0780 7919 0.1818
FOREBAY#2 STAGE-STORAGE TABLE
Elevation Area Volume Volume
Area(sf)
(ns1) (ac) (cu-ff) (ac$)
672.50 1869 0.0429 0 0.0000
673.00 1969 0.0452 958 0.0220
674.00 2367 0.0543 3121 0.0717
675.00 2790 0.0640 5694 0.1307
675.50 3010 0.0691 7142 0.1640
TEIvFORARYPOOL STAGE-STORAGE TABLE I
Elevation Area Volume Volume
Area(sf)
(xxsi) (ac) (cut) (ac8)
675.50 35781 0.8214 0 0.0000
676.00 39613 0.9094 18822 0.4321
677.00 43257 0.9930 60202 1.3820
SA/DA TABLE DATA
Coastal SA/DAtable used? N
Nbuntains/Piedmont SA/DAtable used? Y
SA/DAratio 1.79 From SA/DAtable for Piedmont/Nbuntains(50%impervious,3.0 feet average depth)
Average depth of main pool 3.25 ft Nhin pool volume/NETin pool surface area
DRAWDOWN CALCULATIONS
Drawdown through orifice? Y
Diameter of orifice(if circular) 3.00 in
Area of orifice 0.05 ft2
Coefficient of discharge(CD) 0.60 (unitless)
[hiving head(I0) 0.50 fl
Design volume drawdown time 4.17 days OK,draws down in 2-5 days.