SW3190601_Calcs_20200311

Project Information
Project Name:
KHA Project #:
Designed by:TRC Date:10/3/2019
Revised by:TRC Date:2/13/2020
Checked by:COB Date:2/13/2020
Design Resource:NCDENR - Stormwater Best Management Practices (April 1999)
NCDENR - Updated Draft Manual of Stormwater Best Management Practices (July 2005)
Site Information
County:Union
Region:Mtn. & Piedmont
Sub Area Location:Drainage Area to Pond
Drainage Area (DA) =5.72 Acres
Impervious Area (IA) =3.50 Acres
Percent Impervious (I) =61.19 %
Average Permanent Pool Depth (dav):
dav Option 1 (when shelf is not submerged) =2.66 ft
dav Option 2 (when shelf is submerged) =3.72 ft
Required Surface Area (85% TSS):(Taken from Chapter C-3 of NCDEQ Stormwater BMP Manual)
SA/DA for dav = 3.5 and 60% Impervious =1.93
SA/DA for dav = 3.5 and 70% Impervious =2.30
Surface Area to DA Ratio (SA/DA) =1.97
Required Surface Area at Perm. Pool =4,918 sf
Required Storage Volume (Water Quality):
Design Storm =1.0 inch
Determine Rv Value =0.60 in/in
Design Storm Storage Volume =12,473 cf
Storage Volume Required =12,473 cf
Summary of Proposed BMP
Bottom of Pond Elevation =642.00 ft
Sediment Cleanout Elevation =643.00 ft
Permanent Pool Elevation =648.00 ft
Temporary Pool Elevation =649.03 ft
Top of Berm Elevation =653.50 ft
Surface Area at Permanent Pool =11,899 sf (Required Surface Area = 4918 sf )
Forebay Volume (FV1) =4,726 cf (17.6% of Main Pool Volume)
Permanent Pool Volume (PPV) =31,701 cf
Temporary Pool Volume (TPV) =12,473 cf (Required Volume = 12473 cf )
Total Storage Volume (TSV=PV-PPV) =72,761 cf
Total Pond Volume (PV=PPV+TSV) =104,462 cf
017437002
0.05 + .009 (I) =
Marvin Publix
Water Quality Calculations
Wet Detention Pond 1
Option 1
Option 2
dav = Vperm_pool / Aperm_pool
Proposed Water Quality Volumes
Water Quality Volume Required =12,473
Water Quality Volume Provided =12,473
Elevation Contour Area
Incremental
Volume
Accumulated
Volume, S Stage, Z
sf ft cu ft cu ft ft
642.00 1,294 0 0 0.00 (Bottom of Pond)
643.00 2,408 1,851 1,851 1.00
644.00 3,513 2,961 4,812 2.00
645.00 4,823 4,168 8,980 3.00
646.00 6,332 5,578 14,557 4.00
647.00 8,028 7,180 21,737 5.00 (Bottom of Shelf)
648.00 11,899 9,964 31,701 6.00 (Permanent Pool Elevation)
648.00 11,899 0 0 6.00 (Top of Shelf)
649.00 12,415 12,157 12,157 7.00
649.03 12,445 316 12,473 7.03 (Temporary Pool Elevation)
650.00 12,907 12,354 24,827 8.00
651.00 13,375 13,141 37,968 9.00
652.00 13,818 13,597 51,564 10.00
653.00 14,238 14,028 65,592 11.00
653.50 14,438 7,169 72,761 11.50 (Top of Berm)
Elevation Contour Area
Incremental
Volume
Accumulated
Volume, S Stage, Z
sf ft cu ft cu ft ft
642.00 1,294 0 0 0.00
643.00 2,043 1,669 1,669 1.00
644.00 2,965 2,504 4,173 2.00
645.00 4,061 3,513 7,686 3.00
646.00 5,325 4,693 12,379 4.00
647.00 6,752 6,039 18,417 5.00
648.00 9,999 8,376 26,793 6.00
Elevation Contour Area
Incremental
Volume
Accumulated
Volume, S Stage, Z
sq ft cu ft cu ft ft
643.00 365 0 0 0.00
644.00 548 457 457 1.00
645.00 762 655 1,112 2.00
646.00 1,007 885 1,996 3.00
647.00 1,276 1,142 3,138 4.00
648.00 1,900 1,588 4,726 5.00
Bottom of
Shelf
Elevation
Perimeter (ft)
647.00 550
Width of Shelf
(ft)6
POND
Water Quality Volume -Wet Detention Pond 1
MAIN POOL
FOREBAY
Project Information
Project Name:
KHA Project #:
Designed by:TRC Date:10/3/2019
Revised by:Date:
Checked by:COB Date:2/13/2020
Design Resource:NCDENR - Stormwater BMP Manual (June 2009)
Water Quality Orifice
Incremental Determination of Water Quality Volume Drawdown Time
Zone 2
Q2 = CD * A* (2gH0)^(1/2)
Zone 1 Q1 = 0
Orifice Diameter (D) =2.00 in
Cd =0.6
Area =0.02182 sf
Ei =648.00 Orifice Inv.
Zone 1 Range =648.00 to 648.0833333
Zone 2 Range =648.0833333 to 649.03
Countour Contour
Area
Incremental
Volume Stage, Z Zone Q Drawdown
Time
sq ft cu ft ft cfs min
648.00 11,899.00 0 0.00 1 0.0000 --
648.03 11,914 357 0.03 1 0.0000 --
648.06 11,930 358 0.06 1 0.0000 --
(Orifice Centroid Elevation)648.083 11,942 279 0.08 1 0.0000 --
648.11 11,956 319 0.11 2 0.0172 310
648.16 11,982 598 0.16 2 0.0291 343
648.21 12,007 600 0.21 2 0.0374 267
648.26 12,033 601 0.26 2 0.0442 227
648.31 12,059 602 0.31 2 0.0500 201
648.36 12,085 604 0.36 2 0.0553 182
648.41 12,111 605 0.41 2 0.0600 168
649.00 12,415.00 7,235 1.00 2 0.1006 1,199
649.00 12,418 31 1.00 2 0.1007 5
649.01 12,421 31 1.01 2 0.1008 5
649.01 12,424 31 1.01 2 0.1010 5
649.01 12,427 31 1.01 2 0.1011 5
649.01 12,430 31 1.01 2 0.1013 5
649.02 12,433 31 1.02 2 0.1014 5
649.03 12,445.00 129 1.03 2 0.1020 21
Total (649.03)--12,473 ------2,948
(Minimum Required Treatment Volume Elev.) Drawdown Time = Incremental Volume / Q / 60sec/min
Summary
Total Volume =12,473 cf
Total Time =2,948 min
Total Time =2.05 days*
Max Q =0.102 cfs
*Drawdown time calculated based on minimum required treatment volume and corresponding elevation
Wet Detention Basin
INCREMENTAL DRAWDOWN METHOD
017437002
Incremental Drawdown Method
Marvin Publix
Wet Detention Pond 1
Project Information
Project Name:
KHA Project #:
Designed by:TRC Date:10/3/2019
Revised by:Date:
Checked by:COB Date:2/13/2020
v
Anti-Flotation Device
Riser Width =5 ft
Riser Length (L) =5 ft
Wall Thickness (WT) =6 in
Top Riser Elev. (Top) =652.40 ft 6.4 feet
Bottom Riser Elev. (Bot) =646.00 ft
Height of Riser (H) =6.40 ft = Top - Bot
Area of Riser (A) =25.0 sf (Water Displaced) = Width * L
Volume of Riser (V) =160.0 cf (Water Displaced) = A * H
Volume of Riser Wall (Vrw) =70.4 cf = [(Width*WT/12*2)*(L*WT/12*2)-A]*H
Factor of Safety (SF) =1.10
Weight (W) =9984.0 lbs = V*62.4
Weight Req'd from Anti-Flotation Device (Wreq) =10982.4 lbs = W*SF 6 inches
*Weight of Riser (WR) =8867.0 lbs (Vrw * Buoyant Wt. + Weight of 6" Base)
Additional Volume of Concrete Req'd (Vreq) =14.1 cf = (Wreq-WR)/150 Extend Riser 6 inches
Extend Riser (RE) =6.00 in
Volume of Riser Extension (VRE)=18.0 cf = [(Width*WT/12*2)*(L*WT/12*2)]*RE/12
Volume of Anti-flotation 0'x0'x0' Concrete Slab (Vcs)=0.0 cf = Lengthcs*Widthcs*Depthcs
Volume Provided (Vtot)=18.0 cf = VRE+Vcs
Is the Anti-flotation Device Sufficient (yes/no)?Yes 18.0 >14.1
*Assume buoyant weight of concrete = (150-62.4) pcf
Wet Detention Basin
ANTI-FLOTATION DEVICE SIZING
017437002
Marvin Publix