SW3201003_Calculations_20210305

YARBR+OUGH- ILLIAMS & HOULE, INC.
Planning • .Surveying • Engineering
730 WINDSOR OAK COURT (28273)
P.O. BOX 7007 (28241)
CHARLOTTE, NC
PHONE [phone] FAX [phone]
NC CORPORATE REGISTRATION #C-0475
CALCULATIONS
FOR
AUTO FINANCE & CAR CARE CENTER
DATE:10/ 15/20
REVISION 02/05/21
CONTENTS:
• STORM DRAINAGE CALCULATIONS
• DROP INLET CALCULATIONS
• EROSION SEDIMENT BASIN
CALCULATIONS
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• SKIMMER CALCULATIONS''��
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• SAND FILTER CALCULATIONS
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• RIP RAP APRON CALCULATIONS
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STORM DRAINAGE
CALCULATIONS

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DROP INLET
CALCULATIONS

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EROSION SEDIMENT
BASIN CALCULATIONS

AUTO FINANCE & CAR CARE CENTER
SEDIMENT BASIN CALCULATIONS
DATE: OCTOBER 15 2020
REVISION FEB. 5 2021
BASIN # 1 DRAINAGE AREA 5.49 AC
W ,D
INTENSITY (I) 7.03 (10 yr)
Qio = CIA= 0.6 x 5.49 x 703 A 23.16 cIs
REQUIRED STORAGE =
REQUIRED SURFACE AREA
BASIN STORAGE DIMENSIONS
STORAGE PROVIDED =
TOP OF DAM HEIGHT (Y) _
Z 3 +
SPILLWAY - L = Q / (3 x hl 5)
5.49 x 1800 c 9,882 CF
325 x Q10 7,527 SF
CONTOUR 688
CONTOUR 687
CONTOUR 686
20,058 CF 685
H+SPILLWAY DEPTH +1.0' FREEBOARD
I + 1 = 5 FT
7.25 It 20' MIN,
SURFACE AREA
8,245
7,121
6,174
5,282
TOTAL 20,058
YARBROUGH-WILLIAMS & HOULE, INC.
730 WINDSOR OAK COURT CHARLOTTE, NC 28273
P.O. BOIL 1198 PINEMILLE, NC 28134
PHONE [phone] FAX [phone]
YARBROUGH-IMI.(I E, INC.
730 WINDSM :;HARLLITTE, NC 28273
P.O. BOX ' NC 28134
PHO"' rAX [phone]

SKIMMER
CALCULATIONS

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SAND FILTER
CALCULATIONS

SAND FILTER CALCULATIONS
References: NCDEQ Stormwater BMP Manual Chapter 11
Date : 7-Oct-20 Rev: 02/08/21
PROJECT AUTO FINANCE & CAR CARE CENTER
SAND FILTER 1
Base Data
730 Windsor Oak Ct
Charlotte, NC 28273
704-556-1990
YARBROUGH-WILLIAMS & HOULE, INC.
Planning - Surveying - Engineering
Site Area Post = Total Drainage Area (A) =
Site Area Pre = Total Drainage Area (A) =
Measured Impervious Area -
Hy rrotooic Data
Pre - CN
2.62 ac
4.86 ac
4.86 ac
53.8595
Acreage
Land Use
Soil TvDe
H drolo is rouD
CN
i h
005
Ex Pvmt
98
1.01
481
Woods
ScA
C
70
69.28
0.00
0.00
486
Post- CN
CNP,o
70
A_ crea a
Land Use
Soil Tvpe
H dro11 i roup
CN
(weighted) CN
262
Bld /Pvt/SW
98
5277
2.24
Grass
SCA
C
74
34.15
000
000
4 86
Pre
CN 70
Post
87
CNP„,
87
Steps 1, 2 Determine if the development site and conditions are appropriate for the use of a
Sand Filter pond and consider any site -specific design considerations
Step 3 Compute Water Quality Volume (WQv)
Compute Runoff Coefficient, Rv, using (Schueler's Method) Equation 3.1
Rv = 0.05 + 0.009 (1) 1 = percent impervious over basin area = 538 %
Total Rainfall amount (P) _ ©in
Rv = 0.535 Ro = 1
Compute Water Quality Volume, WQv, using Equation 3 2
Desi n Volume
WQv = 1.ORvA/12 = 0.22 ac-ft or D432 of
Caclulate Discounted Design Volume
Multiply the design volume by 0.75, a "discount" (DDV) that is allowed because stormwater infiltrates so rapidly through the sand media that the
stormwater is treated throughout the storm event. This is used for the sand filter surface area calculations.
DDV = 0,75 WQv = 7073.73 Cf
Convert Water Quality Volume, WQv to inches of runoff using Equation 3.3
WQv = 1.0(Rv) = 0.53 in
Compute Site Hydrologic Input Parameters
Using SCS hydrologic procedures and/or computer models the following data can
be determined for the example development site.

Step 4 Summary of Hydrocad Input and Output
I-IVnPnl Ar.lf' IPIPI IT nATA
Condition
Area ac
CN
tc hours
tc min
Pre-dev
4.86
70
0.08
5
Post dev
4.86
87
008
5
Results of Preliminary Hydrologic Calculations
(From Computer Model Results Using SCS Hydrologic Procedures)
Condition
1 YR
Q2- ear
Q10- ear
Runoff
cfs
cfs
cfs
Pre-Dev
322
3.27
11.12
w/ out controls
Post Dev
10.04
12.64
23.27
w/ controls
Post Dev
0.22
0.39
7.85
POST MODIFIED CN
Step 5 Compute Water Quality Peak Flow (WQp) using modified CN (adjusted) value
Compute modified SCS curve number, CN, using Equation 3 4
CN mod -post = 1000/[10 + 5P + 10WQv - 10(WQv2 + 1 25 WQvP)0 5]
CN mod -post = 95
Compute WQp using SCS the hydrograph procedure documented in the CMSWDM
using Hydrocad hydrologic model A 1-inch, 6-hour balanced storm event is required.
See Hydrocad Report WQp = 6,48 cfs
Step 5 Compute Sedimentation Chamber Minimum Surface Area
Per Section 11.3.5 NCDENR Stormwater BMP Manual
Also Min As (Wz = (240 * Rv * AD] * Rp (ft) = 623.58 sf
As provided = 3250 0 sf
Forebay Chamber Storage -Elevation Data
Elevation
Area sf
Area ac
Ht ft
Inc. Vol ac-ft
Acc. Vol ac-ft
Acc. Vol cf
685
2150.0
0.049
0.0
0.00
0.00
0.00
686
2700.0
0.062
1.0
0.06
0.06
2425.00
687
3250.0
0.075
2.0
0.07
0,12
5400.00
Step 6 Compute Sand Filter Area to Treat Water Quality Volume
The sand filter area is calculated by dividing the Discounted Design Volume (DDV) by the maximum ponding depth of he sand filter
Af=DDV /h
where:
Af = surface area of filter bed (ft2)
DDV = discounted design volume (cf) 7073.73
h = maximumum ponding depth (ft) 5
Af = 1414.7 sf required min. area of sand filter
Est. Sand filter area 37.6 foot by 37.6
Filter Surface Area (AI= ) 1415 sf for calculations
NOTE: top sand filter provided is 44' X 49'
bottom of sand filter (39.5' X 44.5') is used to Calculate outflow through the filter
Actual Sand Surface Area Provided = [ 1425 sf

Step 7 Verify the Volumes
[At (St) + AS (st)) X hm_Fnwr.
Filter area provided = 4738 sf
Forebay area provided = 2975 sf
hMa.FiNer • 1.70 ft max head interpolated
13111 cf >= 9432 cf minimum
Step 8 Develop Water Quality Storage -Elevation Table
Water Qualitv Staraae-Elevation Data fincludina Fnrahavl
Elevation
Area sf
Area ac
Ht ft
Inc. Vol ac-ft
Acc. Vol ac-ft
Acc. Vol c
684.7
2200.0
0.051
000
0.00
0.00
0.00
685
4550.0
0.104
0.30
0.02
0.02
1012.50
686
5650.0
0.130
1.30
0.12
0.14
6112,50
687
6800.00
0.156
2.30
0.14
0.28
12337.50
688
8100.00
1
0.186
3.30
0.17
0.45
689
9150,00
0.210
4.30
020
0.65
690
10300.00
0.236
5.30
022
0.88
M
Top of Sand Filter Elevation
Top of Box Outlet Structure =
WQv Elevation =
Top of Dam
Forebay Weir Elevation =
1 YR WSE =
2 YR WSE =
10 YR WSE =
50 YR WSE =
100 YR WSE =
684.70
688.30
686.40
690.00
687.00
687.62
687.66
688.31
688.64
688.74
WQv release in (max 40 hrs) = IYES
Step 9 Develop Stage -Discharge for Sand Filter Media
Af = (WQv)(df)/[(k)(hf+df)(tf)]
WQv/tf = Qo = Af (k)(hf+df)/(df))
where:
Af = surface area of filter bed provided (ft2) 1426.00 sf
df = filter bed depth (ft) 1 50 ft
k = coefficient of permeability of filter media (ft/day) 35
hA = average height of water above filter bed (ft) 0.85 ft
At Elevation
689
4 3 feet above sand filter
Qo =
19285
=
O:223
rfs
At Elevation
688
3 3 feet above sand filter
Qo =
15960
cfida
0 185
cfs
At Elevation
687
2.3 feet above sand filter
Qo =
12635
cfida
=
0 146
cfs
At Elevation
686
1.3 feet above sand filter
Qo =
9310
cfida
=
0.108
cis
At Elevation
685
0.3 feet above sand filter
Qo =
5985
cfida
=
0.069
cis
At Elevation
6847
sand filter surface
Qo =
0
cfida
=
0.000
cfs
03 1 13
0 069 0 11

Bottom of Sand Filter Elevation =
Time to Drain WQV through sand filter =
SHWT elevation =
Step 10 Design Underdrain System
682.20
40 hr
NOT ENCOUNTERED AT ELEVATION 6?7 5
The underdrain capacity must be greater than the filter media capacity
The capacity must drain the runoff volume from the system within design duration of 40 hours
The design must assume that 50 percent of the underdrain system (perforations and pipe system capacity)
is lost due to clogging_
Design specifications require the underdrain system to be a 6-inch perforated PVC pipe with 3/8-inch
perforations spaced 3 inches on center, along 4 longitudinal rows spaced 90 apart Minimum underdrain
slope is 0.5 percent.
Sand Filter Area = 1415 sf
The filter media is the controlling outflow condition.
Compute minimum drawdown discharge
Water Quality Volume =
Drawdown =
Compute Perforation Capacity
The maximum underdrain spacing is 10 feet on center.
The dimension of the sand filter bottom is roughly
Actual length of pipe containing holes is approx. 39 feet per row.
- 4 parallel 6" PVC underdrain pipes were selected.
Number of perforations =
50 percent of perforations =
Capacity of one hole = CA(2gh)o 5
9432 cf
9432 cf /(120 hrs)(3600 sec/hour)
0,022 cfs
39,5' x 44.5'
4 pipes 4 rows/ft)((39) f /pipe)(4 holes/row)
24961 holes
1248 holes
_(0.6)(3.1416)[(3/8in)(1/24)]2[(64.4)(5.Oft)]os
= 0.0083 cfs
Total Capacity = 0.083 x 1248
10.31 cfs
Filter Media Capacity = 0.096 cfs at 1 foot of head
Total Capacity of 10.31 cfs is greater than Filter Media Capacity and
Minimum Drawdown Discharge
Compute underdrain pipe capacity
Underdrain Pipe Size = © in = Area=
For 6-inch PVC underdrain pipe at 0,005 ft/ft slope:
Capacity of pipe = (1.49/n)(A)(A/P)o 67(S)o 5
_=(1,49/0.013)(0.196)(0 125)067(0 005)0 5
= 0.39 cfs
Fifty percent assuming clogging = 0.20 cfs
The underdrain pipe capacity (0.20 cfs) is greater than the filter media capacity of 0.096 cfs,
and greater than the minimum drawdown capacity requirement (0.022 cfs computed in this step) Therefore
the design is acceptable.
Step 11 Design Overflow Weir
A 16 foot emergency spillway overflow weir is designed with a weir elevation of 688.3 design elevation
Step 12 Access Maintenance Access and Safety Features
All areas of both chambers must be within 25 feet of an access location from the surface that is large enough
for personnel to enter in order to remove trash, debris, sediment, etc.
In addition, the sand filter media must be accessible in order to facilitate complete replacement when the
sand filter ponds runoff without filtration
Check 50 year storm elevation - The 50 year storm events bypasses the sand filter The partial flow
from these storms flowing to the sand filter stays within the sand filters with overflow over the outlet structure.
0.196 sf
0.125

Pre-dev
5ubcat Reach an Lin k

Sf # 1 HydroCad
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
HydroCAD® 10.10-5a s/n 05047 © 2020 HvdroCAD Software Solutions LLC Pace 2
Rainfall Events Listing (selected events)
Event# Event Storm Type Curve Mode Duration B/B Depth AMC
Name (hours) (inches)
1 1 inch
Charlotte 6-hr 1 INCH
Default
6.00 1
1.00 2
2 2-yr
Charlotte 6-hr 2-yr
Default
6.00 1
2.28 2
3 1 yr
Charlotte 24-hr 1-yr
Default
24.00 1
2.58 2
4 10-yr
Charlotte 6-hr 10-yr
Default
6.00 1
3.72 2

Sf # 1 HydroCad Charlotte 6-hr 1 INCH 1 inch Rainfall=1.00"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
HydroCAD® 10.10-5a s/n 05047 © 2020 I�ydroCAD Software Solutions LLC Page 3
Summary for Subcatchment 7S: Pre-dev
Runoff = 0.01 cfs @ 5.55 hrs, Volume= 0.002 af, Depth= 0.00"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs
Charlotte 6-hr 1 INCH 1 inch Rainfall=1.00"
Area (ac) CN Description
4.860 70 Woods, Good, HSG C
4.860 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
min (feet) ft/ft (ft/sec) (cfs
5.0 Direct Entry, Direct Entry
Subcatchment 7S: Pre-dev
Hydrograph
0 014 �--
0013 Charlotte s-hr
0012 I INCH
0011-
001 1 inch Rainfall=1.00''
0.009: Runoff Area=:4.8W0 ac
000°°7 ° LL 7 Runoff Vo,14m'e=0'002 of
° Runoff Depth=0.00"
0-006
0 005 Tc=5.0 m i n
0.004 CN=70
0.003
0.002
0 001
0
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135140
Time (hours)
CT Runoff

Sf # 1 HydroCad Charlotte 6-hr 2-yr Rainfall=2.28"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCADO 10.10-5a s/n 05047 © 2020 HvdroCAD Software Solutions LLC Paae 4
Summary for Subcatchment 7S: Pre-dev
Runoff = 3.27 cfs @ 3.18 hrs, Volume= 0.144 af, Depth= 0.35"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs
Charlotte 6-hr 2-yr Rainfall=2.28"
Area (ac) CN Description
4.860 70 Woods, Good, HSG C
4.860 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, Direct Entry
Subcatchment 7S: Pre-dev
Hydrograph
Charlotte 6-;hr 2-yr
3 Rainfa11=2.28"
Runoff':Area=4.860 ad
Runoff Volume=O'.144 of
3
2 Runoff ;Depth=0.35"
LL Tc=5.0 min
CN-70
1 5 10 15 20 25 30 35 41 45 50 55 .1 65 70 75 81 85 90 95 100 105 110 115 120 125 130 135 140
Runoff

Sf # 1 HydroCad Charlotte 24-hr 1-yr 1 yr Rainfall=2.58"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
HydroCAD® 10.10-5a s/n 05047 © 2020 HydroCAD Software Solutions LLC Paae 5
Summary for Subcatchment 7S: Pre-dev
Runoff = 3.22 cfs @ 12.04 hrs, Volume= 0.200 af, Depth= 0.49"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs
Charlotte 24-hr 1-yr 1 yr Rainfall=2.58"
Area ac CN Description
4.860 70 Woods, Good, HSG C
4.860 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) ft/ft) ft/sec cfs
5.0 Direct Entry, Direct Entry
Subcatchment 7S: Pre-dev
Hydrograph
Charlotte 24-hr 1'-yr
3
1 yr Rainfal1=2.580,'
Runoff Area=4.860!ac
Runoff Volume=0'.200 of
Runoff Depth=0.49"
.2o Tc=5.0 rn i n
CN=70
1 ••r.+.rrs •.w.��- �irfrrrrriri r�-irrrr'rsrisrrfarrerr.+•iris'rr��t�rirra'r'.a�'rr�irrsri�f'rr'r'rf...... ............
/ 1 1 1 / .1 1 :1 91 11 1 1 1 1 135 140
Ll Runofi

Sf # 1 HydroCad Charlotte 6-hr 10-yr Rainfall=3.72"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
HydroCADQ 10.10-5a s/n 05047 © 2020 HydroCAD Software Solutions LLC Paae 6
Summary for Subcatchment 7S: Pre-dev
Runoff = 11.12 cfs @ 3.16 hrs, Volume= 0.464 af, Depth= 1.15"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs
Charlotte 6-hr 10-yr Rainfall=3.72"
Area (ac) CN Description
4.860 70 Woods, Good, HSG C
4.860 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) feet ft/ft (ft/sec) (cfs
5.0 Direct Entry, Direct Entry
Subcatchment 7S: Pre-dev
Hydrograph
t2
112 ds
11 Charlotte 6-hr 10-yr
10 Rainf6ll=3.72"
RunoffArea=4860 ac
$ Runoff Volume=0.464 of
Z, 7
Runoff 'Depth=1.15
o�
LL Tc=5.0 m i n
5
CN-70
A
2
i-
� ... � • �.fr�rr��rr.�.�.rr.Eiirrri.Err.�rrrirrifrirrrrfrrrrrrvrfrfri�rrErt�rtrrr�Errv�iifri�rf�rririr�if
Time (hours)
rJ Runoff

9S )�
Post Development
Sub4
Eacn on L
ink
Sand Filter

Sf # 1 HydroCad
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCAD®10.10-5a s/n 05047 ©2020 H droCAD Software Solutions LLC Page 2
Rainfall Events Listing (selected events)
Event# Event Storm Type Curve Mode Duration B/B Depth AMC
Name (hours) (inches)
1 2-yr
Charlotte 6-hr 2-yr
Default
6.00
1
2.28 2
2 1 yr
Charlotte 24-hr 1-yr
Default
24.00
1
2.58 2
3 10-yr
Charlotte 6-hr 10-yr
Default
6.00
1
3.72 2
4 50 yr
Charlotte 6-hr 50-yr
Default
6.00
1
4.92 2
5 100 YEAR
Charlotte 6-hr 100-yr
Default
6.00
1
5.34 2

Sf # 1 HydroCad Charlotte 6-hr 2-yr Rainfall=2.28"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
HydroCAD® 10.10-5a s/n 05047 © 2020 HvdroCAD Software Solutions LLC Paae 3
Summary for Subcatchment 9S: Post Development
Runoff = 12.64 cfs @ 3.16 hrs, Volume= 0.457 af, Depth= 1.13"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs
Charlotte 6-hr 2-yr Rainfall=2.28"
Area ac CN Description
2.620 98 Paved parking, HSG C
2.240 74 >75% Grass cover, Good, HSG C
4.860 87 Weighted Average
2.240 46.09% Pervious Area
2.620 53.91% Impervious Area
Tc Length Slope Velocity Capacity Description
min feet (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, Post Dev
Subcatchment 9S: Post Development
Hydrograph
14
1 12.&I d5
tte'6-hr 2'-yr ,2 Charlo
11 Rainfall=2.28"
10 Runoff Area=4.860 ac
9 Runoff Volume=0.457 of
�s
Runoff 'Depth=1.13
3 7
6 Tc=5.0 m i n
5 CN=87
4
3
2
1
p .
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 60 85 90 95 100 105 110 115 120 125 130 135 140
Time (hours)
[1 Runoff

Sf # 1 HydroCad Charlotte 6-hr 2-yr Rainfall=2.28"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
HydroCADO 10.10-5a s/n 05047 © 2020 HvdroCAD Software Solutions LLC Paoe 4
Summary for Pond 27P: Sand Filter
Inflow Area = 4.860 ac, 53.91 % Impervious, Inflow Depth = 1.13" for 2-yr event
Inflow = 12.64 cfs @
3.16 hrs, Volume= 0.457 of
Outflow = 0.39 cfs @
5.58 hrs, Volume= 0.457 af, Atten= 97%, Lag= 145.3 min
Primary = 0.39 cfs @
5.58 hrs, Volume= 0.457 of
Routing by Stor-Ind method, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 687.66' @ 5.58 hrs
Surf.Area= 7,664 sf Storage= 17,287 cf
Plug -Flow detention time= 1,063.6
min calculated for 0.457 of (100% of inflow)
Center -of -Mass det. time= 1,063.8
min ( 1,278.7 - 214.9 )
Volume Invert Avail.Stora a Storage Description
#1 684.70' 38,137
cf Custom Stage Data (Prismatic) Listed below
Elevation Surf.Area
Inc.Store Cum.Store
(feet) s -ft
(cubic -feet) (cubic -feet)
684.70 2,200
0 0
685.00 4,550
1,012 1,012
686.00 5,650
5,100 6,112
687.00 6,800
6,225 12,337
688.00 8,100
7,450 19,787
689.00 9,150
8,625 28,412
690.00 10,300
9,725 38,137
Device Routinq Invert
Outlet Devices
#1
Primary
683.39'
24.0" Round Culvert L= 80.0' Ke= 0.500
Inlet / Outlet Invert= 683.39' / 682.91' S= 0.0060 '/' Cc= 0.900
n= 0.012, Flow Area= 3.14 sf
#2
Device 1
684.70'
Special & User -Defined
Head (feet) 0.00 0.30 1.30 2.30 3.30 4.30
Disch. (cfs) 0.000 0.069 0.108 0.146 0.185 0.223
#3
Device 1
687.60'
4.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
#4
Device 1
688.30'
16.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
Primary ❑utFlow Max=0.38 cfs @ 5.58 hrs HW=687.66' (Free Discharge)
L7=Cu1vert (Passes 0.38 cfs of 27.30 cfs potential flow)
2=Special & User -Defined (Custom Controls 0.17 cfs)
3=Sharp-Crested Rectangular Weir (Weir Controls 0.21 cfs @ 0.83 fps)
=Sharp -Crested Rectangular Weir ( Controls 0.00 cfs)

Sf # 1 HydroCad Charlotte 6-hr 2-yr Rainfall=2.28"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCAD®1O.1O-5a s/n 05047 © 2020 H droCAD Software Solutions LLC Page 5
Pond 27P: Sand Filter
Hydrograph
11 Inflow
14-: 1284 ds D Primary
13. Inflow Area=4.860 ac
12-
11 Peak Elev=687.66'
10 Storage=17,287':cf
9
N S
V
7
O
LL g
5
4
3
2
1 9 39 cfx
0
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140
Time (hours)

Sf # 1 HydroCad Charlotte 24-hr 1-yr 1 yr Rainfall=2.58"
Prepared by Yarbrough -Williams & Houle, Inc- Printed 2/16/2021
HydroCAD®10.10-5a s/n 05047 ©2020 HydroCAD Software Solutions LLC Paae 6
Summary for Subcatchment 9S: Post Development
Runoff = 10.04 cfs @ 11.99 hrs, Volume= 0.558 af, Depth= 1.38"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs
Charlotte 24-hr 1-yr 1 yr Rainfall=2.58"
Area (ac) CN Description
2.620
98 Paved parking, HSG C
2.240
74 >75% Grass cover, Good. HSG C
4.860
87 Weighted Average
2.240
46.09% Pervious Area
2.620
53.91% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) feet ft/ft ft/sec) cfs
5.0 Direct Entry, Post Dev
Subcatchment 9S: Post Development
Hydrograph
11
MAX ds
'° Charlotte 24-hr T-yr
9 1 yr Rainfall=2.58"'
Runoff Area=4860 ac
Runoff Volume 0.558 of
6 Runoff Depth=1.38
LL 5 Tc=5.0 m i n
4 CN=87
3-
2
1
1 � FfFF �� �lfFifiiJlJ/7JFJJ,►/I/i//F.r.IJJ!///IF�FFO/F//J/IFIF/.fliyJf.�J//dlFlf/.OyI,Y/!///gyp/JF./�/
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 M
I ❑Runoff

Sf # 1 HydroCad Charlotte 24-hr 1-yr 1 yr Rainfall=2.58"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCADO 10.10-5a s/n 05047 © 2020 H droCAD Software Solutions LLC Page 7
Summary for Pond 27P: Sand Filter
Inflow Area = 4.860 ac, 53.91 % Impervious, Inflow Depth = 1.38" for 1 yr event
Inflow = 10.04 cfs @ 11.99 hrs, Volume= 0.558 of
Outflow = 0.22 cfs @ 16.70 hrs, Volume= 0.558 af, Atten= 98%, Lag= 282.5 min
Primary = 0.22 cfs @ 16.70 hrs, Volume= 0.558 of
Routing by Stor-Ind method, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 687.62' @ 16.70 hrs Surf.Area= 7,610 sf Storage= 16,977 cf
Plug -Flow detention time= 1,185.1 min calculated for 0.558 of (100% of inflow)
Center -of -Mass det. time= 1,185.3 min ( 2,012.0 - 826.7 )
Volume
Invert Avail.Stora a Storage
Description
#1
684.70'
38,137 cf Custom Stage Data (Prismatic) Listed below
Elevation
Surf.Area
Inc.Store
Cum.Store
feet
(s -ft)
(cubic -feet)
cubic -feet)
684.70
2,200
0
0
685.00
4,550
1,012
1,012
686.00
5,650
5,100
6,112
687.00
6,800
6,225
12,337
688.00
8,100
7,450
19,787
689.00
9,150
8,625
28,412
690.00
10,300
9,725
38,137
Device Routinq Invert Outlet Devices
#1
Primary
683.39'
24.0" Round Culvert L= 80.0' Ke= 0.500
Inlet / Outlet Invert= 683.39' / 682.91' S= 0.0060'/' Cc= 0.900
n= 0.012, Flow Area= 3.14 sf
#2
Device 1
684.70'
Special & User -Defined
Head (feet) 0.00 0.30 1.30 2.30 3.30 4.30
Disch. (cfs) 0.000 0.069 0.108 0.146 0.185 0.223
#3
Device 1
687.60'
4.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
#4
Device 1
688.30'
16.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
Primary OutFlow Max=0.22 cfs @ 16.70 hrs HW=687.62' (Free Discharge)
�1=Culvert (Passes 0.22 cfs of 27.09 cfs potential flow)
2=Special & User -Defined (Custom Controls 0.17 cfs)
3=Sharp-Crested Rectangular Weir (Weir Controls 0.04 cfs @ 0.49 fps)
=Sharp -Crested Rectangular Weir ( Controls 0.00 cfs)

Sf # 1 HydroCad Charlotte 24-hr 1-yr 1 yr Rainfall=2.58"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCAD®10.10-5a s/n 05O47 ©2020 H droCAD Software Solutions LLC Page 8
Pond 27P: Sand Filter
Hydrograph
11 o.oa crs
10 Inflow Area=4.660 ac
9 Peak El:ev=687.62'
a Storage=16,97i7 cf
4
3
2
1'F5x;x-,7 7,7 -
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140
Time (hours)
CI Inflow
Cl Primary

Sf # 1 HydroCad Charlotte 6-hr 10-yr Rainfall=3.72"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCAD®10.10-5a s/n 05047 ©2020 H droCAD Software Solutions LLC Page 9
Summary for Subcatchment 9S: Post Development
Runoff = 23.27 cfs @ 3.15 hrs, Volume= 0.964 af, Depth= 2.38"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs
Charlotte 6-hr 10-yr Rainfall=3.72"
Area (ac) CN Description
2.620 98 Paved parking, HSG C
2.240 74 >75% Grass cover, Good, HSG C
4.860 87 Weighted Average
2.240 46.09% Pervious Area
2.620 53.91% Impervious Area
Tc Length Slope Velocity Capacity Description
min feet ft/ft) (ft/sec) (cfs
5.0 Direct Entry, Post Dev
26-
23
22
21
20
19
18
17
16
15
14
13
0 12
LL 11
10
9-
8
7
6
5
4
3
2
1
0
0
Subcatchment 9S: Post Development
Hydrograph
Charlotte 6-hr 10:-yr
Rainfall=3.720'
Runoff'Area=4 860iac
Runoff Volume=0!.964 of
Runoff Depth=2.38"
Tc=5.0 m i n
CN=87
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140
Time (hours)
� Runoff

Sf # 1 HydroCad Charlotte 6-hr 10-yr Rainfall=3.72"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCAD® 10.10-5a s/n 05047 © 2020 H droCAD Software Solutions LLC Page 10
Summary for Pond 27P: Sand Filter
Inflow Area = 4.860 ac, 53.91% Impervious, Inflow Depth = 2.38" for 10-yr event
Inflow = 23.27 cfs @ 3.15 hrs, Volume= 0.964 of
Outflow = 7.85 cfs @ 3.36 hrs, Volume= 0.964 af, Atten= 66%, Lag= 12.4 min
Primary = 7.85 cfs @ 3.36 hrs, Volume= 0.964 of
Routing by Stor-Ind method, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 688.31' @ 3.36 hrs Surf.Area= 8,426 sf Storage= 22,464 cf
Plug -Flow detention time= 526.2 min calculated for 0.964 of (100% of inflow)
Center -of -Mass det. time= 526.4 min ( 735.6 - 209.2 )
Volume Invert
Avail.Stora a Storage Description
#1 684.70'
38,137 cf Custom Stage Data (Prismatic) Listed below
Elevation Surf.Area
Inc.Store Cum.Store
(feet)
s -ft)
(cubic -feet) (cubic -feet
684.70
2,200
0 0
685.00
4,550
1,012 1,012
686.00
5,650
5,100 6,112
687.00
6,800
6,225 12,337
688.00
8,100
7,450 19,787
689.00
9,150
8,625 28,412
690.00
10,300
9,725 38,137
Device Routing
Invert
Outlet Devices
#1 Primary
683.39'
24.0" Round Culvert L= 80.0' Ke= 0.500
Inlet / Outlet Invert= 683.39' / 682.91' S= 0.0060'/' Cc= 0.900
n= 0.012, Flow Area= 3.14 sf
#2 Device 1
684.70'
Special & User -Defined
Head (feet) 0.00 0.30 1.30 2.30 3.30 4.30
Disch. (cfs) 0.000 0.069 0.108 0.146 0.185 0.223
#3 Device 1
687.60'
4.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
#4 Device 1
688.30'
16.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
Primary Outflow Max=7.80 cfs @ 3.36 hrs HW=688.31' (Free Discharge)
=Culvert (Passes 7.80 cfs of 29.95 cfs potential flow)
2=Special & User -Defined (Custom Controls 0.20 cfs)
3=Sharp-Crested Rectangular Weir (Weir Controls 7.55 cfs @ 2.76 fps)
=S ha rp-C rested Rectangular Weir (Weir Controls 0.05 cfs @ 0.33 fps)

Sf # 1 HydroCad Charlotte 6-hr 10-yr Rainfall=3.72"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCADO 10.10-5a s/n 05047 © 2020 H droCAD Software Solutions LLC Page 11
Pond 27P: Sand Filter
Hydrograph
26
!32]dt
24- Inflow Area=4.860 ac
22
Peak Elev=688.31'
20
,$tdrage=22.464 cf
TC
1/1
ii 14
o 12
LL
10
a
2
- -
1 5 10 15 20 25 30 35 41 45 50 55 .1 65 70 75 :1 85 91 95 100 105 110 115 120 125 130 135 140
Li Inflow
❑ Primary

Sf # 1 HydroCad Charlotte 6-hr 50-yr 50 yr Rainfall=4.92"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
HvdroCADO 10.10-5a s/n 05047 © 2020 H droCAD Software Solutions LLC Page 12
Summary for Subcatchment 9S: Post Development
Runoff = 32.67 cfs @ 3.11 hrs, Volume= 1.414 af, Depth= 3.49"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs
Charlotte 6-hr 50-yr 50 yr Rainfall=4.92"
Area ac CN Description
2.620 98 Paved parking, HSG C
2.240 74 >75% Grass cover. Good. HSG C
4.860 87 Weighted Average
2.240 46.09% Pervious Area
2.620 53.91% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) feet ft/ftl ft/sec cfs
5.0 Direct Entry, Post Dev
Subcatchment 9S: Post Development
Hydrograph
36
3 3287cfs
32 Charlotte 6-hr
34
28 50'-yr
26 50 yr. Rainfall=4.92"
24
22 Runoff Area, =4860' ac
20 Runoff Volume=1'.414 of
3 18
M 16 Ruhoff! Depth9.497
14 Tc=S.0 ruin
12:
10 CN=87
8
s-
4
2
'1 / �F///IAI,JdI.APn'/d!I-/A.I9Yi/9.//.PFi////!!iI•/i!//!i////////f///.�//%////////%///if�i%
0
1 15 2'0 25 3040 1 55 60 65 70 75 80 85 90 95 100 165 110 115 120 125 130 135 140
[.:I Runoff

Sf # 1 HydroCad Charlotte 6-hr 50-yr 50 yr Rainfall=4.92"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCADO 10.10-5a s/n 05047 ©2020 HvdroCAD Software Solutions LLC Paae 13
Summary for Pond 27P: Sand Filter
Inflow Area = 4.860 ac, 53.91 % Impervious, Inflow Depth = 3.49" for 50 yr event
Inflow = 32.67 cfs @ 3.11 hrs, Volume= 1.414 of
Outflow = 23.95 cfs @ 3.18 hrs, Volume= 1.414 af, Atten= 27%, Lag= 4.2 min
Primary = 23.95 cfs @ 3.18 hrs, Volume= 1.414 of
Routing by Stor-Ind method, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 688.64' @ 3.18 hrs Surf.Area= 8,776 sf Storage= 25,340 cf
Plug -Flow detention time= 365.6 min calculated for 1.414 of (100% of inflow)
Center -of -Mass det. time= 365.8 min ( 570.6 - 204.7 )
Volume Invert
#1 684.70'
Avail.Storage Storaae Description
38,137 cf Custom Stage Data (Prismatic) Listed below
Elevation
Surf.Area
Inc.Store
Cum.Store
(feet)
(sa-ft)
(cubic -feet)
cubic -feet
684.70
2,200
0
0
685.00
4,550
1,012
1,012
686.00
5,650
5,100
6,112
687.00
6,800
6,225
12,337
688.00
8,100
7,450
19,787
689.00
9,150
8,625
28,412
690.00
10,300
9,725
38,137
Device Routing Invert Outlet Devices
#1 Primary 683.39' 24.0" Round Culvert L= 80.0' Ke= 0.500
Inlet / Outlet Invert= 683.39' / 682.91' S= 0.0060 '/' Cc= 0.900
n= 0.012, Flow Area= 3.14 sf
#2 Device 1 684.70' Special & User -Defined
Head (feet) 0.00 0.30 1.30 2.30 3.30 4.30
Disch. (cfs) 0.000 0.069 0.108 0.146 0.185 0.223
#3 Device 1 687.60' 4.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
#4 Device 1 688.30' 16.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
Primary OutFlow Max=23.89 cfs @ 3.18 hrs HW=688.64' (Free Discharge)
L =Culvert (Passes 23.89 cfs of 31.20 cfs potential flow)
2=Special & User -Defined (Custom Controls 0.21 cfs)
3=Sharp-Crested Rectangular Weir (Weir Controls 13.21 cfs @ 3.34 fps)
=Sharp -Crested Rectangular Weir (Weir Controls 10.47 cfs @ 1.92 fps)

Sf # 1 HydroCad Charlotte 6-hr 50-yr 50 yr Rainfall=4.92"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCAD® 10.10-5a s/n 05047 © 2020 H droCAD Software Solutions LLC Pa a 14
Pond 27P: Sand Filter
Hydrograph
■ Inflow
■ Primary
InflOw + • •
. Peak
• • • •
• • f 1
,r.-
f•;
i

Sf # 1 HydroCad Charlotte 6-hr 100-yr 100 YEAR Rainfall=5.34"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCADO 10.10-5a s/n 05047 © 2020 HydroCAD Software Solutions LLC Page 15
Summary for Subcatchment 9S: Post Development
Runoff = 36.77 cfs @ 3.11 hrs, Volume= 1.575 af, Depth= 3.89"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs
Charlotte 6-hr 100-yr 100 YEAR Rainfall=5.34"
Area ac CN Description
2.620 98 Paved parking, HSG C
2.240 74 >75% Grass cover, Good. HSG C
4.860 87 Weighted Average
2.240 46.09% Pervious Area
2.620 53.91% Impervious Area
Tc Length Slope Velocity Capacity Description
min feet ft/ft) (ft/sec) (cfs
5.0 Direct Entry, Post Dev
Subcatchment 9S: Post Development
Hydrograph
40
❑ Runoff
36
34
32
30
28
26
.. 24
u 22
20
0
ti 18
16
14
12
10
6-
6
4:
2.
Charlotte 6-hr
1007yr
100 YEAR. Rainfall=5.34"
Runoff Area=4.860 ad
Runoff Volume=1.575 of
Runoff :Depth=189''
Tc-5.0 min
CN�87
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100105110115120125130135140
Time (hours)

Sf # 1 HydroCad Charlotte 6-hr 100-yr 100 YEAR Rainfall=5.34"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCADO 10.10-5a s/n 05047 ©2020 H droCAD Software Solutions LLC Page 16
Summary for Pond 27P: Sand Filter
Inflow Area = 4.860 ac, 53.91% Impervious, Inflow Depth = 3.89" for 100 YEAR event
Inflow = 36.77 cfs @ 3.11 hrs, Volume= 1.575 of
Outflow = 29.91 cfs @ 3.16 hrs, Volume= 1.575 af, Atten= 19%, Lag= 3.3 min
Primary = 29.91 cfs @ 3.16 hrs, Volume= 1.575 of
Routing by Stor-Ind method, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 688.74' @ 3.16 hrs Surf.Area= 8,873 sf Storage= 26,140 cf
Plug -Flow detention time= 330.3 min calculated for 1.575 of (100% of inflow)
Center -of -Mass det. time= 330.1 min ( 534.0 - 203.9 )
Volume
Invert Avail.Stora a Storage Description
#1
684.70'
38,137 cf Custom Stage Data (Prismatic) Listed below
Elevation
Surf.Area
Inc.Store Cum.Store
(feet)
(s -ft)
(cubic -feet) (cubic -feet
684.70
2,200
0 0
685.00
4,550
1,012 1,012
686.00
5,650
5,100 6,112
687.00
6,800
6,225 12,337
688.00
8,100
7,450 19,787
689.00
9,150
8,625 28,412
690.00
10,300
9,725 38,137
Device Routinq Invert Outlet Devices
#1
Primary
683.39'
24.0" Round Culvert L= 80.0' Ke= 0.500
Inlet / Outlet Invert= 683.39' / 682.91' S= 0.0060 T Cc= 0.900
n= 0.012, Flow Area= 3.14 sf
#2
Device 1
684.70'
Special & User -Defined
Head (feet) 0.00 0.30 1.30 2.30 3.30 4.30
Disch. (cfs) 0.000 0.069 0.108 0.146 0.185 0.223
#3
Device 1
687.60'
4.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
#4
Device 1
688.30'
16.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
Primary ❑utRow Max=30.14 cfs @ 3.16 hrs HW=688.74' (Free Discharge)
t =Calvert (Passes 30.14 cfs of 31.54 cfs potential flow)
2=Special & User -Defined (Custom Controls 0.21 cfs)
3=Sharp-Crested Rectangular Weir (Weir Controls 14.94 cfs @ 3.49 fps)
Sharp -Crested Rectangular Weir (Weir Controls 14.99 cfs @ 2.16 fps)

Sf # 1 HydroCad Charlotte 6-hr 100-yr 100 YEAR Rainfall=5.34"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCAD®10.10-5a s/n 05047 ©2020 H droCAD Software Solutions LLC Pave 17
Pond 27P: Sand Filter
Hydrograph
40
38.
36
34
28
26
-. 24
22
20
0
LL 18
16
14
12-
10
a
6
d.
Infiow Area=4.860 ac
Peak E f ev=688.74'
Storage=26,14!0 d
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140
Time (hours)
1..1 Inflow
CI Pri l ry

80S Z46P
Post Development 1 in Sand Filter
w /Mod CN
Subca# Reach on L
ink

Sf # 1 HydroCad
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCAD® 10.10-5a s/n 05047 © 2020 H droCAD Software Solutions LLC Page 2
Rainfall Events Listing (selected events)
Event# Event Storm Type Curve Mode Duration B/B Depth AMC
Name (hours) (inches)
1 1 inch Charlotte 6-hr 1 INCH Default 6.00 1 1.00 2

Sf # 1 HydroCad Charlotte 6-hr 1 INCH 1 inch Rainfall=1.00"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCAD® 10.10-5a s/n 05047 © 2020 H droCAD Software Solutions LLC Page 3
Summary for Subcatchment 8S: Post Development 1 in w / Mod CN
Runoff = 6.48 cfs @ 3.11 hrs, Volume= 0.228 af, Depth= 0.56"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs
Charlotte 6-hr 1 INCH 1 inch Rainfall=1.00"
Area (ac) CN Description
4.860 95 postdev
4.860 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
min feet ft/ft(ft/sec) cfs)
5.0 Direct Entry, Post Dev
Subcatchment 8S: Post Development 1 in w / Mod CN
Hydrograph
7
Y Runaff
Charlotte 6' hr
1 INCH
1 inch' Rainfa11=1.00','
Runoff Area=4.860'ac
4 Runoff Volume=0.228 of
3
Runoff'Depth=0.56
Tc=5.0 min
P E r4 CN-95
1 5 10 15 20 25 30 35 41 45 50 55 .1 65 70 75 :/ 85 91 95 100 105 110 115 120 125 130 135 141

Sf # 1 HydroCad Charlotte 6-hr 1 INCH 1 inch Rainfall=1.00"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
HXdroCADO 10.10-5a s/n 05047 © 2020 H droCAD Software Solutions LLC Page 4
Summary for Pond 26P: Sand Filter
Inflow Area = 4.860 ac, 0.00% Impervious, Inflow Depth = 0.56" for 1 inch event
Inflow = 6.48 cfs @ 3.11 hrs, Volume= 0.228 of
Outflow = 0.12 cfs @ 6.00 hrs, Volume= 0.228 af, Atten= 98%, Lag= 173.2 min
Primary = 0.12 cfs @ 6.00 hrs, Volume= 0.228 of
Routing by Stor-Ind method, Time Span= 0.00-140.00 hrs, dt= 0.01 hrs / 2
Peak Elev= 686.40' @ 6.00 hrs Surf.Area= 6,110 sf Storage= 8,601 cf
Plug -Flow detention time= 762.0 min calculated for 0.228 of (100% of inflow)
Center -of -Mass det. time= 762.2 min ( 971.8 - 209.7 )
Volume
Invert Avail.Stora a Storage
Description
#1
684.70'
38,137 cf Custom Stage Data (Prismatic) Listed below
Elevation
Surf.Area
Inc.Store
Cum.Store
feet
s -ft)
(cubic -feet)
cubic -feet)
684.70
2,200
0
0
685.00
4,550
1,012
1,012
686.00
5,650
5,100
6,112
687.00
6,800
6,225
12,337
688.00
8,100
7,450
19,787
689.00
9,150
8,625
28,412
690.00
10,300
9,725
38,137
Device Routing Invert Outlet Devices
#1 Primary 683.39' 24.0" Round Culvert L= 80.0' Ke= 0.500
Inlet / Outlet Invert= 683.39' / 682.91' S= 0.0060 '/' Cc= 0.900
n= 0.012, Flow Area= 3.14 sf
#2 Device 1 684.70' Special & User -Defined
Head (feet) 0.00 0.30 1.30 2.30 3.30 4.30
Disch. (cfs) 0.000 0.069 0.108 0.146 0.185 0.223
#3 Device 1 687.60' 4.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
#4 Device 1 688.30' 16.0' long Sharp -Crested Rectangular Weir 2 End Contraction(s)
Primary OutFlow Max=0.12 cfs @ 6.00 hrs HW=686.40' (Free Discharge)
L7=Culvert (Passes 0.12 cfs of 20.08 cfs potential flow)
2=Special & User -Defined (Custom Controls 0.12 cfs)
3=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs)
=Sharp -Crested Rectangular Weir ( Controls 0.00 cfs)

Sf # 1 HydroCad Charlotte 6-hr 1 INCH 1 inch Rainfall=1.00"
Prepared by Yarbrough -Williams & Houle, Inc. Printed 2/16/2021
H droCAD® 10.10-5a s/n 05047 © 2020 H droCAD Software Solutions LLC Page 5
Pond 26P: Sand Filter
Hydrograph
■ Inflow
7 6.45crs J Q Primary
InflOW Area=4.860 ad
Peak Elev=686.40'
5 Storage=8,60',1 icf
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Figure 8-1 YARBROUGH-W11..I_IAMS & HOM, INC.
730 WINDSOR OAK COURT CHARLOTTE, NC 28273
P.Q. BOX 1198 PINEVILLE, NC 28134
8-5 PHONE VO4) 555-1990 FAX VO4) 556-0505