SW3221001_Design Calculations_20230628

STORM CALCULATIONS
FOR
BRIGHTON PARK
MOUNT PLEASANT, CABARRUS COUNTY, NC
PREPARED BY:
LATHAM-WALTERS ENGINEERING, INC.
16507-A NORTHCROSS DRIVE
HUNTERSVILLE, N.C. 28078
Phone: [phone] Fax: [phone]
N.C. Corporate License C-1815
FOR
NIBLOCK HOMES,LLC
759 CONCORD PARKWAY NORTH SUITE 20
CONCORD,NC 28027
DATE: August 4, 2022
/b.
5 56
=,°° FNGINO-°°° ,
S L. o\
REVISED: 2/9/2023

Carlos L. Ruano P.E.
Latham-Walters Engineer, Inc.
16507-A Northcross Drive
Huntersville, NC 28078
Brighton Park Stormwater System Design Summary
Stormwater system was designed in accordance with the latest version of the NCDOT's
Guidelines for Drainage Studies& Hydraulic Design, NCDOT Subdivision Manual, & Concord's Technical
Standards Manual.
Roadway inlet locations, capacities,gutter spread, and storm drain pipe system was analyzed
and designed using a ten-year discharge (Q10)with a minimum time of concentration of 5 minutes.An
intensity of 4 inches/hour was used for calculating spread and determination of appropriate locations
for inlet placement.Allowable gutter spread is limited to gutter width plus%travel lane (total of 7 feet
with valley gutter) per the latest version of the NCDOT Subdivision Manual. Per Concord UDO, may flow
may spread to crown of street for Local &Alley.
Concord's Rainfall Intensity Table 2-2 was utilized for hydraulic analysis. Coefficient of 0.50 was
determined by the average BUA per lot. Intensity storm of 7.26 in/hr was used for 10-year return period.
Storm pipes were design by Rational method.
Sediment basins&erosion control measures were based off NCDEQ's Erosion &Sediment
Control Planning& Design Manual.

SECTION 2
STORMWATER RUNOFF
20
10 -
8 -
-
0
r 46 Ref40,A
C 2 7o yeas
>+ s°
th a
a) 1 -
0.8 -
0.6 -(75
• 0.4 -
co
ci
02 -
I
0.1 I P , I I I , I ,
0.1 0.2 0.4 0.6 0.8 1 2 4 6 8 10 20
Duration-Hours
Figure 2-2 Intensity-Duration-Frequency Curves for Concord,NC
TABLE 2-3
ORDINATES OF THE IDF CURVES FOR CONCORD,NC
Duration Return Period (years)
Hours Minute 1 2 5 10 25 50 100
s
0 5 4.80 5.66 6.60 7.26 8.00 8.52 8.98
10 3.83 4.54 5.29 5.81 6.38 6.78 7.13
15 3.19 3.80 4.46 4.90 5.39 5.72 6.01 _
30 2.19 2.62 3.17 3.55 3.99 4.31 4.60
1 1.36 1.65 2.03 2.31 2.66 2.92 3.17
2 0.79 0.96 1.19 1.36 1.58 1.75 1.92
3 0.56 0.68 0.85 0.98 1.15 1.29 1.42
6 0.34 0.41 0.51 0.59 0.70 0.79 0.87
12 0.20 0.24 0.31 0.35 0.42 0.48 0.53
24 0.12 0.14 0.18 0.21 0.25 0.28 0.31
Adopted January 10, 2008 2-5 Technical Standards Manual

EXISTING STORM NETWORK ON HWY-73
NC-HWY 73 \
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EXIST. STORM
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Hydraflow Storm Sewers Extension for Autodesk® AutoCAD® Civil 3D® Plan
PROVIDED CALCS
OF PRE & POST OF
THIS SECTION
EX.DI-1
EX.D I-2
EXISTING STORM BEYOND
SCOPE WAS NOT
1 EVAULATED
~ Outfall
Project File: 2020.17-EX.STORM Hwy73.stm Number of lines:2 Date:8/4/2022
Storm Sewers v2018.30

TR55 Tc Worksheet
Hydraflow Storm Sewers Extension for Autodesk®AutoCAD®Civil 3D®by Autodesk, Inc.v2018.30
Line No. 4
4
Description
A B C Totals
Sheet Flow
Manning's n-value = 0.240 0.011 0.011
Flow length (ft) = 100.0 0.0 0.0
Two-year 24-hr precip. (in) = 3.12 0.00 0.00
Land slope (%) = 5.86 0.00 0.00
Travel Time (min) = 9.40 + 0.00 + 0.00 = 9.40
Shallow Concentrated Flow
Flow length (ft) = 629.00 0.00 0.00
Watercourse slope (%) = 4.82 0.00 0.00
Surface description = UnPaved Paved Paved
Average velocity (ft/s) =3.54 0.00 0.00
Travel Time (min) = 2.96 + 0.00 + 0.00 = 2.96
Channel Flow
X sectional flow area (sqft) = 0.00 0.00 0.00
Wetted perimeter(ft) = 0.00 0.00 0.00
Channel slope (%) = 0.00 0.00 0.00
Manning's n-value = 0.015 0.015 0.015
Velocity (ft/s) =0.00 0.00 0.00
Flow length (ft) = 0.0 0.0 0.0
Travel Time (min) = 0.00 + 0.00 + 0.00 = 0.00
Total Travel Time, Tc 12.36 min

Dschedule Page
Line Inlet Gnd/Rim Drng Total Runoff i i Flow Invert Invert Capac Line Line Line Vel Line Cover
No. ID El Up Area Area Coeff Inlet Sys Rate Up Dn Full Size Length Slope Dn ID Up
(ft) (ac) (ac) (C) (in/hr) (in/hr) (cfs) (ft) (ft) (cfs) (in) (ft) (%) (ft/s) (ft)
1 EX.DI-2 622.95 0.33 8.05 0.50 7.24 5.61 22.56 614.15 605.72 46.25 24 236.654 3.56 14.62 3 6.80
2 EX.DI-1 625.15 7.72 7.72 0.50 5.61 5.61 21.67 621.97 616.05 86.05 24 48.000 12.33 22.79 4 1.18
Project File: 2020.17-EX.STORM Hwy73.stm Number of lines:2 Date: 8/4/2022
NOTES: Intensity=88.24/(Inlet time+ 15.50)A 0.83--Return period=10 Yrs. ; "Critical depth
Storm Sewers

PROPOPSED STORM NETWORK ON HWY-73
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1 _ - , '1/4PROP. E
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30d ., 1 14 1 \ • . 1 POE 1 1
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OLEANDER STRE[T
MYHI'Rl.N'RAT,
PROP. STORM

Hydraflow Storm Sewers Extension for Autodesk® AutoCAD® Civil 3D® Plan
5 SDMH-2
6 CB-2
7 8 DGI-4
CB-3
BRENNAN
ENTRANCE
DGI-8
3
DI-5
2
OLEANDER
ENTRANCE EX.DI-2
1
4
Out
4
Riser-2
SEE WQ CALCS
Project File: 2020.17-Prop.STORM Hwy73.stm Number of lines:8 Date:2/9/2023
Storm Sewers v2018.30

Dschedule Page
Line Inlet Gnd/Rim Drng Total Runoff i i Flow Invert Invert Capac Line Line Line Vel Line Depth Depth Cover
No. ID El Up Area Area Coeff Inlet Sys Rate Up Dn Full Size Length Slope Dn ID Dn Up Up
(ft) (ac) (ac) (C) (in/hr) (in/hr) (cfs) (ft) (ft) (cfs) (in) (ft) (%) (ft/s) (ft) (ft) (ft)
1 EX.DI-2 622.95 0.38 1.57 0.50 7.26 6.48 8.20 614.15 605.72 46.25 24 236.654 3.56 11.10 3 0.57 1.02** 6.80
2 DI-5 627.92 0.57 1.18 0.50 7.26 6.72 4.37 620.99 616.41 21.16 18 132.430 3.46 9.43 4 0.46 0.80** 5.43
3 DGI-8 635.53 0.61 0.61 0.60 7.26 7.26 2.66 632.00 621.24 15.13 15 229.890 4.68 5.10 0.55 0.65** 2.28
4 Riser-2 638.00 0.01 0.01 0.01 7.26 7.26 2.75 630.39 617.77 35.98 18 126.170 10.00 12.01 0.28 0.63** 6.11
5 SDMH-2 631.55 0.01 1.39 0.01 7.26 7.01 4.84 627.10 627.00 8.48 18 18.000 0.56 4.95 0.81 0.85** 2.95
6 CB-2 632.87 0.21 1.38 0.50 7.26 7.06 4.87 627.44 627.30 8.51 18 25.000 0.56 4.98 0.81 0.85** 3.93
7 CB-3 632.87 0.11 1.17 0.50 7.26 7.14 4.18 627.84 627.64 8.48 18 36.000 0.56 4.78 0.74 0.78** 3.53
8 DGI-4 0.00 1.06 1.06 0.50 7.26 7.26 3.85 628.53 628.09 5.67 15 67.000 0.66 4.96 0.76 0.79** n/a
Project File: 2020.17-Prop.STORM Hwy73.stm Number of lines:8 Date: 2/10/2023
NOTES: Intensity=71.97/(Inlet time+ 12.40)A 0.80--Return period=10 Yrs. ; **Critical depth
Storm Sewers

SAND FILTER-2
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Mt. Pleasant, NC Brighton Park
Sand Filter Calculation 2
1. Calculate Runoff Coeff,(Rv)
Drainage area to filter,Ad= 10.33 ac
Impervious area to filter forebay= 4.43 ac.
Impervious percentage= 42.86%
Rv=0.05+0.9(la) = 0.43569888
2. Calculate req'd water quality volume(WQV) WQV=(Rv/1 x Ad/1 x 43560 sf/1 ac x Rd/1 x ft/12 in)
WQV= 16338 cf (used to size Af)
WQV= 0.3751 ac-ft.
Storage: Cum
Elev. Area Vol. Vol
632.5 15777 0 0
634 18796 25929.75 25929.75
636 22040 40836 66765.75
638 25511 47551 114316.75
Calculate Depth for WQ Volume:
632.5 0
633.45 16338
634 25929.75
Elevation of WQ Volume= 633.45
3. Discount WQv:
0.75 x WQv 12253.34 cuft
4. Site Hydrologic Input Parameters:
Cn Pre= 68.0
Cn Post= 81.0 to pond
Table 4.8.3 Results of Hydrologic Calculations from HydroCad
Condition Q 1-year Q 10-yr. Q 25-yr Q 50 yr
Runoff
Pre Dev. 6.28 25.11 34.11 42.44
Post. Dev. 23.81 57.82 72.24 85.12
Routed 0.46 2.75 10.34 25.88
Peak Stage 634.32 636.11 636.41 636.81
Disch.Time 140 hours 1.2' Freeboard

5.Minimum Surface Area for Sand Media Equation 2:Minimum Surface Area for an Infiltration System
2042 SA(ft2) DV"12
2 FS SA = FS" K"T
12253 DV(FT3) where: SA =required minimum surface area of infiltration system(fK)
FS =factor of safety(minimum of 2 is recommended)
2 K(in/hr) DV =design volume(ft3)
K =hydraulic conductivity of soil(in/hr)
72 T(hours) T =maximum dewatering time(72 hours)
6.Sediment Sand Sizing
12253 Design Volume(ft3)
6127 Sediment Chamber(ft3)
6127 Sand Chamber(ft3)
7.Sand Filter Drawdown Calculation
Coeff. Of Permeability of filter media=2 in/hr 0.166667 ft/hr
Volume of water drained in one hour=0.167 ft/hr x SA ft2= 340.3707 cf/hour 0.095 cfs
Drawdown Time=WQV/Drawdown Rate= 48.00 hrs 2 days
8.Underdrain Calculations:
78 I.f of underdrain shown; provide 6"perforated pvc pipe with 3/8"perforations spaces 3"o.c.-4 longitudinal rows
spaced 90 degrees apart.
150 I.f.of pipe I.f.x 4 rows/ft x 4 holes/ft= 2400 holes
50%of perforations= 1200 holes
Capacity of one hole= 0.0083 cfs based upon CA(2gh)^0.5
Total Capacity= 9.96 cfs which is 105.3 times the capacity of the sand filter.
Total Capacityof 6"PVC©0.50%is 0.40 cfs(0.20 cfs assuming 50%clogged) from Mannings and BMP Manual.
9.Antiflotation Calculation
7.5 Height of Riser,ft.
6 Area of Riser,s.f.
45 Volume of Riser,c.f.
2808 Weight of Water©62.4 pcf
3088.8 Weight of water with safety factor of 1.1
82.6 Buoyant Wt.of Concrete=(145-62.4)pcf
1.38 Volume of Concrete Req'd in c.y.
37.39 Volume of Concrete Req'd in c.f.
45 Volume of Concrete in Structure(cf)
-7.61 Volume of Concrete Required(cf) (If negative,additional concrete weight not required)
0.5 ft thick
2.8 Length/Width

Brighton Park Latham-Walters Engineering, Inc.
16507-A Northcross Drive
Mt. Pleasant, NC Huntersville, NC 28078
10. Infiltration Rate
Q =Af(k)(h+df)/(df)
where Af= surface area of filter bed = 2042 sf
df =filter bed depth, ft. = 1.5 ft.
k = coefficient of permeability of filter media (ft/day) = 4 ft/day
h = average height of water above filter bed (ft) 1,2, etc.
h Q Q
cf/day cfs
1 13614.83 0.158
2 19060.76 0.221
3 24506.69' 0.284
4 29952.62 0.347
5 35398.55 0.410
6 40844.48 0.473
7 46290.41 0.536
8 51736.34 0.599
9 57182.28 0.662
10 62628.21 0.725

Inlet Report
Hydraflow Express Extension for Autodesk®AutoCAD®Civil 3D®by Autodesk, Inc. Thursday,Jan 12 2023
PROP. DI-5 DA: .61 ac 1:7.26 C: .6
Drop Curb Inlet Calculations
Location = Sag Compute by: Known Q
Curb Length (ft) = 12.00 Q (cfs) = 2.66
Throat Height (in) = 5.00
Grate Area (sgft) = -0- Highlighted
Grate Width (ft) = -0- Q Total (cfs) = 2.66
Grate Length (ft) = -0- Q Capt (cfs) = 2.66
Q Bypass (cfs) = -0-
Gutter Depth at Inlet (in) = 2.11
Slope, Sw (ft/ft) = 0.300 Efficiency (%) = 100
Slope, Sx (ft/ft) = 0.300 Gutter Spread (ft) = 0.59
Local Depr (in) = -0- Gutter Vel (ft/s) _ -0-
Gutter Width (ft) = -0- Bypass Spread (ft) = -0-
Gutter Slope (%) = -0- Bypass Depth (in) = -0-
Gutter n-value = -0-
III dimensions in fe+l
I
ra%
`F
'I
I
0.59 3.00 0.59

Inlet Report
Hydraflow Express Extension for Autodesk®AutoCAD®Civil 3D®by Autodesk, Inc. Thursday,Jan 12 2023
EX. DI-2 DA: .38 ac 1:7.26 C: .6
Drop Curb Inlet Calculations
Location = Sag Compute by: Known Q
Curb Length (ft) = 12.00 Q (cfs) = 1.68
Throat Height (in) = 5.00
Grate Area (sgft) = -0- Highlighted
Grate Width (ft) = -0- Q Total (cfs) = 1.68
Grate Length (ft) = -0- Q Capt (cfs) = 1.68
Q Bypass (cfs) = -0-
Gutter Depth at Inlet (in) = 1.55
Slope, Sw (ft/ft) = 0.300 Efficiency (%) = 100
Slope, Sx (ft/ft) = 0.300 Gutter Spread (ft) = 0.43
Local Depr (in) = -0- Gutter Vel (ft/s) = -0-
Gutter Width (ft) = -0- Bypass Spread (ft) = -0-
Gutter Slope (%) = -0- Bypass Depth (in) = -0-
Gutter n-value = -0-
All dimensions in feet
I
IRA
\I 'I
0.43 3.00 0.43

Channel Report
Hydraflow Express Extension for Autodesk®AutoCAD®Civil 3D®by Autodesk, Inc. Thursday,Jan 12 2023
VCD-1 DA: 2.68 ac C:0.6 I: 7.26IN/HR
Trapezoidal Highlighted
Bottom Width (ft) = 2.00 Depth (ft) = 1.55
Side Slopes (z:1) = 3.00, 2.00 Q (cfs) = 11.67
Total Depth (ft) = 2.00 Area (sqft) = 9.11
Invert Elev (ft) = 600.00 Velocity (ft/s) = 1.28
Slope (%) = 2.00 Wetted Perim (ft) = 10.37
N-Value = 0.150 Crit Depth, Yc (ft) = 0.75
Top Width (ft) = 9.75
Calculations EGL (ft) = 1.58
Compute by: Known Q
Known Q (cfs) = 11.67
Elev (ft) Section Depth (ft)
603.00 3.00
602.50 2.50
602.00 2.00
v
601.50 = 1.50
601.00 1.00
600.50 0.50
600.00 0.00
599.50 -0.50
0 2 4 6 8 10 12 14 16
Reach (ft)

Channel Report
Hydraflow Express Extension for Autodesk®AutoCAD®Civil 3D®by Autodesk, Inc. Thursday,Jan 12 2023
VCD-2 DA: 1 .06 ac C:0.6 I: 7.26IN/HR
Trapezoidal Highlighted
Bottom Width (ft) = 2.00 Depth (ft) = 1.01
Side Slopes (z:1) = 3.00, 2.00 Q (cfs) = 4.620
Total Depth (ft) = 2.00 Area (sqft) = 4.57
Invert Elev (ft) = 600.00 Velocity (ft/s) = 1.01
Slope (%) = 2.00 Wetted Perim (ft) = 7.45
N-Value = 0.150 Crit Depth, Yc (ft) = 0.46
Top Width (ft) = 7.05
Calculations EGL (ft) = 1.03
Compute by: Known Q
Known Q (cfs) = 4.62
Elev (ft) Section Depth (ft)
603.00 3.00
602.50 2.50
602.00 2.00
601.50 1.50
601.00 0 1.00
600.50 0.50
600.00 0.00
599.50 -0.50
0 2 4 6 8 10 12 14 16
Reach (ft)

Channel Report
Hydraflow Express Extension for Autodesk®AutoCAD®Civil 3D®by Autodesk, Inc. Thursday,Jan 12 2023
VCD-3 DA: 0.61 ac C:0.6 I: 7.26IN/HR
Trapezoidal Highlighted
Bottom Width (ft) = 2.00 Depth (ft) = 0.78
Side Slopes (z:1) = 3.00, 2.00 Q (cfs) = 2.660
Total Depth (ft) = 2.00 Area (sqft) = 3.08
Invert Elev (ft) = 600.00 Velocity (ft/s) = 0.86
Slope (%) = 2.00 Wetted Perim (ft) = 6.21
N-Value = 0.150 Crit Depth, Yc (ft) = 0.33
Top Width (ft) = 5.90
Calculations EGL (ft) = 0.79
Compute by: Known Q
Known Q (cfs) = 2.66
Elev (ft) Section Depth (ft)
603.00 3.00
602.50 2.50
602.00 2.00
601.50 1.50
601.00 1.00
v
600.50 0.50
600.00 0.00
599.50 -0.50
0 2 4 6 8 10 12 14 16
Reach (ft)

Channel Report
Hydraflow Express Extension for Autodesk®AutoCAD®Civil 3D®by Autodesk, Inc. Thursday,Jan 12 2023
VCD-4 DA: 0.57 ac C:0.6 I: 7.26IN/HR
Trapezoidal Highlighted
Bottom Width (ft) = 2.00 Depth (ft) = 0.75
Side Slopes (z:1) = 3.00, 2.00 Q (cfs) = 2.480
Total Depth (ft) = 2.00 Area (sqft) = 2.91
Invert Elev (ft) = 600.00 Velocity (ft/s) = 0.85
Slope (%) = 2.00 Wetted Perim (ft) = 6.05
N-Value = 0.150 Crit Depth, Yc (ft) = 0.32
Top Width (ft) = 5.75
Calculations EGL (ft) = 0.76
Compute by: Known Q
Known Q (cfs) = 2.48
Elev (ft) Section Depth (ft)
603.00 3.00
602.50 2.50
602.00 2.00
601.50 1.50
601.00 1.00
v
600.50 0.50
600.00 0.00
599.50 -0.50
0 2 4 6 8 10 12 14 16
Reach (ft)

Channel Report
Hydraflow Express Extension for Autodesk®AutoCAD®Civil 3D®by Autodesk, Inc. Thursday,Jan 12 2023
VCD-5 DA: 0.38 ac C:0.6 I: 7.26IN/HR
Trapezoidal Highlighted
Bottom Width (ft) = 2.00 Depth (ft) = 0.62
Side Slopes (z:1) = 3.00, 2.00 Q (cfs) = 1.660
Total Depth (ft) = 2.00 Area (sqft) = 2.20
Invert Elev (ft) = 600.00 Velocity (ft/s) = 0.75
Slope (%) = 2.00 Wetted Perim (ft) = 5.35
N-Value = 0.150 Crit Depth, Yc (ft) = 0.25
Top Width (ft) = 5.10
Calculations EGL (ft) = 0.63
Compute by: Known Q
Known Q (cfs) = 1.66
Elev (ft) Section Depth (ft)
603.00 3.00
602.50 2.50
602.00 2.00
601.50 1.50
601.00 1.00
v
600.50 - 0.50
600.00 0.00
599.50 -0.50
0 2 4 6 8 10 12 14 16
Reach (ft)