SW4221001_Design Calculations_20230302

21-025
STORMWATER
IMPACT ANALYSIS
FIELDCREST SUBDIVISION
PHASE II
Thom Road
Haw River, NC 27258
Engineer of Record: Chad E. Abbott, PE
[e-mail] / 919-230-0996 Ext. 101
1St Submittal: August 29, 2022
2nd Submittal: January 13, 2023

Ca�OEESIGN & 2537E. LYON STATION RD, STE 102
PO BOX 361
ENGINEERING, PLLC CREEDMOOR, NC27522
CLIENT -FOCUSED • COMPREHENSIVE • COST-EFFECTIVE 919 230-0996
Table of Contents
DASummary................................................................................................................................1
PipeCalculations..........................................................................................................................2

CaIOEESIGN &
ENGINEERING, PLLC
CLIENT -FOCUSED • COMPREHENSIVE • COST-EFFECTIVE
2537E. LYON STATION RD, STE 102
PO BOX 361
DA SUMMARY
CREEDMOOR, NC 27522
919 230-0996

2537 E. Lyon Station Road
Suite 102, PO Box0361
FIRM LIC #:
aDESIGN
ENGINEERING, RLLC
Creedmoor, NC 27522
P-1764
919-230-0996
Project NO:
21-025
Calculated/
Joel H. Sain, EIT
Project Name:
Fieldcrest Subdivision
Prepared by:
Thom Road
Project Location:
Checked by:
Chad E. Abbott, PE
Haw River, NC 27258
Property BUA
Summary
Lot
Size (sf)
Size (ac)
Impervious (sf)
Impervious (ac)
BUA Percentage
1
44,355
1.02
5,500
0.13
12%
2
45,319
1.04
5,500
0.13
12%
3
47,840
1.10
5,500
0.13
11%
4
43,969
1.01
5,500
0.13
13%
5
44,353
1.02
5,500
0.13
12%
6
45,447
1.04
5,500
0.13
12%
7
46,477
1.07
5,200
0.12
11%
8
50,105
1.15
5,200
0.12
10%
9
49,866
1.14
5,200
0.12
10%
10
46,154
1.06
5,200
0.12
11%
11
45,654
1.05
5,200
0.12
11%
12
46,436
1.07
5,200
0.12
11%
13
49,229
1.13
5,200
0.12
11%
14
44,340
1.02
5,200
0.12
12%
15
44,673
1.03
5,200
0.12
12%
16
45,667
1.05
5,200
0.12
11%
17
46,714
1.07
5,200
0.12
11%
18
54,022
1.24
5,200
0.12
10%
19
175,278
4.02
5,200
0.12
3%
20
46,080
1.06
5,200
0.12
11%
21
45,551
1.05
5,200
0.12
11%
22
43,995
1.01
5,200
0.12
12%
23
51,583
1.18
5,200
0.12
10%
24
61,661
1.42
5,200
0.12
8%
25
59,644
1.37
5,200
0.12
9%
26
45,157
1.04
5,200
0.12
12%
27
44,332
1.02
5,200
0.12
12%
ROW
1 79,763
1.83
36,000
0.83
45%
Total
11,493,6641
34.29
1 178,200
3.41
1 11.93%
Total property area
Total coastal wetlands area
Total surface water
Total project area
1,493,664 sf
34.29 ac
0 sf
0.00 ac
6,987 sf
0.16 ac
1,486,676 sf
34.13 ac
Project percent of impervious area 11.99%

2537 E. Lyon Station Road
DESIGN
ENGINEERING, RLLC
Suite 102, PO Box0361
Creedmoor, NC 27522
FIRM LICA
P-1764
919-230-0996
Project NO:
21-025
Calculated/
Prepared by:
Joel H. Sain, EIT
Project Name:
Fieldcrest Subdivision
Project Location:
Thom Road
Haw River, NC 27258
Checked by:
Chad E. Abbott, PE
PRE -DEVELOPMENT
DA-A: MOTES CREEK
LAND DESCRIPTION
AREA (SF)
AREA (AC)
CN
C
PERVIOUS / LANDSCAPE
335,894
7.71
-
-
TOTAL DA-Al
335,894
7.71
-
-
DA-B: CATERPILLAR CREEK
PERVIOUS / LANDSCAPE
924,661
21.23
-
-
WOODED
226,121
5.19
-
-
TOTAL DA-131
1,150,783
26.42
-
-
TOTAL PRE-DA
1,486,676
34.13
-
-
POST -DEVELOPMENT
DA-A: MOTES CREEK (LOT 3-8)
LAND DESCRIPTION
AREA (SF)
AREA (AC)
CN
C
ROOF AND CONCRETE
32,400
0.74
-
-
PAVING IN ROW
11,000
0.25
-
-
PERVIOUS / LANDSCAPE
279,882
6.43
-
-
TOTAL DA-A
323,282
7.42
-
-
DA-B: CATERPILLAR CREEK (LOT 1-2 AND 9-27)
ROOF AND CONCRETE
109,800
2.52
-
-
PAVING IN ROW
25,000
0.57
-
-
PERVIOUS / LANDSCAPE
802,473
18.42
-
-
WOODED
226,121
5.19
-
-
TOTAL DA-B
1,163,395
26.71
-
-
TOTAL POST-DA
1,486,676
34.13
-
-
DA-A: MOTES CREEK (WS-V; NSW)
DA-B: CATERPILLAR CREEK (WS-II; HQW)
EXISTING BUA
0 SF
0.00 AC
0 SF
0.00 AC
REMOVED BUA
0 SF
0.00 AC
0 SF
0.00 AC
PROPOSED BUA
43,400 SF
1.00 AC
134,800 SF
3.09 AC
TOTAL BUA
43,400 SF
1.00 AC
134,800 SF
3.09 AC
TOTAL DA
323,282 SF
7.42 AC
1,163,395 SF
26.71 AC
NET BUA
43,400 SF
1.00 AC
134,800 SF
3.09 AC
NET DA
323,282 SF
7.42 AC
1,163,395 SF
26.71 AC
BUA PERCENTAGE
13.42%
11.59%

CaIOEESIGN &
ENGINEERING, PLLC
CLIENT -FOCUSED • COMPREHENSIVE • COST-EFFECTIVE
2537E. LYON STATION RD, STE 102
PO BOX 361
CREEDMOOR, NC 27522
919 230-0996
PIPE CALCULATIONS

Hydrology Report
Hydraflow Express Extension for AUtodeskS AutoCADO Civil 31DO by Autodesk, Inc. Thursday, Apr 21 2022
Thom Road Culvert Runoff
Hydrograph type = Rational Peak discharge (cfs) = 6.141
Storm frequency (yrs) = 25 Time interval (min) = 1
Drainage area (ac) = 1.650 Runoff coeff. (C) = 0.47
Rainfall Inten (in/hr) = 7.919 Tc by User (min) = 5
OF Curve = 21-025 Intensity.IDF Rec limb factor = 1.00
Q (cfs)
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0 00
0
Runoff Hyd - Qp = 6.14 (cfs)
Hydrograph Volume = 1,842 (cuft); 0.042 (acft)
Runoff Hydrograph
25-yr frequency
5 10 v vv
Time (min)

62-1-
65.-
625.00
624.00
623.00
Culvert Report
Hydraflow Express Extension for AUtodeskS AutoCADO Civil 3DO by Autodesk, Inc. Thursday, Apr 21 2022
Thom Road Culvert Details
Invert Elev Dn (ft)
= 623.50
Calculations
Pipe Length (ft)
= 63.00
Qmin (cfs)
= 6.50
Slope (%)
= 1.00
Qmax (cfs)
= 6.50
Invert Elev Up (ft)
= 624.13
Tailwater Elev (ft)
= (dc+D)/2
Rise (in)
= 18.0
Shape
= Circular
Highlighted
Span (in)
= 18.0
Qtotal (cfs)
= 6.50
No. Barrels
= 1
Qpipe (cfs)
= 6.50
n-Value
= 0.012
Qovertop (cfs)
= 0.00
Culvert Type
= Circular Concrete
Veloc Dn (ft/s)
= 4.15
Culvert Entrance
= Square edge w/headwall (C)
Veloc Up (ft/s)
= 5.28
Coeff. K,M,c,Y,k
= 0.0098, 2, 0.0398, 0.67, 0.5
HGL Dn (ft)
= 624.74
HGL Up (ft)
= 625.12
Embankment
Hw Elev (ft)
= 625.67
Top Elevation (ft)
= 627.00
Hw/D (ft)
= 1.03
Top Width (ft)
= 26.00
Flow Regime
= Inlet Control
Crest Width (ft)
= 5.00
El-(f) ThGm Road Culvert p Details
------------ --
H. Depth {ft)
3.a7
2.a7
1.37
0.37
-0.13
-1.13
622.00 -2.13
0 5 1❑ 15 20 25 30 35 40 45 50 55 60 65 70 75 an m
Circular Culvert HGL Embank
Reach {R)

Thom Road Culvert Outlet Protection
3Dp
_ T
Outlet W = Do + 0.4La
pipe li
diameter (Do) La
Tailw r 0.5Do
10
La=7'
3 5 10 20 50 100 200 500
Discharge (ft3/sec)
d0 = 18"
Q=6.5cfs
V = 5.28 ft/s
Curves may not be extrapolated.
Figure 8.06b Design of outlet protection from a round pipe flowing full, maximum tailwater condition (TW > 0.5 diameter).
dmax = 1.5 x d50 = 1.5 x 0.1 =0.15'
Apron thickness = 1.5 x 0.15 = 0.225' = 2.7"
w1= 3 x 18/12 = 4.5'
w2 = 18/12 + 0.4 x 7 = 4.3'
8.06.4
3
Od50 = 0.1'
1000
Use: LxWxT = 7'x5'x22"
Rev. 12/93

Hydrology Report
Hydraflow Express Extension for AUtodeskS AutoCADO Civil 31DO by Autodesk, Inc.
Proposed Road Culvert Runoff
Hydrograph type = Rational
Storm frequency (yrs) = 25
Drainage area (ac) = 4.140
Rainfall Inten (in/hr) = 7.919
OF Curve = 21-025 Intensity.IDF
Q (cfs)
14.00
12.00
10.00
: M
. 11
4.00
2.00
0.00
0
— Runoff Hyd - Qp = 13.44 (cfs)
Thursday, Apr 21 2022
Peak discharge (cfs)
= 13.44
Time interval (min)
= 1
Runoff coeff. (C)
= 0.41
Tc by User (min)
= 5
Rec limb factor
= 1.00
Runoff Hydrograph
25-yr frequency
5
Hydrograph Volume = 4,032 (cuft); 0.093 (acft)
Q (cfs)
14.00
12.00
10.00
M
. We
4.00
2.00
-X- 0.00
10
Time (min)

Culvert Report
Hydraflow Express Extension for AUtodeskS AutoCADO Civil 3DO by Autodesk, Inc. Thursday, Apr 21 2022
Proposed Road Culvert Details
Invert Elev Dn (ft)
= 624.95
Calculations
Pipe Length (ft)
= 45.00
Qmin (cfs)
= 13.50
Slope (%)
= 1.00
Qmax (cfs)
= 13.50
Invert Elev Up (ft)
= 625.40
Tailwater Elev (ft)
= (dc+D)/2
Rise (in)
= 18.0
Shape
= Circular
Highlighted
Span (in)
= 18.0
Qtotal (cfs)
= 13.50
No. Barrels
= 2
Qpipe (cfs)
= 13.50
n-Value
= 0.012
Qovertop (cfs)
= 0.00
Culvert Type
= Circular Concrete
Veloc Dn (ft/s)
= 4.28
Culvert Entrance
= Square edge w/headwall (C)
Veloc Up (ft/s)
= 5.37
Coeff. K,M,c,Y,k
= 0.0098, 2, 0.0398, 0.67, 0.5
HGL Dn (ft)
= 626.20
HGL Up (ft)
= 626.40
Embankment
Hw Elev (ft)
= 626.99
Top Elevation (ft)
= 629.00
Hw/D (ft)
= 1.06
Top Width (ft)
= 26.00
Flow Regime
= Inlet Control
Crest Width (ft)
= 5.00
El-(ft)
630.00
629.OD
62S.OD
627.OD
626.00
625.00
624.00
623.00
0
Proposed Road Culvert Details
5 10 15 20 25 30 35 40 45 50 55 60
Circular Culvert HGL Embank
H. Depth {ft)
4.60
3.60
2.60
1.60
0.60
-0.40
-1.40
-2.40
65
Reach {R)

Proposed Road Culvert Outlet Protection
3Dp
_ T
Outlet W = Do + 0.4La
pipe li
diameter (Do) La �I
Tailw r 0.5Do
20
La = 18'
10
3 5 10 20 50 100 200 500
Discharge (ft3/sec)
d0 = 18"
Q = 13.5 cfs
V = 5.37 ft/s
Curves may not be extrapolated.
Figure 8.06b Design of outlet protection from a round pipe flowing full, maximum tailwater condition (TW > 0.5 diameter).
dmax= 1.5xd50= 1.5 x 0.25 = 0.375'
Apron thickness = 1.5 x 0.375 = 0.563' = 6.75"
w1= 3 x 18/12 = 4.5'
w2= 18/12+0.4x 18=8.7'
8.06.4
3
Od50 = 0.25'
1000
Use: LxWxT = 18'x9'x22"
Rev. 12/93

Hydrology Report
Hydraflow Express Extension for AUtodeskS AutoCADO Civil 3DO by Autodesk, Inc. Thursday, Apr 21 2022
Lot 17 Driveway Runoff
Hydrograph type
= Rational
Peak discharge (cfs)
= 8.476
Storm frequency (yrs)
= 25
Time interval (min)
= 1
Drainage area (ac)
= 2.230
Runoff coeff. (C)
= 0.48
Rainfall Inten (in/hr)
= 7.919
Tc by User (min)
= 5
OF Curve
= 21-025 Intensity.IDF
Rec limb factor
= 1.00
Q (cfs)
10.00
4.00
2.00
0.00 -110
0
— Runoff Hyd - Qp = 8.48 (cfs)
Runoff Hydrograph
25-yr frequency
5
Hydrograph Volume = 2,543 (cuft); 0.058 (acft)
Q (cfs)
10.00
4.00
2.00
X- 0.00
10
Time (min)

Culvert Report
Hydraflow Express Extension for AUtodeskS AutoCADO Civil 31DO by Autodesk, Inc.
Thursday, Apr 21 2022
Lot 17 Driveway Details
Invert Elev Dn (ft)
= 606.35
Calculations
Pipe Length (ft)
= 30.00
Qmin (cfs)
= 8.50
Slope (%)
= 1.00
Qmax (cfs)
= 8.50
Invert Elev Up (ft)
= 606.65
Tailwater Elev (ft)
= (dc+D)/2
Rise (in)
= 18.0
Shape
= Circular
Highlighted
Span (in)
= 18.0
Qtotal (cfs)
= 8.50
No. Barrels
= 1
Qpipe (cfs)
= 8.50
n-Value
= 0.012
Qovertop (cfs)
= 0.00
Culvert Type
= Circular Concrete
Veloc Dn (ft/s)
= 5.18
Culvert Entrance
= Square edge w/headwall (C)
Veloc Up (ft/s)
= 5.96
Coeff. K,M,c,Y,k
= 0.0098, 2, 0.0398, 0.67, 0.5
HGL Dn (ft)
= 607.66
HGL Up (ft)
= 607.78
Embankment
Hw Elev (ft)
= 608.57
Top Elevation (ft)
= 609.25
Hw/D (ft)
= 1.28
Top Width (ft)
= 20.00
Flow Regime
= Inlet Control
Crest Width (ft)
= 5.00
El-(ft)
610.00
�8.❑0
F C4.❑❑
6❑6.00
6❑5.❑❑
Lot 17 Driveway Details
5 10 15 20 25 30 35 40 45
Circular Culvert HGL Embank
H. Depth {ft)
3.35
235
1.35
0.35
-0.65
-1.65
50
Reach {R)

Lot 17 Driveway Outlet Protection
3Dp
_ T
Outlet W = Do + 0.4La
pipe li
diameter (Do) La �I
Tailw r 0.5Do
10
La=7'
3 5 10 20 50 100 200 500
Discharge (ft3/sec)
d0 = 18"
Q=8.50cfs
V = 5.96 ft/s
Curves may not be extrapolated.
Figure 8.06b Design of outlet protection from a round pipe flowing full, maximum tailwater condition (TW > 0.5 diameter).
dmax = 1.5 x d50 = 1.5 x 0.1 =0.15'
Apron thickness = 1.5 x 0.15 = 0.225' = 2.7"
w1= 3 x 18/12 = 4.5'
w2 = 18/12 + 0.4 x 7 = 4.3
8.06.4
3
d50 = 0.1'
'0
1000
Use: LxWxT = 7'x5'x22"
Rev. 12/93