20190624 Ver 1_2018-11-27_Old Airport Rd_Redline Calculations_20190510

Date: 11/26/2018 Kimley-Horn & Associates, Inc.
Raleigh, NC
Project Number: 12718003
Designed By: ANN
County: Craven Checked By: DWT
Ditch Computation Sheet
Description
Normal
Ditch Location
D.A.
(acres)
C
Q25
(cfs)
Slope
(ft / ft)
Base
Width
Side
Slopes
Depth
(ft)
Velocity
(fps)
Remarks
Liner Type
From
To
L/M/R
18+92 -L-
19+00 -L-
R
0.87
0.57
3.70
0.0800
0
4:1/3:1
0.62
2.72
Class 'B' Rip Rap
19+00 -L-
22+75 -L-
R
0.87
0.57
3.70
0.0024
0
4:1/3:1
0.93
1.22
Grass
22+75 -L-
25+50 -L-
R
0.22
0.62
1.02
0.0040
0
4:1/3:1
0.52
1.07
Grass
25+50 -L-
29+50 -L-
R
0.62
0.58
2.67
0.0035
0
4:1/3:1
0.77
1.29
Grass
29+50 -L-
32+00 -L-
R
1.03
0.58
4.51
0.0040
0
4:1/3:1
0.91
1.55
Grass
32+00 -L-
32+60 -L-
R
1.03
0.58
4.51
0.0033
0
4:1/3:1
0.95
1.44
Grass
32+60 -L-
35+00 -L-
R
1.66
0.55
6.82
0.0063
0
4:1/3:1
0.98
2.04
Grass
35+00 -L-
36+00 -L-
R
1.66
0.55
6.82
0.0350
0
4:1/3:1
0.71
3.87
Grass
36+20-L-
37+00-L-
R
2.61
0.51
9.97
0.0288
0
4:1/3:1
0.85
3.96
Grass
37+00 -L-
42+30 -L-
R
2.61
0.51
9.97
0.0022
0
4:1/3:1
1.37
1.51
Grass
42+30 -L-
45+35 -L-
R
2.61
0.51
9.97
0.0010
0
4:1/3:1
1.59
1.12
Grass
45+35 -L-
46+70 -L-
R
2.61
0.51
9.97
0.0017
0
4:1/3:1
1.44
1.37
Grass
46+70 -L-
48+00 -L-
R
1.17
0.50
4.34
0.0082
0
4:1/3:1
0.79
2.01
Grass
48+00 -L-
51 +75 -L-
R
1.17
0.50
4.34
0.0057
0
4:1/3:1
0.84
1.75
Grass
52+80 -L-
55+50 -L-
R
0.52
0.66
2.58
0.0024
0
4:1/3:1
0.89
0.93
Grass
Page 1 of 3

Ditch Computation Sheet
Description
Normal
Ditch Location
D.A.
(acres)
C
Q25
(cfs)
Slope
(ft / ft)
Base
Width
Side
Slopes
Depth
(ft)
Velocity
(fps)
Remarks
Liner Type
From
To
L/M/R
55+50 -L-
64+15 -L-
R
1.61
0.65
7.89
0.0027
0
4:1/3:1
1.21
1.54
Grass
64+50 -L-
67+55 -L-
R
1.98
0.63
9.42
0.0035
0
4:1/3:1
1.23
1.77
Grass
67+55 -L-
70+03 -L-
R
2.32
0.61
10.58
0.0028
0
4:1/3:1
1.34
1.68
Grass
70+03 -L-
72+65 -L-
R
2.69
0.59
11.91
0.0029
0
4:1/3:1
1.39
1.75
Grass
72+65 -L-
73+35-L-
R
2.82
0.59
12.48
0.0024
0
4:1/3:1
1.47
1.65
Grass
75+61 -L-
76+22 -L-
R
3.44
0.57
14.687
0.0205
0
4:1/3:1
1.05
3.84
Grass
76+43 -L-
77+10 -L-
R
3.44
0.57
14.687
0.0037
0
4:1/3:1
1.44
2.02
Grass
78+10 -L-
79+50 -L-
R
3.61
0.57
15.369
0.0077
0
4:1/3:1
1.28
2.69
Grass
79+50 -L-
79+95 -L-
R
3.61
0.57
15.369
0.0204
0
4:1/3:1
1.06
3.88
Grass
83+59 -L-
86+50 -L-
R
0.75
0.47
2.63
0.0167
0
4:1/3:1
0.57
2.31
Grass
86+50 -L-
87+00 -L-
R
0.75
0.47
2.63
0.0328
0
4:1/3:1
0.50
2.98
Grass
18+62 -L-
20+10 -L-
L
0.87
0.51
3.35
0.0017
0
4:1/3:1
0.96
1.04
Grass
20+10 -L-
22+00 -L-
L
0.87
0.51
3.35
0.0031
0
4:1/3:1
0.86
1.31
Grass
22+00 -L-
24+50 -L-
L
0.87
0.51
3.35
0.0025
0
4:1/3:1
0.89
1.21
Grass
24+50 -L-
27+70 -L-
L
1.23
0.41
3.81
0.0025
0
4:1/3:1
0.94
1.25
Grass
27+70 -L-
32+00 -L-
L
3.33
0.45
11.28
0.0032
0
4:1/3:1
1.34
1.79
Grass
Page 2 of 3

Ditch Computation Sheet
Description
Normal
Ditch Location
D.A.
(acres)
C
Q25
(cfs)
Slope
(ft / ft)
Base
Width
Side
Slopes
Depth
(ft)
Velocity
(fps)
Remarks
Liner Type
From
To
L/M/R
32+00 -L-
33+65 -L-
L
3.33
0.45
11.28
0.0062
0
4:1/3:1
1.18
2.30
Grass
33+65 -L-
36+00 -L-
L
3.33
0.45
11.28
0.0191
0
4:1/3:1
0.96
3.50
Grass
36+20 -L-
38+00 -L-
L
2.74
0.57
11.77
0.0161
0
4:1/3:1
1.01
3.32
Grass
38+00 -L-
46+90 -L-
L
2.01
0.54
8.08
0.0020
0
4:1/3:1
1.29
1.38
Grass
46+90 -L-
52+55 -L-
L
1.53
0.51
5.89
0.0042
0
4:1/3:1
1.00
1.69
Grass
52+55 -L-
57+50 -L-
L
0.75
0.51
2.83
0.0025
0
4:1/3:1
0.84
1.16
Grass
57+50 -L-
62+50 -L-
L
0.75
0.56
3.13
0.0020
0
4:1/3:1
0.91
1.09
Grass
62+50 -L-
73+50 -L-
L
1.98
0.55
8.17
0.0020
0
4:1/3:1
1.30
1.39
Grass
73+50 -L-
76+10 -L-
L
3.39
0.48
12.31
0.0096
0
4:1/3:1
1.13
2.76
Grass
76+10 -L-
77+00 -L-
L
3.39
0.48
12.31
0.0059
0
4:1/3:1
1.24
2.30
Grass
77+00 -L-
79+54 -L-
L
3.39
0.48
12.31
0.0215
0
4:1/3:1
0.97
3.74
Grass
83+82 -L-
86+15 -L-
L
0.82
0.55
3.35
0.0215
0
4:1/3:1
0.60
2.70
Grass
86+15 -L-
87+50 -L-
L
0.54
0.52
2.11
0.0151
0
4:1/3:1
0.53
2.11
Grass
10+41-Y2-
13+25 -Y2-
L
1.22
0.67
6.07
0.002
0
4:1/3:1
1.16
1.29
Grass
10+45 -Y2-
13+50 -Y2-
R
0.53
0.44
1.73
0.002
0
4:1/3:1
0.76
0.86
Grass
Page 3 of 3

Date 11/26/2018
Project No. 012718003 I.D. No.
PIPE DATA SHEET
Sheet
County Craven Designed By DWT Checked By
1 of 1
LDR
Shoulder CL Elev. 18.72
PLAN SUMMARY DATA
Elev 18.95
Drainage Area
57.71
ac
Design Freq.
50
yr
Station
36+12 -L-
Design Disch.
111.00
cfs
Skew
84.30 °
H
Design H.W. Elev.
16.57
ft
Size/Type Pipe
2-42" RCP
H.W.
T.W.
Q100 Disch.
127.00
cfs
Type Entrance
Groove End with
HW LSo
��
Q100 H.W. Elev.
16.89
ft
Direction of Flow
Rt to Lt
Overtopping Freq.
yr
Hydrological Method USGS
Inv. Elev. 13.00 So = 1.25 % Inv. Elev. 12.25
Overtopping Disch.
207.10
cfs
HW Control Elev
18.95
L = 60.00
Overtopping Elev.
18.95
ft
Size & Type Pipe
Freq
(Yrs.)
Q
(cfs)
Nat.
H.W
Allow.
H.W.
T.W.
INLET CONTROL
OUTLET CONTROL
H.W.
Elev.
Vo
(ft/s)
COMMENTS
HW/D
H.W.
Ke
do
do+d
ho
H
LSo
H.W.
2
2 - 42" RCP
10
75.00
0.62
0.76
2.67
0.2
1.90
2.70
2.70
0.12
0.75
2.82
15.82
1 9.94
Outlet Control
2 - 42" RCP
25
95.00
0.62
0.88
3.09
0.2
12.1512.83
2.83
0.43
0.75
3.25
16.25
10.51
Outlet Control
2 - 42" RCP
50
111.00
0.62
0.97
3.40
0.2
2.33
2.92
2.92
0.66
0.75
3.57
16.57
10.91
Outlet Control
2 - 42" RCP
100
127.00
0.62
1.06
3.72
0.2
2.50
3.00
3.00
0.89
0.75
3.89
16.89
11.29
Outlet Control
SUMMARY AND RECOMMENDATIONS: 2-42" RCP
USGS method used to determine discharge. 15% imperviousness used to account for future development. Water will breach Shld pt at sta. 36+12 -L-
elevation = 18.95. This vields 2.38' of freeboard during the 50-vr storm.

OLD AIRPORT RD
OUTFALL ANALYSIS

OUTFALL ANALYSIS 36+12 -L- (LT)
Description:
The proposed outfall are dual 42" RCPs that outlet at Sta. 36+12 -L- (LT) replacing existing dual
24" RCPs. The pipes discharge into an existing wetland. The inlet and outlet were raised 0.5' from
existing inverts to maintain tailwater depth in the proposed 42" pipes.
Photo 1: Existing Condition Downstream of Outlet
Photo 2: Existing Condition of Outlet

Analysis:
• There are no adverse effects on the downstream receiving water.
• There are no downstream inadequacies that would adversely impact the highway.
• There will be no effects to the adjacent property from the 25-yr storm.
• The outfall has a pre -construction flow of 219.32 cfs and post -construction flow of 225.94 cfs.
This yields a percent increase of 3.00%. The pre -construction velocity is 4.34 fps and the post -
construction velocity is 4.37 fps. This yields a percent increase of 0.70%. The pre -construction
water surface is 2.25 ft and the post -construction water surface is 2.27 ft which yields a percent
increase of 0.90%. The minor increases are due to the addition of impervious area.
• Based on the minimal impact to the downstream facilities, no corrective measures are needed.
• No actions recommended at this time.

OUTFALL ANALYSIS 13+23 -Y2- (LT)
Description:
The outfall at Sta. 13+23 -Y2- (LT) is a proposed ditch that outlets to an existing 15" RCP. There
is a ditch downstream of the existing 15" driveway pipe.
Photo 1: Existing Condition of Upstream of Outlet
Analysis:
• There are no adverse effects on the downstream receiving water.
• There are no downstream inadequacies that would adversely impact the highway.
• There will be no effects to the adjacent property from the 25-yr storm.
• The outfall has a pre -construction flow of 2.04 cfs and post -construction flow of 3.49 cfs. This
yields a 70.80% increase. The pre -construction velocity is 1.54 fps and the post -construction
velocity is 1.76 fps. This yields a percent increase of 14.30% increase. The pre -construction water
surface is 0.66 ft and the post -construction water surface is 0.81 ft which yields a percent increase
of 22.70%. The increases are due to the addition of impervious area and consideration of future
development per city zoning maps.
• Based on the minimal impact to the downstream facilities, no corrective measures are needed.
• No actions recommended at this time.

Kimley>»Horn
Project Information
Project Name: Old Airport Rd
KHA Project #: 012718003
Designed by: ANN Date: 11/26/2018
Checked by: DWT Date: 11/26/2018
Revised by: Date:
25 Year Analysis
Pre- vs Post -Construction Discharges
EXISTING
CONDITIONS
PROPOSED
CONDITIONS
Station/Structure #
DRAINAGE
AREA
A (acres)
RUNOFF
COEFF.
C
Time of
Concentration
Tc (min)
Storm
Intensity
I (in/hr)
Q
TOTAL
Q10 (cfs)
Station/Structure #
DRAINAGE
AREA
A (acres)
RUNOFF
COEFF.
C
Time of
Concentration
Tc (min)
Storm
Intensity
I (in/hr)
O
TOTAL
Quo (cfs)
DISCHARGE
DIFF.
(CFS)
DISCHARGE
INCREASE
M)
36+12 -L- LT/0204
63.75
0.46
10.00
7.50
219.32
36+12 -L- LT/0204
63.75
0.47
10.00
7.50
225.94
6.63
3.0
13+23 -Y2- LT
0.70
0.39
10.00
7.50
2.04
13+23 -Y2- LT
0.70
0.67
10.00
7.50
3.49
1.44
70.8
Note: Future development was taken into account during the computing of the proposed C-values.
Page 1 of 1

Kimley>Morn
Project Information
Pre
Downstream
Outfalls
Post
Downstream
Outfalls
Downstream
Outfalls
Qzs Outfall Channel Analysis
Project Name: Old Airport Rd
KHA Project M 012718003
Designed by: ANN Date: 11/26/2018
Checked by: DWT Date: 11/26/2018
Revised by: Date:
Outlet
DA
C
Tc
izs
Qns
s
Fore Slope
Backslope
Base Width
Ditch
Existing
I Design Depth
y
V
Manning's
(ac)
Value
(min)
(in/hr)
(cfs)
(ft/ft)
(ft)
Type
Depth (ft)l
of Ditch (ft.)
(ft)
(fps)
n
36+12 -L- LT/0204
63.75
0.46
10.00
7.50
219.32
0.0090
10A
10A
0
Exist Wetland
N/A
Leave as is
2.25
4.34
0.035
13+23 -Y2- LT
0.70
0.39
10.00
7.50
2.04
0.0062
3:1
3:1
0
Exist Swale
N/A
Leave as is
0.66
1.54
0.035
Outlet
DA
C
Tc
izs
Qzs
s
Fore Slope
Backslope
Base Width
Ditch
Existing
Design Depth
y
V
Manning's
(ac)
Value
(min)
(in/hr)
(cfs)
(ft/ft)
(ft)
Type
De th (ft)
of Ditch (ft.)
(ft)
(fps)
n
36+12 -L- LT/0204
63.75
0.47
10.00
7.50
225.94
0.0090
10:1
10:1
0
Exist Wetland
N/A
Leave as is
2.27
4.37
0.035
13+23 -Y2- LT
0.70
0.67
10.00
7.50
3.49
0.0062
3:1
3:1
0
Exist Swale
N/A
Leave as is
0.81
1.76
0.035
Outlet
Depth
Velocity
Depth
Velocity
Change
Change (ft)
Change (fps)
Change (%)
36+12 -L- LT/0204
0.02
0.03
0.9
0.7
13+23 -Y2- LT
0.15
0.22
22.7
14.3
Page 1 of 1