SW3240101_Design Calculations_20240913

CEST
Storm wa ter Calculations
For
Huntley Brothers Home Office
12400 Old Camden Road
Midland, NC 28107
CONCORD PROJECT NO. 210123.000
Owner:
Client: Huntley Brothers ��
Client Representative: Ed Huntley \N CARD` '_�,
8217 Fairview Road �?� EESSIp �y�
Charlotte, NC 28227 QUO .�
P.980.237.3291 - SEAL
[e-mail] = 054 2 Preparer's Name: Nancy E. Warlick, PE �i 1,404
CESI '% /ZABEt k \\\.
NCBELS Corporate License Number C-0263 /" g/12/2024
PO Box 268
Concord, NC 28026
M.704.648.2684
[e-mail]

- Narrative and Summary of Results
- Impervious Area Summary
- Pre-Development Calculations
- Pre Development Nodal Diagram
- Pre-Development Drainage Areas
WET POND DETAILS
TOP OF POND 678.5
BOTTOM OF MAIN PC 669.5
BOTTOM OF FOREBA 669
- Hydraflow Results
- Riprap Calculations
- Appendix

SUMMARY OF RESULTS
PRE-DEVELOPMENT DRAINAGE AREA SUMMARY
DRAINAGE AREA AREA (ACRES) TC CN
Pre DA-A 13.190 18.20 62.2
Total 13.190
POST DEVELOPMENT DRAINAGE AREA SUMMARY
DRAINAGE AREA AREA (ACRES) TC CN
Post DA-Wet Pond 16.896 10.00 59.2
Post DA- Bypass 8.520 10.00 60.0
Total 25.416
PRE-DEVELOPMENT RUNOFF RESULTS
DRAINAGE AREA 1 YR/24 HR 10 YR/24 HR 100 YR/24 HR
Pre DA 2.343 18.96 45.4
POI 4.358 30.04 68.09
POST-DEVELOPMENT RUNOFF RESULTS
DRAINAGE AREA 1 YR/24 HR 10 YR/24 HR 100 YR/24 HR
Post DA-Wet PoNd 16.18 36.68 60.33
Post DA- Bypass 2.02 15.71 36.91
Wet Pond 1 0.09 3.92 41.04
POI 2.08 15.80 72.21
POST DEVELOPMENT PEAK-STAGE RESULTS
1 YR/24 HR 10 YR/24 HR 100 YR/24 HR
WP1 (T.O.B. = 685.00) 675.80 676.72 677.40
SOIL AREA SUMMARY
Pre-development Post-Development
Hydrologic Soil Group C 12,139 sq. ft 12,139 sq. ft
Hydrologic Soil Group B 562,417 sq. ft 683,514 sq. ft

pret—Development Drainage Area
FREEBOARD
100 YEAR 24 HOUR ELEVATION 675.80 2.70
10 YEAR 24 HOUR ELEVATION 676.72 1.78
1 YEAR 24 HOUR ELEVATION 677.40 1.10
WATER QUALITY/PONDING ELEVATION 677.50 1.00
OUTLET STRUCTURE DETAILS
RIM ELEVATION 679.00
SLOT WEIR ELEVATION (D) 0.00
SLOT WEIR WIDTH (D) 0.00
OUTLET STRUCTURE SIZE 4.00' X 4.00'
STRUCTURE FOOTING DETAILS (K)
FOOTING LENGTH 6.00
FOOTING WIDTH 6.00
FOOTING DEPTH 6.00
WET POND DETAILS
TOP OF POND 678.50
BOTTOM OF MAIN POOL 669.50
BOTTOM OF FOREBAY 669.00

3. Impervious Area Summary
Pre-Development
Total Existing On-Site inpervious area 0 SQ FT
Post-Development
Total on-site impervious area 208,226 SQ FT
On-site area required to be treated by SCM 208,226 SQ FT1
Total area treated by SCM 208,226 SQ FT
Equal to the post-development impervious area minus the Pre-devlopment Impervious
Impervious area not being treated by SCM is located at entrance to site. Driveway sheet
flows North towards Zane Road therefore, not being treated by Sand Filter

Pre-Development Drainage Area
Pre Development Nodal Diagram
PRE DA
POI

Pre-Development Drainage Area
Land use Condition Hydrologic Area(SF) Area(Acres) Cn Weighted Cn
Soil Group
Woods good B 436,471 10.020 60 45.6
Open Space good B 138,085 3.170 69 16.6
Impervious N/A B - - 98 0.0
574,556 13.190 62.2
tc Calculation L up down slope n pipe size(in) area(sf) perimeter
(ft)
Sheet Flow 100 706.87 706.39 0.48% 0.15 Grass:Short Praire
Shallow Concentrated 426 706.39 674.71 7.44% Un-Paved
CALCULATED TC= 18.20 MIN SEE HYDRAFLOW TR-55 TC CALCULATION SHEET
TC USED IN CALCULATION= 18.20 MIN MINIMUM TC OF 10 MINUTES
WET POND DETAILS
TOP OF POND 0.011
BOTTOM OF MAIN POOL 0.05
BOTTOM OF FOREBAY 0.06
Grass:Dense Grass 0.24
Grass:Bermuda Grass 0.41
Range:Natural 0.13
Woods:Light Underbrush 0.4
Woods:Dense Underbrush 0.8
Roughness Coefficients(Manning's N)for Channel Flow
Excavated Channels:Short Grass 0.027

Post-Development Drainage Area
Post Development Nodal Diagram
Post DA-
Post DA-WP BYPASS
SF1
POI

Post-Development Drainage Area-Wet Pond
Land use Condition Hydrologic Area(SF) Area(Acres) Cn Weighted Cn
Soil Group
Open Space good B 527,763 12.116 61 43.7
Impervious(Asphalt/Concrete) N/A B 25,413 0.583 98 2.0
Impervious(Gravel) N/A B 173,405 3.981 85 12.2
Impervious(Building) N/A B 9,408 0.216 98 1.3
735,989 16.896 59.2
TC USED IN CALCULATION= 10.00 MIN MINIMUM TC OF 10 MINUTES
WET POND DETAILS
TOP OF POND 678.5
BOTTOM OF MAIN POOL 669.5
BOTTOM OF FOREBAY 669

Wet Detention Pond Design Calculations
Area(sq.ft.) Area(acres) Attenuation Requirements
Total Drainage Area 735,989 16.896 1-year,24-hour storm
Pervious Area 527,763 12.116 10-year,24-hour storm
Impervious Area 208,226 4.780 Emergency Spillway Requirement
100 year,24-hour storm,6"freeboard
Simple Method for Runoff Volume
Rv=0.05+0.9*IA 0.30 Rv=Runoff Coefficient(unitless)
IA=Impervious fraction 0.28
DV=3630*RD*Rv*A 18,684 DV=Design Volume(cu ft)
RD=Design Storm Depth(in) 1.0
A=Drainage Area(ac) 16.896
Average Depth Double Interpolation from SA/DA Table
DA,=VPP/APP 1.82 3.00 1.82 4.00
0.90 3.25 3.97 2.64
VPP=Volume of permanent pool(Main Body only) 3,303 0.28 1.02
App=Area of permanent pool(Main Body only) 1,819 1.00 3.55 4.45 2.79
Main Pool Volume(SA/DA Method)
Total DA 735,989
SA/DA 1.02
Surface Area Required(DA*((SA/DA)/100)) 7,543
Surface Area Provided(Main Body only) 1,819
Table 1:Piedmont and Mountain SA/DA Table(Adapted from Driscoll,1986)
3.00 4.00 5.00 6.00 7.00 8.00
0.10 0.51 0.43 0.37 0.30 0.27 0.25
0.20 0.84 0.69 0.61 0.51 0.44 0.40
0.30 1.17 0.94 0.84 0.72 0.61 0.56
0.40 1.51 1.24 1.09 0.91 0.78 0.71
0.50 1.79 1.51 1.31 1.13 0.95 0.87
0.60 2.09 1.77 1.49 1.31 1.12 1.03
0.70 2.51 2.09 1.80 1.56 1.34 1.17
0.80 2.92 2.41 2.07 1.82 1.62 1.40
0.90 3.25 2.64 2.31 2.04 1.84 1.59
1.00 3.55 2.79 2.52 2.34 2.04 1.75

Forebay 1 Main Bay Forebay 2
Incremental Cumulative Incremental Cumulative Incremental Cumulative
Elevation Area Depth Volume Volume Elevation Area Depth Volume Volume Elevation Area Depth Volume Volume
669.00 13 - 669.50 4,998 669.5 12
670.50 356 1.50 277 - 670.50 5,968 1.00 5,483 5,483 670.50 356 1.00 184 -
671.50 772 1.00 564 750 671.50 6,930 1.00 6,449 _ 11,932 671.50 740 1.00 548 730
672.50 1,259 1.00 1,016 1,766 672.50 8,004 1.00 7,467 19,399 672.50 1,225 1.00 983 1,713
673.50 1,819 1.00 1,539 3,305 673.50 9,150 1.00 8,577 27,976 673.50 1,781 1.00 1,503 3,216
Temporary Pool
Incremental Cumulative
Elevation Area Depth Volume Volume
673.50 13,386 - - -
674.50 15,000 1.00 14,193 14,193
675.50 16,686 1.00 15,843 30,036
676.50 18,444 1.00 17,565 47,601
677.50 20,274 1.00 19,359 66,960
678.50 22,176 1.00 21,225 88,185
24,678 12,338.78
Permanent Pool Volume: 33,919 32,903 16,451.70
Forebay Volume: 6,520
Forebay Percentage 19.2%

Wet Pond CESI Land Development Services
JOB NO.: 210123.000 BY: MAC P.O.Box 268
DATE: 9/10/2024 P.M: NEW Concord,NC 28026
REVISED: FLOATATION CALCULATIONS
Calculations Given Data Standard Footing Assumptions
Density of Concrete 150 Ibs/ft^3 1. Footing base to be 1 ft.wider than structure
Density of Water 62.4 Ibs/ft^3 on all sides.
Safety Factor(S.F.) 2
Equations used:
Outlet Structure Weight, W(s)= (w+2t)^2*h-w^2*(h-t)x D(c)
where, w= outlet box inside dimension,ft.
Displaced Water Weight, W(w)= (w+2t)^2 x D(w)x h t= structure wall thickness,ft.
h= height of structure,ft.
Required Base Weight, W(b)= (W(w)x S.F.)-W(s) D(c)= density of concrete,lbs/ft^3
WET POND DETAILS D(w)= density of water,lbs/ft^3
TOP OF POND fired Footing Volume,V(f)= W(b)/Dc-Dw S.F.= safety factor
BOTTOM OF MAIN PC 674
BOTTOM OF FOREB/ 675
Elevation at bottom of structure= 669.50
Elevation at top of structure= 678.50
Height of structure,h= 9.00 ft. Outlet Structure Weight, W(s)= 13350 lbs
Structure wall thickness,t= 6 in. Displaced Water Weight, W(w)= 14040 lbs
Average outlet box inside dimension, w= 4 ft. Req'd Base Weight, W(b)= 14730 lbs
Footing Size
Required Footing Volume, V(fr)= 168 cf Standard Footing Length,L= 6.00 ft.
Provided Footing Volume, V(fp)= 216 cf Standard Footing Width, W= 6.00 ft.
Footing Check okay Minimum Footing Depth,D= 1.00 ft.
Footing Size to be used: Length= 6.00 ft.
Width= 6.00 ft.
Depth= 6.00 ft.

Post-Development Drainage Area-Bypass
Land use Condition Hydrologic Area(SF) Area(Acres) Cn Weighted Cn
Soil Group _ _
Woods good B 371,131 8.520 60 60.0
371,131 8.520 60.0
TC USED IN CALCULATION= 10.00 MIN MINIMUM TC OF 10 MINUTES

Wet Detention Pond 1 BMP Design (NCDENR)
Date 9/11/2024
Project Number 210123.000
Project Huntley Brothers Facility
%TSS Requirement 90% •
Drainage Area 7.40 ac Double Interpolated SA/DA Ratio
Impervious Area 4.78 ac Pool Depth (ft)
Impervious % 65% Imp % 4.50 5.00 5.50
60% 2.70 2.50 2.40
Estimated Avg. Depth 5 ft 65% 2.88 2.64 2.54
SA/DA Ratio 2.64 % 70% 3.10 2.80 2.70
SA Required 0.20 ac Table 10-3
SA Required 8503 sf
SA Provided 22176.00 sf
SA Provided 0.51 ac
Pool Depth Provided 5.00 ft
Rv = 0.05 + 0.9 *IA SIMPLE METHOD PER NCDENR BMP MANUAL SECTION 3.3.1
Rv = Runoff coefficient [storm runoff (in)/storm rainfall (in)], unitless
Impervious fraction [impervious portion of drainage area
IA = (ac)/drainage area (ac)], unitless
**V = Volume of runoff that must be controlled for the design storm (ft3)
RD = Design storm rainfall depth (in) (Typically, 1.0" or 1.5")
A = Watershed area (ac)
WQv = 3630 * RD * Rv * A
Rv 0.63 (1 inch)
WQv 33,919 (2 inch)

Permament Pool
ABS 12750.00 sf
APP 12750.00 sf
ABP 4998.05 sf
Depth= 4.00 ft
Calc Avg. Depth 3.28 Must be greater than Estimated
Volume Calculation
Stage Area Inc. Vol. Acc Vol.
669.5 4998 0.00 0.00 Bottom (not Sediment)
670.5 5968 5483.00 5483.00
671.5 6930 6449.00 11932.00
672.5 8004 7467.00 19399.00
673.5 9150 8577.00 27976.00 pp
Temporary Pool Volume
Volume Calculation
Stage Area Inc. Vol. Acc Vol.
673.5 13386 8577.00 8577.00 PP
674.5 15000 14193.00 22770.00
675.5 16686 15843.00 38613.00
676.5 18444 17565.00 56178.00
677.5 20274 19359.00 75537.00
678.5 22176 21225.00 96762.00 Top of Dam (allow 1 ft FB)
Assumed Stage Interval for Treatment of WQv 674.5
Interpolate 0.10 area between even stages at WQv stage
Volume Calculation
Stage Area Inc. Vol. Acc Vol.
674.5 15000.00 0.00 22770.00 Lower WQv stage
674.6 15168.60 1508.43 24278.43
674.7 15337.20 1525.29 25803.72 <--
674.8 15505.80 1542.15 27345.87
674.9 15674.40 1559.01 28904.88
675.0 15843.00 1575.87 30480.75
675.1 16011.60 1592.73 32073.48
675.2 16180.20 1609.59 33683.07
675.3 16348.80 1626.45 35309.52
675.4 16517.40 1643.31 36952.83
675.5 16686.00 1660.17 38613.00 Higher WQv Stage
Calc WQV Stage 675.3

Calculate Orifice Size
Treatment Vol 33,919 CF 33,919
Draw Down Time 2 DAYS 5
Draw Down Time 172,800 sec 432,000
Flow(Q) 0.196 CFS 0.079
Cd 0.6 0.6
H/3 0.600 ft 0.600
Area of orifice 0.053 sf 0.021 Orifice: 2
Dia. 3.11 in 1.97 < Plate Hole: 3
Center Offset: 8/16
Draw Down Time: 4.82

Hydraflow Results

1
Hydrograph Summary Report
Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk,Inc.v2021
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 2.343 2 728 14,268 PRE DA
3 SCS Runoff 16.18 2 720 41,961 POST DA-WET POND
4 SCS Runoff 2.017 2 724 9,504 POST DA-BYPASS
6 Reservoir 0.156 2 1446 35,571 3 675.80 35,276 WET POND ROUTING
8 Combine 2.343 2 728 14,268 1, PRE DA
9 Combine 2.122 2 724 45,076 4,6, POST DA-ROUTED
210123.000 Stormwater Calculations.gpw Return Period: 1 Year Wednesday, 09/ 11 /2024

2
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk, Inc.v2021 Wednesday,09/11 /2024
Hyd. No. 1
PRE DA
Hydrograph type = SCS Runoff Peak discharge = 2.343 cfs
Storm frequency = 1 yrs Time to peak = 728 min
Time interval = 2 min Hyd. volume = 14,268 cuft
Drainage area = 13.190 ac Curve number = 60*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 18.20 min
Total precip. = 2.90 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
*Composite(Area/CN)=[(10.022 x 60)+(3.167 x 61)]/13.190
PRE DA
0 (cfs) Hyd. No. 1 -- 1 Year 0 (cfs)
3.00 3.00
I
2.00 2.00
1.00 1.00
0.00 — 1 \ 0.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Hyd No. 1 Time (min)

3
Hydrograph Summary Report
Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk,Inc.v2021
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 18.96 2 726 65,109 PRE DA
3 SCS Runoff 36.68 2 720 96,511 POST DA-WET POND
4 SCS Runoff 15.71 2 722 43,371 POST DA-BYPASS
6 Reservoir 7.096 2 736 88,085 3 676.72 51,916 WET POND ROUTING
8 Combine 18.96 2 726 65,109 1, PRE DA
9 Combine 15.87 2 722 131,457 4,6, POST DA-ROUTED
210123.000 Stormwater Calculations.gpw Return Period: 10 Year Wednesday, 09/ 11 /2024

4
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk, Inc.v2021 Wednesday,09/11 /2024
Hyd. No. 1
PRE DA
Hydrograph type = SCS Runoff Peak discharge = 18.96 cfs
Storm frequency = 10 yrs Time to peak = 726 min
Time interval = 2 min Hyd. volume = 65,109 cuft
Drainage area = 13.190 ac Curve number = 60*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 18.20 min
Total precip. = 5.10 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
"Composite(Area/CN)=[(10.022 x 60)+(3.167 x 61)]/13.190
PRE DA
Q (cfs) Hyd. No. 1 -- 10 Year Q (cfs)
21.00 21.00
18.00 I 18.00
15.00 15.00
12.00 12.00
9.00 9.00
6.00 6.00
3.00 3.00
0.00 — �- 0.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Hyd No. 1 Time (min)

5
Hydrograph Summary Report
Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk,Inc.v2021
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 45.40 2 726 145,383 PRE DA
3 SCS Runoff 60.33 2 720 162,532 POST DA-WET POND
4 SCS Runoff 36.91 2 722 96,844 POST DA-BYPASS
6 Reservoir 46.97 2 726 153,960 3 677.40 65,003 WET POND ROUTING
8 Combine 45.40 2 726 145,383 1, PRE DA
9 Combine 79.81 2 724 250,804 4,6, POST DA-ROUTED
210123.000 Stormwater Calculations.gpw Return Period: 100 Year Wednesday, 09/ 11 /2024

6
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk, Inc.v2021 Wednesday,09/11 /2024
Hyd. No. 1
PRE DA
Hydrograph type = SCS Runoff Peak discharge = 45.40 cfs
Storm frequency = 100 yrs Time to peak = 726 min
Time interval = 2 min Hyd. volume = 145,383 cuft
Drainage area = 13.190 ac Curve number = 60*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 18.20 min
Total precip. = 7.60 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
"Composite(Area/CN)=[(10.022 x 60)+(3.167 x 61)]/13.190
PRE DA
Q (cfs) Hyd. No. 1 -- 100 Year Q (cfs)
50.00 50.00
I
40.00 40.00
30.00 30.00
20.00 20.00
10.00 10.00
0.00 — - 0.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Hyd No. 1 Time (min)

7
Hydraflow Rainfall Report
Hydraflow Hydrographs Extension for Autodesk®Civil 3D®by Autodesk, Inc.v2021 Wednesday,09/11 /2024
Return Intensity-Duration-Frequency Equation Coefficients(FHA)
Period
(Yrs) B D E (N/A)
1 62.1764 12.7000 0.8901
2 69.8703 13.1000 0.8658
3 0.0000 0.0000 0.0000
5 79.2597 14.6000 0.8369
10 88.2351 15.5000 0.8279
25 102.6072 16.5000 0.8217
50 114.8193 17.2000 0.8199
100 127.1596 17.8000 0.8186
File name:Concord IDF Curve.IDF
Intensity= B/(Tc + D)^E
Return Intensity Values(in/hr)
Period
(Yrs) 5 min 10 15 20 25 30 35 40 45 50 55 60
1 4.82 3.86 3.23 2.79 2.46 2.20 1.99 1.82 1.68 1.56 1.46 1.37
2 5.69 4.61 3.89 3.38 2.99 2.69 2.44 2.24 2.07 1.93 1.81 1.70
3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
5 6.57 5.43 4.65 4.08 3.65 3.30 3.02 2.79 2.59 2.42 2.27 2.15
10 7.24 6.04 5.21 4.59 4.12 3.74 3.43 3.17 2.95 2.77 2.60 2.46
25 8.25 6.95 6.03 5.34 4.80 4.38 4.02 3.73 3.48 3.26 3.07 2.91
50 9.04 7.65 6.66 5.92 5.34 4.87 4.49 4.16 3.88 3.65 3.44 3.25
100 9.83 8.36 7.30 6.50 5.87 5.36 4.94 4.59 4.29 4.03 3.80 3.60
Tc=time in minutes.Values may exceed 60.
?00114.000 Pitts School Flex Park Final Engineering\2-Engineering\2-Calculations\4-Erosion Control\Concord PCP.pcp
Rainfall Precipitation Table (in)
Storm
Distribution 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr
SCS 24-hour 2.90 3.50 0.00 4.40 5.10 6.00 6.80 7.60
SCS 6-Hr 2.06 2.48 0.00 3.09 3.57 4.21 4.72 5.23
Huff-1st 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-2nd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-3rd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-4th 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-Indy 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Custom 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Riprap

DESIGN OF RIPRAP OUTLET PROTECTION
User Input Data
Calculated Value
Reference Data
Designed By: GAK Date: 12/19/2022
Checked By: NDB
Company: CESI
Project Name: Huntley Brothers
Project No.: 210123.000
Site Location (City/Town) Midland, NC
Culvert Id. FES-100
Step 1. Determine the tailwater depth from channel characteristics below the
pipe outlet for the design capacity of the pipe. If the tailwater depth is less
than half the outlet pipe diameter. it is classified minimum tailwater condition.
If it is greater than half the pipe diameter,it is classified imaximtun condition.
Pipes that outlet onto wide flat areas with no defined channel are assumed
to have a muunnun tailwater condition unless reliable flood stage elevations
show otherwise.
Outlet pipe diameter, Do (in.) 24
Tailwater depth (in.) 0
Minimum/Maximum tailwater? Min TW (Fig. 8.06a)
Discharge (cfs) 12.90 See 10 year Stormwater Calculation results
Step 2. Based on the tailwater conditions determined in step 1. enter Figure
8.06a or Figure 8.06b.and determine d;,,riprap size and minimum apron length
(La). The d;0 size is the median stone size in a well-graded riprap apron.
Step 3. Determine apron width at the pipe outlet the apron shape. and the
apron width at the outlet end from the same figure used in Step 2.

Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap d50, (ft.) 0.45
Minimum apron length, La (ft.) 13
Apron width at pipe outlet (ft.) 6 6
Apron shape Trapezoidal
Apron width at outlet end (ft.) 15 2
Step 4. Determine the maximum stone diameter_
= 1.5 x d50
Minimum TW Maximum TW
Max Stone Diameter, dmax (ft.) 0.675 0
Step 5. Determine the apron thickness:
Apron thickness = 1.5 x d Use class b riprap
Minimum TW Maximum TW
Apron Thickness(ft.) 1.0125 0
RIP RAP CLASS MINIMUM MIDRANGE MAXIMUM
A 2 IN (0.17 FT) 4 IN (0.33 FT) 6 IN (0.5 FT)
B 5 IN (0.42 FT) 8 IN (0.67 FT) 12 IN (1 FT)
1 5 IN (0.42 FT) 10 IN (0.83 FT) 17 IN (1.42 FT)
2 9 IN (0.75 FT) 14 IN (1.17 FT) 23 IN (1.92 FT)
Step 6. Fit the riprap apron to the site by making it level for the minimum
length, L.. from Figure 8.06a or Figure 8.06b. Extend the apron farther
downstream and along channel banks until stability is assured. Keep the
apron as straight as possible and align it with the flow of the receiving stream.
Make any necessary alignment bends near the pipe outlet so that the entrance
into the receiving stream is straight.
Some locations may require lining of the entire channel cross section to assure
stability.
It may be necessary to increase the size of riprap where protection of the
channel side slopes is necessary (Appendix 8.05). Where overfalls exist at
pipe outlets or flows are excessive, a plunge pool should be considered, see
page 8.06.8_

Outlet W • Do + La 90 . : :... ..
pipe tir
oe
diameter (0 0)
La -- s1 AO
'/.44
ilwater t 0.5Do ; , t.'
..,, .
. 7 dollmnllir 1:r .��
°\Pp 60 1 in
0�e�°, I 1 1: :: N!!1
mil , >, I, rwli n1r
La=13 iifa! dip ) 11�'.n1.1 4
n q 9 ' C. ►.111111Hflh!1J Iii1
Inman _4
04riP
31i !I!{{1 q: - C:=III:iOn"! :.e..._ �`d "`._... UiL. 4AJ
d.
20V iII if/1104
I ;0400,10t50:100:040, .1r. _ =
■ ... 1 111Il ch
i J _ __ '!Aiu'.tli1r/•• p 4. -111r 2 N
1iiiiiim 0.
...,. I', : lir: .;. r' 1NM' �,iiii IMIIIIII
_.. .... „�� '.Ii i iiii hmin
ire
�■■ 25 'ii�,,1 . .ar4 Ill Ili a
.,... ._ .. v . *110. Es
,.- gP iiii iIlNI 11ii1=ZfJ iaV �1 1�i ti-umi= i ..1 ,..
�� ..��� :IIII rtt�. d50=0.45
0
3 5 20 50 100 200 500 1000
12.90 cfs Discharge(ft3/sec)
Curves may riot be extrapolated.
Figure 8.06a Design of outlet protection protection from a round pipe flowing full,minimum tailwater condition(T,•<0.5 diameter)
Rey-.11'93 8.06.3

DESIGN OF RIPRAP OUTLET PROTECTION
User Input Data
Calculated Value
Reference Data
Designed By: GAK Date: 12/19/2022
Checked By: NDB
Company: CESI
Project Name: Huntley Brothers
Project No.: 210123.000
Site Location (City/Town) Midland, NC
Culvert Id. FES-99
Step 1. Determine the tailwater depth from channel characteristics below the
pipe outlet for the design capacity of the pipe. If the tailwater depth is less
than half the outlet pipe diameter. it is classified imninrunm tailwater condition.
If it is greater than half the pipe diameter,it is classified nnaximtunn condition.
Pipes that outlet onto wide flat areas with no defined channel are assumed
to have a muuinnuu tailwater condition unless reliable flood stage elevations
show otherwise.
Outlet pipe diameter, Do (in.) 24
Tailwater depth (in.) 0
Minimum/Maximum tailwater? Min TW (Fig. 8.06a)
Discharge (cfs) 26.56 See 10 year Culvert Calculation results
Step 2. Based on the tailwater conditions determined in step 1. enter Figure
8.06a or Figure 8.06b.and determine d;,,riprap size and minimum apron length
(La). The d;0 size is the median stone size in a well-graded nprap apron.
Step 3. Determine apron width at the pipe outlet the apron shape. and the
apron width at the outlet end from the same figure used in Step 2.

Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap d50, (ft.) 0.5
Minimum apron length, La (ft.) 16
Apron width at pipe outlet (ft.) 6 6
Apron shape Trapezoidal
Apron width at outlet end (ft.) 18 2
Step 4. Determine the maximum stone diameter_
= 1.5 x d50
Minimum TW Maximum TW
Max Stone Diameter, dmax (ft.) 0.75 0
Step 5. Determine the apron thickness:
Apron thickness = 1.5 x d Use class B riprap
Minimum TW Maximum TW
Apron Thickness(ft.) 1.125 0
RIP RAP CLASS MINIMUM MIDRANGE MAXIMUM
A 2 IN (0.17 FT) 4 IN (0.33 FT) 6 IN (0.5 FT)
B 5 IN (0.42 FT) 8 IN (0.67 FT) 12 IN (1 FT)
1 5 IN (0.42 FT) 10 IN (0.83 FT) 17 IN (1.42 FT)
2 9 IN (0.75 FT) 14 IN (1.17 FT) 23 IN (1.92 FT)
Step 6. Fit the riprap apron to the site by making it level for the minimum
length, L.. from Figure 8.06a or Figure 8.06b. Extend the apron farther
downstream and along channel banks until stability is assured. Keep the
apron as straight as possible and align it with the flow of the receiving stream.
Make any necessary alignment bends near the pipe outlet so that the entrance
into the receiving stream is straight.
Some locations may require lining of the entire channel cross section to assure
stability.
It may be necessary to increase the size of riprap where protection of the
channel side slopes is necessary (Appendix 8.05). Where overfalls exist at
pipe outlets or flows are excessive, a plunge pool should be considered, see
page 8.06.8_

3 o ----
Outlet W • De + La 90 . : :... ..
Pipe tir
diameter (Ob)
La -- s1 AO `�
ilwater t 0.5Do 6
_GIN , Immilf
10
: �I �II �III 1:r �.�I
�e-- �: :::: : .. 4rII. ' .b'e -\0D mown
°\ r,. IIIIIIIIIII
._ « ,. � � p r ruunnlr
01 If I La=16 IIH!! I1.::_ ,�..:!:_.::._ 4,'•.. I;I1ir�
30 1
� ttf . . 1IIII
20 ' III.r . _:__; • : \•I:+,I• �'� 'lliUI:.;01ir491.4.41/
°-'ari'. -- / .,4,A S3
uu
,il .
-.
ki
f• II . . '
.=
,i ,
1iiII1IiI
111111 u.. _ O IIII�� II• .illy'
193
AIP'.tll I / •vIIIII 2
. : ,......
--.... .I I I i..... ,ll� IIIII'1 040 (IIII V)
• Jill ilirii ::.i : • _it ; i 25 i„ . ��, Av.
0.r "-Air "1'WM ,..
I::: ,„2 it s=I ,,,,.imitniiiiiii n
r
.. It •o dl_. ••.. .;
illii�,�/� 111M1
5
V v u �rlr ��ir.� d 50=0.5
s �'�� r
i: ; _.__•I-,�_11. • 1111 1 A .
D
3 5 10 20 50 100 200 500 1000
Discharge(ft3/sec)
I 26.56 cfs
Curves may riot be extrapolated.
Figure 8.06a Design of outlet protection protection from a round pipe flowing full,minimum tailwater condition(T,•<0.5 diameter)
Rey-.11'93 8.06.3

TRAPEZOID RIPRAP APRON FES-100 FES-99
RIP RAP CLASS B B
WIDTH AT PIPE OUTLET (FT.) 6.00 6.00
WIDTH AT APRON OUTLET (FT.) 15.00 18.00
LENGTH OF APRON (FT.) 13.00 16.00
MINIMUM DEPTH OF APRON (FT.) 1.01 1.13

Appendix

Table 4: HSGs for North Carolina Soil Types *
Urban areas runoff curve numbers fro SCS method (SCS 1986)
Cover Description Curve Number by HSG
A B J C D
Fully developed urban areas
Open Space (lawns, parks,golf courses, etc.)
Poor Condition (<50%Grass Cover) 68 79 86 89
Fair Condition (50%to 75%Grass Cover) 49 69 79 84
Good Condition (>75%Grass Cover) 39 61 74 80
Impervious areas:
Paved parking lots, roofs, driveways, etc.) 98 98 98 98
Streets and roads:
Paved; curbs and storm sewers 98 98 98 I 98
_ Paved; open ditches 83 89 98 98
Gravel 76 85 89 91
Dirt 72 82 85 88
Developing Urban Areas
_ Newly graded areas 77 86 91 94
Pasture (<50%ground cover or heavily grazed) 68 79 86 89
_ Pasture (50%to 75%ground cover or not heavily grazed) 49 69 79 84
Pasture (>75%ground cover or lightly) 39 61 74 80
Meadow-continuous grass, protected from grazing and
generally mowed for hay 30 58 71 78
Brush (<50%ground cover) 48 67 77 83
Brush (50%to 75% ground cover) 35 56 70 77
Brush (>75%ground cover) 30 48 65 73
Woods (forest liter, small trees, and brush destroyed by heavy 45 66 77 83
grazing or regular burning
Woods (Woods are grazed but not burned, and some forrest 36 60 73 79
litter covers the soil)
Woods (Woods are protected from grazing, and litter and brush 30 55 70 77
adequately cover the soil)
*Table taken from NCDECI Sormwater Design Manual Part B: Calculations Guidance, revised 3/5/2017