20220902_ESC_Calculations_77-01

APPENDIX B - CALCULATIONS

PHASE I DITCH CALCULATIONS

Civil & Environmental Consultants, Inc.
Project Name: Rockingham Quarry
CEC Project No.: 304-408
Description: 25-Year Stormwater Ditch Calculations
2.5' Deep V-Ditch
By:
CTH
Date:
9/1/2022
Checked By:
ERR
Date:
9/1/2022
Total Flow (cfs) 50.33

Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.
Perimeter Ditch #1
Triangular
Side Slopes (z:1)
= 3.00, 3.00
Total Depth (ft)
= 2.50
Invert Elev (ft)
= 270.00
Slope (%)
= 2.00
N-Value
= 0.060
Calculations
Compute by:
Known Q
Known Q (cfs)
= 50.33
Highlighted
Depth (ft)
Q (cfs)
Area (sqft)
Velocity (ft/s)
Wetted Perim (ft)
Crit Depth, Yc (ft)
Top Width (ft)
EGL (ft)
Thursday, Sep 1 2022
= 2.17
= 50.33
= 14.13
= 3.56
= 13.72
= 1.78
= 13.02
= 2.37
Elev (ft) Section Depth (ft)
273.00
272.50
3.00
2.50
v
—
272.00
2.00
271.50
1.50
271.00
1.00
270.50
0.50
270.00
269 50
0.00
_n Fn
2 4 6 8 10 12 14 16 18 20 vVV
Reach (ft)

ECMDS 7.0
Page 1 of 1
NORTH
AMERICAN
GREEN'
CHANNEL ANALYSIS
> > >Perimeter Ditch #1
Name
Perimeter Ditch #1
Discharge
50.33
Channel Slope
0.02
Channel Bottom Width
0
Left Side Slope
3
Right Side Slope
3
Low Flow Liner
Retardence Class
C 6-12 in
Vegetation Type
Mix (Sod and Bunch)
Vegetation Density
Fair 50-64%
Soil Type
Clay Loam (CL)
SC150
North American Green
5401 St. Wendel-Cynthiana Rd.
Poseyville, Indiana 47633
Tel. [phone]
>Fax [phone]
www.nagreen.com
ECMDS v7.0
Normal
Permissible
Calculated
Safety
Staple
Phase
Reach
Discharge
Velocity
Mannings N
I
I
Remarks
I
Depth
Shear Stress
Shear Stress
Factor
Pattern
SC150
Straight
50.33 cfs 5.39 rt/s
1.76 ft
0.035 2 Ibs/ft2
2.2 Ibs/ft2
0.91
UNSTABLE D
Unvegetated
Underlying
Straight
50.33 cfs 5.39 ft/s
1.76 ft
0.035 2.18 Ibs/ft2
1.04 Ibs/ft2
2.09
STABLE D
Substrate
Unreinforced Vegetation
Normal
Permissible
Calculated
Safety
Staple
Phase
Reach
Discharge
Velocity
Mannings N
I
I
Remarks
I
Depth
Shear Stress
Shear Stress
Factor
pattern
Unreinforced
Straight
50.33 cfs 4.48 ft/s
1.94 ft
0.044 4 Ibs/ft2
2.42 Ibs/ft2
1.66 STABLE
Vegetation
Underlying
Straight
50.33 cfs 4.48 ft/s
1.94 ft
0.044 3.08 Ibs/ft2
1.15 Ibs/ft2
2.68 STABLE
Substrate
https:Hecmds.com/project/153102/channel-analysis/228492/show 9/1/2022

EXISTING PERMITTED SEDIMENT CHANNEL CALCULATIONS
(*PERFORMED BY PHILIP BAILEY, APRIL 25, 2019)

Rockingham Quarry • Mining Permit No. 77-01 Vulcan Construction Materials, LLC
Mining Permit Modification — April 25, 2019
Pit No.2 Sediment Channel
The Pit No.2 Sediment Channel is designed to control runoff from the maximum
5 8 a c r e d r a i n a g e a r e a. The Sediment Channel will be constructed with a single outfall at Sta
23+25; please refer to the included site plan for dimensional data and location. The Sediment
Channel will be installed according to the requirements of the included construction
specifications and maintenance plans SEDIMENT CHANNELS, ROCK WEIR OUTLETS, and
OUTLET PROTECTION.
Sediment Storage Volume
The maximum disturbed drainage area for this sediment channel is 19 acres during initial
construction. Once the sediment channel and berms are complete, then the quarry pit excavation
to top of rock will commence. Once this excavation commences, any sediment laden water from
the excavation will be trapped in the quarry excavation, requiring a pump to remove the water.
The pump line will discharge in the sediment channel at Sta 12+16. This sediment channel is
designed to provide a sediment storage volume of at least 3,600 cubic feet per acre of disturbed
drainage area. The proposed Sediment Channel provides 74,696 cubic feet of storage volume; 19
acres of disturbance requires (19 ac x 3,600 cubic ft / ac = 68,400 cubic feet), which provides 10%
more than the required storage. Please refer to the included sediment storage volume calculations.
Watershed Modeling
The Rational Method was utilized to predict surface runoff. The included design
calculations describe input data used in the method to determine and peak discharge.
Design Storm Events
The rock check dams and outfall spillways of the Sediment Channel are designed to safely
pass the peak flow of runoff from a 100 year — 24 hour storm with a minimum of 1 foot of
freeboard. The peak outflow occurs at Sta 23+25 outfall and the 100 year — 24 hour storm is 130.7
cfs. All the rock check dams and outfall spillways are designed to pass 78.4 cfs. Please refer to
the design computations.

Pit No.2 Sediment Channel
Rock Weir Outlet at Sta 23+25
Design Computations
Drainiage Basin Characteristics
Total Drainage Area -
58
Acres
Runoff Coefficient, C -
0.35
Travel Length -
2397
feet
Time of Concentration (Tc) -
20.0
min
Intensity, i2 -
3.67
in/hr
Intensity, i25 -
5.50
in/hr
Intensity, i,00 -
6.44
in/hr
Peak Runoff Discharge, Q2 -
74.5
cfs
Peak Runoff Discharge, Q25 -
111.7
cfs
Peak Runoff Discharge, Q,00 -
130.7
cfs
Spillway Design
Invert Elevation -
201.9 ft
Bottom Width -
50 ft
Total Depth -
2 ft
Freeboard -
1.00 ft
Side Slopes -
5 :1
Capacity with 1' Freeboard -
168.4 cfs
100 Year Storm Flow Depth -
0.8 ft
Average 100 Year Velocity -
0.5 fps

Sediment Channel
Sta 11 +75 to Sta 23+25
Design Computations - Sediment Storage and Stormwater Flow
Sub Basin Sediment Storage Characteristics
NCDEQ Requirements - 3,600 CU FT PER ACRE
Total Drainage Area -
29.00
Acres
Disturbed Drainage Area -
16.00
Acres
Required Sediment Storage -
63,579.0
cu-ft
Required Sediment Storage -
1.460
ac-ft
Runoff Coefficient, C -
0.4
Travel Length -
2397
feet
Time of Concentration (Tc) -
20.0
min
Intensity, iz -
3.67
in/hr
Intensity, i25 -
5.50
in/hr
Intensity, i,00 -
6.44
in/hr
Peak Runoff Discharge, Qz -
44.7
cfs
Peak Runoff Discharge, Q25 -
67.0
cfs
Peak Runoff Discharge, Q,00 -
78.4
cfs
Sediment
Channel
Cell
Channel
Slope
%
Ponded
Ponded
Length
Minimum
Pond
Depth
D, (ft)
Check
Dam
Height
D2 (ft)
Bottom
Channel
Width
(ft)
Channel
Side Slope
(z:1)
100 Yr Flow
Depth Over
Check Dam
(ft)
Volume
(cu-ft)
Total
Volume
(cu-ft)
Total
Volume
(ac-ft)
Sta 12+00 to Sta 14+50
2.00
250
0
5
5
2
1.0
7,329.2
7,329.2
0.168
Sta 15+00 to Sta 22+50
0.00
750
5
5
5
1 2
1 1.0
1 56,250.01
63,579.2
1.460

Sediment Channel
Sta 23+25 to Sta 29+20
Design Computations - Sediment Storage and Stormwater Flow
Sub Basin Sediment Storage Characteristics
NCDEQ Requirements - 3,600 CU FT PER ACRE
Total Drainage Area -
8.00
Acres
Disturbed Drainage Area -
3.00
Acres
Required Sediment Storage -
10,800.0
cu-ft
Required Sediment Storage -
0.248
ac-ft
Runoff Coefficient, C -
0.4
Travel Length -
636
feet
Time of Concentration (Tc) -
10.0
min
Intensity, iz -
4.54
in/hr
Intensity, i25 -
6.38
in/hr
Intensity, i,00 -
7.15
in/hr
Peak Runoff Discharge, Qz -
15.3
cfs
Peak Runoff Discharge, Q25 -
21.4
cfs
Peak Runoff Discharge, Q,00 -
24.0
cfs
Sediment
Channel
Cell
Channel
Slope
%
Ponded
Ponded
Length
Minimum
Pond
Depth
D, (ft)
Check
Dam
Height
D2 (ft)
Bottom
Channel
Width
(ft)
Channel
Side Slope
(z:1)
100 Yr Flow
Depth Over
Check Dam
(ft)
Volume
(cu-ft)
Total
Volume
(cu-ft)
Total
Volume
(cu-ft)
Sta 24+00 to Sta 24+50
0.00
50
5
5
5
2
0.4
3,750.0
3,750.0
0.086
Sta 24+50 to Sta 25+75
4.00
125
0
5
5
2
0.4
3,683.4
7,433.4
0.171
Sta 26+25 to Sta 27+50
4.00
125
0
5
5
2
0.4
3,683.4
11,116.8
0.255