20230918_ESC

NORMAN SAND
HEDRICK INDUSTRIES
Norman Sand Mine Permit # 62-36
B.V. HEDRICK GRAVEL AND SAND COMPANY
Mining Permit Modification
Erosion Control Calculations
7-Sep-23
ECE!ED
SEP 18 10n
LAND QUALITY
MINING PROGRAM

Construction Sequence
1. Obtain approval from NCDENR prior to any land disturbing activities.
2. Locate and flag clearing limits for each area to be affected.
3. Construct sediment and erosion control measures in accordance with the submitted plans
and details prior to any earth disturbing activities.
4. Clear and grub the project area in accordance with its intended use. Only those areas immediately
needed should be disturbed.
5. Direct all runoff to the approximate erosion control structure(s)through the use of temporary and
permanent diversions.
6. Seed and stabilize all disturbed areas once construction activities are complete.
NOTES:
1.Inspection and maintenance of sediment basins and diversion ditches shall take place monthly
and/or after each major rainfall event. At such time,all damage shall be immediately repaired
and accumulated sediment and debris removed. Any necessary stone replacement shall also
be made at this time. Structures shall be reshaped to maintain the required design volume.
2. Basins and diversion ditch locations shall be adjusted in the field as necessary to
conform to actual topography.
3. Silt fence will additionally be installed as a back-up measure where needed to insure that
no sediment leaves the property. Details are provided.

INPUT
EROSION CONTROL TRAP NO. N26
Sediment Basin with Rock Dam DRAINAGE AREA 10
REF:N.C.EROSION AND SEDIMENT CONTROL DISTURBED AREA 10
PLANNING AND DESIGN MANUAL C 0.35
TIME OF CONC. 5
INTENSITY 7.39
1. TRAP NO. N26 ALLOW.WEIR DEPTH 2
WEIR LENGTH 16
2. DETERMINE RUNOFF FOR 25-YEAR STORM VOLUME PROVIDED 2 2533.59
STORAGE DEPTH 5 -
DRAIN.AREA(AC.) 10 ACRES SURFACE AREA PROVIDED
DIST.AREA(AC.) 10 ACRES
C 0.35
TIME OF CONC. 5 MINUTES
INTENSITY(25 YR.) 7.39 IN./HR. FIG.8.03(c)Greensboro,NC
Q=CIA 25.9 C.F.S.
3. DETERMINE STORAGE CAPACITY REQUIRED:
3600 CF/AC x DIST.AREA=STORAGE VOLUME
STORAGE VOLUME= 36000
4. SIZE BASIN:
Surface Area=(Q25 x 0.01)Acres 0.26 Ac.= 11266.79 sf
Length=2 x Width
WIDTH 75.1 FEET Bottom Area Provided 10382.12
LENGTH 150.1 FEET Storage Area Provided 11266.79
DEPTH 3.20 FEET Surface Area Proided 11266.79
Bottom Elevation 616
VOLUME= 36000 CUBIC FEET
S. EMBANKMENT
DEPTH TO WEIR 5 FEET
DEPTH TO TOP OF EMBANKMENT 7 FEET
2:1 SIDE SLOPES
V TOP WIDTH
6. SPILLWAY: FROM NC EROSION AND SEDIMENT CONTROL PLANNING
AND DESIGN MANUAL,TABLE 6.60A
WEIR LENGTH= 16 FEET
7. STONE SIZE: USE CLASS B EROSION CONTROL STONE WITH D50
EQUALTO 9". PLACE NCDOT#57 STONE ONE FOOTTHICK
ON THE FACE OF THE DAM.
8. FILTER CLOTH: PLACE EROSION CONTROL FILTER CLOTH BENEATH
DAM TO PREVENT PIPING.

` I Rock Abutment
2 `
Weir Elevation
Class and II
Riprap ' y
1'min.NC DOT#5 r
or# washed stone
stone ( �'
Min.1.5'thick
jt
Rock Apron
f � n 1
Cut-off Trench
Filter Fabric
Cross-Section View
Figure 6.63a Rock Dam cross section
Spillway Details
Figure 6.632 Rock Dam plan view and Top of rack abutment
spillway details n!,�W& 4w
7T2'min
Slope foundat Spillway
P Y
Filter fabric
—.——--- Natural Ground
h:
Gravel
`� ------
E 12'min
�.- - �'. ► a Flow Level apron
Spillway
r-
4i M
Rock Abutment