Phase 2 Drainage_Phase 2 Drainage Report_3.14.23

AMERICAN
Engineering
Business License C-3881
Drainage Report
Nelson's Creek
Phase 2
Yadkinville Rd./U. S. 601 at Country Lane/SR 1461
Mocksville, North Carolina 27028
Prepared For
C2C Land Development, LLC
P. O. Box 4628
Mooresville, North Carolina 28117
Contact: Richard Denzler(800-369-0120)
Prepared by
American Engineering Associates Southeast
4020 Westchase Blvd., Suite 450
Raleigh, NC 27607
June 23, 2022
Rev. 9/9/22 �... . ,,
Rev.ll/18/22 �.�' � CAR0 j'•,
Rev. 2/8/23 �::F� S�'••.,?q'�.
Rev. 3/14/23
Q. S A
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1

Drainage Report
Table of Contents
General 3
Erosion Control 3
Major Stream Crossings and Other Outlet Rip-Rap Calculations 4
Geotechnical Report 4
Drainage Calculations 4
Post-Construction Permitting and Stream Buffer Requirement 4
Pre-development vs. Post-development Flows 4
Appendix 6
2

Nelson's Creek, Phase 2
General
This project is located in Mocksville, North Carolina on the east side of U. S. 601 between
Country Lane on the north side and a property line approximately 2500' south of this. Most of
the area fronting Yadkinville Rd. and Country Lane have already been developed though this
project will access both of these roads when complete. The area along Yadkinville Rd. is mostly
commercial property and the developed area along Country Lane is residential property.
Nelson Creek goes through the middle of this project dividing the project between Phase 1 and
Phase 2. Nelson Creek is in the Yadkin River Basin. When the project is complete, there will be
a crossing over Nelson Creek connecting the two parts of the project.
The purpose of the project is to provide for a single family subdivision. Phase 1 will have 198
lots while Phase 2 will have 185 lots for a total of 383 lots. The size of Phase 2 is 91.74 acres.
Erosion Control
Erosion control for this project will largely be by the use of sediment basins. Due to the large
nature of the project many of the basins needed will be in the interior of the project. These will
not discharge directly to the outside of the project. It will be necessary to construct part of the
storm drain system early in the project so that it can be used to drain the clean water exiting the
interior sediment basins.
These interior sediment basins will not have an emergency overflow weir as such would only
send the water over other bare areas. Instead the riser is sized to carry the full 10 year flow to the
pipe system.
Sediment basins adjacent to the downstream edge of the project will have emergency overflow
weirs. Those with a drainage area of larger than five acres will have a combination of riser and
emergency overflow weir to drain the ten year storm. All sediment basins will have a skimmer
sized to draw down the water below the emergency overflow weir or riser between two and five
days after a storm has ended.
Calculations for these sediment basins are in the Erosion Control section of the Appendix. The
first calculations in the section will be a program written in MicroSoft Excel to identify the size
of the basin needed. For the basins which have a riser discharging directly to the off-site a
calculation of the rip-rap needed is shown using the New York State DOT method.
Following this is the schedule showing the Contractor the pertinent elevations and dimensions,
etc. for each sediment basin. A second sheet not on the plans is shown for the calculation of the
skimmer size for each basin. Following this is a sheet calculating the outlet velocity for the
sediment basin discharges to be used in the NYSDOT rip-rap calculation method. Following this
is the NCDENR calculation sheets for each sediment basin.
3

Major Stream Crossings and Other Outlet Rip-Rap Calculations
Two stream crossings are in the project. Frontiersman Drive over an unnamed tributary is in
Phase 2 of this project. Calculations are in the Appendix showing the rip-rap calculations for the
crossings. Rip-rap calculations for the other permanent pipe outlets are also shown. The flow
calculations are by John R. Harmon, P. E. # 9810.
Geotechnical Report
The geotechnical report by Ground Technological Services, Inc. is in the Appendix.
Drainage Calculations
Drainage calculations for the permanent pipe drain system by John R. Harman, P. E. # 9810 are
in the Appendix along with the rainfall rates for the Rational Method for this location.
Post-Construction Permitting and Stream Buffer Requirement
Exhibits in the Appendix show our project in relation to areas which require post-construction
permitting. As can be seen on these exhibits our project is outside the area where post-
construction permitting is required.
The other exhibit shows that the stream is Classified Class C waters. Per NC Administrative
Code 15A NCAC 02B our site drains to Nelson Creek within the Yadkin—Pee Dee Basin, which
is a Class C surface water. This receiving water is not a Trout Stream, not an Outstanding
Resource Water(OWR), High Quality Waters (HQW), Nutrient Sensitive Water(NSW), and not
within a Water Supply Watershed, or the Goose Creek Watershed. The Town of Mocksville
does not have a local approved buffer requirement. Therefore, there should not be a minimum
buffer required.
Pre-development vs. Post-development Flows
Because of concerns about impacts downstream, a dry pond is added to Phase 1 to compensate
for the added impervious area for both Phases 1 and 2. The resulting flows are summarized
below:
Storm Pre-development Flow Post-development Flow
1 Year 171.94 cfs 167.90 cfs
2 Year 206.91 cfs 201.06 cfs
5 Year 251.74 cfs 241.75 cfs
10 Year 283.73 cfs 270.48 cfs
100 Year 376.50 cfs 354.80 cfs
As can be seen above, the post-development flows are less than the pre-development flows for
each storm that is listed.
4

Detailed calculations by John R. Harman, P. E. #9810 are in the Appendix.
Y:Vobs\21-0004 Mocksville(R210004)\Documents\Reports\Drainage Report(Ph.2).docx
5

Appendix
USGS Map
Geotechnical Report
Drainage Calculations
Erosion Control Calculations
Major Stream Crossings and Permanent Rip-rap Outlets
Post-Construction Permitting Exhibit and Stream Buffer Requirement
6

USGS Map

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Geotechnical Report
7

ROCK PROBE AND GENERAL SOILS
CLASSIFICATION EVALUATION REPORT
FOR
Nelson Site
Yadkinville Road
Mocksville, North Carolina
GTSI-GE0202112-402
January 12, 2022
Prepared for:
C2C Land Development LLC
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Prepared By:
Ground Technological Services, Inc.
2067 North Highway 16
Denver, North Carolina 28037
[phone]

Ground Technological Services,Inc.(GTSI)has completed the subsurface rock and general soils
classification evaluation for the proposed project. Twenty-Seven (27) fifteen-foot borings were
attempted with a Track Mounted Power Auger to perform these services.
The boring locations were determined by C2C Land Development LLC utilizing a preliminary site
plan. The boring locations were field determined by GTSI utilizing GPS coordinates. Site access
was required for all boring locations due to dense woods. Soils encountered within the borings
ranged from fine sandy clayey silts to fine sandy silts.No water was noted at boring termination and
no rock was encountered in the performance of the borings. The boring location plan and boring
coordinates are attached for your review.
This report has been prepared in accordance with generally accepted soil and foundation
engineering practices. In the event any changes occur in the design, nature, or location of the
proposed facilities, Ground Technological Services, Inc. should review the applicability of
conclusions and recommendations in this report.
GTSI appreciates the opportunity to provide these services to you. If you should have any questions
please ca us at your convenience.
L c r,
Pre s ent ta���on»rsgy,
VA C •,
•� 4 .es•�^s $
c
Donna H. Barbour, P.E. a0'1�' 'w�,td� `��°�J��' /
Professional Engineer v*M0,,'
�U• oils �

Table of Location Coordinates and Boring Termination
Depths
Nelsons Creek- Mocksville, NC(Davie County)
Planned Boring
Boring t# Latitude Longitude
Depth Termination
B-1 15' 35'54'54.62"N 80'34'44.76"W
B-2 15' 35054'51.90"N 80'34'42.77"W
B-3 15' 35'54'48.90"N 80034'40.30"W
B-4 15' 35'54'45.07"N 80'34'38.71"W
B-5 15' 35'54'46.99"N 80'34'37.49"W
B-6 15' 35054'53.79"N 80034'35.30"W
B-7 15' 35054'35.48"N 80'34'30.64"W
B-8 15' 35054'47.16"N 80'34'33.26"W
B-9 15' 35'54'48.58"N 80'34'29.81"W BMP
B-10 15' 35054'52,15"N 80034'30.77"W BMP
B-11 15' 35054'34.04"N 80034'24.54"W
B-12 15' 35°54'37.41"N 80°34'24.48"W
B-13 15' 35"54'41.85"N 80034'26.55"W
B-14 15' 35'54'42.36"N 80°34'23.02"W
B-15 15' 35'54'43.34"N 80'34'20.93"W BMP
B-16 15' 35054'33.40"N 80'34'16.52"W
B-17 15' 35'54'37.31"N 80'34'16.88"W BMP
B-18 15' 35'54'42.12"N 80034'18.71"W
B-19 _ 15' 35054'47.26"N 80034'19.22"W
B-20 15' 35'54'33.02"N 80'34'4.61"W
B-21 15' 35'54'37.42"N 80034'4.08"W
B-22 15' 35'54'38.03"N 80'34'11.36"W
B-23 15' 35054'40.65"N 80'34'11.57"W
B-24 15' 35'54'40.29"N 80'34'3.97"W
B-25 15' 35-54'41.05"N 80'34'9.42"W
B-26 15' 35'54'45.67"N 80034'13.03"W
B-27 15' 35054'48.21"N 80'34'15.82"W

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Drainage Calculations
8

1219/21, 8:00 PM Precipitation Frequency Data Server
NOAA Atlas 14,Volume 2,Version 3
Location name: Mocksville, North Carolina, USA* f° r
Latitude: 35.9124°, Longitude: -80.5717' j
Elevation: 756.8 ft**
source:ESRI Maps
-source:USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M.Bonnin,D.Martin,B.Lin,T.Parzybok,M.Yekta,and D-Riley
NOAA,National Weather Service,Silver Spring,Maryland
PF tabular I PF graphical I Maps & aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hour)1 Jj
Average recurrence interval(years)
Duration �r---� I �r -��
25 - 50 100 �_ 200 500 � 1000
5-min 4.44 5.27 6.18 6.82 7.56 8.08 8.53 8.95 9.42 T 9.74
(4.10-4.82) (4.87-5 72) 5.70-6.72) 6.26-7.40 (6.91-8.21) (7.33-8.77) 1 (8.00-9.78) 8.30-10.4) (8.50-10.8)
3.55 4.21 4.94 5.45 6.02 6.43 6.78 7.09 7.45 7.67
1 0-min (3.2� {3.89-4.56) (4,56-5.38) (5.01-5.92) (5.51-6.54) (5.84-6.98) (6.11-739) 1 (6.34-7-75) (6.56-8.19) (6.69-8.48)
15-min 2.96 3.53 4.17 4.60 5.09 5.42 5.72 5.96 6.25 6.42
(2.73-321) (3.26-3.84) (3.85-4.54) (4.22-4.99) (4.66-5.53) (4.93-5.90) 5.15-6.22) (533-6.52) 5.51-6.67) (5.60-7.10)
2.
2.
[Tomin 1 1.870320) 2.25 2465 2.39.22) 3.06 3362 3.45 4?09) (3 4.0944) (3.94 4877 (4.55408) 4.85747 (4.53 5075
F60_;ir, 11 1.26 1.53 1.90 2.17 2.51 2.77 3.01 3.26 3.57 3.80
(1.17-1.37) {1.41-1$6 1.75-2.07) (1.99-2,36) 2.30-2.73) (2.51-3.01) (2.72-3.28) 2.91-3.56) (3.15-3.92) (3.31-4.19)
2-hr 0.741 0.898 1.12 1.29 1.52 1.69 1.86 2.03 2.25 2.42
(0.684-0.804) (0.829-0.978) (1.03-1.22) (1,19-1.41) (1.38-1.65) (1.53-1.84) (1.67-2.03) (1.80-2.22) (1.97-2,48) (2.09-2.68)
3-h r
1.23 1113 1.49 1.80
0.529 6.641 0.804 0.928 1.10 -15 -2.0 0)8(0.488-0.576),(0.592-0.700) (0.741-0.877) (0.851-1.01).,(0.996-1.19) (1.11-1.33) (1.32-1.63) 55
0.324
6-hr (0299-0 353) (0.362-0.428),(0.452-0 536) (0.521--0 618) 0.601-0.2730 0.681-0 820) (0.749-0 911)i1(0.816-21?01 0.903-4.14 0-967-13.24)
12-hr 'I{0.1078-0 210)j 0.2015-0.255) 0269-0 320) (0.311-0 370) 0.367--0 439) (0s4010-0.493) (0.453.0.550) 0.495-0.609) 0.551---0 691) (0.592--04755)
24-hr 0.117 0.142 0.179 0.207 0.247 0.278 0.310 0.343 0.389 0.425
(0.109-0.126) (0.132-0.153) (0.166-0.193) 0.192-0.224),(0.228-0.266 (0,256-0.300))(0.28� 0.314-0.370) (0.354-0.420) (0.385-0.460)1
2-da 0.069 0.083 0.103 0.119 0.140 0.157 0.175 0.192 X20.214-0.254)
0.235
(0064-0.074)I 0.077-0.089 0.096-0.111)'(0.110-0.128) (0.130-0.151) (0.145-0.169) (0.161-0.188 0.176-0.207)
00122 0.1340.098 0.1640.058 0.073 day 0.049 I 1 -0131)I 163 0.150-0.1 78)(0.045-0.052): 0.055-0.063 0.068-0.078) (0.091-0.106) 0:102-0.118)' 0.123-0.145) 0.138-0.
0.119 0.039
0.087 0.09
4-day 0.036-0 041) 0.04 30 050 0.054-0 061) 0.06 00 071) (0.07 20 083) (0.80-0 093) 0.089-0.6103) (0.97-0.6113)J(0.109-0.128) (0.1017-0..1139)
7-day 0.025 0.030 0. IF 037 0.042 0.049 1 0.054 F 0.060 0.065 IF 0.073 0.079
(0.024-0.027) 8 0 4-0.039)0.02032) 0.03 ,(0.039-0.045) 0.046-0.052) 0.050-0.058) (0.055-0.064 0.061-0.070) (0.067-0.079) (0.072-0.085)
10-day 0.020 0.024 0.029 F 0.033 7F 0.038 0.042 71 0.046 IF 0.050 1 0.055 r 0.059
0.019-0.022) 0.023-0.026) (0.027-0.031) (0.031-0.035),(0.035-0.040), (0.039-0.044)1(0.043-0.049) 0.046-0.053) 0.051-0.059 (0.055-0.063)
0.014 0.016 0.019 0.021 0.024 0.027 0.029 0.032 0.035 0.037
20-day 0.013-0.014) (0.015-0.017) 0.018-0.020) (0.020-0A22) 0.023-0.026).(0.025-0.028) (0.027-0.031) (0.029-0.033) (0.032-0.037) (0.035-0.040)k
30-day 0.011 0.013 0.015 0.017 =01.9 0.021 0.022 0.024 0.026 0.027
(0.011-0.012) 0.013-0.014):(0.015-0.016) {0.016-0.018) 0.019-0.021) 0.021-0.023) 0.022-0.025) (0.024-0.027 0.025-0.029)_
45-day 0.009 0.011 0.013 0.014 0.015 0.016 0.017 0.019 0.020 0.021
(0.009-0.010 (0.011-0.012) (, 0.012-0.013) (0.013-0.014) 0.015-0.0161 (0.016-0.017) (0.017-0.018)1(0.018-0.019) (0.019-0.021) 0.020-0.022)
60-day 0.008 0.010 0.011 0.012 0.013 0.014 0.015 0.016 0.017 0.018
(0.008-0.009) (0.009-0.010) (0.011-0.012) (0.012-0.013) (0.013-0.014) 0.014-0.015) (0.014-0.016) 0.015-0.017) 0.016-0.018) 0.017-0.019
t Precipitation frequency(PF)estimates in this table are based on frequency analysis of partial duration series(PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90%confidence interval.The probability that precipitation frequency estimates(for a
given duration and average recurrence interval)will be greater than the upper bound(or less than the lower bound)is 5%.Estimates at upper bounds are not
checked against probable maximum precipitation(PMP)estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
I Back to Top
PF graphical
https://hdsc.nws noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.9124&Ion=-80.5717&data=intensity&units=english&series=pds 1/4

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SEDIMENT BASIN DESIGN SB 2-1
6/9/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
Y:1Jobs121-004 Mocksville(R210004)1Documents\Reports\SB 2-1.xls
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-1
Total Drainage Area (acres) 0.58
Step 1. Determine peal- floc,-. � . for the basin draulage area Gtzpvel-,c,ix SA")
Q10 (cfs) 2.43
Step ?. Determne site linlitations for the sedllllent pool elevation,e111eraenc'
spillway or top of the dale.
Minimum pool elevation (ft) 802
Maximum pool elevation (ft) 805.5
Step 3. Deterllune basin vohunes:
• Compute II ului11Un volume required (1SOO ft- acre disturbed)_
• SpeclfE sediment cleanout level to be nuffked on riser (one-halt the deslall
t olunie referenced to the top of the riser) alld sedlnlent storage area to be
cleared after The darn is built.
Disturbed acreage (ac) 0.54
Min Volume (ft) 972
Sediment cleanout elevation (ft) 802
Sediment Storage Area 280

Y:IJobs121-004 Mocksville(R210004)1DocumentslReports\SB 2-1.xls SB 2-1
Step 4. Determine area and Shape of basin:
• Check length widths ratio (should be 'A to 6:1).
• Compute the basin surface area at prrnclpal spllltyay elevation.
• Check the ratio of basin surface area to pear iilfhow rate (should be greater
than or equal to 435 ft'.cfs). Employ diversions with additional traps gild
basins to reduce area drained.
Deterilune barrel capaciry required for site conditions (ininiinu m capacity for Q`
is the 2-Fear peak runoff, Q,.
Length/width ratio 2•23
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 1078
Ratio: basin surface area/Q10 443.621399
Is ratio >= 435 ft2/cfs? YES
Step 5. Deterillllle the principal spllhyay discharge capacity.
• The combiled capacities of the principal and emergence spillways must be
at least the 10-year peak flow for the entire watershed of the basil_
• The principal spillwa-v is analyzed for three possible limiting flog;- types:
Nkeir flow. Orifice flora- and Pipe floxy. The principal spillway discharge
capacity is the smallest of these three flog- rates. Discharges through a
skimmer should be disregarded during this computation. Weir, orifice and
pipe flow may be detennlined by the followmi g equations:
1. l eir Flow-- Q = CLH'-`
where:
Q= discharge in cubic feet per second(cfs)
C =weir coefficient. use 3.1 for corrugated metal pipe risers.
L= circumference of the riser in.feet
H =head above riser crest nil feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?. Orifice Flory: Q = CA (2gH)'-'
xi-here:
6/9/22

0 = discharge nn cubic feet per second (cfs) SB 2-1
C =orifice coefficient. use C = 0.6 for corrugated metal pipe risers.
A= cross-sectional area of the riser pipe in square feet
g =acceleration due to gravity. 3 ft sec'
H =head abo-ve riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
ugh
i_ Pipe Floe: �� _ �3 1 _ F,+� L
-where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel m square feet
g = acceleration due to gravity_ 2.1 ft sec'
h =head above the centerline of the outlet end of the barrel
K„ = coefficient of nunor losses, can be asstuned to be 1.0 for
most principal spillway systems
L = barrel length iu feet
K,, =pipe friction coefficient:
5067n2 (See Table 8'07a for KF values for
diva common size of pipe_)
n =Maiming s coefficient of roughness. use n = 0.0—5 for
eomigated metal pipe
n = 0.015 for reinforced concrete pipe
di = inside diameter of the barrel in niches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1_5 times that of the barrel. Spillway hydraulics are improved by
maximizing weir flow and n„n,nuzuna orifice flow. See Table 8.07b for
reconunended riser barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-1
Inside diameter of barrel, d; (in) 0 6/9/22
Pipe friction coefficient, Kp #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
RISER
Select trail risei and barrel dimensions L:se the :eii. orifice and pipe flo-a-
equations to determine ifthe -:ear peak discharge is passed without actsvating
The emergency spillwa.,•. Determine riser size from Figure 3.0Ib_ Check the
head and stage requirements. If the design l.tage is too high_ choose larger Table 8.07b
dimension,and recalculate As a m inimtuu.set the elevation of the riser at the
same elevation as the top of the sediment pool. A ri_•er height to f times the
barrel diameter is recommended. Select the Type of trash guard.
Select a dewatering device. If a skimmer is used. refer to the manufacturers
dewaterinz data. or Table 6.64.b
Step 6. Design anti-seep collar.
Ensure that antiseep collars are no closer than _2 ft fiom a pipe joint. Collar
must project at least I ` ft from the pipe Indicate watertight connections_
Step 7. Design antiflotation block_
Determine the weight of water displaced by the empty riser, and desten a
block with buoyant weight 1.1 times the weight of v:ater displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet.
Determine discharge velocity from the barrel Design outlet protection to
assure stable conditions. Riprap placement is usually necessar (Appendix
S.06)-
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway
• Determine the required capacity for the emergency spillway as
QE= Q.o—Q, (QF,' Q,)
• From Table=or Table®select the width and depth of the outlet. Table 8.07c
depending on soil conditions. In general. the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flog•.
• An acceptable alternative is the use of the weir equation
Q = CLH'

-;.'here this option is used the maxinium value of C mould be=.s. L SIB 2-1
is the bottom width of the spill, ay at the crest. and H is the depth of 6/9/22
f.ow above the ,pilhvay crest in feet. Vote Minning's channel equation
shculd not be used to size the spill.;ay crest_ However. it should be used
to design the outlet channel below the spola-a,.crest
• The total of the emergenc;; and principle spillway capacities must equal
cr exceed the required l0-Near peak dischuge.
• Set the elevation of the crest of the emergency: _pilh—va,.a Minimum of I
foot above the crest of the riser.
OPTION 1
Q10 2.43
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance,vl-dch should be 1.5 times the :width of the control
section with a smooth transition to the;width of the couucl section. Approach
channel should slope toward the resev.-oir no less:than 10 0.
Width of control section (ft) 6
Width of entrance (ft) 4
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillwa, control section
• Locate the control section in the spilliva-y near where it intersects the
extension of the centerline of the dam
• Keep a level area to extend at least 20 f@ upstream fiom the outlet end of
the control section_ tc ensure a straight alignment.
• Side slopes should be 3:1,
Step 11. Design spillway exit section.
• Spil-twa_; exit should align with the control section and have the same

SB 2-1
YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-1.x1s
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 4
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 4.6669
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 4.6669 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom:width and side slopes. SB 2-1
• Slope should be sufficient to maintain supercritical flog.but make sure it 6/9/22
does not create ezosive velocities for site conditions. (Stay within slope
ranges in appzopriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flogs in the emergency spillway:.
• Constructed height should be 10% greater than the design to allow for
settlement.
• Base top width on the deszen height.
• Set side slopes 2.5:1 or flatter.
• Determine depth of cutoff trench from site borings It should extend to a
stable,tight soil layer(a minimum of?ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6.20, Temporm;t,Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Tempora),Seeding,- 614,Mulching;and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not m
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
YAJobs121-004 Mocksville(R210004)1DocumentslReports1SB 2-1.xls

SEDIMENT BASIN DESIGN SB 2-2
6/9/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
Y:IJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-2.zls
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-2
Total Drainage Area (acres) 2.7
Step 1. Deternune peak flog-. C�„J. for the basin drainage area S.01?
Q10 (cfs) 10.49
Step 2. Deteniune any site linutations for the sedunentpool elevation,einergencN
spill-wa- or top of the dwii_
Minimum pool elevation (ft) 803
Maximum pool elevation (ft) 806.5
Step 3. Deternune Basin volumes.
• Compute muurntin2`-oluine required(1800 ft` acre disturbed)
• Speci Y sediment cleanout level to be marked on riser (one-half the design
volume referenced to the top of the riser) and sediment storage area to be
cleared after the dam is built
Disturbed acreage (ac) 2.45
Min Volume (ft) 4410
Sediment cleanout elevation (ft) 804
Sediment Storage Area 2856

YAJobM21-004 Mocksville(R210004)1Documents\Reports\SB 2-2.xls SB 2-2
Step 4. Determine area and shape of baser_
• Check length width ratio (should be —2:1 to 6:1)
• Compute the basin surface area at principal spilhwav elevation.
• Check the ratio of basin surface area to peak Inflow rate (should be greater
thaii or equal to 435 ft'-cfs). Employ diversions with additional traps and
basins to reduce area drained
Deternriue barrel capacity required for site conditions (uunimum capacity for Qy,
is the 2-year peak runoff. Q_.
Length/width ratio 2.09
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 4606
Ratio: basin surface area/Q10 439.084843
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spill-way discharge capacity-
• The combined capacities of the principal and emergency spillways must be
at least the 10-vear peak flog;- for the entire watershed of the basin.
• The principal spillway is analyzed for three possible limiturg flow tzpes:
Weir flow_ Orifice flow. and Pipe flow. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation. Weir, orifice and
pipe flow may be determined by the following equations:
1. N eir Flow-- Q = CLH'-
where-
Q = discharge in cubic feet per second(cfs)
C =weir coefficient- use 3_1 for cornigated metal pipe risers.
L=circumference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?. Orifice Flogs-: Q = CA (29H)
gvhere:
6/9/22

Q = discharge ui cubic feet per second (cfs) SB 2-2
C = orifice coefficient_ use C = 0.6 for comiRated metal pipe risers.
A= cross-sectional area of the riser pipe in square feet
g = acceleration due to gravity- 3 2' ft�seer
H =head above riser crest un feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
'Izh a,
3. Pipe Flow: ( _ 1 ; K,+� L
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g =acceleration due to gravity- 32.2 fusee'
h =head above the centerline of the outlet end of the barrel
K.,, = coefficient of Honor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
K, =pipe friction coefficient:
_ 5087n' (See Table E7a for KR Values for
di4'3 common size of pipe_)
n =Manning's coefficient of roughness. use n =0.025 for
comigated metal pipe
n =0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.; times that of the barrel. Spillway hydraulics are unproved by
rnaxi*»izmg weir flow and nunmi nzulg orifice flow. See Table 8.07b for
recommended risevbarrel proportions
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft) 1
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-2
Inside diameter of barrel, d; (in) 0 6/9/22
Pipe friction coefficient, Kp #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
RISER
Select trail riser and barrel dimensions Use the weir, orifice and pipe flow
equations to determine if the?_ear peak discharge is passed without acts.•atrng
the emergency spillva•a_,-. Determine riser size from Figure 8.07b. Check the
head and stage requirements. If the design stage is too high. choose larger Table 8.07b
dimensions and recalculate As a minimum.set the elevation of the riser at the
same elevation as the top of the sediment pool. A riser height 2 to times the
barrel diameter is recommended. Select the t-; e of trash guard.
Select a detvaterrn? device. If a skimmer is used. refer to the manufacturers
de;cateang data. or Table 6.6.1 b
Step 6. Design antiseep collar.
Ensure that anti-seep collars are no closer than 2 ft from a pipe joint. Collar
must project at least I f ft fi-om the pipe Indicate watertight connections.
Step 7. Design antiflotation block_
Determine the weight of:rater displaced by the empty- riser. and design a
block with buo,.ant freight 1 1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet
Determine discharge velocity From the barrel. Design outlet protection to
assure stable conditions. Riprap placement is usually- necessary (_4pperjdis
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency-spill-,vay.
• Determine the required capacrn•for the emergency spill-,,;ay as
QC = Q.G—Q, (QF > QZ)
• From.Table®or Table®select the width and depth of the outlet. Table 8.07c
depending on soil conditions In general. the Crider bottom widths and Table 8.07d
lower- slopes are preferred to minimize exit velocities at supercritical
flour
• An acceptable alternative is the use of the weir equation
0 = CLH'

':'here this option is used, the maxuuiun:value of C should be 2 S L SB 2-2
is the bottom width of the spillway at the crest. and:1 is the depth of 6/9/22
f above the spills,a-; :rest in fee:. 'Note- Manning•s channel equatten
should not be used to size the spillway crest. However.it should be used
to design the outlet channel below the spilhu a-:crest.
• The total of the emergency and principle spillway capacities must equal
cr exceed the required 10-year peak discharge.
• Set the ele•:ation of the crest of the emetgency spillway a minimum of 1
foot above the crest z)f the riser
OPTION 1
Quo 10.49
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reser.-oif no less than 100.
Width of control section (ft) 15
Width of entrance (ft) 10
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam
• Keep a level area to extend at least 20 ft upstream from the outlet end of
the control section_to ensure a straight alignment.
• Side slopes should be 3:1.
Step 12. Design spillway exit section.
• Spillway exit should align .with the control section and have the same

SB 2-2
YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-2.x1s Page 5B
6/9/22
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 10
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 11.6673
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 11.6673 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-2
• Slope should be sufficient to maintain supercritical flow,but make sure it 6/9/22
does not create erosive velocities for site conditions. (Stay within slope
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 100to greater than the design to allow far
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter_
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a minimum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill_
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6.-10, Temporan�Diversions)_
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, TemporarY Seeding; 6.14, Mulching;and 6.15,
Riprap)_
• Select groundcover for emergency spill ay to provide protection for
design flow velocity and site conditions_ R.iprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-2.xis

SEDIMENT BASIN DESIGN S B 2-3
6/9/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-3.xis
Designed By: PNJ Date: 6/9f22.
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-3
Total Drainage Area (acres) 2.72
Step 1. Determine peak flog'. Q1,.. for the basin drainage area (_�p��e�;rr'i� SA;)
Q10 (cfs) 11.23
Step ?. Deternune and-site linutarions for the sediment pool elevation,eniergencN
spillx-,-av or top of the dun.
Minimum pool elevation (ft) 804
Maximum pool elevation (ft) 807.5
Step 3. Deternurie basin voltulles:
• Compute nuiurnum volume required (1800 fC acre disturbed)
• SpecifY sediment cleanour le`-el to be marked on riser (one-half the design
ohune referenced to the top of the riser) and sediement storage area to be
cleared after the dani is built
Disturbed acreage (ac) 2.72
Min Volume (ft) 4896
Sediment cleanout elevation (ft) 805
Sediment Storage Area 3010

YAJobs121-004 Mocksville(R210004)1DocumentslReports\SB 2-3.xls SB 2-3
Step 4. Deternune area and shape of basin_
• Check leuath,width ratio (should be :1 to 6:1).
• Compute the basin surface area at principal spillway-elevation_
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or equal to 435 ft' cfs). Etnplo,- diversions with additional traps and
basins to reduce area drained
Determine barrel capacity required for site conditions (nunimum capacity for (1).
is the 2-Fear peak runoff. QL.
Length/width ratio 2.04
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 4900
Ratio: basin surface area/Q10 436.331256
Is ratio >= 435 ft2/cfs? YES
Step -5. Determuue the principal spillway- discharge capacity-.
• The combined capacities of the principal and emergency spillways must be
at least the 10-year peak flow for the entire watershed of the basin.
• The principal spillway is analyzed for three possible limiting floe- types-
Weir flow_ Orifice floe-_ and Pipe flow_ The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skinnier should be disregarded during this computation. Weir, orifice and
pipe flow may be deternuned b� the following equations:
1. Ueir Floly: Q = CLH'
where:
Q = discharge in cubic feet per second(cfs)
C =weir coefficient_ use 3.1 for corrugated metal pipe risers.
L= circumference of the riser to feet
H =head above riser crest inn feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
'. Orifice Flow: Q = CA (2gH)
where:
6/9/22

Q = discharge in cubic feet per second (cfs) SB 2-3
C = orifice coefficient. use C = 0.6 for corrugated metal pipe risers.
A= cross-Sectional area of the riser pipe in square feet
g = acceleration due to gravim-. 3 2.2 ft sec-'
H = head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
2gh
i_ Pipe Flow: Q = a11 - K, +K- L
`
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity. 32.2 fuser'
h =head above the centerline of the outlet end of the barrel
K, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spiffi ay systems
L =barrel length in feet
K. =pipe friction coefficient:
5087n2 (See TableEa for Kp values for
di4 3 eomiuon size of pipe.)
n =Mannuig-s coefficient of roughness. use n =0.025 for
corrugated metal pipe
n =0.01 5 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are unproved by
maximizing weir flow and nunm' zing orifice flow. See Table 8.07b for
recommended riser:barrel proportions.
Barrel diameter (ft) 4
Barrel cross-sectional area, a (ft2) 12.6
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft) O
Minor loss coefficieint, Km o 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-3
Inside diameter of barrel, d; (in) 48 6/9/22
Pipe friction coefficient, KP 0.01823
Discharge, Qo (cfs) 0 0
RISER
Select trail riser and barrel dimensions U e the ,vein. orifice and pipe P.ox
equations to determine if the 2-vein peak discharge is passed without aCT]vating
the emergenc_; spillway. Determine rt;iet size from Figure 8.0-b. Check the
head and stage requirements. If the design stage ii too high, choose larder Table 8.07b
dimensions and recalculate. As a minimum.set the ele•:ancn of the riser at the
same elevation as the top of the sediment pool- A riser height_2 to` times the
barrel diameter is recommended. Select the roe of trash guard.
Select a dewaterinQ device. If a skimmer is used, refer to the manufacturers.
dea.atering data, or Table 6.64 b.
Step 6. Design antiseep collar
Ensure that antiseep collars are no closer than - ft from a pipe joint_ Collar
must project at least 1.= ft from the pipe. Indicate watertight connections.
Step ?. Design antiflotation block_
Determine the weight of water displaced by the empty riser, and design a
block with buo,;ant i eight 1 1 times the-weight of v;ater displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step 8. Design outlet.
Determine discharge velocity- from the barrel. Design outlet protection to
assure stable conditions. Riprap placement is usually necessar v (.4ppendi_t
S.Q6)
Discharge velocity, V (ft/s) 0 0
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergence spillway.
• Determine the required capacin;for the emergency spillway as
Qe= Q,o—Q, (Qt,- Q')
• From Tabl 8.07c or Table®select the width and depth of the outlet. Table 8.07c
depending on soil conditions_ In general. the wider bortcm widths and Table 8.07d
loner slopes are preferred to minimize exit velocities at supercritical
flog;•
• An acceptable alternative is the use of the weir equation
Q = CLH'

'.'here this option is used. the maxuuiuu:-clue of C should be= 3. L SIB 2-3
is the botT.oru idth of the spill,:a'. at the crest. and H is the depth of 6/9/22
flogs-above the spillw a,-crest in feet. Note: Manning's channel equanon
should not be used to size the spillway crest. Howe-:er. it should be used
to design the outlet channel belzw the sprlht av crest.
• The total of the emergency and principle spilhva--capacities must equal
or exceed the required 10-year peal:discharge.
• Set the elevation of the crest of the emeraeiicv: pill,va,a niimrntiru of I
foot above the crest of the riser.
OPTION 1
Q10 11.23
QP 0
Emergency spillway capacity, Qe (cfs) 11.23
Qp + Qe 11.23
Does (Qp + Qe) equal or exceed Q10? YES, PROCEED
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
ate straight_ The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the resew:oir no less than 100-
Width of control section (ft) 15
Width of entrance (ft) 10
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillwa_; near where it intersects the
extension of the centerline of the dam
• Keep a level area to extend at least 20 ft upstream from the outlet end of
the control section-to ensure a straleht alignment_
• Side slopes should be 3:1.
Step 12. Design spillway exit section.
• Spillway exit should align with the control section and have the Same

SB 2-3
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-3.x1s Page 5B
6/9/22
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 10
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Q. (cfs) 11.6673
11.6673
YES, PROCEED
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 11.6673 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-3
• Slope should be sufficient to maintain supercritical flow,but make sure it 6/9/22
does not create erosive velocities for site conditions. (Sta}-%.'ithin slope
ranges in appiopsiate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spilhvay.
• Constructed height should be 100.0 greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:I or flatter.
• Determine depth of cutoff trench from site borings It should extend to a
stable,tight soil layer(a minimum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications. 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications 6.10, Temporary Seeding; 6.14, lfniching;and 6.15,
Riprap).
• Select groundcover for emergency spilbaay to provide protection for
design flow velocity and site conditions. Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
YAJobs121-004 Mocksville(R210004)1DocurnentslReportslSB 2-3.xis

SEDIMENT BASIN DESIGN SB 2-4
6/9/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-4.xls
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-4
Total Drainage Area (acres) 2.98
Step 1. Detern-Une lc flo.{�. ��peak- - r i,,. for the IJaS121 drainage area S, s i
Q10 (cfs) 12.28
Step -". Deternuile ail-,.site limitations for the sediment pool elevation,eiiieraencN
spillway or top of the dais_
Minimum pool elevation (ft) 783
Maximum pool elevation (ft) 786.5
Step 3. Determine basil t oltuues:
• Compute Inn-11111un1 volume required(1800 ft'were disturbed)
• 5peclfz- sediment cle niout level to be marked oIl riser (one-half the design
ti oltlme referenced to the top of the riser) rind sediment storacre area to be
cleared after the Lkiim is built.
Disturbed acreage (ac) 2.98
Min Volume (ft) 5364
Sediment cleanout elevation (ft) 784
Sediment Storage Area 3367

Y:IJobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-4.xls SB 2-4
Step 4. Determine area and shape of basil:
• C heel: length width ratio (should be 2:1 to 6:1;).
• Compute the basin surface area at principal spillt-av elevation.
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or equal. to 435 ft',cfs)_ Employ diversions with additional traps and
basins to reduce area drained
Deterizune barrel capacity required for site conditions (nuinimura capacit-v for Q_
is the '-`'ear peak runoff. Q'.
Length/width ratio 2.06
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 5355
Ratio: basin surface area/Q10 436.074919
Is ratio >= 435 ft2/cfs? YES
Step -5. Determine the principal spill;-ay discharge capacity-.
• The combined capacities of the principal and emergency spillvays must be
at least the 10-near peak floc for the entire watershed of the basic.
• The principal spill-way is analyzed for three possible limiting flog- types:
NVeir flow— Orifice floti. and Pipe floe,-. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through�a
skuluner should be disregarded during this computation. NVeir. orifice and
pipe flo-,N may be determined by the followni lg equations:
1. �Veir Flown Q = CLH'-;
cohere:
Q = discharge lil cubic feet per second(cfs)
C =weir coefficient_ use 3.1 for corrugated metal pipe risers
L= circtunference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?_ Orifice Flow Q = CA (2gH)'
where:
6/9/22

0 = discharge in cubic feet per second (cfs) SB 2-4
C =orifice coefficient. use C = 0.6 for corrugated metal pipe risers.
A= cross-sectional area of the riser pipe iii square feet
g =acceleration due to grab ity. 31__' ft.sec'
H =head above riser crest izi feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
,gh c'
3. Pipe Flow: O = a [1 +K:,- +K L J
where:
Q = discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g
= acceleration clue to gravity_ 32.2 ft sec-
h =head above the centerline of the outlet end of the barrel
K, , = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway. systems
L =barrel length in feet
Kr =pipe friction coefficient:
5067n2 (See Table EEfor KP values for
dig'' common size of pipe.)
n =Mann ing-s coefficient of roughness. use n =0.0_25 for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di = inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are improved by
maximizing weir flow and nvninuzuig orifice floe_ See Table 8.07b for
recommended riser.barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-4
Inside diameter of barrel, d; (in) 0 6/9/22
Pipe friction coefficient, Kp #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
RISER
Select trail riser and barrel dimensions Use the orifice and pipe flow
equations to determine if the'-:e u peat-discharge is passeci w.thcut acn-.•atiug
the emergency spillwa_,-. Determine nier size from Fiame 3.07b. Check the
head and stage requirements. If the design stage is too high. choose larger Table 8.07b
dimes-,ions and recalculate. As a minimiuu.set the elevation of the riser at the
same elevation as the for of the sediment pool. A riser height' to: times the
barrel diameter is recommended. Select the type of trash guard
Select a dev.•atertn, de-:ice. If a skimmer is used. refer to the manufacturers
de;vaterina data. or Table 6 64 b
Step 6. Design anuseep collar
Ensure that antiseep collars are no closer than ' ft from a pipe joint. Collar
must project at least 1 - ft from the pipe. Indicate watertight connections_
Step 7. Design antiflota ion block.
Determine the weight of water displaced by the empty riser. and design a
block with buoyant weight 1 1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet
Determine dischar?e -velocity from the barrel. Design outlet protection to
assure stable conditions_ Riprap placement is usually necessar ti (_iRvendis
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway.
• Determine the required capacity for the emergency,•spillt ay as
• Frcm TablE=oi Table®select the-width and depth of the cutlet Table 8.07c
depending on soil conditions_ In general. the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize emit velocities at supercritical
flow
• An acceptable alteinati:-e is the use of the-weir equation
0 = CLH'

'Khere this option is used. the maximtim:-aloe of C should be = 8. L SB 2-4
is the bottom width of the spill•:ar at the crest. and H is the depth of 6/9/22
flotir above the spill::a-;:rest in fee:. Note -lanning's channel equation
should not be used to size the spill:wa_;crest_ Howe-,er.it should be used
to design the outlet channel below the spill:.-av crest
• The total of the emergency and principle spillway capacities must equal
cr exceed the required 10-rear peak discharge.
• Set the elevation of the crest of the emergency spillway a nummum of 1
foot above the crest of the inset.
OPTION 1
Quo 12.28
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section
:adjust the spillway alignment so that the control section and outlet section
are straight. The entrance:width should be 1 S times the width of the control
section with a smooth transition to the width of the councl section. Approach
channel should slope toward the ieser:oir no less than 100.
Width of control section (ft) 18
Width of entrance (ft) 12
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spilltrav near where it intersects the
extension of the centerline of the dam.
• Keep a le:el area to extend at least 20 ft upstream from the outlet end of
the control section. to ensure a straight atip=ent.
• Side slopes should be ; 1.
Step 12. Design spillway exit section.
• Spillwa-; exit should alien with the control section and have the same

S B 2-4
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-4.x1s Page 5A
6/9/22
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 12
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 14.0007
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 14.0007 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-4
• Slope should be sufficient to maintain supercritical flow. but make sure it 6/9/22
does not create erosive velocities €or site conditions. (Stay within slope
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 100o greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5.1 or flatter.
• Determine depth of cutoff trench from site borings_ It should extend to a
stable.tight soil layer(a minimum of 2 ft deep)_
• Select borrow site—the emergency spillway cut-%ill provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specicarions: 6.10, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Srandards
and Specifications: 6.10, Temporaty Seeding; 6.14,Mulching,-and 6.1.1,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning sighs as needed
YAJobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-4.xis

SEDIMENT BASIN DESIGN S B 2-4A
6/10/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-4A.xis
Designed By: PNJ Date: 6/to/z,7-
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 24A
Total Drainage Area (acres) 0.44
Step 1. Deternne peak flow. «�U. for the basin drainage area (_ R.pe?,,a'ix S.U�)
Q10 (cfs) 1.56
Step 2. Determne any site linutations for the sediment pool elevation,einergency
spillway or top of the darn-
Minimum pool elevation (ft) 787
Maximum pool elevation (ft) 790.5
Step 3. Determine basin volinues.
• Compute nuiunium volume required(1800 ft' acre disturbed)_
• Spec ifi sediment cle-mout level to be marked on riser (oie-half the desiQu
ohune referenced to the top of the riser) and sediment storage area to be
cleared after the dani is built.
Disturbed acreage (ac) 0.35
Min Volume (ft) 630
Sediment cleanout elevation (ft) 788
Sediment Storage Area 140

Y:1Jobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-4A.xls SB 24A
Step 4. Deternune area and shape of basin:
• Check length,width ratio (should be 2:1 to 6:1). Page 2
• Compute the basin surface area at pruicipal spillwa-,7 elevation_
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or equal to 43 ft=-cfs). Employ diversions with additional traps and
basins to reduce area drained.
Deteniuue barrel capaciry required for site conditions (ininimUni capacity for Q,
is the 2-year peak runoff, Q,.
Length/width ratio 2.21
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 798
Ratio: basin surface area/Q10 511.538462
Is ratio >= 435 ft2/cfs? YES
Step 5. Deternune the principal spilhvay discharge capaeih-.
• The combined capacities of the principal and emergency spillways must be
at least the 10-rear peak flow for the entire watershed of the basic_
• The principal spillway is analyzed for three possible limiting floxv types:
'Weir floxv. Orifice flow.. and Pipe flog-. The pruicipal spillway discharge
capacity° is the smallest of these three flow rates. Discharges through a
skimiuer should be disregarded during this computation. Weir_ orifice and
pipe floe may be determined by the folloxvmi g equations:
1. Aeir Flow- Q = CLH'
where:
Q = discharge in cubic feet per second(cfs)
C =weir coefficient. use 3.1 for corrugated inetal pipe risers.
L= circumference of the riser in feet
H =head above riser crest iu feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
Qw (cfs) 0
?. Orifice Flow: Q = CA (29H)
where.
6/10/22

0 = discharge ill cubic feet per second (cfs) SB 24A
C = orifice coefficient_ use C =0.6 for cormgated metal pipe risers Page 3
A= cross-sectional area of the riser pipe in square feet
g =acceleration due to aravivy, 32.2 ft.sec'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
3 Pipe e [ - .+K,L
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity_ 32.2 ft,'sec'
h =head above the centerline of the outlet end of the barrel
K,,, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length iu feet
K, =pipe friction coefficient:
5087n2 (See Tableff for KR values for
di4'3 common size of pipe.)
n =Manning s coefficient of roughness_ use n =0.02-5 for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least l.ti tinges that of the barrel. Spillway hydraulics are improved by
maximizing weir flow and nitnimizing orifice floe•_ See Table 8.07b for
recommended riser,,-barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 24A
Inside diameter of barrel, d; (in) 0 6/10/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select ;rail riser and barrel dimensions. Use the weir. orifice and pipe flow
equations to determine if the 2-year peak discharge is passed without acti atimg
The eniergenc.,- spill-way. Determine riser size from Figure 85.07b Check the
head and stage requirements. If the design stage is too hi-h, choose larder Table 8.07b
dimemsicus and recalculate As a minimiim.set the elevation of the riser at the
same elevation as the top cf the sediment pool. Ariser height 2 to 5 times the
barrel diameter is recommended Select the rope of trash guard.
Select a de%vaterin-, device. If a skimmer is used, refer to the manufacturers
dewatetine data. or Table 6.64.b
Step 6. Design antiseep collar
Ensure that antiseep collars are no closer than 2 ft from a pipe joint_ Collar
must project at least 1 ' ft fi-om the pipe_ Indicate watertight connections_
Step 7. Design antifiotatron block.
Determine the weight of:eater displaced by the empty riser. and design a
block with buo•:ant weight 1 1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet
Determine discharge ti elocir,F from the ban-el. Design outlet protection to
assure stable conditions_ Riprap placement is usually necessar v (.4ppettdix
S_06')
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency-spillway.
• Determine the required capacity for the emergency spillwa as
• From Table=oi Table®select the width and depth of the cutlet. Table 8.07c
depending on soil conditions. In general_ the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = CLH'5

'Khere this option is used. the maximum value of C should be 2 S. L SB 24A
is the bottom width of the .PAlt+:a-, at the crest. and H is the depth of 6/10/22
flow above the spilltca-;crest in feet. Note: 1\fanning s channel equation
should not be used to size the spillwa% crest. However.it should be used Page 5
to design the outlet channel below the spillway crest
• The total of the emergency and principle spillwat*capacities must equal
or exceed the requited 10Near peak dischatge.
• Set the elevation of the crest of the emergence- spillway a minimum of 1
foot above the crest of the riser
OPTION 1
Quo 1.56
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
:adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance width should be I times the width of the control
section with a smooth transition to the width of the control section. approach
channel should slope tort-ard the reservoir no less than 106
Width of control section (ft) 6
Width of entrance (ft) 4
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the 3pilltvay near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream from the outlet end of
the control section. to ensure a straight alignment.
• Side slopes should be ?:1.
Step 12. Design spillway exit section.
• Spillway exit should align with the control section and have the same

SB 2-4A
YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-4A.x1s Page 5A
6/10/22
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 4
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 4.6669
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 4.6669 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 24A
• Slope should be sufficient to maintain supercritical flow-but make sure it 6/10/22
does not create erosive velocities for site conditions. (Stay within slope
ranges in appr opriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10% greater than the design to allow for
settlement.
• Base top width on the design height-
Set side slopes_'.5.1 or flatter.
• Determine depth of cutoff trench from site bongs- It should extend to a
stable,tight soil layer(a minimum of? R deep).
• Select borrow site—the emergency spillway cut-mill provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6.20, Tentporari,Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Temeporart Seeding; 6.14, 'Lfidching,-and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 155. Safety.
• Construct a fence and install warning signs as needed.
YAJobs121-004 Mocksville(R210004)IDocurnentslReportslSB 2-4A.xis

SEDIMENT BASIN DESIGN SB 2-4B
6/10/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocuments\Reports1SB 2-4B.xis
Designed By: PNJ Date: (6//a/zz-.
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-4B
Total Drainage Area (acres) 2.32
Step 1. Deternune peak floe-. Q,,,, for the basin drainage area S.U-i).
Q10 (cfs) 8.22
Step 2. Deter iune any Site 1iI11itatioI s for the sediment pool elevatioII,emergency
spillt�a� or top of the dram_
Minimum pool elevation (ft) 782
Maximum pool elevation (ft) 785.5
Step 3. Deternliile basal 1-oltuue5.
• Compute niiiinnuni-volume required(1800 ft' acre disturbed}
• Specifi- sediment clemiout level to be marked on riser (one-half the design
t-ohiine referenced to the top of the riser) wid sediment storage area to be
cleared after the daili is built
Disturbed acreage (ac) 1.83
Min Volume (ft) 3294
Sediment cleanout elevation (ft) 783
Sediment Storage Area 2016

Y:1Jobs121-004 Mocksville(R210004)1Documents\ReportslSB 2-4B.xls SB 2-413
Step 4. Determine area and shape of basin: Page 2
• Check length 1..vidth ratio (should be 2:1 to 6:1)
• Compute the basin surface area at principal spillway elevation_
• Check the ratio of basin surface area to peak uifiou- rate (should be greater
than or equal to 435 ft':cfs). Employ diversions with additional traps and
basins to reduce area drained
Deterrnnune barrel capacity required for site conditions (minimum m capacity for Q`
is the 2--,..ear peak runoff. Q2-
Length/width ratio 2.05
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 3612
Ratio: basin surface area/Q10 439.416058
Is ratio >= 435 ft2/cfs? YES
Step -5. Determine the principal spillway discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the 10-year peak flow for the entire watershed of the basin.
• The principal spillway is analyzed for three possible limiting flog- types:
Weir flow, Orifice flow. and Pipe flow. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation. Weir, Orifice and
pipe floe may be determined by the following equations'.
1. Weir Flou-: Q = CLH-
where
Q = discharge ui cubic feet per second(cfs)
C =weir coefficient- use 3_"1 for corrugated metal pipe risers.
L= circumference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
Orifice Floe: Q = CA (2gH)
where:
6/10/22

'0 = cscharge rll cubic feet per Second (cfs) SB 24B
C =orifice coefficient_ use C = 0.6 for corrugated metal pipe risers Page 3
A= cross-sectional area of the riser pipe in square feet
g =acceleration due to gravity-. 3?.1 ff.sec'
H =head above riser crest In feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
ugh G:
3. Pipe Flow: Q = a l l +K:,.+V,-L
where:
Q = discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity_ 32.2 fuser'
h =head above the centerline of the outlet end of the barrel
Km = coefficient of minor losses, can be asstnned to be 1.0 for
most principal spillway, systems
L =barrel length in feet
K, =pipe friction coefficient-.
_ 5037n' (See Table EEI for KF values for
diva common size of pipe.)
n =Mai unung s coefficient of roughness_ use n = 0.025 for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di = inside diameter of the barrel iv inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1_5 times that of the barrel_ Spillway hydraulics are improved by
maximizing weir flow and nim nizitng orifice flora. See Table 8.O7b for
recommended riser'barrel proportions_
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-413
Inside diameter of barrel, d; (in) 0 6/10/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select trail riser and barrel dimensions Use the weir, orifice and pipe$ow
equations to determine if the 2-}'ear peak discharge is passed without activating
The emergency spilhva_,-. Determine riser size from Figure 3.O-"b. Check the
head and stage requirements. If the design stage is too high. choose larger Table 8.07b
dimensions and recalculate. As a minimum.set the elevation of the riser at the
same elevation as the top of the sediment pool_ _a riser height 2 to- times the
barrel diameter is recommended. Select the rape of trash guard_
Select a dewatenng device. If a skimmer is used, refer to the manufacturers
de..-atering data_ or Table 6 64 b
Step 6. Design antiseep collar.
Ensure that anti.seep collars are no closer than 2 tt from a pipe joint. Collar
must project at least 1 > ft from the pipe. Indicate watertight connections_
Step 7. Design autifiotation block.
Determine the weight of .cater displaced by the empty riser. and design a
block with buoyant weight 1.1 times the weight of ivater displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step 8. Design outlet
Determine discharge velocity from the barrel. Design outlet protection to
assure stable conditions. Riprap placement is usually necessar Y (Appendix
5.O6')_
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergence spilh.ay.
• Determine the required capacity for the emergency spillway as
Qe= Q,p-Q, (Qp? Qz)
• From Table=or Table®select the width and depth of the outlet. Table 8.07c
depending on soil conditions. In general_ the ,cider bottom widths and Table 8.07d
lower slopes are preferred to minimize e%it velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = CLH'

,['Here this option is used the maximum value of C should be= S. L SIB 2-413
is the bottom width of the spillway at the crest- and H is the depth of 6/10/22
flow above the suillivav crest in feet. Note: `tlanniva s channel equau•on
should not be used to size the spill,,a.: crest. Ho:t-e er.it should be used Page 5
to design the outlet channel below the spill ay crest
• The total of the emergency and principle spillwav capacities must equal
or exceed the required 10-:-ear peal,diwharae.
• Set the elevation of the crest of the emeraenc.- spilh ay a minsrntuu of l
foot above the crest of the riser.
OPTION 1
Quo 8.22
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight. The entrance width should be 1 - times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than 20 0.
Width of control section (ft) 12
Width of entrance (ft) 8
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam.
• beep a level area to extend at least 20 ft upstream from the outlet end of
the control section,to ensure a straight alignment.
• Side slopes should be 3:1
Step 12. Design spillway exit section
• Spillway exit should alien with the control section and have the same

SB 2-4B
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-4B.x1s Page 5A
6/10/22
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 8
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 9.33381
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 9.33381 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 24B
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/10/22
does not create etosi-:e velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dart a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10% gxeater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter.
• Determine depth of cutoff trench from site borings. It should emend to a
stable,tight soil layer(a minimum of ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill_
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Temporar0�Seeding; 6.14, 'lfulching.•and 6.15,
Riprap),
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
Y:Wobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-413.xis

SEDIMENT BASIN DESIGN S B 2-5
6/10/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-5.xls
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-5
Total Drainage Area (acres) 2.55
Step 1. Deterinnine peak flow. 01J. for the basin draiinage area ORpFmcii-Y S.03)
Q10 (cfs) 10.18
Step 2. Deternnine any site linutations for the sedinnent pool elevation_einergenc v
spillway or top of the darn_
Minimum pool elevation (ft) 796
Maximum pool elevation (ft) 799.5
Step 3. Deterinuie basui voluunnes=
• Compute nnlnnllunn volume required (1800 f- acre disturbed)
• Specify sediment cleanout level to be marked on riser (one-half the design
oluune referenced to the top of the riser) and seduneut storage area to be
cleared after the da-un is built
Disturbed acreage (ac) 2.43
Min Volume (ft) 4374
Sediment cleanout elevation (ft) 797
Sediment Storage Area 2030

Y:1Jobs121-004 Mocksville(R210004)IDocumentslReports\SB 2-5.xls SB 2-5
Step 4. Determine area and shape of basin: Page 2
• Check length width ratio (should be 2:1 to 6:1 X
• Compute the basin surface area at principal spillway elevation.
• Check the ratio of basin surface area to peak uiflow rate (should be greater
thain or equal to 435 ft cfs)_ Employ- diversions with additional traps and
basins to reduce area drained
Detennine barrel capacim•required for site conditions (nuinimuun capacity for Q`
is the 2-year peak runoff. Q.,.
Length/width ratio 5.68
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 4452
Ratio: basin surface area/Q10 437.328094
Is ratio >= 435 ft2/cfs? YES
Step 5. Deternune the principal spillway discharge capacity..
• The combined capacities of the principal and emergency spillways roust be
at least the 10-rear peals flo« for the entire watershed of the basin_
• The principal spillway is analyzed for three possible limiting floxv types:
�Veir flow, Orifice flow. and Pipe flow. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation. Weir_ orifice and
pipe floe-may be detennnined by the follow ing equations:
L Weir Float-: Q = CLH-
tthere-
Q= discharge nil cubic feet per second(cfs)
C =weir coefficient. use 3-1 for corrugated nnetal pipe risers.
L=circumference of the riser ni feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
Q, (cfs) 0
7. Orifice Flout-: Q = CA(29H)'
where:
6/10/22

0 = discharge ui cubic feet per second(cfs) SB 2-5
C =orifice coefficient. use C= 0.6 for corrugated metal pipe risers. Page 3
A= cross-sectional area of the riser pipe ui square feet
g = acceleration due to gravity. 32.2 ft sec-
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
'gh
3. Pipe Floe-: Q = a [1 + K,+K, L
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity. 32.2 ft sec'
h =head above the centerline of the outlet end of the barrel
K,, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spilltv,ay systems
L =barrel length in feet
K, =pipe friction coefficient:
_ 5087n2 (See TableEa far KR values for
di4'' common size of pipe.)
n =Manning-s coefficient of roughness, use n =0.025 for
comigated metal pipe
n =0.015 for reinforced concrete pipe
di = inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are improved by
maxniiizmg weir floe- and minimizing orifice floe-. See Table 8.07b for
recommended riser.'barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-5
Inside diameter of barrel, d; (in) 0 6/10/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select nail riser and barrel dimensions 1' se the .ei:_ orifice and pipe flow
equations to determine if the'=;ear peak discharge is passed without activating
the emergency -�pilhvay. Determine riser size from Figure 3.0,b_ Check the
head and stage requirements. If the design stage is too high. choose larger Table 8.07b
dimensicros and recalculate. As a minimum.set the elevation of the riser at the
same elevation as the top of the sediment pool_ A riser height' to` times the
barrel diameter is recommended. Select the rvpe of trash guard_
Select a dewaterma, device. If a skimmer is used. refer to the mantuactuters
de.cateting data, or Table 6.64 b
Step 6. Design antiseep collar.
Ensure that antiseep collars are no closer titan ' ft from a pipe joint. Collar
must pioject at least 1_` ft from the pipe. Indicate watertight connections.
Step 7. Design anti$otation block_
Determine the weieht of water displaced by the empty riser, and design a
block with buo}ant weight 1 1 times the weight of i ater displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet.
Determine discharge velocity from the barrel. Design outlet protection to
assure stable conditions. Riprap placement is usually necessar v (Appendix
S 061_
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency-spillway.
• Determine the required capacity for the emergency spillway as
QC= Q,o—QR �Qp' Q�)
• From Table=or Table g=select the width and depth of the outlet. Table 8.07c
depending on soil conditions_ Im general. the ;eider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = CLH'

'there this option n used. the maximum value of C should be 2 3. L SIB 2-5
is the bottom ivldth oz the spsllv:av at the crest_ and H is the depth of 6/10/22
flow above the spillway crest in feet. Note: Manning"s channel equation
should not be used to size the spillwa-;crest. However,it should be used Page 5
to design the outlet channel below the spillway c est.
• The total of the emergency and principle spillway capacities must equal
or exceed the requited 10-}ear peak discharge.
• Set the elevation of the crest of the emergency spi11,.4a a minimum of 1
foot above the crest of the riser.
OPTION 1
Q10 10.18
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance vadth should be 1 J times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than 100_
Width of control section (ft) 15
Width of entrance (ft) 10
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway, near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 1-0 ft upstream fiom the outlet end of
the control section,to ensure a straight alignment.
• Side slopes should be 3:1.
Step 12. Design spillway exit section.
• Spillway exit should alien with the control section and have the same

SB 2-5
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-5.x1s Page 5A
6/10/22
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 10
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 11.6673
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 11.6673 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-5
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/10/22
does net create erosive velocities for site conditions (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may�be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a mintmum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10% greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter.
• Determine depth of cutoff trench from site borings. It should extend to a
stable.tight soil layer(a minimum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 1.1. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6.20, Temporary Diversions)_
• Select surface protection measures to control erosion(Practice Standards
and Specifications. 6.10, Temporary Seeding;6.14, Mulching;and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 13. Safety.
• Construct a fence and install warning signs as needed_
Y:1Jobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-5.xls

SEDIMENT BASIN DESIGN SB 2-6
6/10/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-6.xls
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-6
Total Drainage Area (acres) 1.13
Step 1. Deternulne peak flog". 01, for the basin drainage area G- Rve;,,dix S'.r s)
Q10 (cfs) 4.66
Step ?. Detemune any site linutations for the sediment pool elevation,emergenc`-
spilEvae or top of the darn
Minimum pool elevation (ft) 813
Maximum pool elevation (ft) 816.5
Step 3. Detenmuie basil-k-ohuiies:
• Compute minniluim volume required(1800 fr acre disturbed')
• Specifi- sediment cleanout level to be marked on riser (one-half the desian
E-ohume referenced to the top of the riser) and sedmient Storage area to be
cleared after the darn is built.
Disturbed acreage (ac) 0.71
Min Volume (ft) 1278
Sediment cleanout elevation (ft) 814
Sediment Storage Area 465

YAJobs121-004 Mocksville(R210004)MocumentslReports\SB 2-6.xls SB 2-6
Step 4. Deternune area and shape of basin: Page 2
• Check length width ratio (should be 2--1 to 6:1).
• Compute the basin surface area at principal spilhyay eleyatioii_
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or equal to 435 ft',-:cfs). Employ diversions with additional traps and
basins to reduce area drained.
Deternmie barrel capacity required for site conditions (minimum capacity for Q`
is the ,-year peak ruuioff. Q,.
Length/width ratio 5.63
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 2033
Ratio: basin surface area/Q10 436.266094
Is ratio >= 435 ft2/cfs? YES
Step 5. Detenuuie the principal spill-way discharge capacity
• The combined capacities of the principal and emergency spillways must be
at least the 10-year peak flog;- for the entire watershed of the basin_
• The principal spillway is anal-yzed for three possible liniitimg flow types-
Weir floNti; Orifice flow. and Pipe flow. The principal spillway discharge
capacity- is the smallest of these three flow rates_ Discharges through�a
skinuuer should be disregarded during this computation. weir, orifice and
pipe flow may be determined by the follows' i equations:
1. Weir Floe-: Q = CLH`.v
where:
Q = discharge in cubic feet per second(cfs)
C =weir coefficient. use 3.1 for corrugated metal pipe risers
L= circumference of the riser in feet
H =head above riser crest 'in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?. Orifice Flow: Q = CA(2gH)'"�
where: 6/10/22

Q = discharge ul cubic feet per second(cfs) SB 2-6
C = orifice coefficient- use C = 0.6 for comiaated metal pipe risers Page 3
A= cross-sectional area of the riser pipe ill square feet
g = acceleration due to efavity. 32.2 ft sec'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
2gh
3. Pipe Flo«: Q = a 1 K.+K L `,
R
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity- 32_2 fuser'
h =head above the centerline of the outlet end of the barrel
Kr, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
K,, =pipe friction coefficient:
_ 5087n2 (See Table 8 07a for K.values for
dia.a common size of pipe_)
n =Niarnlins s coefficient of roughness- use n =0,025 for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di = inside diameter of the barrel -in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are improz•ed by
maximizing weir flow and n,i,iirtliziilg orifice flow. See Table 8.07b for
reconunended nsevbarrel proportions
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-6
Inside diameter of barrel, d; (in) 0 6/10/22
Pipe friction coefficient, Kp #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select hail rise: and barrel dimensions Use the o eir. orifice and pipe fl,-n-
equations to determine if the 2-year peak discharge is passed without activating
The emergence;spillis-a_,-. Determine user size from Figure 8.07b Check the
head and stage requirements. If the design stage is too high, chcose lamer Table 8.07b
dimensioms and recalculate. As a minimum.set the elevation of the riser at the
same elevation as the top cf the sediment pool. A riser height'to ` times the
barrel diameter rs recommended Select the rope cf trash guard_
Select a detratering device. If a skimmer is used. refer to the manufacturers
dewateting data, of Table 6.6.1_b.
Step 6. Design annyeep collar.
Ensure that antiseep collars are no closer than 2 ft from a pipe joint. Cella:
must project at least 1 ? ft from the pipe_ Indicate watertight connections
Step 7. Design antiflotation block.
Determine the weight of water- displaced b`. the emptg riser. and desten a
block with buoyant weight 1.1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet.
Determine dischuge velocity from the barrel. Design outlet protection to
assure stable conditions Riprap placement is usually necessary (_4ppendix
S.06)-
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergence spillway.
• Determine the required capacir;for the emergence;spillway as
Qe= Q-o-Qp (Op z 00
• From Table=or Table®select the width and depth of the outlet Table 8.07e
depending on soil conditions. In general. the wider bottom widths and Table 8.07d
lower Slopes are preferred to minimize eNit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
0 = CLH'`

'S'here This option is used the maxllmuu:-slue of C should be = 8 L SIB 2-6
is the bottom width of the spilh ay at the crest. and H is the depth of 6/10/22
floty above the spilhvav crest in feet. 'Note: Nianning's channel equation
should not be used to size the spillway crest. However.it should be used Page 5
to design the outlet channel belo-.v the spill: a, cie.;t.
• The total of the emergency and principle spillwa-:capacities must equal
cr exceed the required 10 gear peak discharge.
• Set the elevation of the crest of the emergenc: ,pilhi-ay a lninimiLun of i
foot above the crest :)f the riser.
OPTION 1
Quo 4.66
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance,vidth should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reser:oir no less than 110
Width of control section (ft) 6
Width of entrance (ft) 4
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam.
• Keep a le-vel area to extend at least 10 ft upstream from the outlet end of
the control section.to ensure a straight alignment.
Side slopes should be 3:1.
Step 12. Design spillway exit section_
• Spil way exit should align with the control section and hate the same

S B 2-6
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-6.x1s Page 5A
6/10/22
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 4
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 4.6669
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 4.6669 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side dopes. SB 2-6
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/10/22
does not create erosive velocities for site conditions. (Stay-within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 100t,6 greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter.
• Determine depth of cutoff trench from site borings. It should extend to a
stable.tight soil layer(a minimum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specy1carions: 6.10, Temporar-1-Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications. 6.10, Temporaty Seeding;6.14, !Mulching,and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ R.iprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed_
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-6.xls

SEDIMENT BASIN DESIGN S B 2-7
8/25/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
Y:1Jobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-7.xis
Designed By: PNJ Date: 8 2 !Yzz .
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-7
Total Drainage Area (acres) 0.9
Step 1. Deternune peak flog-. 01.1 for the basin drainage area S.0 )
Q10 (cfs) 3.7
Step 2. Deteniune any site limitations for the sediment pool elevation,emergency
spillway or top of the darn_
Minimum pool elevation (ft) 789
Maximum pool elevation (ft) 792.5
Step 3. Detennitie basin volluiies.
• C omplrte n]]ninium volume required(1 S00 ft- 'acre disttubed)
• Speciffi sediment cleanout level to be marled on riser (one-half the design
t olume referenced to the top of the riser) and sediment storage area to be
cleared after the dam is built.
Disturbed acreage (ac) 0.9
Min Volume (ft) 1620
Sediment cleanout elevation (ft) 790
Sediment Storage Area 616

Y:IJobs121-004 Mocksville(R210004)IDocuments\ReportslSB 2-7.xls SB 2-7
Step 4. Determine area and shape of basil: Page 2
• Check length width ratio (should be 2:1 to 6:1)
• Compute the basin surface area at principal spillway elevation.
• Check the ratio of basin surface area to peak inflow rate (Should be greater
than or equal to 435 ft':cfs)_ Employ diversions with additional traps and
basins to reduce area drained.
Determine barrel capacity required for site conditions (minimums capacity for Q"
is the -year peak runoff. Q,.
Length/width ratio 2.07
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 1624
Ratio: basin surface area/Q10 438.918919
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spillway-discharge capacity.
• The combined capacities of the principal and emergence spill-ways must be
at least the 10-year peak flow for the entire watershed of the basin_
• The principal spillway is anal-,zed for three possible limiting flow, types:
N eir flow Orifice floiw. and Pipe flow. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation_ Weir, orifice and
pipe flog-may be determined by the following equations:
1. Weir Flow: Q = CLH'-
where:
Q = discharge lll cubic feet per second(cfs)
C = weir coefficient. use 3.1 for corrugated metal pipe risers.
L= circumference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 10 0
Head above riser crest, H (ft)
QW (cfs) 0
2. Orifice Flow: Q = CA (2gH)°-'
where: 8/25/22

Q = discharge ui cubic feet per second (cfs) SB 2-7
C =orifice coefficient. use C = 0.6 for comiaated metal pipe risers. Page 3
A= cross-sectional area of the riser pipe ui square feet
g =acceleration due to gravity. 3_'.1 ft-seer
H =head above riser crest M feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
ugh 4,
3- Pipe Flog-: Q = a �l _Km+Kt L
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g =acceleration due to gra,sty_ 3`'2 ft seer
h =head above the centerline of the outlet end of the barrel
K, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spil1w,ay systems
L =barrel length in feet
Kp =pipe friction coefficient:
_ 5067n2 (See Table E for Kp -:alues for
64'3 common size of pipe-)
n =\danning-s coefficient of roughness_ use n =0.025 for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are 'unproved by
maximizing weir flow and minitti;7ing orifice flow. See Table 8.07b for
recommended riserbarrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-7
Inside diameter of barrel, d; (in) 0 8/25/22
Pipe friction coefficient, Kp #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select trail riser and barrel dimensions Use the J.'eir. orifice and pipe flow
equations to determine if the gear peak discharge is passed withcut activating
the emergency spillwa_,•. Determine riser size from Figure 8.0?b- Check the
head and stage requirements. If the design stage is too high, choose larger Table 8.07b
dimensions and recalculate. As a minimum,set the elevation of the rises at the
same elevation as the top of the sediment pool. A riser height 2 to.5 times the
barrel diameter is recommended- Select the tti-pe of trash guard-
Select a dewatering device. If a skimmer is used. refer to the manufacturers
dewateting data, or Table 6,64 b.
Step 6. Design antiseep collar-
Ensure that antiseep collars are no closer than 2 ft from a pipe joint- Collar
must project at least 1 5 ft from the pipe. Indicate watertight connections.
Step 7. Design antiflotation block.
Determine the weight of water displaced by the empty riser, and design a
block with buoyant weight 1.1 times the weisht of eater displaced.
Riser Height -
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet.
Determine discharge velocity from the barrel. Design outlet protection to
assure stable conditions. R.iprap placement is usuallv necessai-y (Appe►tdir
S.06)-
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway-
• Deteimuine the required capaciry for the emergency spillway as
Qe= Q,0—QQ (Q�7 Qz)
• From Table®or Table®select the width and depth of the outlet. Table 8.07c
depending on soil conditions. In general. the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
0 = CLH'5

vVhere this option is used. the maximum.-slue cf C should be= 8 L SB 2-7
is the bottom width of the spill, ay at the crest. and H is the depth of 8/25/22
$ots above the spillwa-;crest in feet. Note: Mining s channel equation
should not be used to size the spillway crest. However. it should be used Page 5
to design the cutlet channel below the spillway crest
• The total of the emergenc j- and principle spillway capacities must equal
or exceed the required 10--Year peak discharge.
• Set the elevation of the crest of the emergency spillway a minimum of 1
foot above the crest of the riser.
OPTION 1
Quo 3.7
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alienment so that the control section and outlet section
are straight. The entrance width should be 1 5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than 20 o.
Width of control section (ft) 6
Width of entrance (ft) 4
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam.
• keep a level area to extend at least ?G ft upstream fi-om the outlet end of
the control section,to ensure a straight alignment.
• Side slopes should be 3:1.
Step 12. Design spillway exit section_
• Spillway exit should align with the control section and have the same

SB 2-7
Page 5A
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-7.x1s 8/25/22
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 4
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 4.6669
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 4.6669 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-7
• Slope should be sufficient to maintain supercritical flow.but make sure it $/25/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the ex►t channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10% greater than the design to allow for
settlement.
• Base top width on the design height_
• Set side slopes 2.51 or flatter_
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a uununum of 2 R deep).
• Select borrow site—the eule: spillway cut Rill provide a significant
amount of fill_
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Spec fications: 6 20, Temporary Dn%ersions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Temporary Seeding;614,Mulching;and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils_
Step 1-5. Safety.
• Construct a fence and install warning signs as needed_
Y:WobM21-004 Mocksville(R210004)IDocumentslReportslSB 2-7.xls

SEDIMENT BASIN DESIGN S B 2-8
6/15/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocuments\ReportslSB 2-8.x1s
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-8
Total Drainage Area (acres) 1.41
Step 1. Deternulle peak-flog-. Cale, for the basin drailk-lge area (lvver,,ix S.0-1)
Q10 (cfs) 5.82
Step 2. Deterinille any site linutations for the Sediment pool elevation,elnergencN
spillway or top of the dam_
Minimum pool elevation (ft) 790
Maximum pool elevation (ft) 793.5
Step 3. Determine basic volumes
• Compute n1immum volume required(1800 fr''acre disturbed)_
• 5pecifi� sediment eleanout level to be marked on riser (one-half the design
E-ohune referenced to the Lop of the f1Ser) and Sedlnlel2t SLoiacr area to be
cleared after the dale is built.
Disturbed acreage (ac) 1.41
Min Volume (ft) 2538
Sediment cleanout elevation (ft) 791
Sediment Storage Area 920

YAJobs121-004 Mocksville(R210004)1DocumentslReports\SB 2-8.xls SB 2-8
Step 4. Deternnine area grid shape of basin: Page 2
• Check length'width ratio (should be -':1 to 6:1).
• Compute the basin surface area at principal spillway elevation_
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or equal to 435 ft':efs)_ Employ diversions with additional traps and
basins to reduce area drained.
Deternurne barrel capacity required for site conditions (minimum capacity for Q.,
is the 'I-year peak runoff, Q:.
Length/width ratio 4.42
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft2) 2544
Ratio: basin surface area/Q10 437.113402
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spill-way discharge capacity.
• The combined capacities of the principal and emergency spillways roust be
at least the I0-year peak flog, for the entire watershed of the basin.
• The principal spillway is analyzed for three possible iinuting flow, types:
Welt flow, Orifice flow, and Pipe flow-. The principal spillway discharge
capacity is the smallest of these three float- rates. Discharges through�a
skimmer should be disregarded during this computation. 'Weir, orifice and
pipe floe may be determined by-the followilor equations:
1. Weir Flout-: Q = CLH'
where:
Q= discharge in cubic feet per second(cfs)
C =their coefficient. use 3.1 for corrugated metal pipe risers.
L=circumference of the riser irn feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
- Orifice Floe-: Q = CA(2g ff-
where:
6/15/22

O = discharge un cubic feet per second (cfs) S B 2-8
C = orifice coefficient. use C =0.6 for corrugated metal pipe risers Page 3
A= cross--sectional area of the riser pipe in square feet
g =acceleration due to grab its-. 3?. ft sec'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
gh c
3. Pipe Flo«: 0 = a [I + KI,+ItL L
where:
Q = discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity. 3 ft'sec-
h =head above the centerline of the outlet end of the barrel
Km = coefficient of manor losses, can be assumed to be 1.0 for
most principal spillw-a-V systems
L =barrel length in feet
K, =pipe friction coefficient:
5087W (See Table 8A7a for KP values for
dia:a common size of pipe.)
n =-Manning-s coefficient of rou� ess. use n = 0.025 for
corrugated metal pipe
n = 0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 tines that of the barrel Spillway hydraulics are impro-.•ed by
maximizing weir flow and miuuuizing orifice floe. See Table 8.07b for
reconnmended riser.barrel proportions
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-8
Inside diameter of barrel, d; (in) 0 6/15/22
Pipe friction coefficient, KP #DIV/O!
Discharge, Qo (cfs) #DIV/O! 0
Page 4
RISER
Select trail riser and barrel dimensions Use tine weii. orifice and pipe flour
equations to determine if the_'_{eat peal:discharge is passed without activating
The emergency spillwa3-. Determine riser size from Figure 8.07b. Check the
head and stage requirements. If the design sage is too high, choose larger
dimensions and recalculate As a ininimumi.set the elevation of the riser at the Table 8.07b
same elevation as the top of the sediment pool. A riser height to 5 times the
barrel diameter is recommended. Select the type of trash guard.
Select a dewatenng device. If a skimmer is used. refer to the manufacturers
dewatetina data. or Table 6.64.b
Step 6. Design antiseep collar.
Ensure that antiseep collars are no closer than 2 ft from a pipe joint. Collar
must project at least 1 5 ft fi-om the pipe_ Indicate watertight connections_
Step 7. Design antiflotation block.
Deteimine the weight of.rater displaced by the empty riser. and design a
block with buoyant weight 1.1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step 8. Design outlet.
Determine discharge velocity, from the barrel. Design outlet protection to
assure stable conditions. Riprap placement is usually necessan; (Appe?idix
S.06)-
Discharge velocity, V (ft/s) #DIV/O! #DIV/O!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway.
• Determine the required capacir;for the emergency spillway as
QE= 0.0-Qr (OF,? Q')
• From Table®or Table g�select the width and depth of the outlet. Table 8.07c
depending on soil conditions_ In general- the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
0 = CLH'

'-.%'here this option n used, the maximum value of C should be= S. L SB 2-8
is the bottom width of the spills.-ay at the crest. and H is the depth of 6/15/22
frog-above the spilt ay crest in feet. Note_ Manning s channel equatLen
shculd not be used to size the spillwa-, crest Ho:,etier.it should be used Page 5
to design the outlet channel below the spillway crest.
• The total of the emergenc and principle =pill:iav capacities must equal
cr exceed the required 10-year peak discharge.
• Set the ele;-atrcn of the crest of the emergency spillway a m+ntinrun of 1
foot above the crest of the riser.
OPTION 1
Quo 5.82
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and cutlet section
are straight. The entrance width should be 1 -5 times the :width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the resen-oir no less than
Width of control section (ft) 9
Width of entrance (ft) 6
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spilliray near inhere it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream $om the outlet end of
the control section_to ensure a straight alignment.
• Side slopes should be ?:1
Step 12. Design spillway exit section.
• Spillway exit should align with the control section and have the same

SIB 2-8
6/15/22
YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-8.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 6
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 7.00036
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 7.00036 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-8
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/15/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 14°•6 greater than the design to allow for
settlement.
• Base top width on the design height_
• Set side slopes 2.5:1 or flatter_
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a minimum of 2 ft deep)_
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Spec cations: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Temporary Seeding,-614,Mulching;and 6.15,
Riorap).
• Select groundcover for emergency- spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils_
Step 15. Safety.
• Construct a fence and install watume signs as needed.
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-8.xls

SEDIMENT BASIN DESIGN S B 2-8A
6/15/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobM21-004 Mocksville(R210004)1Documents1Reports\SB 2-8A.xis
Designed By: PNJ Date: 2—
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-8A
Total Drainage Area (acres) 3.88
Step 1. Deternune peak flog-. Q,,_ for the basin draiuiage area (iRvew;ix S.03)
Q10 (cfs) 5.82
Step?. Determine an- site limitations for the sediment pool elevation,emergence
spillway or top of the darn_
Minimum pool elevation (ft) 815
Maximum pool elevation (ft) 818.5
Step 3. Deternuue basui volmies:
• Compute 1111uniun7 v oluine required(1800 fe acre disturbed)
• Specify sediment cleanout level to be marked on riser (one-half the design
--ohune referenced to the top of the riser) and seduient storage area to be
cleared after the dam is built.
Disturbed acreage (ac) 3.88
Min Volume (ft) 6984
Sediment cleanout elevation (ft) 816
Sediment Storage Area 4770

Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-8A.xls SB 2-8A
Step 4. Detemine area and shape of basin: Page 2
• Check length width ratio (should be 3:1 to 6:1;.
• Compute the basin surface area at principal splllwaV elevation.
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or equal to 43-5 ft' cfs). Employ diversions with additional traps and
basins to reduce area drained-
Determine barrel capacity required for site conditions (minimum capacity for Q-
is the 2-`'ear peak runoff. Q,.
Length/width ratio 2.02
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 7021
Ratio: basin surface area/Q10 1206.35739
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spiffivay discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the 10-rear peak flow for the entire watershed of the basui_
• The principal spillway is anah7ed for three possible limiting flow. ti�Ws:
Weir flow, Orifice flow. and Pipe flow. The principal spillway discharge
capacity is the smallest of these three flow- rates. Discharges through�a
skimmer should be disregarded during this computation. Weir, orifice and
pipe flow ma-y•be deternuned by the following equations:
1. Weir Flow: Q = CLH'-y
where:
Q = discharge in cubic feet per second(cfs)
C =weir coefficient. use 3_1 for corrugated metal pipe risers
L=circumference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 6.28318531
Head above riser crest, H (ft) 0.5
Q, (cfs) 7.33075685
?. Orifice Flow: Q = CA(29H)`''-'
where:
6/15/22

« = discharge ui cubic feet per second(cfs) SB 2-8A
C = orifice coefficient. use C = 0.6 for corrugated metal pipe risers. Page 3
A= cross-sectional area of the riser pipe in square feet
g =acceleration due to gravity_ 32.1 fusee=
H =head above riser crest iri feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 3.14159265
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft) 0.5
Discharge, Qo (cfs) 10.6961888
Riser Diameter (in.) ' 24
,gh
3_ Pipe Flow: 0 = a [1 — 1.+K,L J
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity_ 32.2 ft,ser'
h =head above the centerline of the outlet end of the barrel
Km = coefficient of minor losses_ can be assumed to be 1.0 for
most principal spillway systems
L =barrel len_Qth in feet
K� =pipe friction coefficient:
_ 5087n' (See Table $.ova for KF values for
dja,3 common size of pipe_)
n =Mazniing's coefficient of roughness. use n =0.025 for
corrugated metal pipe
n = 0.01 ti for reinforced concrete pipe
di = inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are improved by
maximizing weir flow and minimimig orifice floe. See Table 8.07b for
recommended riser:'barrel proportions.
Barrel diameter (ft) 2
Barrel cross-sectional area, a (ft2) 3.1
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft) 1
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-8A
Inside diameter of barrel, d; (in) 24 6/15/22
Pipe friction coefficient, Kp 0.04593
Discharge, Qo (cfs) 17.8269813 17.8269813
Page 4
RISER
Select trail riser and barrel dimensions Use the v:eir. orifice and pipe flow
equations to determine if the'-Near peak discharge is passed without acti:-ating
the emergency spillwa_r. Determine riser size from Figure 8.07-b. Check the
head and stage requirements. If the design --rage is too high, choose larger Table 8.07b
dimensions and recalculate. As a minimum,set the elevation of the riser at the
same elevation as the top of the sediment pool_ A riser height' to` times the
barrel diameter is teccmmended. Select the type of trash guard
Select a dewatering device. If a skimmer is used,refer to the manufacturers
de:catering data. or Table 6.64.b.
Step 6. Design antiseep collar.
Ensure that antnseep collars are no closer than , ft fiom a pipe joint. Collar
must project at least l.` ft from the pipe. Indicate watertight connections
Step ?. Design anuflotation block.
Determine the weight of water displaced by the empty riser. and design a
block with buoyant weight 1 1 times the tiseight of water displaced.
Riser Height 3.5
Weight of water displaced by the empty riser 686.453703
Buoyant weight 755.099073
Step 8. Design outlet.
Determine discharge velocity- from the barrel. Design outlet protection to
assure stable conditions. Riprap placement is usually necessai v (4ppendix
Discharge velocity, V (ft/s) 5.67450438 5.67450438
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway.
• Determine the required capacir;for the emergency spillway as
Qe= Q,o—Q:; (QF-t Q')
• From Table®or Table®select the width and depth of the cutlet. Table 8.07c
depending on soil conditions. In general, the :rider bottom widths and Table 8.07d
lower slope: are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = cLHi

't.'here this option n used. the maxzm.uu value of C should be_ S. L SIB 2-8A
is the bottom width of the spillway at the crest.and H is the depth of 6/15/22
flow above the spillway crest in feet. dote: Manning"s channel equation
should not be used to size the spilhwa-;crest_ How ,er.it should be used Page 5
to design the outlet channel below the spillw av crest
• The total of the emergency and principle spillwa -capacities must equal
cr exceed the requited 10-7,ear peak discharge.
• Set the elevation of the crest of the emergency spillwaw a minimum of 1
foot above the crest of the riser_
OPTION 1
Q1 0 5.82
QP 7.33075685
Emergency spillway capacity, Qe (cfs) -1.5107568
Qp + Qe 5.82
Does (Qp + Qe) equal or exceed Q10? YES, PROCEED
Step 10. Spillway approach section.
Adjust the spillway alienment so that the control section and outlet section
aie straight_ The entrance width should be 1.5 times the;width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reser:oir no less than 100.
Width of control section (ft)
Width of entrance (ft)
Slope of approach channel (%) 3
Is width of the entrance section 1.5xcontrol section
width? #DIV/0!
Is approach channel >/= 2%? YES, PROCEED
No spillway this basin.
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream from the outlet end of
the control section.to ensure a straight alignment.
• Side slopes should be ;:1
Step 11. Design spillway exit section.
• Spilltivay exit should align with the control section and have the same

bottom width and side slopes. SB 2-$A
• Slope should be sufficient to maintain supercritical flow,but make sure it 6/15/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water mat_,be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10°•o greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter,
• Determine depth of cutoff trench from site borings_ It should e:ctend to a
stable,tight soil layer(a minimum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill_
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specicarionr: 6.10, Temporary Diversions)_
• Select surface protection measures to control erosion(Practice Srandards
and Specifications: 6.10, Temporary Seeding; 6.14,lfulching;and 6.15,
R'T'- F!-
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 1-5. Safety-
- Construct a fence and install warning sins as needed_
YAJobs121-004 Mocksville(R210004)WocumentslReportslSB 2-8A.xls

SEDIMENT BASIN DESIGN SB 2-8B
6/16/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocumentslReports\SB 2-8BAs
Designed By: PNJ Date: GII&12,Z.
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-813
Total Drainage Area (acres) 2.39
Step 1. Detern nine peak Hots_ 01,. for the basin drauiage area ORveirdix S,0.)
Q10 (cfs) 9.85
Step 3. Deternune any site linutations for the sediment pool elevation,eniergenc-v
spillway or top of the clam_
Minimum pool elevation (ft) 793
Maximum pool elevation (ft) 796.5
Step 3. Deterniuie basin vol umes_
• Compute mmnnlum v ollume required(1800 ft' acre disturbed)
• Specift- secliiuent cleanout level to be imarked on riser (one-half the design
vohume referenced to the top of the riser) and sediment storage area to be
cleared after the dani is built.
Disturbed acreage (ac) 2.39
Min Volume (ft) 4302
Sediment cleanout elevation (ft) 794
Sediment Storage Area 2560

Y:1Jobs121-004 Mocksville(R210004)1Documents\Reports\SB 2-8B.x1s SB 2-813
Step 4. Deterillume area and shape of basin: Page 2
• Check length 'Vidth ratio (should be ':1 to 6:1).
• Compute the basin surface area at principal spilb a-v ele.ation.
• Check the ratio of basin surface area to peak unfiow, rate (should be greater
than or equal to 435 ft')cfs)_ EniploS- diversions with additional traps and
basuns to reduce area drained.
Determine barrel Capacity required for site conditions (nunimluu Capacity for Q;
is the 2-year peak runoff. Q,.
Length/width ratio 2.04
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 4324
Ratio: basin surface area/Q10 438.984772
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spillway discharge capacity.
• The combined capacities of the principal and emergency spillways nnust be
at least the 10-rear peak flow for the entire watershed of the basin.
• The principal spillway is analyzed for three possible limiting flog tapes:
%'eir flogs; Orifice flo«v. and Pipe floe,-. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation. Weir_ orifice and
pipe flog may be detenluned by the followui la equations:
1_ N eir Flog;-: Q = C LH'
where:
Q= discharge ui cubic feet per second(cfs)
C =weir coefficient. use 3.`I for corrugated metal pipe risers
L= circuunference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?_ Orifice Flo«: Q = CA (2gl-1 f
where:
6/16/22

Yy Q =discharge In cubic feet per second (cfs) SB 2-8B
C =orifice coefficient, use C = 0.6 for cornlaated metal pipe risers Page 3
A= cross-sectional area of the riser pipe in square feet
g =acceleration due to gravity, 31.2 ft�sec'
H =head above riser crest ul feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
3. Pipe Flo1v: Q = a 1 + K,_+K,L J
where:
Q=discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g =acceleration due to gravity_ 32.2 fuser'
h =head above the centerline of the outlet end of the barrel
K, = coefficient of moor losses, can be assumed to be 1.0 for
most principal spilb ay systems
L =barrel leng,th in feet
K, =pipe friction coefficient:
_ 5087n2 (See Table s.E for KP values for
dia.a common size of pipe.)
n =N-darnzing's coefficient of roughness_ use n =0.025 for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1-5 times that of the barrel. Spillway hydraulics are unproved by
maximizing weirflow and minimizing orifice flo-%v- See Table 8.07b for
recommended riser-barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-813
Inside diameter of barrel, d; (in) 0 6/16/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select trail riser and barrel dimensions. UG e the :err. orifice and pipe flow
equations to determine if the _ear peak discharge is passed withcut activating
the emergenc_, spill-ray. Determine riser size fi-om Figure 8.07b Checl:the
head and stage requirements. If the design :tape is too high, choose larger
dimensions and recalculate. As a mi-mm uu.set the elevation of the riser at the Table 8.07b
same elevation as the top of the sediment pool. A riser height 2 to J times the
barrel diameter is recommended. Select the t7,-pe of trash guard.
Select a dewatering device. If a skimmer is used. refer to the manufacturers
dewateiine data. or Table 6.64 b.
Step 6. Design antiseep collar.
Ensure that antrseep collars are no closer than i ft from a pipe joint. Collar
must project at least 1_= ft from the pipe. Indicate watertight connections.
Step '. Design anti$otation block_
Determine the freight of water displaced by the empty; riser. and design a
block with buoyant weight 1.1 times the-.•eight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step 3. Design outlet_
Determine discharge velocinr from the barrel Design outlet protection to
assure stable conditions. Riprap placement is usually necessary (_appendix
5.06).
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spill-a ay.
• Determine the required capacir;for the emergency,•spillway as
Qe= Q,t,—Q, (Qt ? Q')
• From Table=or Table®select the width and depth cf the outlet. Table 8.07c
depending on soil conditions. In general. the ,rider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
$ow_
• An acceptable alternative is the use of the weir equation
0 = CLHi`-

Where this option is used. the max lintim:-clue of C should be 2 3 L SIB 2-81B
is the bottom width of the spill-,ray at the crest. and H is the depth of 6/16/22
fio%v above the spillwa-;crest in feet. Note: Rlanning's channel equation
should not be used to size the spillway crest. However.it should be used Page 5
to desisn the outlet channel below the spilliav crest
• The total of the emergency and principle spillway capacities must equal
ci exceed the required 10-:°eai peal.discharge.
• Set the elevation of the crest of the emergency spilhwaw a minimum of 1
foot above the crest of the riser.
OPTION 1
Quo 9.85
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. approach
channel should slope toward the resen-oir no less than In 0.
Width of control section (ft) 15
Width of entrance (ft) 10
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spill:way control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam.
• keep a level area to extend at least 20 tt upstream fi-orn the outlet end of
the control section_to ensure a straight alignment.
• Side slopes should be?:1.
Step 12. Design spillway exit section.
• Spillway exit should align with the control section and have the same

SB 2-8B
6/16/22
YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-8B.As
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 10
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 11.6673
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 11.6673 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-8B
• Slope should be sufficient to maintain supercritical flow,but make sure it 6/16/22
does act create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment_
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10°6 greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or Satter_
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a in1a:aiuni of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6.10, Temporary Diversions)_
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Temporary Seeding; 6.14, fulching;and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geote..tile
fabric may be required in erodible soils or when the spilharay is not in
undisturbed soils_
Step 1-5. Safety.
• Construct a fence and install warning signs as needed_
YAJobM21-004 Mocksville(R210004)1DocumentslReportslSB 2-8B.xls

SEDIMENT BASIN DESIGN SB 2-9
6/13/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-9.xls
Designed By: PNJ Date: ,2-
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-9
Total Drainage Area (acres) 3.94
for the basin drainage area (_�ppey;�il S.OS)
Step 1. Detefilune peak flow- 01c.
Q10 (cfs) 16.25
Step 3. Deternlllle any"site linutatlons for the sedllllent pool elevation,emergency
spillt-%-av or top of the dale.
Minimum pool elevation (ft) 782
Maximum pool elevation (ft) 785.5
Step 3. Deternune basin volinues.
• Compote nuiliniiini voliuue required (1800 fC,acre disturbed)-
• 5pecifi sediment cle-mout level to be marked on riser (one-half the design
volume referenced to the top of the riser) and sediment storage area to be
cleared after the darn is built.
Disturbed acreage (ac) 3.94
Min Volume (ft) 7092
Sediment cleanout elevation (ft) 783
Sediment Storage Area 3969

Y:\Jobs\21-004 Mocksville(R210004)\Documents\ReporWSB 2-9.xis SB 2-9
Step 4. Deternnine area and shape of basin: Page 2
• Check len4th width ratio (should be 2:1 to 6:1).
• Compute the basin surface area at principal spillwa-v elevatioin_
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or equal to 435 ft'-cfs)_ Emplo-y diversions with additional traps and
basins to reduce area drained.
Deterunine barrel capacity required for site conditions (nunimtunr capacity for 0,
is the -year peak runoff. Qom.
Length/width ratio 5.8
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 7105
Ratio: basin surface area/Q10 437.230769
Is ratio >= 435 ft2/cfs? YES
Step 5. Detemuine the principal spilhvay discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the 10-year peak flow for the entire watershed of the basin.
• The principal spillwav is analyzed for three possible hmitung flog types:
Weir floxv, Orifice flour. and Pipe flow. The principal spillway discharge
capacity- is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation Weir. orifice and
pipe floe- may be determined by the following equations:
1. Vveir Flows Q = CLH'
where-
Q = discharge in cubic feet per second(cfs)
C =weir coefficient. use 3.1 for corrugated metal pipe risers.
L = circumference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
-1_ Orifice Flom-: Q = CA(2gH)='
«,-here:
6/13/22

Q = discharge in cubic feet per second (cfs) SB 2-9
C =orifice coefficient. use C = 0.6 for comugated metal pipe risers. Page 3
A= cross-sectional area of the riser pipe in square feet
g = acceleration due to gravity 3'_� ft-sec'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
,f c;
3. Pipe Flow: Q = n [1 -K:, +KF L
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g =acceleration due to gravity, 3?2 ft-'sec'
h =head above the centerline of the outlet end of the barrel
Kn, = coefficient of Honor losses, can be assunned to be 1.0 for
most principal spillway systems
L =barrel length iu feet
K" =pipe friction coefficient:
5087n2 (See Table sA7a for KF values for
di;'3 common size of pipe.)
n =Manning.-s coefficient of roughness. use n =0.015 for
corrugated metal pipe
n = 0.01 i for reinforced concrete pipe
di = inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5) times that of the barrel. Spillway hydraulics are improved by
maximizing weir flow and g orifice flox,.,. See Table 8.07b for
recommended riser.barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-9
Inside diameter of barrel, d; (in) 0 6/13/22
Pipe friction coefficient, Kp #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select wail riser and barrel dimen_ions Uz,e the weir. orifice and pipe tow
equations to determine if the 2-year peak discharge is passed;without activating
the emergenc-y.spillwa_t- Determine riser size from Figure 8.0-b_ Check the
head and stage requirements. If the design stage is too high, choosem larger Table 8.07b
dimensions and recalculate As a minimum,set the elevation of the riser at the
same elevation as the top of the sediment pool A riser height 2 to ` times the
barrel diameter is recommended Select the rtipe of trash guard_
Select a de-watering device. If a skimmer is used. refer to the manufacturers
dewatering data. or Table 6 64 b_
Step 6. Design antiseep collar.
Ensure that antiseep collars are no closer than 2 ft from a pipe joint. Collar
roust project at least 1 5 ft from the pipe_ Indicate ixatertight connections.
Step 77. Design anti$otation block_
Determine the weight of water displaced by the empty riser, and design a
block with buo•;ant weight 1 1 times the weight of water displaced.
Riser Height'
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet
Determine discharge velocity from the banel. Design outlet protection to
assure stable conditions. Riprap placement is usually necessary (Appe?idix
S.0 )-
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergence spillway_
• Determine the requiied capacity for the emergency spillway as
Qe= Q.c—Q, (Qp;_> Q)
• From Table=or Table®select the width and depth of the outlet. Table 8.07c
depending on soil conditions. In general. the wider bottom widths and Table 8.07d
lower slope, are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = CLH'`

'.'here this option is used the maximum.-slue of C should be = 8. L SIB 2-9
is the bottom width or the spillway at the crest. and H is the depth of 6/13/22
flow above the spillwa-;crest in feet. 'Note: Manning's channel equation
should not be used to size the spillway crest. Howe-,er.it should be used Page 5
to design the outlet channel below the spol av cze,t
• The total of the emergency and principle spillway capacities must equal
or exceed the required 10-year peak di,charge.
• Set the elevation of the crest of the emergeucy spillway a minimum of i
foot ab.:a the crest of the riser.
OPTION 1
Quo 16.25
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than 240.
Width of control section (ft) 24
Width of entrance (ft) 16
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam
• Keep a level area to extend at least 20 ft upstream fi-om the outlet end of
the control section_to ensure a straight alignment.
• Side slopes should be 3:1
Step 12. Design spillway exit section-
- Spill«vay exit should align with the control section and have the same

SB 2-9
6/13/22
Y:\Jobs\?1-004 Mocksville(R210004)\Documents\Reports\SB 2-9.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 16
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Q. (cfs) 18.6676
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 18.6676 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-9
• Slope should be sufficient to maintain supercritical flow,but make sure it 6/13/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may•be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillwray.
• Constructed height should be 10% greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter_
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a minimum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill-
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Snecicarions: 6.20, TemporatyDiversions).
• Select surface protection measures to control erosion(Practice Standands
and Specifications: 6.10, Temporaty Seeding; 6.14,Mulching;and 6.15,
Ripr'ap)-
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotestile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
YAJobsk21-004 Mocksville(R210004)1DocumentslReportslSB 2-9.xls

SB 2-10
SEDIMENT BASIN DESIGN
6/13/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures,
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)1Documents\ReportslSB 2-10.xis
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-10
Total Drainage Area (acres) 1.26
Step 1. Detertnnine peal:flow, Q1,1 for the basin drainage area (_j vex,rig:S.0 )
Q10 (cfs) 5.2
Step 2. Determine an-,-site linnitationns for the sediment pool elevation,emergency
spillway or top of the dani_
Minimum pool elevation (ft) 790
Maximum pool elevation (ft) 793.5
Step 3. Determine basin volumes:
• Compute nnunirmuim`-ohune required(1800 ft-'acre disturbed)
• Specif- sediment cleanout level to be marked on riser (one-half the design
volume referenced to the top of the riser) and sediment storage area to be
cleared after the dam is built.
Disturbed acreage (ac) 1.26
Min Volume (ft) 2268
Sediment cleanout elevation (ft) 791
Sediment Storage Area 600

Y:1Jobs121-004 Mocksville(R210004)1Documents\ReportMSB 2-10.xis SB 2-10
Step 4. Determine area and shape of basum: Page 2
• Check length width ratio (should be 2_1 to 6:1)
• Compute the basin surface area at principal spillway elevation.
• Check the ratio of basin surface area to peak inflow- rate (should be greater
than or equ a.1 to 43-5 ft':'cfs). Employ diversions with additional traps and
basins to reduce area drained.
Determine barrel capacity required for site conditions (rninimuun capacity for Q,
is the ?-year peak ruumoff. Qc.
Length/width ratio 5.7
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft2) 2280
Ratio: basin surface area/Q10 438.461538
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spill -ay discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the 10-y-ear peak flow for the entire watershed of the basin.
• The principal spillway is analyzed for three possible linmitmg flow, types:
Weir flow, Orifice flonv. and Pipe flow. The principal spillway discharge
capacity- is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation. Weir, orifice and
pipe fio,,v may be determined by the following egiuitions:
1. l eir Flow-. Q = CLH'-g
where:
Q = discharge in cubic feet per second (cfs)
C =weir coefficient_ use 3.1 for corrugated metal pipe risers.
L=circumference of the riser um feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
_ Orifice Flow,-: Q = CA(29H)c-=
where:
6/13/22

Q = discharge ui cubic feet per second (cfs) SB 2-10
C =orifice coefficient. use C = 0.6 for corrugated metal pipe risers_ Page 3
A=cross-sectional area of the riser pipe in square feet
g =acceleration due to gravity. 32.2 ft sec'
H =head above riser crest ui feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
2sh n:
3. Pipe Floe: Q = a �1 +�+Itr L J
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity, 32.2 ft'secr
h =head above the centerline of the outlet end of the barrel
Km = coefficient of minor losses, can be assurned to be 1.0 for
most principal spillway systems
L =barrel length in feet
Kr =pipe friction coefficient:
_ 5087n2 (See Table 8A7a for KF values for
di4'3 common size of pipe.)
n =Mannnig-s coefficient of roughness. use n =0.025 for
eomigated metal pipe
n = 0.01- for reinforced concrete pipe
di =inside diameter of the barrel m' inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 tunes that of the barrel. Spilhvay hydraulics are improved by
maximizing wellflour and minial,i�itlg orifice flow- See Table 8.07b for
recommended riser.-barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-10
Inside diameter of barrel, d; (in) 0 6/13/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select trail tiser and barrel dimensions. Use the wei- orifice and pipe flow
equations to determine if the?-yeas peak discharge is passed n°ithcut activating
the emergency-spillwa_i. Determine riser size from Figure 3.0^b. Check the
head and stage requirements. If the design stage is too high, choose lamer Table 8.07b
dimensrcn_and recalculate. as a minimum,set the elevation of the riser at the
same elevation as the top of the sediment pool. A riser height 2 to= times the
barrel diameter is recommended. Select the type cf trash guard
Select a dewatertug device. If a skimmer is used. refer to the manufacturers
dewatering data. or Table 6.64.b
Step 6. Design antiseep collar.
Ensure that antiseep collars are no closer than ? ft from a pipe joint. Collar
must project at least 1 : ft from the pipe. Indicate watertight connections.
Step 7. Design antiflotation block_
Determine the weight of water displaced by the empty- riser. and design a
block with buoyant iveight 1.1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet
Determine discharge velocity fi-om the barrel. Design outlet protection to
assure stable conditions. Riprap placement is usually necessai Y (4ppeiidix
S.06).
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency-spillway.
• Determine the required capacity for the emergency,-spillway as
Qe= Q.o—Qo (Qp a Qz)
• From Table®or Fable®select the width and depth of the outlet. Table 8.07c
depending on soil conditions. In general. the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = CLHI 5

%S'here this option is used the maximum m value of C should be_' 8. L SIB 2-10
is the bottom;width of the spillway at the crest. and H is the depth of 6/13/22
Pow abo.-e the spillway crest in feet. \ote: :�lanninq's channel equatr.-n
should not be used to size the spill;waz;crest_ Hotiwe er.it should be used Page 5
to design the outlet channel below the --pill:wav crest
• The total of the emergency and principle spillway capacities must equal
or exceed the required 10-year pear discharge
• Set the elevation of the crest of the emergency spill;wav a minimum of 1
foot above the crest of the riser.
OPTION 1
Quo 5.2
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
:adjust the spillway alignment so that the control section and cutlet section
are straight_ The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than 200.
Width of control section (ft) 9
Width of entrance (ft) 6
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream fiom the cutlet end of
the control section_to ensure a straight alignment,
• Side slopes should be 3:1.
Step 12. Design spillway exit section-
- Spillway, exit should align with the control section and have the same

SB 2-10
6/13/22
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-10.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 6
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Q. (cfs) 7.00036
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 7.00036 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-1 O
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/13/22
does not create erosive velocities for site conditions. (Star within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment_
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10% greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter.
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a minimum of 2 ft deep).
• Select borrow-site—the emergency spillway cut will provide a significant
amount of fill_
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6 20, Temporary Dive►sions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Temporary Seeding; 6.14,Mulching;and 6.15,
Riprap)-
• Select groundcover for emergency spillway to provide protection for
design flow- velocity and site conditions_ R.iprap stone over geotextue
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
Y:Wobsl21-004 Mocksville(R210004)1DocumentslReportslSB 2-10.xis

SEDIMENT BASIN DESIGN SB 2-11
6/13/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-11.xis
Designed By: PNJ Date: 61;312.2—
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-11
Total Drainage Area (acres) 1
Step 1. Determine peak fio-,\-. (SIC, for the basin drainage area Ovvel,,it-S-03)
Q10 (cfs) 4.13
Step 2. Determine any site limitations for the sediment pool elevation,ermergency
spillway or top of the dam_
Minimum pool elevation (ft) 813
Maximum pool elevation (ft) 816.5
Step 3. Determine basin voluines
• Compute rimuni un volume required(1800 ft' acre disturbed)_
• Specifi• sediment eleanout level to be marked on riser (one-half the design
volume referenced to the top of the riser) and sediment storage area to be
cleared after the darn is built.
Disturbed acreage (ac) 1
Min Volume (ft) 1800
Sediment cleanout elevation (ft) 814
Sediment Storage Area 456

Y:Wobs121-004 Mocksville(R210004)1Documents\Reports\SB 2-11.xis SB 2-1 1
Step 4. Determine area and shape of basal: Page 2
• Check length-width ratio (should be _2:1 to 6:1).
• Compute the basin surface area at principal spillway elevation_
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or egikal to -4� ft,,cfs). Employ diversions with additional traps and
basins to reduce area drained.
Determine barrel capacity required for site conditions (nunimumi capacity for Q`
is the ?-year peak runoff. Q2.
Length/width ratio 4.5
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 1800
Ratio: basin surface area/Q10 435.835351
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spillway discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the 10-year peak flow for the entire watershed of the basin.
• The principal spillway is analyzed for three possible limiting flog;- tz-Ws:
Weir flow Orifice flotN-. and Pipe flow- The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skinuner should be disregarded during this computation. Weir, orifice and
pipe flow may be determined by the followmi g equations:
1. N eir Flow-. Q = CLH—
where:
Q = discharge ui cubic feet per second(efs)
C =weir coefficient. use 3.1 for corrugated metal pipe risers.
L=eircurmference of the riser in feet
H =head above riser crest un feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 3.92699082
Head above riser crest, H (ft) 0.5
Q. (cfs) 4.58172303
?. Orifice Flog: Q = CA(29H)`~
where: 6/13/22

•Q = discharge 111 cubic feet per second (cfs) SB 2-11
C =orifice coefficient, use C =0.6 for corrugated metal pipe risers page 3
A= cross-sectional area of the riser pipe in square feet
g =acceleration due to aravim-, 32.1 ft sec'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 1.22718463
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft) 0.5
Discharge, Qo (cfs) 4.17819874
Riser Diameter (in.) 15
+gh c
;. Pipe Floe: Q = a 1 +K.+K; L J
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity 32.2 ft,'sec'
h =head above the centerline of the outlet end of the barrel
Km = coefficient of minor losses, can be assumed to be 1.0 for
most principal spill-,ay systems
L =barrel length in feet
K�; =pipe friction coefficient:
_ 5087n2 (See Table 8A7a for KF values for
di4,3 commlon size of pipe_)
n =Manuing's coefficient of roughness. use n =0.025 for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are improved by
maximizing weir flow and imnin,izing orifice flow. See Table 8.07b for
recommended riser.barrel proportions_
Barrel diameter (ft) 1.5
Barrel cross-sectional area, a (ft2) 1.8
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft) 1
Minor loss coefficieint, Km 1.0
Barrel length, L (ft) 110

Mannings coeffienct of roughness, n 0.025 SB 2-11
Inside diameter of barrel, d; (in) 18 6/13/22
Pipe friction coefficient, KP 0.06740
Discharge, Qo (cfs) 4.62204394 10.027677
Page 4
RISER
Select trail nisei and barrel dimensions- Use the weir, orifice and pipe fion-
equations to determine if the.2-Near peak discharge is passed without activatui z
The emergency-spillway. Determine riser size from Figure 8.07b. Check the
head and stage requirements. If the design stage is too high. choose larger Table 8.07b
dimensions and recalculate. As a minimum,set the elev aiion of the riser at the
same elevation as the top of the sediment pool. A riser height to= times the
barrel diameter is recommended. Select the tvpe of trash zuar•d-
Select a dewatering device. If a skimmer is used, refer to the manufacturers
de- atenna data. or Table 6.64 b-
Step 6. Design antrseep collar.
Ensure that antrseep collars are no closer than 2 ft from a pipe point Collar
must project at least I_J ft from the pipe- Indicate watertight connections_
Step 7. Design antr8otationblock-
Determine the weight of seater displaced by the empty- riser. and design a
block with buo•,,ant weight 1.1 times the weight of water displaced.
Riser Height 3.5
Weight of water displaced by the empty riser 268.145978
Buoyant weight 294.960575
Step S. Design outlet
Determine discharge velocity from the barrel. Design outlet protection to
assure stable conditions. Ripr-ap placement is usually necessar,- (Appe?jdi_t
S 06)-
Discharge velocity, V (ft/s) 2.61554183 5.67450438
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway.
• Determine the required capacir.for the emergeriv spilla•a,;as
Qe= Q.0—Q� (QC�t Q')
• From Table®or Table=select the width and depth of the outlet. Table 8.07c
depending on soil conditions- In general, the eider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow-
• An acceptable alternative is the use of the weir equation
Q = CLH'_

aVhere this option i_ used, the maximum value of C should be?.3. L SIB 2-11
is the bottom width of the spill,cay at the crest. and H is the depth of 6/13/22
flow above the spillway crest in feet. dote: Nin. ming's channel equation
should not be used to size the spillway crest. However. it should be used Page 5
to design the outlet channel below the ,pdhvav crest
• The total of the emergency and principle spillway capacities must equal
or exceed the required 10-year peak discharge.
• Set the elevation of the crest of the emergency spillway a minimum of 1
foot above the crest of the riser.
OPTION 1
Quo 4.13
QP 4.17819874
Emergency spillway capacity, Qe (cfs) -0.0481987
Qp + Qe 4.13
Does (Qp + Qe) equal or exceed Q10? YES, PROCEED
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight- The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than 2%-
Width of control section (ft)
Width of entrance (ft)
Slope of approach channel (°/t,) 2
Is width of the entrance section 1.5xcontrol section
width? #DIV/0!
Is approach channel >/= 2%? YES, PROCEED
No spillway this basin
Step 11. Spillway control section
• Locate the control section in the spilhyay near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream from the outlet end of
the control section,to ensure a straight alignment.
• Side slopes should be 3:1.
Step 12. Design spillway exit section_
• Spillway exit should align with the control section and have the same

bottom:width and side slopes. SB 2-1 1
• Slope should be sufficient to maintain supercriucai flow.but make sure it 6/13/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10°o greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 15:1 or flatter_
• Determine depth of cutoff trench from site bortngs. It should extend to a
stable,tight soil layer(a tummit m of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specyications: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications. 6.10, Temporary Seeding;6_14,Lfulching;and 6.15,
Ripr•ap).
• Select groundcoe er for emergency spillway to provide protection for
design flow velocity and site conditions. Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
YAJobs121-004 Mocksville(R210004)1Documents\ReportslSB 2-11.xis

SEDIMENT BASIN DESIGN SB 2-12
6/14/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
Y:Wobs121-004 Mocksville(R210004)1Documents1Reports\SB 2-12.xis
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-12
Total Drainage Area (acres) 2.35
Step 1. Determine peak fio-wl 0,011 for the basin drainage area S'.03).
Q10 (cfs) 9.71
Step 2. Deternninne any site linnitationns for the sediment pool elevation,emergency
spillway or top of the damn_
Minimum pool elevation (ft) 781
Maximum pool elevation (ft) 783.5
Step 3. Determitne basin vohunnes:
• Compute mununum volume required(1800 fr.acre disturbed)
• Specify sediment cieanout level to be marked on riser (one-half the design
olunie referenced to the top of the riser) and sediment storage area to be
cleared after the darn is built
Disturbed acreage (ac) 2.35
Min Volume (ft) 4230
Sediment cleanout elevation (ft) 781
Sediment Storage Area 2310

YAJobs121-004 Mocksville(R210004)IDocuments\Reports\SB 2-12.xis SB 2-12
Step 4. Determine area and shape of basin: Page 2
• Check lenQth'width ratio (should be 2:1 to 6:1).
• Compute the basin surface area at principal spillway elevation.
• Check the ratio of basin surface area to peak inflows- rate (should be greater
than or equal to 435 ft',-cfs). Employ diversions with additional traps and
basins to reduce area drained.
Determine barrel capacity required for site conditions (nninimuun capacity for Qy
is the 2-year peak runoff, Qc.
Length/width ratio 3.76
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 4340
Ratio: basin surface area/Q10 446.961895
Is ratio >= 435 ft2/cfs? YES
Step 5. Detemiine the principal spills{ay discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the 1 0-year peak floe for the entire watershed of the basin_
• The principal spillway is analyzed for three possible limiting flox types:
Weir flog, Orifice flocs-_ and Pipe flow-. The principal spiffivay discharge
capacity is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation- Weir, orifice and
pipe flow may be determined by the following equations:
L Weir Flow: Q = CLH'-=
where:
Q =discharge in cubic feet per second(cfs)
C =Weir coefficient. use 3.1 for corrugated metal pipe risers.
L=circumference of the riser in feet
H =head above riser crest iu feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?_ Orifice Flow: Q = CA(2gH)'-4
xvhere: 6/14/22

Q = discharge ui cubic feet per second(cfs) SB 2-12
C =orifice coefficient use C = 0.6 for corrugated metal pipe risers page 3
A= cross-sectional area of the riser pipe ui square feet
g =acceleration due to gravity.. 3?.? ft seer
H =head above riser crest ui feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
?gh
3. Pipe Floe: Q = a I 1 +K_, +Kt L
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g =acceleration due to gravity. 32_2 ft%ser'
h =head above the centerinie of the outlet end of the barrel
K,, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
Kp =pipe friction coefficient:
_ 5087n2 (See Table s.o�a for KP values for
diva common size of pipe.)
n =Manning-s coefficient of roughness, use n =0.025 for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are improved by
maximizing weir flow and g orifice flow. See Table 8.07b for
recommended riser,barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coeiicieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-12
Inside diameter of barrel, d; (in) 0 6/14/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select trail riser and barrel dimensions Use the eir_ orifice and pipe flaw
equations to determine if the 2-year peak discharge is passed:without activating
the emergency spill-way. Determine riser size from Figure 8.07b. Check the
head and stage requirements. If the design stage is too high, choose larger Table 8.07b
dimensions and recalculate. As a minimum,set the elevation of the riser at the
same elevation as the top of the sediment pool- A riser height 2 to D5 times the
barrel diameter is recommended Select the type of trash guard.
Select a dewatering device. If a skimmer is used. refer to the manufacturers
dewatering data, or Table 6.64_b-
Step 6. Design antiseep collar.
Ensure that antiseep collars are no closer than '- ft from a pipe joint Collar
must project at least 1 5 R from the pipe. Indicate watertight connections-
Step 7. Design antiflotation block_
Determine the weight of water displaced by the empty riser, and design a
block with buoyant weight 1.1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet
Determine discharge -velocity from the barrel. Design outlet protection to
assure stable conditions. Riprap placement is usually necessar v (4pperidix
s.o6)-
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway.
• Determine the required capacity for the emergency spillway as
Qe= Q,o—Q': (QF,2 Q2)
• From TableE=or Table®select the width and depth of the outlet_ Table 8.07c
depending on soil conditions- In general_ the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow--
• An acceptable alternative is the use of the weir equation
Q = CLH'5

';.'here this option is used. the maximum value of C should be= 8. L SIB 2-12
is the bottom width of the spillway at the crest_ and H is the depth of 6/14/22
flow above the spillway crest in feet. Note-Manning's channel equation
should not be used to size the spillway crest. However.it should be used Page 5
to design the outlet channel below the spilh4 a� crest.
• The total of the emergency and principle spill -ay capacities must equal
or exceed the required 10-year peak discharge.
• Set the elevation of the crest of the emergeucy spillway a minimum of 1
foot above the crest of the riser.
OPTION 1
Q10 9.71
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section_
Adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance width should be 1_-5 times the Width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than_110.
Width of control section (ft) 15
Width of entrance (ft) 10
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillti-ay control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam
• Peep a level area to extend at least 20 ft upstream fi-om the outlet end of
the control section_to ensure a straight alignment.
• Side slopes should be 3:1.
Step 12. Design spillway exit section.
• Spillwaq exit should align with the control section and have the same

SB 2-12
6/14/22
YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-12.xis
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 10
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Q. (cfs) 11.6673
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 11.6673 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side.slopes. SB 2-12
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/14/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a ini:unitau of 1 fl above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10% greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter.
• Determine depth of cutoff trench from site bonngs_ It should extend to a
stable,tight soil layer(a iulnunum of 2 ft deep).
• Select borrow site—the erne:eeu.y spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design di-,ersions. to protect embankment and spillway
(Practice Standards and Speciftcarions: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Temporary Seeding;614,Mulching;and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions. Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
YAJobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-12.xis

SEDIMENT BASIN DESIGN SB 2-13
6/16/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocumentslReports\SB 2-13.x1s
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-13
Total Drainage Area (acres) 2.8
Step 1. Determine peal-fio-w. 01,— for the basin draMaae area Oppei�di S.03)
Q10 (cfs) 11.54
Step?. Determine ant site limitations for the sediment pool elevation,emergency
spillway or top of the dcinl_
Minimum pool elevation (ft) 750
Maximum pool elevation (ft) 753.5
Step 3. Determine basal volmiles
• Compute llllnlllluni volume required(1800 ft.' acre disturbed)_
• Specifl: sediment cleanout le`-el to be marked on riser (one-half the design
olunle referenced to the top of the riser) gild seciul1e11t Stoiaa area i0 be
cleared after the dale is built
Disturbed acreage (ac) 2.8
Min Volume (ft) 5040
Sediment cleanout elevation (ft) 751
Sediment Storage Area 2912

YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-13AS SB 2-13
Step 4. Determine area and shape of basin: Page 2
• Check length width ratio (should be 3:1 to 6:1).
• Compute the basin surface area at principal spillway elevation.
• Check the ratio of basin surface area to peak inflow rate (should be greater
thaii or equal to 435 ft:,-cfs)- Elnplo-,- diversions with additional traps and
basins to reduce area drained
Determine barrel capacity required for site conditions (minimum capacity for Q_,
is the !-year peak runoff. Q,,.
Length/width ratio 3.15
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft2) 5040
Ratio: basin surface area/Q10 436.741768
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spillway discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the 10-year peak flow for the entire watershed of the basin.
• The principal spiffivay is analyzed for three possible hinitmg flow types:
Weir flow, Orifice flora-. and Pipe flow. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skinntner should be disregarded during this computation Weir, orifice and
pipe flow may be deternuned by the following equations:
1. Weir Flow- Q = C LH'-`
inhere:
Q = discharge in cubic feet per second(cfs)
C =weir coefficient_ use 3.1 for corniQated metal pipe risers.
L=circumference of the riser in feet
H =head above riser crest iu feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?_ Orifice Flow: Q = CA(29H)'
where: 6/16/22

Q = discharge 1r1 cubic feet per second (cfs) SB 2-13
C =orifice coefficient. use C = 0.6 for corrugated metal pipe risers. Page 3
A= cross-sectional area of the riser pipe in square feet
g =acceleration due to gravity. 3 2-2 ft sec'
H =head above riser crest ui feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
ugh
3- Pipe Flow: O = a [l +K.+Kr L
where-.
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity. 32.2 ft'sec2
h =head above the centerline of the outlet end of the barrel
K,,, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway s`-stems
L =barrel length in feet
KP =pipe friction coefficient:
_ 5087n2 (See Table $ 7a for KF values for
dia'' common size of pipe-)
n =Manning's coefficient of roughness. use n =0.025 for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di = inside diameter of the barrel iv inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1-5 times that of the barrel. Spillway hydraulics are improved by
imaximizing weir floe- and minimizing orifice flow- See Table 8.07b for
recommended risevbarrel proportions
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) �. 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-13
Inside diameter of barrel, d; (in) 0 6/16/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select trail riser and barrel dimensions. [;se the weir. orifice and pipe floe-
equations to determine rf the_-:eer peak discharge is passed:i-ithout acts.•arrng
the emergency sptlltva_,-. Determine riser size from Figure 8.07-b Check the
head and stage requirements. If the design stage is too high_ choose larger Table 8.07b
dimensions and recalculate As a minimum.set the elevation of the riser at the
same elevation as the top of the sediment pool. A riser height' to -5 times the
barrel diameter is recommended. Select the type of trash guard.
Select a dewaterin- device. If a skimmer is used. refer to the manufacturers
de;eaterina data. or Table 6.64 b
Step 6. Design antiseep collar.
Ensure that anrr.seep collars are no closer than 2 ft from a pipe joint_ Collar
must project at least 1.5 ft from the pipe. Indicate%vatertiglat connections.
Step 7. Design antiflotation block.
Determine the weight of water displaced by the empty riser. and design a
block with buoyant.-eight 1.1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet_
Determine discharge velociry from the barrel Design outlet pr.-tection to
assure stable conditions. R.iprap placement is usually necessary (_�ppeiidis
5.06).
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway.
• Determine the required capacir;for the emergency spillway as
Qe= Q,o—Q� (QF Q')
• From Table®or Table®select the width and depth of the outlet. Table 8.07c
depending on soil conditions. In general. the udder bottom widths and Table 8.07d
loner slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the u>e of the weir equation
Q = CLH'

'%'here this option i=used, the maximum value of C should be _.8. L SIB 2-13
is the bottom width of the spillr:av at the crest. and H is the depth of 6/16/22
loin above the spillv:a-;crest in feet. Vote- Manning's channel equation
should not be used to size the spillwaT crest. However-it should be used Page 5
to design the outlet channel below the-spillway crest.
• The total of the emergency and principle spillway capacities must equal
cr exceed the requited I 0-Near peak discharge.
• Set the elevation of the crest of the emeraeticv spill,va-'•a minimum of 1
foot above the crest of the riser.
OPTION 1
Quo 11.54
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance width should be 1.? times the width of the control
section with a smooth transition to the:width of the control section. Approach
channel should slope toward the reservoir no less than 10 0
Width of control section (ft) 1.5
Width of entrance (ft) 1.2
Slope of approach channel (%) 3
Is width of the entrance section 1.5xcontrol section
width? NO, REVISE DESIGN
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream fr-am the outlet end of
the control section to ensure a straight alr�?n ent
• Side slopes should be ?:1.
Step 12. Design spillway exit section.
• Spillway exit should align vath the control section and have the same

SB 2-13
6/16/22
YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-13.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 10
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 11.6673
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 11.6673 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-1 3
• Slope should be sufficient to maintain supercritical flow--but make sure it 6/16/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• E-tend the exit channel to a point where the water mat_-be released without
damage.
Step 13. Size the embankment_
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway
• Constructed height should be 10°a greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter_
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a wily nLum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill-
Step 1.1. Erosion control
• Locate and design diversions to protect embankment and spillway
(Py-actice Standards and Specyications: 6.20, Tempora?y Diversions).
• Select surface protection measures to control erosion(P►•actice Standards
and Specifications.- 6.10, Temporary Seeding; 614, Mulching;and 6.15,
Riprap)-
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions. Riprap stone over eeotestile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed-
YAJobs121-004 Mocksville(R210004)1DocumentslReportsM 2-13.xis

SEDIMENT BASIN DESIGN SB 2-14
6/16/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
Y:1Jobs121-004 Mocksville(R210004)1DocumentsMeports\SB 2-14.xis
Designed By: PNJ Date: 6 f16/12 .-
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-14
Total Drainage Area (acres) 1.39
Step 1. Deteriluile peak fio-, , QIc. for the basin drainage area (_4pperrdix S.03)
Q10 (cfs) 5.72
Step 2. Deteniune any site 1i111itations for the sediment pool elevation,emergency
spiUwav or top of the dani_
Minimum pool elevation (ft) 800
Maximum pool elevation (ft) 803.5
Step 3. Deteri11i11e basin volinues:
• Compute nm11ni ntim volt nle required(1800 ft'.acre disturbed)
• Specif-, sediiment cleanout level to be inarked oil riser (one-half the design
ohinie referenced to the top of the riser) and sediment storage area to be
cleared after the drum is built
Disturbed acreage (ac) 1.39
Min Volume (ft) 2502
Sediment cleanout elevation (ft) 801
Sediment Storage Area 1218

Y:%Jobs121-004 Mocksville(R210004)\DocumentslReports\SB 2-14.xis SB 2-14
Step 4. Detertnune area and shape of basil: Page 2
• Check leiiQth'width ratio (should be 2:1 to 6:1).
• Compute the basin surface area at prulcipal spillway elevation_
• Check the ratio of basin surface area to peak itlflow rate (should be greater
than or equal to 435 ft','cfs). Employ- diversions with additional traps and
basins to reduce area drained.
Determine barrel capacity required for site conditions (nunimu m capacity for Q,
is the ,-Fear peak runoff, 02.
Length/width ratio 2.06
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 2520
Ratio: basin surface area/Q10 440.559441
Is ratio >= 435 ft2/cfs? YES
Step 5. Deternine the principal spillway discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the I0-ye-r peak float= for the entire watershed of the basal.
• The principal spillway is analyzed for three possible hmrtung flout. types:
Weir floxv. Orifice flow. and Pipe flout- The pruicipal spillway discharge
capacity is the Smallest of these three float- rates. Discharges through�a
skinner should be disregarded during this computation. Weir. orifice and
pipe flout may be deternuned by the followmi g equations:
L l eir Flout-: Q = CLH'-�
where:
Q = discharge ui cubic feet per second(cfs)
C =weir coefficient. use 3.1 for corrugated metal pipe risers.
L=circuunference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
Qw (cfs) 0
?. Orifice Flow: Q = CA(2gHf
where:
6/16/22

Q = discharge ui cubic feet per second (cfs) SB 2-14
C =orifice coefficient- use C = 0.6 for corrugated metal pipe risers Page 3
A= cross-sectional area of the riser pipe in square feet
g =acceleration due to gravity- 32.21 ft,sec'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
3_ Pipe FloN%: Q = a [1 _I +Kt L
where:
Q = discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity. 32.2 fuser'
h =head above the centerline of the outlet end of the barrel
K,,, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
K�; =pipe friction coefficient:
5087n= (See Table El for KP values for
dia.a common size of pipe.)
n =Nfannillg-s coefficient of roughness. use n =0.025 for
comigated metal pipe
n = 0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 15 times that of the barrel. Spillway hydraulics are improved by
maximizing weir flow and minimizing orifice flow. See Table S 07b for
reconunended riser.barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-14
Inside diameter of barrel, d; (in) 0 6/16/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select trail riser and barrel dimensions. Use the wei<. orifice and pipe f'.lx
equations to determine if the_2-1.earpeakdischarye is passed without acti,-ating
The emergency,• spill-ray. Determine riser size from Figure 8.07b_ Check the
head and stage requirements. If the design itape i too high, choose larger Table 8.07b
dimensions and recalculate. As a minimum,set the elevation of the riser at the
same elevation as the top of the sediment pool. A riser height to 5 times the
barrel diameter is recommended. Select the type of trash guard
Select a dewaterin? device. If a skimpier is used. refer to the manufacturers
dewaterina data. or Table 6 64.b
Step 6. Design antiseep collar.
Ensure that antiseep collars are no closer than ' ft from a pipe joint_ Cellar
must project at least 1 5 ft from the pipe. Indicate watertight connections.
Step 7. Design antiflotation block.
Determine the weight of water displaced by the empty riser, and design a
block with buoyant weight 1.1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step 8. Design outlet
Determine discharge velocity from the barrel. Design outlet protection to
assure stable conditions. Riprap placement is usually necessary (-4ppertdix
S 06-)
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway.
• Determine the required capacity for the emergeency spillway as
Qe= Q.0—QQ IQF> Q'7
• From Tabl =or Table®select the width and depth of the cutlet. Table 8.07C
depending on soil conditions_ In general. the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = CLH'`

Where this option is used. the maximum c-alue of C should be ?3. L SIB2-14
is the bottom-width of the spillway-at the crest. and H is the depth of 6/16/22
flogs above the spills.-a-;.crest in feet. dote: Manning's channel equate-an
should not be used to size the spillway crest. Ho:t e-:er.it should be used Page 5
to design the outlet channel below the spAl,cway crest.
• The total of the emergency and principle spillway capacities must equal
or exceed the required 10-year peak discharge.
• Set the elevation of the crest of the emergency spi11, av a mimmtun of i
foot above the crest of the riser.
OPTION 1
Q10 5.72
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance width should be 1.5 times the width of the control
section with a smooth transition to the:width of the control section. Approach
channel should slope toward the reservoir no less than 2°o.
Width of control section (ft) 1.5
Width of entrance (ft) 1.2
Slope of approach channel (%) 3
Is width of the entrance section 1.5xcontrol section
width? NO, REVISE DESIGN
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream from the outlet end of
the control section, to ensure a straight alignment.
• Side slopes should be 3:1.
Step 12. Design spillway exit section.
• Spillway exit should alien with the control section and have the same

SB 2-14
6/16/22
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-14.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 8
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 9.33381
#DIV/0!
#DIV/O!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 9.33381 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-14
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/16/22
does act create erosive velocities for site conditicns (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the`rater may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of I ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be IU°•o greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter.
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a minimum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specyications: 6.20, Temporaty Diversions).
• Select surface protection measures to control erosion(Practice Standards
and.Specifications.- 6.10, Temporary Seeding; 6.14, fulching,-and 6.15,
piprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions. Riprap stone over geotexhle
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 1-9. Safety.
• Construct a fence and install warning signs as needed.
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-14.x1s

SEDIMENT BASIN DESIGN SB 2-15
8/25/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocuments\ReportMSB 2-15.xis
Designed By: PNJ Date: BIZSILL
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-15
Total Drainage Area (acres) 1.24
Step 1. Determine peak flow, Q,., for the basin drainage area S.O i)
Q1O (cfs) 5.11
Step 2. Determine any site limitations for the sediment pool elevation,eimergenqv
spillway or top of the damn_
Minimum pool elevation (ft) 785
Maximum pool elevation (ft) 788.5
Step 3. Determine basin volumes:
• Compute muzumum Volume required(1800 ft':acre disturbed)_
• Specify sediment cleanout level to be marked on riser (one-half the design
volume referenced to the top of the riser) and sediment storage area to be
cleared after the dam is built_
Disturbed acreage (ac) 1.24
Min Volume (ft) 2232
Sediment cleanout elevation (ft) 786
Sediment Storage Area 1026

Y:1Jobs121-004 Mocksville(R210004)1DocumentslReportMSB 2-15.xis SB 2-15
Step 4. Determine area and shape of basui: Page 2
• Check length-width ratio (should be 2 A to 6:1)-
• Compute the basin surface area at principal spillway elevation.
• Check the ratio of basin surface area to peak icnflow-rate (should be greater
than or equal to 43 5 ft',-'cfs)- Employ diversions with additional traps and
basins to reduce area drained-
Determine barrel capacity required for site conditions (minimum capacity for Qr,
is the ,-year peak runoff, Q.,-
Length/width ratio 2.06
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft2) 2244
Ratio: basin surface area/Q10 439.138943
Is ratio >= 435 ft2/cfs? YES
Step 5. Deternune the principal spilhw-ay discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the 10-year peak floe-for the entire watershed of the basin.
• The principal spillway is anal-y2ed for three possible limiting flow- types:
I'eir flow; Orifice flow.. and Pipe flow. The principal spillway discharge
capacity is the smallest of these three flow- rates. Discharges through a
skimmer should be disregarded during this computation. Weir, orifice and
pipe flow-may be determined by the follouti-ing equations:
1- Weir Flow-: Q = CLH'-5
where:
Q=discharge in cubic feet per second(cfs)
C =weir coefficient, use 3.1 for corrugated metal pipe risers.
L= circumference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
Qom, (cfs) 0
?. Orifice Flow: Q = CA(2gH)°
where: 8/25/22

_ Q = discharge in cubic feet per second(cfs) SB 2-15
C = orifice coefficient. use C= 0.6 for corrugated metal pipe risers Page 3
A= cross-sectional area of the riser pipe ui square feet
g = acceleration due to gravity. 32.2 ft.sec-'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
Igh c
i. Pipe Flow: Q = a [1 +I,:=+Kr L
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g =acceleration due to gravity_ 3?.? ft'sec-
h =head above the centerline of the outlet end of the barrel
K,,, = coefficient of mirror losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
K, =pipe friction coefficient:
_ 5087n2 (See Table 8 07a for KR values for
64 3 common size of pipe_)
n =Maiming's coefficient of roiiahness, use n =0.025 for
comigated metal pipe
n =0.015 for reinforced concrete pipe
di =inside diameter of the barrel ui inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are improved by
niaximizing weir flow and minir21;7;ng orifice flow. See Table 8.07b for
recommended riser.-barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-15
Inside diameter of barrel, d; (in) 0 8/25/22
Pipe friction coefficient, KP #DIV/O!
Discharge, Qo (cfs) #DIV/O! 0
Page 4
RISER
Select trail riser and barrel dimensions. Use the weir. orifice and pipe flow
equations to determine if the_'-year peak discharge is passed without activating
the emergence; spillway Determine riser size from Figure S.O,b. Check the
head and stage requirements. If the design stage is too high, choose larger Table 8.07b
dimensions and recalculate. As a minimum_set the elevation of the rises at the
same elevation as the top of the sediment pool_ A riser height' to 5 times the
barrel diameter is recommended. Select the type of trash Guard.
Select a dewatering device. If a skimmer is used, refer to the manufacturers
de.eaterine data, or Table 6.64.b.
Step 6. Design antiseep collar.
Ensure that anti.seep collars are no closer than ? ft from a pipe joint_ Collar
must project at least 1 5 ft from the pipe. Indicate ivatertight connections.
Step ?. Design antiflotatron block_
Determine the weight of water displaced by the empty riser. and design a
block with buoyant Freight 1.1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet_
Determine discharge velocity, from the barrel. Design outlet protection to
assure stable conditions_ Riprap placement is usually-necessar-y (.4ppetzdi-r
S.O6)_
Discharge velocity, V (ft/s) #DIV/O! #DIV/O!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergence spillway.
• Determine the required capacirr for the emergency spiffivay as
QE= Q,o-Q" (Qt,? GO
• From Table=or Table®select the vndth and depth of the outlet. Table 8.07c
depending on soil conditions. In general. the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
floc°
• An acceptable alternative is the use of the weir equation
Q = CLH'

'X'here this option is used the maxinitim value of L should be 2 S. L SB 2-15
is the bottom width of the spill;:ay at the crest. and H is the depth of 8/25/22
flow above the spillr,-a_, crest in feet dote: Manning"s channel equation
should not be used to size the spfflwat;crest Ho.z,e-:er.it:•hould be used Page 5
to desizn the outlet channel below-the spill:-,--ay crest
• The total of the emergenc}' and principle spfflwa°r capacities must equal
or exceed the requited 10-year peak discharge
• Set the elevation of the crest of the emergent:- spillway a minimum of 1
foot above the crest of the riser.
OPTION 1
Q10 5.11
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spilhvay alignment so that the control section and outlet section
are straight_ The entrance width should be 1 5 times the :width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than?"o
Width of control section (ft) 9
Width of entrance (ft) 6
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam
• Keep a level area to extend at least?0 ft upstream from the outlet end of
the control section_to ensure a straight alignment_
• Side slopes should be 3:1.
Step 12. Design spillway exit section_
• Spillway exit should alien with the control section and have the same

SB 2-15
8/25/22
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-15.xis
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 6
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 7.00036
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 7.00036 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-15
• Slope should be sufficient to maintain supercritical flow-,but make sure it 8/25/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment_
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10% greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5A or flatter.
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a tuimmum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Temporary Seeding; 6.14,!Lfulching;and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
YAJobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-15.xis

SEDIMENT BASIN DESIGN SB 2-16
6/20/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
Y:1Jobs121-004 Mocksville(R210004)1Documents\ReportslSB 2-16.xis
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-16
Total Drainage Area (acres) 0.86
Step 1. Deterlll1lie peak flo-w. ��1��.. for the basin draulage area (Avve7.dix S.OS)
Q10 (cfs) 3.53
Step ?. Determine ails site linutations for the sediment pool elevation,emergency
spill vav or top of the dam_
Minimum pool elevation (ft) 798
Maximum pool elevation (ft) 801.5
Step 3. Deternune basill volumes:
• Compute inuinllum voluiue required(1800 ft' acre disturbe4)
• Speclf<- sediment cleallout level to be marked on riser (one-half Elie design
volmne referenced to the top of the riser) and Sedilllellt storage area to be
cleared after the dale is built
Disturbed acreage (ac) 0.86
Min Volume (ft3) 1548
Sediment cleanout elevation (ft) 799
Sediment Storage Area 559

Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-16AS SB 2-16
Step 4. Determine area and shape of basin: Page 2
• Check length width ratio (should be 2:1 to 6:1}.
• Compute the basin surface area at pruiclpal spillway elevation.
• Check the ratio of basin surface area to peak uiflouu rate (should be greater
than or equal to 435 ft-refs). Employ diversions with additional traps and
basins to reduce area drained_
Determine barrel capacity required for site conditions (minimum capacity"for Q-,
is the -year peak runoff, Q-
Length/width ratio 2.11
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 1539
Ratio: basin surface area/Q10 435.977337
Is ratio >= 435 ft2/cfs? YES
Step -. Determine the principal spillway discharge capacrq
• The combined capacities of the principal and emergency- spillways must be
at least the 10-rear peak flow for the entire watershed of the basin.
• The principal spilh;-av is analyzed for three possible limiting flow types:
'Weir flocs•, Orifice flow. and Pipe flow- The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skunmer should be disregarded during. this computation. � eir, orifice and
pipe floe-may be determined by the followm' c, equations.
1. N eir Flo«-: 0 = CLH'-`
where-
0 = discharge in cubic feet per second(cfs)
C =weir coefficient_ use 3.1 for eorr,,ated metal pipe risers.
L=circumference of the riser un feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?. Orifice Flow: Q = CA(2gH),-=
where:
6/17/22

Q = discharge in cubic feet per second (;cfs) SB 2-16
C = orifice coefficient_ use C = 0.6 for comwated metal pipe risers Page 3
A= cross-sectional area of the riser pipe in square feet
g = acceleration due to gravity- 32_2 ft,sec=
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
,gh
i. Pipe Flow: (� = cl i +Iit L
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel ui square feet
g = acceleration due to gravity. i? 2 ft see'
h =head above the centerline of the outlet end of the barrel
Km = coefficient of nunor losses_ can be assumed to be 1.0 for
most principal spillway systems
L =barrel length iu feet
K, =pipe friction coefficient:
_ 5087n2 (See Table 8.o7a for KP values for
diva common size of pipe.)
n =Manning s coefficient of roughness. use n = 0.025 for
corrugated metal pipe
n = 0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.-"-) times that of the barrel. Spillway hydraulics are improved by
Maximizing weir flow and n,;,,;n„Zing orifice flow_ See Table 8.0`,b for
reconuiiended riser:'barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-16
Inside diameter of barrel, d; (in) 0 6/17/22
Pipe friction coefficient, KP #DIV/0!
Discharge, % (cfs) #DIV/0! 0
Page 4
RISER
Select :tail riser and barrel dimen-Adis Use the v,-eii. orifice and pipe foss
equatio m to determine if the-2-_:ear peak discharge is passed without actr.atinL7
the emergency spillway. Determine ri_et size from Figure 8.07b Check the
head and stage requirements. If the design stage is too high. choose larger Table 8.07b
dimension.:and recalculate As a minimiuu.set the ele•:aticn of the riser at the
same ele.•atton as the top of the sediment pool_ Ariser height _2 ro ` times the
barrel diametet is recommended. Select the icpe of trash mrard
Select a dev.-aterm- device. If a skimmer is used. refet to the manufacturer,
de,.vateting data, of Table 6 64 b
Step 6. Design antiseep collar.
Ensure that antiseep collars are no closer than '_ ft from a pipe Joint. Collar
must project at least 1_= ft from the pipe. Indicate watertight connecCons.
Step 7. Design autiflotation block_
Determine the weight of water displaced by the empty riser. and design a
block with buo-:ant weight 1.1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0'
Buoyant weight 0
Step S. Design outlet
Determine discharge -velocity from the barrel. Design outlet protection to
assure stable conditions. Riprap placement is usuall V necessat_r idevendix
S 06j.
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9, Design emergency spillway.
• Determine the required capacir;for the emergenc-�spills-;ay as
QE — c—Ct (Q�.—' C')
• From Table=of T able®select the width and depth of the outlet Table 8.07e
depending on soil conditions. In general_ the ;cider bottom widths and Table 8.07d
lo;cer slopes are preferred to minimize exit velocities at supercritical
flow
• �n acceptable alternative is the use of the weir equation
0 = CLHI`

';here-,his option 1= Used, the maximum value of C.. shoLld be_ S. L SB 2-16
is the bottom width of the spllly a at the crest. and H 1s the depth of 6/17/22
fkow above the crest in fee:_ Note:Manning s channel equation
should not be used to size the spillway crest_ Howe er. it should be used Page 5
-:
TO design the outlet channel bek)v.- the spillwa-:rest.
• The fatal of the emergency and principle spilhra capacities must equal
et exceed the required lU ear peak discharge
• Set the elevation of the west of the emergency spill,.va a minimum of 1
foot above the crest of the riser.
OPTION 1
Quo 3.53
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway;approach section.
Adjust the spill:l'a_r alignment so that the control section and outlet section
are straight. The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than_°o.
Width of control section (ft) 6
Width of entrance (ft) 4
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spilhva?r near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream from the outlet end of
the control section_to ensure a straight alignment.
• Side slopes should be 3:1
Step 12. Design spillway exit section.
• Spillway exit should align with the control section and have the same

SB 2-16
6/17/22
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-16.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 4
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 4.6669
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 4.6669 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-16
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/17/22
does not create erosive velocities for site conditions (Star within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10% greater than the design to allow for
settlement_
• Base top width on the design height.
• Set side slopes-1.5:1 or flatter.
• Determine depth of cutoff trench from site borings_ It should extend to a
stable.tight soil layer(a minnuum of 2 ft deep).
• Select borrow site-the emergency spillway cut will provide a significant
amount of fill_
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6?0, Tempora►y Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Temporary Seeding; 614, lfulching;and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils_
Step 1 . Safety.
• Construct a fence and install warning signs as needed.
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-16.xis

SEDIMENT BASIN DESIGN SB 2-17
8/25/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)1Documents1Reports1SB 2-17.xis
Designed By: PNJ Date: e/23/Z Z
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-17
Total Drainage Area (acres) 0.94
Step 1. Determine peak flow, Q,.1 for the basin drainage area (_-tppeiidix S.0 )
Q10 (cfs) 3.71
Step 2. Determine any site limitations for the sediment pool elevation,emergency
spillway or top of the dam_
Minimum pool elevation (ft) 777
Maximum pool elevation (ft) 780.5
Step 3. Determine basin vohunes:
• Compute ininimnum volume required(1600 fr',acre disturbed)
• Spec sediment eleanout level to be marked on riser (one-half the design
s-ohtnie referenced to the top of the riser) and sediment storage area to be
cleared after the dam is built.
Disturbed acreage (ac) 0.88
Min Volume (ft) 1584
Sediment cleanout elevation (ft) 778
Sediment Storage Area 616

Y:IJobs121-004 Mocksville(R210004)IDocuments\Reports1SB 2-17.xis SB 2-17
Step 4. Detennune area and shape of basin_ Page 2
• Check length tim idth ratio (should be _11 to 6:1).
• Compute the basin surface area at principal spillway elevation.
• Check the ratio of basin surface area to peak uiflow rate (Should be greater
than or equal to 435 ft':cfs). Employ diversions with additional traps and
basins to reduce area drained.
Determine barrel capacity required for site conditions (minimum capacity for Q.
is the 2-gear peak runoff. Q.,.
Length/width ratio 2.07
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 1624
Ratio: basin surface area/Q10 437.735849
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spillway discharge capacity
• The combumed capacities of the principal and emergency spillways must be
at least the 10-year peak flow for the entire watershed of the basin_
• The principal spill ay is analyzed for three possible linuting flow types:
Weir flow; Orifice flow. and Pipe floe.-. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation_ ��eir. orifice and
pipe flow may be determined by the followumg equations:
1_ 'Weir Flow: Q = C LH'
where:
Q=discharge in cubic feet per second(cfs)
C =weir coefficient, use 3.1 for corrugated metal pipe risers.
L=circumference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?_ Orifice Flow: Q = CA(2gH)c";
where: 8/25/22

y�•Q = discharge ui cubic feet per second (cfs) SB 2-17
C =orifice coefficient. use C = 0.6 for corrugated metal pipe risers Page 3
A=cross-sectional area of the riser pipe u1 square feet
g =acceleration due to gravit-y, 32.2 ft:sec'
H =head above riser crest in feet
Orifice coefficient, Qo 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
�g n_
I- Pipe Floti�,: Q = a [l +K,+K L `
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g =acceleration due to gravity, 3—2 ft'sec2
h =head above the centerline of the outlet end of the barrel
Kn, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
K9 =pipe friction coefficient:
_ 5087n2 (See Table for KR values for
di4l common size of pipe.)
n =Nia nnmg's coefficient of roughness. use n =0.025 for
corrugated metal pipe
n = 0.015 for reinforced concrete pipe
di =inside diameter of the barrel un inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are unproved by
maximizing weir flow and mininii ing orifice flow- See Table 8.07b for
recommended riser.'barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-17
Inside diameter of barrel, d; (in) 0 8/25/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select trail riser and barrel dimensions. Use the weir. orifice and pipe flow
equations to determine if the 2%ear peak discharge is passed without actisatincr
the emergency spillway. Determine riser size from Figure 8.07"b. Check the
head and stage requirements. If the design stage is too high, choose lamer Table 8.07b
dimensions and recalculate. As a minimum_set the elevation of the riser at the
same elevation as the top of the sediment pool. Ari.ser height?to 5 times the
barrel diameter is recommended. Select the type of trash guard-
Select a dewatering device. If a skimmer is used. refer to the manufacturers
dewatetine data. or Table 6-64-b.
Step 6. Design antiseep collar.
Ensure that antiseep collar are no closer than , ft from a pipe joint. Collar
must project at least 1.5 ft from the pipe. Indicate watertight connections.
Step 7. Design antiflotation block-
Determine the weight of neater displaced by the empty riser. and design a
block with buoyant weight 1.1 times the weight of water-displaced.
Riser Height L,`,�
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet
Determine discharge velocity from the barrel_ Design outlet protection to
assure stable conditions. Riprap placement is usually necessary (Appendix
3 Q6)-
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway.
• Determine the required capacity for the emergency spillway as
Qe= Q-p—Op (Qp-� Q_)
• From Table®or Table®select the width and depth of the cutlet. Table 8.07c
depending on soil conditions_ In general_ the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize esit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = CLH'

'%%'here this option is used. the maximum value of C should be 2 8. L SB 2-17
is the bottom width of the spillway at the crest_ and H is the depth of 8/25/22
flow above the spillwa-;crest in feet. Note: Manninz's channel equation
should not be used to size the spillw-a-y crest. However. it should be used Page 5
to design the outlet channel below-the spillway crest
• The total of the emergent y and principle spillway capacities must equal
or exceed the requited 10-year peak discharge.
• Set the elevation of the crest of the emergency spillway a minimum of 1
foot above the crest of the riser.
OPTION 1
Q10 3.71
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight. The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reser-voir no less than 2100.
Width of control section (ft) 6
Width of entrance (ft) 4
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream from the cutlet end of
the control section_to ensure a straight alignment_
• Side slopes should be 3:1.
Step 12. Design spillway exit section_
• Spillway exit should alien with the control section and have the same

SB 2-17
8/25/22
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-17.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 4
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Q. (cfs) 4.6669
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 4.6669 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-17
• Slope should be sufficient to maintain supercritical flout-,but make sure it 8/25/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10°6 greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter_
• Determine depth of cutoff trench from site borings. It should extend to a
stable.tight soil layer(a anniunim of 2 ft deep).
• Select borrow site—the eme:een:y spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications.- 6.10, Temporary Seeding;6.14, Mulching;and 6.1 J,
Riprap)-
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions. Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
Y:Wobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-17.xis

SB 2-18
SEDIMENT BASIN DESIGN
6/22/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
Y:1Jobs121-004 Mocksville(R210004)1DocumentslReports\SB 2-18.x1s
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-18
Total Drainage Area (acres) 0.87
Step 1. Deternune Peak- flow. Uic- for The basin dramaQe area (A,?Dendix S.T 3)_
Q1O (cfs) 3.58
Step 2. Detemmne any site linutations for the sedimentpool elevation,emergency,
spill,,,,-aN-or top of the dain
Minimum pool elevation (ft) 777
Maximum pool elevation (ft) 781.5
Step 3. Determine basin voltinies:
• Compute niuurnum volinue required 1800 ft- acre disturbed)
• Specifi- sediment cleanout level to be marked on riser (one-half the design
t oltune referenced to the top of the riser) and sediment storage area to be
cleared after the dam is built
Disturbed acreage (ac) 0.87
Min Volume (ft) 1566
Sediment cleanout elevation (ft) 778
Sediment Storage Area 572

Y:1Jobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-18.xis SB 2-1 8
Step 4. Derernune area and shape of basin: Page 2
• Check length width ratio (should be :1 to 6A)
• Compute the basin 'iurface area at principal spillway elevation.
• Check the ratio of basin surface :area to peal- inflow rate (.should be greater
than or equal to 43-5 ft',cfs)_ Employ diversions with additional traps and
basins to reduce area drained
Determine barrel capacity required for site conditions (nninimuin capacity for 0,
is the ,-year peak nanoff_ Q,.
Length/width ratio 2.15
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 1566
Ratio: basin surface area/Q10 437.430168
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spillway discharge capacity
• The combined capacities of the principal and emergency spillways mast be
at least the 10-x ear peak flow for the entire watershed of the basin.
• The principal spillway.- is analyzed for three possible limiting floc types:
«'eir flow. Orifice flow. and Pipe floxv. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation. Weir. orifice and
pipe floe- may be determined by the following equations:
1. 1A.eir Flow: Q = CLH'-=
where:
Q = discharge in cubic feet per second(cfs)
C =weir coefficient. use 3.1 for corrwmted metal pipe risers.
L = circuiinference of the riser in feet
H =head above riser crest ui feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?. Orifice Flow-- Q = CA (29H)=
where:
6/20/22

Y` 0 = discharge 111 cubic feet per second (cfs) SB 2-18
C = orifice coefficient_ use C = 0.6 for corrugated metal pipe risers. Page 3
A= cross-Sectional area of the riser pipe in square feet
g = acceleration due to gravity. 3`.2 ft sec'
H = head above riser crest ill feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
'gh
3. Pipe Flog\-: Q = a [1 -1x+K;r L
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity- 32.2 ft sec-
h =head above the centerline of the outlet end of the barrel
K,,, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
K.r =pipe friction coefficient:
_ 5087n2 (See Table FFa for KF values for
di4'' common size of pipe.)
n =Mann- lg s coefficient of roughness_ use n =0.01-5 for
corrugated metal pipe
n = 0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1_5 times that of the barrel. Spillway hydraulics are improved by
maxiiuizmg weir flow and lnluli,n;7ing orifice flow. See Table 8.0 b for
recommended riser:'barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-18
Inside diameter of barrel, d; (in) 0 6/20/22
Pipe friction coefficient, Kp #DIV/O!
Discharge, Qo (cfs) #DIV/O! 0
Page 4
RISER
Select trail tiser and barrel dimen.-Acas Use the v:ei . orifice and pipe flow
equations to determine if the' ear peat:discharge is passed w,.theut actn"Itrng
The emergenc_;spill-.ra.:. Determine riser size from Ftguie 8.07-b. Check the
head and stage requirements. If the design •:twee is too high. choose larger Table 8.07b
dimensions and recalculate Asa minimum_set the ele:-anon of the riser at the
same ele•:ation as the tap of the sediment pool. A riser height-' to= times the
barrel diameter cs recommended Select the t.;Pe of trash ward
Select a det.-aterrng device If a skimmer is used. refer to the manufacttuers
de•.saterina data, or Table 6 64 b
Step 6. Design antrseep collar.
Ensure that anrrseep collars are no closer than 2 ft from a pipe Joint. Collar
must project at least 1 5 ft from the pipe. Indicate watertight connections_
Step 7. Design antrfiotation block
Determine the weight of :rater displaced b-, the emptz; riser, and design a
block with buoyant weight 1.1 tunes the;eight of ivater displaced.
Riser Height Pr
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step 8. Design outlet
Determine discharge ti elocin- from the barrel Design outlet protection to
assure stable conditions. Riprap placement is usually necessary ( Rpe?idis
S 06
Discharge velocity, V (ft/s) #DIV/O! #DIV/O!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway.
• Determine the required capacity f.a th/e�eme/rsrenc.;spillwa}-as
• From Table=or Table®select the width and depth of the cutler. Table 8.07c
depending on soil conditions In general. the wider bottom widths and Table 8.07d
lower slope: are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the wen equation
Q = CLH'

':%liere this option i_ used the rnaxinium value of C should be 2 S L SB 2-18
is tile'aottoni width of the sp:llr:a:at the crest. and H is the depth of 6/20/22
to-n-above tie cp,1h a} crest in fee-. \cte: Manning s channel equarnon
should not be used to size the spill+. a::crest. Ho�s-e-:er.it should be used Page 5
to desr.Lyn the outlet channel belrw the -.ptlh,-a_:crest
• The total of the emergency and prmctple spill.va: capacities must equal
c:exceed the required 10-sear peak discharge.
• Set the elevation of the crest of the emergency pliPaay a minrmmu of 1
foot abcs e the crest of the riser.
OPTION 1
Quo 3.58
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
:adjust the spillway alignment so that the control section and outlet section
are straight_ The enhance width should be 1 5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope to:u-ard the reservoir no less than
Width of control section (ft) 6
Width of entrance (ft) 4
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spilhva_; near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream ftorn the cutlet end of
the control section_ to ensure a straight alignment_
• Side slopes should be ?:1.
Step 12. Design spills;-ay exit section.
• Spillway exit should align with the control section and have the same

SB 2-18
6/20/22
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-18.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 4
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Q. (cfs) 4.6669
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 4.6669 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-18
• Slope should be sufficient to maintain supercritical flow-but make sure it 6/20/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway-
• Constructed height should be 10°o greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 1.5:1 or flatter.
• Determine depth of cutoff trench from site bonngs_ It should extend to a
stable.tight soil layer(a minimum of?ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specificarions: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specij9cations. 6.10, Temporati�Seeding; 6.14, liulching,-and 6.15,
Ripr•ap).
• Select groundcover for emergency spill.av to provide protection for
design flow velocity and site conditions_ Riprap stone over geotestrle
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
Y:kJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-18.xis

SEDIMENT BASIN DESIGN SB 2-18A
6/22/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-18A.xls
Designed By: PNJ Date: 6/22/7_Z
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-18A
Total Drainage Area (acres) 1.35
Step 1. Deternune peal-fio x_ 0 . for the basin drainage area S.0-1).
Q10 (cfs) 5.58
Step ?. Deternune any site limitations for the sediment pool elevation,emergency
spillway or top of the ckun_
Minimum pool elevation (ft) 765
Maximum pool elevation (ft) 768.5
Step 3. DeTerinuie basin voltinnes:
• Compute inuinuunn volunne required(1 SOO ft- acre disturbed)
• Specifi sediment cleanout le`-el to be marked on riser (one-half the deslall
t ollulle referenced to the top of the riser) and sediment storage area to be
cleared after The dani is built.
Disturbed acreage (ac) 1.35
Min Volume (ft) 2430
Sediment cleanout elevation (ft) 766
Sediment Storage Area 714

YAJobs121-004 Mocksville(R210004)IDocuments\ReportslSB 2-18A.xls SB 2-18A
Step 4. Determine area and shape of basin-_ Page 2
• Check length width ratio (should be 2:1 to 6:1)
• Compute the basin surface area at principal spillwa-,-elevation.
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or egiml to 435 ft' cfs)_ Eimplo-%- diversions with additional traps and
basins to reduce area drained.
Determine barrel capacity required for site conditions (minimum capacity for C,,
is the 2-`•ear peak nuioff. Q,,.
Length/width ratio 5.52
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 2436
Ratio: basin surface area/Q10 436.55914
Is ratio >= 435 ft2/cfs? YES
Step -5. Determine the principal spilhi-ay discharge eapacih-.
• The combined capacities of the principal and emergency spillways must be
at least the 10-rear peak floe-for the entire watershed of the basin.
• The principal spillway is analyzed for three possible linuimg flog- types:
Weir flout, Orifice flow. and Pipe flow. The principal spillway discharge
capacity is the smallest of these three flow rates_ Discharges through a
ski nuner should be disregarded during this computation N eir. orifice and
pipe flog-may be determined by the follo%vmi g equations:
1_ weir Flog: Q = CLH'-
where:
Q = discharge in cubic feet per second(cfs)
C =weir coefficient_ use 3.1 for corrugated metal pipe risers_
L= circumference of the riser in feet
H =head above riser-crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?. Orifice Flow: Q = CA (2gH)'
where:
6/20/22

Y- 0 = discharge uu cubic feet per second (cfs) SB 2-18A
C =orifice coefficient. use C = 0.6 for corrugated metal pipe risers Page 3
A= cross-sectional area of the riser pipe in square feet
g = acceleration due to gravity. i2.1 ft sec
H =head above riser crest In feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
,gh 1.
1 Pipe Flow- 0 = a [1 = K:,_+K, L
where:
Q = discharge ill cubic feet per second(cfs)
cn, =cross-sectional area of the barrel In square feet
g = acceleration due to Qraviry- 31.1 ft, sec
h =head above the centerline of the outlet end of the barrel
Km, = coefficient of minor losses. can be assumed to be 1.0 for
most principal spillw,ay systems
L =barrel length in feet
Kr =pipe friction coefficient:
_ 5037n (See TableEa for KF v,-dues for
dl4'a common size of pipe_)
n =Manning-s coefficient of roughness_ use n =0.015 for
comlgated metal pipe
n = 0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least L-5 times that of the barrel. Spillway hydraulics are improved by
maxilnizina weir flow and nurunuzing orifice fioiA. See Table 9.0?b for
recommended riser-barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-18A
Inside diameter of barrel, d; (in) 0 6/20/22
Pipe friction coefficient, Kp #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select trail riser and barrel dimen_ions tine the wei:. orifice and pipe Row
equations to determine if the=-veai peak discharge is passed'. -thcut aci1-.-atrng
The emergency spillzva_,. Determine riser size from FiEru e 3.07b Check the
head and stage requirements. I:the design stage is too high. choose larger Table 8.07b
dimensions and recalculate Asa minimum.set the elevation of the riser at the
same elevation as the top of the sediment pool. A riser height-' to 5 times the
barrel diameter is recommended. Select the t-;oe of trash-bard_
Select a dev.-atering device. If a shimmer is used. refer to the manufacturers
deuaterimg data. or Table 6.64.b
Step 6. Design antiseep collar.
Ensure that antiseep cellars are no closer than 2 ft from a pipe joint_ Collar
must project at least 1.: ft from the pipe Indicate watertight connections.
Step -. Design anttflotation block_
Determine the «-eight of water displaced by the empty riser. and design a
block with buoyant weieht 1 1 times the Freight of water displaced.
Riser Height OW
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet
Determine discharge velocit,,, from the barrel. Design outlet protection to
assure stable conditions_ Riprap placement is usually uecessar Y (-�ppendis
S 06).
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency-spillway
• Determine the required capacir;for the emergency spillway as
QE= Q_o—Qy (OF.> Q')
• From Tabl =or Table®select the width and depth of the outlet. Table 8.07c
depending on soil conditions. In general. the wider bottom widths and Table 8.07d
lotcei slopes• are preferred to minimize exit velocities at supercritical
fl otv
• An acceptable alternative is the use of the weir equation
Q = CLH'`

't:`here this option is used.the maxitnuin:aloe of C should he_ S. L SIB 2-18A
is the bottom width of the spilly:a-:at the crest. and H is the depth of 6/20/22
fiov.-above the spillway crest in fee:. Note Manning's channel equation
should not be used to size the spillway crest. However. it should be used Page 5
to desiga the outlet channel below the spillway crest
• The total of the emergenc—and principle spillwa_:capacities must equal
cr exceed the requited 1_0-year pear discharge.
• Set the ele,auon of the crest of the emer?enc_: spillwiy a mininnun of 1
foot above the crest of the riser
OPTION 1
Quo 5.58
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight. The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than 210
Width of control section (ft) 9
Width of entrance (ft) 6
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam
• Keep a level area to extend at least 20 ft upstream from the outlet end of
the control section-to ensure a straight alignment_
• Side slopes should be 3:1
Step 12. Design spillway;exit section.
• Spillway exit should align with the control section and have the same

SB 2-18A
6/20/22
YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-18A.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 6
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Q. (cfs) 7.00036
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 7.00036 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-18A
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/20/22
does uct create erosive velocities for site conditions (Stay within slope Page 6
ranges in appiopriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 1016 greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 22.5:I or flatter.
• Determine depth of cutoff trench from site bonags_ It should extend to a
stable,tight soil layer(a mini num of 2 ft deep).
• Select borrow site—the emergency slAlway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specicarions. 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications. 6.10, Temporary Seeding: 614, Mulching;and 6.1.5,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ R.iprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 1-. Safety.
• Construct a fence and install warning signs as needed.
YAJobsk21-004 Mocksville(R210004)kDocumentsIReportskSB 2-18A.xis

SEDIMENT BASIN DESIGN SB 2-19
6/21/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-19.xis
Designed By: PNJ Date: GAV2 Z
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-19
Total Drainage Area (acres) 4.15
Step 1. Determine peak fio.v_ Q1,1 for the basin draulage area S.OS)
Q10 (cfs) 14.81
Step 2. Determine anv site linutations for the sechnient pool elevation,emergency
spillway or top of the dam_
Minimum pool elevation (ft) 787
Maximum pool elevation (ft) 790.5
Step 3. Deternlule basin voltulles
• Compute iiiinununi volume required (1800 ft' acre disturbed)_
• Specify- sediment cleatlout level to be narked on riser (one-half the destgtl
ohuiie referenced to the top of the riser) wid sediment storage area to be
cleared after the dani is built_
Disturbed acreage (ac) 3.45
Min Volume (ft) 6210
Sediment cleanout elevation (ft) 788
Sediment Storage Area 3591

Y:1Jobs121-004 Mocksville(R210004)IDocuments\Reports\SB 2-19.xis SB 2-19
Step 4. Deternune area and shape of basil(: Page 2
• Check length width ratio (should be -1:1 to 6:1)
• Compute the basin surface area at principal spilllvay elevation.
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or equ a1 to 435 ft-.,cfs)- Enlplo • diversions with additional traps and
basuls to reduce area drained
Deteriume, barrel capacity required for site conditions (minimum capaclt`' for Q:
is the 2-year peak runoff, Q'.
Length/width ratio 5.29
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 6475
Ratio: basin surface area/Q10 437.204591
Is ratio >= 435 ft2/cfs? YES
Step 5. Deteriluile the principal spillway discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the 10-year peak flow for the entire watershed of the basal.
• The principal spillway is analyzed for three possible linutulg flow types:
«eir flotiv, Orifice flow. and Pipe flo,,v. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation. Weir, orifice and
pipe floe may be determined by the following equations:
1. %X eir Flow-- Q = C LH'-=
-where:
Q = discharge 111 cubic feet per second(cfs)
C =weir Coefficient_ use 3.1 for Corrugated metal pipe risers.
L= circumference of the riser In feet
H =head above riser crest u1 feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?. Orifice Flow: Q = CA(2gH)'
where:
6/21/22

« = discharge ui cubic feet per second (cfs) SB 2-19
C =orifice coefficient- use C = 0.6 for cornigated metal pipe risers Page 3
A=cross-sectional area of the riser pipe ui square feet
g =acceleration due to 4ravim7. 3 2.2 ft:sec'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
,Lrh
3. Pipe Floe,: 0 _ cl �1 T K. +K, L
where:
Q = discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity- 32-2 ft'sec-
h =head above the centerline of the outlet end of the barrel
Kn, = coefficient of ninor losses, can be assiuned to be 1.0 for
most principal spillway systems
L =barrel length In.feet
KF =pipe friction coefficient:
5067n= (See Table $.ova for KF values for
dia,a common size of pipe.)
n =Mantiiug's coefficient of roughness. use n =0.0'5) for
comigated metal pipe
n =0.015 for reinforced concrete pipe
di =inside diameter of the barrel ui inches
Select riser and barrel di pensions so that the riser has a cross-sectional area
at least 1.5 tines that of the barrel. Spillway hydraulics are unproved by
Inaximizing weir flog;• and minimizing orifice flow- See Table 8 07b for
reconunended riser:'barrel proportions
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-19
Inside diameter of barrel, d; (in) 0 6/21/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select ttail riser and barrel dimensions L%e :be y.eii orifice and pipe Plow
equations to determine if the 2 eat peak discharge is passed w thcut act.,-ating
Tile eme1`2enc_; spilltca.;. Determine n-.et size from Ftaru-e 3.0-6. Check the
head and stage requirements. If the design stage is too hieh. choose larser
dimensions and recalculate. As a nummu m.set the elevaticn of the riser at the Table 8.07b
same elevation as the top of the sediment pool A riser height' to` times the
barrel diameter is recommended. Select the rype cf trash?uard.
Select a deg watering device. If a skimmer isused. refer to the manufacturers
dewaterma data- or Table 6 64 b
Step 6. Design annseep collar.
Ensure that anti.seep collars are no closet than '_ ft from a pipe joint. Collar
must project at least 1 ` ft fi-om the pipe Indicate watertight connections.
Step Design anttflotation block_
Determine the � --eight of water displaced by the empty- riser. and design a
block with buoyant weight 1 1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step 8. Design outlet.
Determine discharge velocity from the barrel Design outlet protection to
assure stable conditions_ Riprap placement is usually necessary (_fppendix
S ?bj_
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spills:ay
• Determine the required capacir;for the emergency spills:ay as
(QF. 0,)
• From Table®or Table®select the width and depth of the cutlet. Table 8.07c
depending on soil conditions. In general. the xider bottom widths and Table 8.07d
loiter slopes are preferred to minimize exit velocities at supercritical
flow•
• an acceptable alternative is the use of the weir equation
Q = CLH'

%%'here this option i_used, the maximmn value of C should be 2 S. L SB 2-19
is the bottom width of the spillv;a•:at the crest. and H is the depth of 6/21/22
flow above the spillway crest in feet. 'Note: Tannina s channel equatica
should not be used to size the spillway crest Hcnk-ever. it should be used Page 5
to design the outlet channel below: the >pill:ca:cent
• The rotal of the emergency and principle spill:t-a:-capacities must equal
or exceed the required 10-rear peak discharge
• Set the elevation of the crest of the emersenc: :pill;sa: a minimiun of 1
foot above the crest of the riser
OPTION 1
Quo 14.81
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
aie straight The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control_-ection. Approach
channel should slope toward the re°•erg:oir no less than 10 c
Width of control section (ft) 21
Width of entrance (ft) 14
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the piRwa.; near where it intersects the
extension of the centerline of the dam
• Keep a level area to extend at least 20 ft upstream fioui the outlet end of
the control section_to ensure a straight alignment.
• Side slopes should be 3:1.
Step 12. Design spillway exit section.
• Spillway exit should align with the control section and have the same

SB 2-19
6/21/22
YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-19.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 14
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 16.3342
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 16.3342 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-19
• Slope should be sufficient to maintain supercritical fio%v-_but make sure it 6/21/22
does not create erosi..e velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel ro a point where the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be W% greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter_
• Determine depth of cutoff trench from site borings It should extend to a
stable.tight soil layer(a nunumun of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Spectflcarions: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Pracrice Srandards
and Specifications. 6.10, Temporary Seeding; 6.14,MIching;and 6.1.5,
Riprap)_
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextde
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed
YAJobs121-004 Mocksville(R210004)kDocuments1ReportskSB 2-19.xis

SEDIMENT BASIN DESIGN SB 2-20
6/21/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-20.xis
Designed By: PNJ Date: 6 z-7lZ-2-
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-20
Total Drainage Area (acres) 0.46
Step 1. Deter11u11e peak fimv- Q _ for the basin drainage area S,(;)
Q10 (cfs) 1.91
Step 2. Determine am-site limitations for the sediment pool elevation,ernergencv
spill,xay or top of the cUnl_
Minimum pool elevation (ft) 784
Maximum pool elevation (ft) 787.5
Step 3. Deterninie basin voltulles:
• Compute 11111lln1urn volume required(ISOO fr acre disturbed)
• Specifi sediment cleanout level to be narked on riser (one-half the design
s olunle referenced to the top of the riser) and sediment storage area to be
cleared after the dani is built.
Disturbed acreage (ac) 0.46
Min Volume (ft) 828
Sediment cleanout elevation (ft) 785
Sediment Storage Area 46

Y:1Jobs121-004 Mocksville(R210004)IDocuments\ReportslSB 2-20.xis SB 2-20
Step 4. Determine area and shape of basui= Page 2
• Check length'width ratio (should be 2.1 to 6:1).
• Compute the basin surface area at principal spillway elegy:ation_
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or equid to 435 ft-",,:cfs)- Employ diversions with additional traps and
basins to reduce area drained
Determine barrel capacity required for site conditions (nunimtun capaan_-for Q
is the 2-`'.ar peak runoff, Qc.
Length/width ratio 4
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 900
Ratio: basin surface area/Q10 471.204188
Is ratio >= 435 ft2/cfs? YES
Step -5. Determine the principal spillway discharge capacitz-.
• The combined capacities of the principal and emergency spillways must be
at least the 10--,ear peak flow for the entire watershed of the basim.
• The principal spillway is analyzed for three possible limiting flog- types:
«eir flow, Orifice float-. and Pipe floiy-_ The principal spillway discharge
capacity is the smallest of these three floe- rates_ Discharges through�a
skinuner should be disregarded during this computation. X- eir. orifice and
pipe floe' may be determined by the followui lcr equations:
1. l eir Flow Q = CLH'
where:
Q = discharge in cubic feet per second(cfs)
C =weir coefficient_ use 3.1 for corrugated metal pipe risers_
L= circtunference of the riser in feet
H =head above riser crest iu feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?_ Orifice Floe,•: Q = CA(2gH)'=
where:
6/21/22

0 = discharge ui cubic feet per second (cfs) SB 2-20
C =orifice coefficient. use C = 0.6 for corrugated metal pipe risers Page 3
A= cross-sectional area of the riser pipe in square feet
g = acceleration due to gravty_ j,_2 ft sec'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)P
firth l
i. Pipe Flow- a _ LEI [1 — Kr,. + 1;_ L J
where:
Q = discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g =acceleration due to gravity_ 12.22 ft'sec-
h =head above the centerline of the outlet end of the barrel
K,,, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length 'in feet
K� =pipe friction coefficient:
_ 5087n2 (See TableEa for KF values for
dii4'1 common size of pipe.)
n = Niannulg-s coefficient of roughness, use n = 0,025 for
comgated metal pipe
n = 0.01? for reinforced concrete pipe
di = inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are improved by
nnaximizmg weir flow and mini,,,izing orifice $oxx. See Table 8.0 7b for
recommended riser,'barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-20
Inside diameter of barrel, d; (in) 0 6/21/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/O! 0
Page 4
RISER
Select hail rise: and bariel dimensions. L'se the ;�:eir. orifice and pipe floe
equations to determine,f the,-vea:peak discharge is passed without actn.ating
the emerzenc_,- spillway. Determine riser size from Figure 3.07.b Check the
tread and stage requirements. If the design stage is too high_ choose larger Table 8.07b
dimensions and recalculate As a uunimtun.set the elevation of the riser at the
same elevation as the top of the sediment pool. A riser height 2 to` times the
barrel diameter is recommended. Select the ripe of tra_h shard.
Select a den-ateiing device. If a slimmer is used. refer to the manufactuters
cle,t;atering data_ or Table 6 64 b.
Step 6. Design antt_eep collar.
Ensute that antrseep collars are no cioser than , ft from a pipe point_ Collar
roust project at least 1 ft from the pipe. Indicate watertight connections_
Step ?. Design antifiotation block_
Determine the weight of water displaced by the empr; riser, and design a
block with bu.ov ant Freight 1.1 times the r:eight of water displaced.
Riser Height f
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step 8. Design outlet_
Determine discharge ,;elocit-, from the barrel. Design outlet protection to
assure stable conditions Riprap placement is usually necessa:v +:4ppet!dis
Discharge velocity, V (ft/s) #DIV/O! #DIV/O!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency-spillxay.
• Determine the required capacity for the emergency spill.-ay as
Oe= Q.0—Q, (0F•2 Q')
• From Table=or Table=select the width and depth of the cutlet Table 8.07c
depending on soil conditions. In general. the wide: bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
0 = CLHI`

:%'here this option n used. the maximum:-slue ,o C should be = S L SB 2-20
is the bottom width of the spilh a:° at the crest. and H is the depth of 6/21/22
f otti-above the spilh a crest in feet. 'Note: Manning'; channel equation
should not be used to size the spillv.-a-., nest_ However. it should be used Page 5
to design the outlet channel belo..t- the spill-,t a%1 crest
• The total of the emergency and principle spillway capacities must equal
or exceed the required 10- •ear peal-discharge.
• Set the elevation of the crest of the emergenc v -:pill,.~av a minimum of l
foot above the crest of the riser.
OPTION 1
Quo 1.91
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillwa,approach section.
Adjust the spilln-av alignment so that the control section and outlet section
are straight The entrance tcidth should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than 10 c
Width of control section (ft) 1.5
Width of entrance (ft) 1.2
Slope of approach channel (%) 3
Is width of the entrance section 1.5xcontrol section
width? NO, REVISE DESIGN
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillwa_v near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 30 ft upstream fi om the outlet end of
the control section-to ensure a straight alignment.
• Side slopes should be 3:1
Step 11. Design spillway;exit section-
- Spillway exit should alien r.•ith the control section and have the same

SB 2-20
6/21/22
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-20.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 4
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Q. (cfs) 4.6669
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 4.6669 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-20
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/21/22
does nct create erosive velocities for site conditions. (Sta,, within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water maybe released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10% gxeater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or Satter.
• Determine depth of cutoff trench from site borings_ It should extend to a
stable.tight soil layer(a mmumum of i ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications. 6.10, Temporary Seeding; 6.14,fulching;and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 1-. Safety.
• Construct a fence and install warning signs as needed.
Y:Wobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-20.xis

SEDIMENT BASIN DESIGN SB 2-20A
6/21/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
Y:1Jobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-20A.xls
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-20A
Total Drainage Area (acres) 1.37
Step 1. Deternulle peak f OX. 'Q,,, for the basin drainage area G- vpe};crix S.US)
Q10 (cfs) 5.49
Step?. Deternune tun-site linutarlons for the sediment pool elevation,emergenc-
spillwa,,11 or top of the dram_
Minimum pool elevation (ft) 793
Maximum pool elevation (ft) 796.5
Step 3. Deteriniue basin vohmies:
• Compute i1minnuln volume required(1S00 ft',acre disturbed)
• Speciffi sediment cleanout level to be marked on riser (one-Half the desigll
volume retereIlced to the top of The riser) and sedunent storage area to be
cleared after the dain is built
Disturbed acreage (ac) 1.31
Min Volume (ft) 2358
Sediment cleanout elevation (ft) 794
Sediment Storage Area 700

Y:IJobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-20A.x1s SB 2-20A
Step 4. Determine area and shape of basin: Page 2
• C heck lengtli w-idtll ratio (should be _'=1 to 6:1)
• Compute the basin surface area at prulcipal spillway ele t ation_
• Check the ratio of basin surface area to peak 111fiow rate (should be greater
than or equal to 43- ft' cfs). Emplo-- diversions with additional traps and
basins to reduce area drained
Deterilline barrel capacity required for site conditions (nummum capacity for Q`
is the 2-Fear peak runoff,
Length/width ratio 5.43
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft2) 2394
Ratio: basin surface area/Q10 436.065574
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spilhi ay discharge capacit-%"
• The combined capacities of the principal and emergency spilhyays must be
at least the 10-rear peak floe- for the entire watershed of the basin.
• The principal spillway is analyzed for three possible limiting flow tt-pes:
Weir floe-, Orifice flow-. and Pipe flow-. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation_ W-eir, orifice Gild
pipe floe-max be determined by the following equations:
1. l eir Floe-: Q = CLH'
where:
Q = discharge nl cubic feet per second(cfs)
C =weir coefficient- use 3_"1 for corrugated metal pipe risers.
L= circuumiference of the riser in feet
H =head above riser crest um feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
Qw (cfs) 0
?. Orifice Flow-. Q = CA (2gH)'
where:
6/21/22

•0 = discharge ui cubic feet per second (cfs) SB 2-20A
C =orifice coefficient_ use C =0.6 for corrugated metal pipe risers Page 3
A=cross-Sectional area of the riser pipe 1r1 square feet
9 =acceleration due to gravity. 32.2 ft sec'
H = head above riser crest iii feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
,gh
;. Pipe Flog: G = �1 1 + Km+K, L
where:
Q = discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
9
= acceleration due to gra ti iR'_ 312 ft:'sec-
h =head above the centerline of the outlet end of the barrel
Km = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
K,; =pipe friction coefficient:
_ 5087112 (See Table 8.o7a for KF ti.alines for
di4'' common size of pipe.)
n ='_viiiniiiig s coefficient of roughness, use n =0.025 for
corrugated metal pipe
n = 0.015 for reinforced concrete pipe
di = inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 tunes that of the barrel. Spillway hydraulics are improved by
nkXximizing weir floe and inuil'11117111 orifice flow- See Table 9.07b for
recommended riser.'barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-20A
Inside diameter of barrel, d; (in) 0 6/21/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select nail riser and barrel dimensions Use the .eir, orifice and pipe flow
equations to determine if the-' ear peak discharge is passed w:thctit aci]vating
the emergenc_, spillway. Determine river size from Ft.-ire 8.0-b Check the
head and stage requirements. If the design stage is too high. choose larger Table 8.07b
dimemicn-�and recalculate As a munimu m_set the elevation o f the riser at the
same elevation as the top of the sediment pool. A riser height'to - times the
barrel diameter is recommended. Select the rape of tra.:h guard_
Select a den•atering de ice If a skimmer is used. refet to the manufacturers
de:wateiime data. or Table 6.64 b
Step 6. Design antiseep collar.
Ensure that antiseep cellars are no closer than 2 ft from a pipe joint_ Collar
must project at least 1 ` ft fi-cm the pipe Indicate watertight connections.
Step ?. Design antiflotation block_
Determine the weight of :water displaced by the empty riser, and design a
block with buoy{ant .weight 1 1 times the weight of-,ater displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet.
Determine discharge :elocin- from the barrel Design outlet protection to
assure stable conditions. Riprap placement is usually necessar v (--Lp erldix
8.06)
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway
• Determine the required capacity for the emergency spillway as
QE= Q.0-Q, 1QF, 7 Q7!
• From Table®or Table®select the width and depth of the cutlet, Table 8.07c
depending on soil conditions. In general. the wider bottom ;widths and Table 8.07d
lower slope_ are preferred to minimize exit velocities at supercritical
float-
• An acceptable alternative is the use of the weir equation
Q = CLH]°

:Where this option is used. the maximum value o'C should be - S. L SIB2-20A
is the bottom w dtli of the ,cillwav at the crest- and H is the depth of 6/21/22
f'.o:y above the spillwa-v crest in feet. Vote Manning"s channel equation
should not be used to size the spillwi-v crest How ,er,it should be used Page 5
to design the outlet channel below the spilhy av crest
• The total of the emergency and principle spillway capacities must equal
cr exceed the requited !)_year peak dischai ge.
• Set the elevation of the crest of the emergency spilhvay a minimum of 1
foot above the crest of the riser
OPTION 1
Q1 0 5.49
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillu-av approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight The entrance width should be 1 5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reser:oir no less than 11 o_
Width of control section (ft) 1.5
Width of entrance (ft) 1.2
Slope of approach channel (%) 3
Is width of the entrance section 1.5xcontrol section
width? NO, REVISE DESIGN
Is approach channel >/= 2%i? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillwa_; near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 0 ft upstream horn the cutlet end of
the control section_to ensure a straight alignment.
• Side slopes should be ?:1
Step 12. Design spillway exit section_
• Spillway exit should align with the control section and have the same

SB 2-20A
6/21/22
YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-20A.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 6
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 7.00036
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 7.00036 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-20A
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/21/22
does not create erosrve velocities for site conditions. (Stay withrn slope Page 6
ranges in appiopriate design tables.}
• Extend the a.it channel to a point where the water ma%r be released without
damage.
Step 13. Size the embankment_
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10"o greater than the design to allow- for
settlement.
• Base top width on the design height.
• Set side slopes 15:1 or flatter.
• Determine depth of cutoff trench from site borings. It should extend to a
stable,tight soil laver(a minimum of? R deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill_
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(_Practice Standards and Specificarions: 6.20, Tempora►I7Diversions).
• Select surface protection measures to control erosion(Py-acrice Standards
and Specifications. 6.10, Temporary Seeding; 614,fulching;and 6.15,
Riprap).
• Select groundcover for emergence spillway to provide protection for
design flow velocity and site conditions. Riprap stone over geotextde
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
Y:1Jobs121-004 Mocksville(R210004)1DocumentslRepottslSB 2-20A.xls

SEDIMENT BASIN DESIGN SB 2-21
1/5/23
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
Y:1Jobs121-004 Mocksville(R210004)1Documents\ReportslSB 2-21.xis
Designed By: PNJ Date: 1 S Z3
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-21
Total Drainage Area (acres) 2.05
Step 1. Deternune peak- floe- Q,,, for the basin drainage area (_��aer;tr'i� S.03)
Q10 (cfs) 8.45
Step 2. Detenriine an-,, site 1i11utations for the sediment pool elevation.emergence
spillway or top of the darn_
Minimum pool elevation (ft) 775
Maximum pool elevation (ft) 778.5
Step 3. Deternune basin vohulies:
• Compute nlinlnlllnl v olurne required (1800 ft-' acre disturbed)
• Specift sediment cleanout level to be marked on riser (one-half the design
oliime referenced to the top of the riser) and sediment storage area to be
cleared after the dun is built.
Disturbed acreage (ac) 2.05
Min Volume (ft) 3690
Sediment cleanout elevation (ft) 776
Sediment Storage Area 3700

Y:1Jobs121-004 Mocksville(R210004)IDocuments\ReportslSB 2-21.xis SB 2-21
Step 4. Determine area and shape of basin: Page 2
• Check length width ratio (should be 2:1 to 6:1)
• Compute the basin surface area at principal splllwav elevation_
• Check the ratio of basin surface area to peak uiflot; rate (should be greater
than or equal to 435 ft- cfs). Employ- diversions With additional traps and
basins to reduce area drained
Determine barrel capacity regtured for site conditions (minimum capacity for 0-
is the 2-year peak runoff, Q_
Length/width ratio 5.92
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 3700
Ratio: basin surface area/Q10 437.869822
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spillway discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the 10-rear peak flo« for the entire watershed of the basin.
• The principal spillway is analyzed for three possible limiting flog;' types:
Weir floxw_ Orifice flow. and Pipe flow. The principal spill-,way discharge
capacity is the smallest of these three floe- rates. Discharges through a
skimmer should be disregarded during this computation. Weir. orifice and
pipe floe-may determined by the following equations:
1. l eir Flow: Q = CLH'
where-
0= discharge in cubic feet per second(cfs)
C =weir coefficient_ use .3.1 for corrugated metal pipe risers.
L= circumference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
?_ Orifice Flow: Q = CA(2gH)'
where:
1/5/23

Q = discharge in cubic feet per second (cfs) SB 2-21
C =orifice coefficient. use C = 0.6 for corrugated metal pipe risers Page 3
A= cross-sectional area of the riser pipe in square feet
g =acceleration due to gravity. _3 2.2 ft,sec'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
ugh 1
i. Pipe Flow: Q = a [1 +1,+K L J
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g =acceleration due to gravity. 3''_2 ft•sec'
h =head above the centerline of the outlet end of the barrel
Km = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
K� =pipe friction coetFicienr
_ 5067n- (See Table sA7a for KF values for
di4'3 common size of pipe.)
n =Nian nuig s coefficient of roughness. use n =0.025 for
corrugated metal pipe
n = 0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are ilmproti ed by
maximizing weir flow and ni niiuizing orifice flow- See Table 8.07b for
recommended riser Darrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-21
Inside diameter of barrel, d; (in) 0 1/5/23
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select wail rise: and barrel dimensions L'se the eir. orifice and pipe flow
equations to determine if the.2-year peak discharge is passed without acts aTing
The emergence; spillway. Determine riser size from Figure 8_07b. Check the
head and stage requirements. If the design _tale is too high, choose larger Table 8.07b
dimensions and recalculate. As a m inimam.set the eleraTion of the riser at the
same elevation as the top of the sediment pool. A riser height' ro 5 times the
barrel diameter i;recommended. Select the r-vpe of trash ward_
Select a dewatering deice. If a skimmer is used. refer to the manufacturers
de;raterine data, or Table 6.64 b
Step 6. Design antiseep collar.
Ensure that antiseep collars are no closet than ? ft from a pipe joint. Collar
must project at least 1 _5 ft fi-om the pipe. Indicate watertight connections_
Step 7. Design antiflotation block_
Determine the weight of water displaced by the empty riser. and design a
block with buoyant a eieht 1 1 times the weight of v;ater displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step 8. Design outlet
Determine discharge velocity from the barrel Design outlet protection to
assure stable conditions. Riprap placement is usually necessar (Apperrdrr
8 06�
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spill;=ray.
• Determine the required capacity for the emergency spillwav as
QC = Q.c—C, (QF.> 'Q_)
• From TableE=or Table®select the width and depth of the cutlet. Table 8.07c
depending on soil conditions_ in general. the ;rider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternati.-e is the use of the ri-eir equation
0 = CLH'

4�"here this option is used,the maximum value of C should be_'.8. L SB 2-21
is the bottom width of the spillway at the crest.and H is the depth of 1/5/23
flow above the spillway crest in feet. Vote: Manning's channel equation
should not be used to size the spillway crest_ However.it should be used Page 5
to design the outlet channel below the spillway crest.
- The total of the emergency and principle spil1w.ay capacities must equal
or exceed the required 10-rear peak discharge.
• Set the elevation of the crest of the emergency spillway a minimum of 1
foot above the crest of the riser.
OPTION 1
Q10 8.45
QP #DIV/0!
Emergency spillway capacity, Qe MS) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than 2%.
Width of control section (ft) 12
Width of entrance (ft) 8
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam
• Keep a level area to extend at least 20 ft upstream from the outlet end of
the control section.to ensure a straight alignment.
• Side slopes should be 3:1.
Step 12. Design spillway exit section.
• Spillway exit should alien with the control section and have the same

SB 2-21
1/5/23
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-21.xis
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 8
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 9.33381
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 9.33381 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-21
• Slope should be sufficient to maintain supercritical flow,but make sure it 1/5/23
does net create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables.)
• Extend the exit channel to a point where the water may,be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10% greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5-1 or flatter.
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a minimum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards-and Specifications: 6.20, Temporaty Diversions)_
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Tempormy Seeding; 6.14, Mulching-and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riptap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning suns as needed.
Y:1Jobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-21.xis

SEDIMENT BASIN DESIGN SB 2-21A
6/21/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-21A.xis
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-21A
Total Drainage Area (acres) 1.55
Step 1. Determine peal- floe-. 0fc- for the basin draillase area I;4upe;., ix S.0 9
Q10 (cfs) 6.04
Step ?. Deterilune any site linutations for the sediment pool elevation,elneraency
spillway or top of the daui_
Minimum pool elevation (ft) 795
Maximum pool elevation (ft) 798.5
Step 3. Deterinine- basin vohmies:
• Compute 111 inutim volunle required(1800 ft3 acre distu bed')
• Specifi sediment eieanotlt level to be uiarited on riser (one-half the desia�l
voliune referenced to the top of the risen) mid sediment storage area to be
cleared after the dzuu is built
Disturbed acreage (ac) 1.55
Min Volume (ft) 2790
Sediment cleanout elevation (ft) 796
Sediment Storage Area 777

Y:1Jobs121-004 Mocksville(R210004)IDocumentslReportslSB 2-21A.xls SB 2-21 A
Step 4. Detemmne area and shape of basal: Page 2
• Check length width ratio (should be -`:1 to 6:1)
• Compute the basin surface area at principal spillway elevation.
• Check the ratio of basin surface area to peak inflow rate (should be greater
than or equal to -l» tt- cis)_ Employ diversions with additional traps and
basins to reduice area drained.
Deterniule barrel capacity required for site conditions (nuninnun capacity for Q__
is the ,-year peak ninoff_ Q.,.
Length/width ratio 5.95
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 2793
Ratio: basin surface area/Q10 462.417219
Is ratio >= 435 ft2/cfs? YES
Step -5. Determine the principal spillway- discharge capacity-.
• The combined capacities of the principal and emergency spillways must be
at least the 10-rear peak flow for the entire watershed of the basal.
• The principal spillway is analyzed for three possible limiting flo-%v types:
Weir flow, Orifice floxv. and Pipe flout-. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skmuuer should be disregarded during this computation V-eir, orifice and
pipe flow may be determined by the following equations:
1. 'Weir Flom-: Q = CLH'
where:
Q = discharge ul cubic feet per second(cfs)
C =«-eir coefficient- use 3.1 for corn►gated metal pipe risers.
L=circuunference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 6.28318531
Head above riser crest, H (ft) 0.5
QW (cfs) 7.33075685
Orifice Flow: Q = CA(2gH)'
where:
6/21/22

y- Q=discharge in cubic feet per second(cfs) SB 2-21A
C =orifice coefficient. use C=0.6 for corrugated metal pipe risers. Page 3
A=cross-sectional area of the riser pipe in square feet
g =acceleration due to gravity.. 32.2 ft sec'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 3.14159265
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft) 0.5
Discharge, Qo (cfs) 10.6961888
Riser Diameter (in.)� 24
2gh 0
3. Pipe Flow: Q = a I 1 +K.+Kn L
where:
Q=discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity, 32.2 ft/ser'
h =head above the centerline of the outlet end of the barrel
K,,, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
Kp =pipe friction coefficient:
5087n2 (See Table for Kp values for
di4t' common size of pipe_)
n =Manning's coefficient of roughness, use n =0.025 for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are improved by
maximizing weir flow and minimising orifice flow. See Table 8.07b for
recommended risevbarrel proportions.
Barrel diameter (ft) 2
Barrel cross-sectional area, a (ft2) 3.1
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft) 1
Minor loss coefficieint, Km 1 .0
Barrel length, L (ft) 35

Mannings coeffienct of roughness, n 0.025 SB 2-21A
Inside diameter of barrel, d; (in) 24 6/21/22
Pipe friction coefficient, Kp 0.04593
Discharge, Qo (cfs) 13.2737833 17.8269813
Page 4
RISER
Select trail list: and barrel dimen_•icas tse the ,vei: orifice and pipe f_on-
equation.to deteirnine if the 2 eat peak discharge is passed`.v lthetit acti:'acing
The emergency Determine ri._er size from Figure 8.07b Check the
head and stage requirements. If the design ;rage is too high, choose larger
dimemioas and recalculate As a nunimmu_set the elevaticu of the riser at the Table 8.07b
same elevation as the top of the sediment pool. A riser height -' to = times the
barrel diameter is teccmniended. Select the ripe of trash grla.d
Select a dewatering de-:ice. If a skimmer is used, refer to the manufacturers
dewatering data_ or Table 6 64 b
Step 6. Design ans.�eep collar
Ensure that autiseep collars are no closer than 2 ft from a pipe joint Collat
must project at least 1.` ft from the pipe Indicate watertight connections_
Step +. Design antifiotation block
Determine the weight of water displaced by the empty- riser, and design a
block with buovant weight 1 1 blues the,T;eight of v.-atei displaced.
Riser Height 3.5
Weight of water displaced by the empty riser 686.453703
Buoyant weight 755.099073
Step S. Design outlet.
Determine discharge velocin from the barrel, Design outlet protection to
assure stable conditions. Riprap placement is usually necessai_, (AR endis
S 06)
Discharge velocity, V (ft/s) 4.22517646 5.67450438
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergenc°;spillway
• Determine the required capacit;for the emergency spill-,vay as
• From Table®or Table®select the width and depth of the cutlet Table 8.07e
depending on soil conditions_ In general_ the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = cLHi

':here this option is used the maxrm:un value 3:C should be ' S t_ SIB 2-21A
is the'bottom:rrdth 0:the spill :a: at the crest. and F.is the depth cf 6/21/22
P,ov.- above the still,;a-;' crest in feet. Note Manniug s channel equation
should not be used to size the spillwa_;crest Hoare-:er.it _hould be used Page 5
to de_izn the outlet channel below the splll, a% crest
• The total of the emergenc,: and principle spill a—..,capacities mist equal
cr exceed the required 10 ear peak discharge
• Set the elevation of the crest of the emer?enc: a minimum of
foot above the crest of the riser.
OPTION 1
Quo 6.04
Qp 7.33075685
Emergency spillway capacity, Qe (cfs) -1.2907568
Qp + Qe 6.04
Does (Qp + Qe) equal or exceed Q10? YES, PROCEED
Step 10. Spillway approach section.
Adjust the Spillwat, alignment so that the control section and cutlet section
are straight. The entrance width should be 1.5 time_ the width of the control
section with a smooth transition to the width of the control secticu. Approach
channel should slope tcward the reservoir no less than 2'o
Width of control section (ft) 1.5
Width of entrance (ft) 1.2
Slope of approach channel (%) 3
Is width of the entrance section 1.5xcontrol section
width? NO, REVISE DESIGN
Is approach channel >/= 2%? YES, PROCEED
No spillway this basin
Step 11. Spillway:control section
• Locate the control section in the spillway near where it intersects the
emensiou of the centerline of the dam.
• Keep a le-..-el area to extend at least -'C ft upstream loin the outlet end of
the control section. to ensure a itrarght alignment.
• Side slopes should be ;:1_
Step 12. Design spilhwav exit section.
• Spil-twa-; exit should align with the control section and have the same

bottom width and side slopes. SB 2-21 A
• Slope should be sufficient to maintain supercritical flow-but make sure it 6/21/22
does not create erosive velocities for site conditions (Stan within slope Page 6
ianges in appiopnate design tables.)
• Extend the exit channel to a point where the rater may be released i.;-ithout
damage.
Step 13. Size the embankment_
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10% greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 15:1 or flatter.
• Determine depth of cutoff trench from site borings. It should extend to a
stable.tight soil layer(a minimum of? ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and.Specicafions: 6.20, Temporary Diversions)_
• Select surface protection measures to control erosion(Practice Srandards
and Specifications. 6.10, Tempora►y Seeding; 6.14,liulching;and 6.15,
Rip''ap)-
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions. Riprap stone over geotestile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils
Step 15. Safety.
• Construct a fence and install warning signs as needed.
YAJobs121-004 Mocksville(R210004)1DocumentslReportMSB 2-21A.xis

SEDIMENT BASIN DESIGN SB 2-22
1/5/23
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-22.xis
Designed By: PNJ Date: W12-3
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-22
Total Drainage Area (acres) 1.11
Step 1. Deterilutie peak fio-w. Q,,, for the basin draiiiage area G_ Rv iia;X S.03)
Q10 (cfs) 4.57
Step 2. Deternune any Site 11n11taC1oi1S for the sediment pool elevation,emergenc`'
spill,.ti-at-or top of the dani_
Minimum pool elevation (ft) 773
Maximum pool elevation (ft) 776.5
Step 3. Determine basil vohniies=
• Compute 1111111nium vohune required(1800 fC acre disturbed)
• 5pecif�- Sediment cleanout level to be marked oIl riser (one-half the design
ohutie referenced to the top of the riser) and sediment storage area to be
cleared after the dam is buih.
Disturbed acreage (ac) 1.11
Min Volume (ft) 1998
Sediment cleanout elevation (ft) 774
Sediment Storage Area 460

Y:1Jobs121-004 Mocksville(R210004)IDocuments1ReportslSB 2-22.xis SB 2-22
Step 4. Detennune area and shape of basun: Page 2
• Check length width ratio (should be 2:1 to 6:1).
• Compute the basin surface area at pruicipal spillWaV elet-ation.
• Check the ratio of basin surface area to peal- uiflow rate (should be greater
than or equal to 43 i ft :cfs). Employ diversions with additional traps and
basuis to reduce area drained
Detertnnirne barrel capacity required for site conditions (n inimu m capacity for Qi
is the ,-year peak runoff. Q,
Length/width ratio 5.58
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 2014
Ratio: basin surface area/Q10 440.700219
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spill-%vay discharge capacity.
• The combined capacities of the principal and emergency spillways must be
at least the 10-y ear peak flow for the entire watershed of the basin.
• The principal spillway is analyzed for three possible limiting flog' types:
Weir flow_ Orifice flog;-. and Pipe flow- The pruicipal spillway discharge
capacity- is the smallest of these three flow rates. Discharges through�a
skimmer should be disregarded during this computation. Weir, orifice and
pipe flow may be determined by the followuig equations:
1. l eir Flow: Q = CLH' r
where:
Q = discharge ui cubic feet per second(cfs)
C =weir coefficient. use 3.'1 for corrugated nnetal pipe risers.
L = circumference of the riser itn feet
H =head above riser crest iu feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
�. Orifice Flow: Q = CA(29H)=
,xhere:
1/5/23

0 = discharge ui cubic feet per second (cfs) SB 2-22
C =orifice coefficient. use C = 0.6 for comwated metal pipe risers Page 3
A=cross-sectional area of the riser pipe in square feet
g =acceleration due to aravimr. 3 2.2 ft:sec`
H =head above riser crest In feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Q. (cfs) 0
Riser Diameter (in.)
' h c:
i. Pipe Flow: 0 = a [1 +�+ltip L
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g =acceleration due to gravity. 32.2 ft�sec'
h =head above the centerline of the outlet end of the barrel
K,,, = coefficient of nunor losses_ can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
K� =pipe friction coefficient:
_ 5087n= (See Table F07a for K.values for
diva comruon size of pipe_)
n =Manlung-s coefficient of roughness. use n =0.025 for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di = inside diameter of the barrel in inches
Select user and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are improved bi-
maximizing 1%--eir low and miniurizing orifice flow. See Table 8.0+b for
recommended riser-barrel.proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-22
Inside diameter of barrel, d; (in) 0 1/5/23
Pipe friction coefficient, Kp #DIV/O!
Discharge, Qo (cfs) #DIV/O! 0
Page 4
RISER
Select trail riser and barrel dimensions Use the weir. orifice and pipe flo�x
equations to determine if the year peak discharge is pa sled.i thcut activating
the emergency spill.ya_,. Determine ricer size from Figure 8.07b Check the
head and stage requirements. If the design stage is too high. choose larger
dimensions and recalculate. As a minimum.set the elevation of the riser at the Table 8.07b
same elevation as the top of the sediment pool. A riser height_2 to` times the
barrel diameter is recommended. Select the type of trash guard_
Select a dev.-ateimg device. If a skimmer is used. refet to the manufacturers
dewaterina data. or Table 6 64 b.
Step 6. Design anti.seep collar_
Ensure that antiseep collars are no closer than , ft from a pipe joint_ Collar
must project at least 1_5 8 fi-om the pipe. Indicate watertight connections
Step 7. Design antiflotation block_
Determine the weight of water displaced by the empty riser, and design a
block with buoyant weight 1.1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet.
Determine discharge velocity from the barrel Design outlet protection to
assure stable conditions_ Riprap placement is usually necessar Y (Aoperdir
Discharge velocity, V (ft/s) #DIV/O! #DIV/O!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway
• Determine the required capacrn•for the emergency spillwa}-as
Qe = Q.o—Qc (Op? Q2)
• From Table®or Table®select the width and depth of the cutlet. Table 8.07c
depending on soil conditions_ In general. the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = CLHi

';'here this option is used. the maxinlum value of C, should be_.S. L SIB 2-22
is the bottom width of the spill.:a at the crest. and H is the depth of 1/5/23
£ow above the spithvat�crest in feet dote: Manning's channel equation
should not be used to size the spillway crest. Ho—e er.it should be used Page 5
to design the outlet channel below the spillway crest.
• The total of the emergency and principle spillwa:• capacities must equal
cr exceed the required 10-Neat peal:discharge
• Set the elevation of the crest of the emergency: . ilh-vat•a mrnrmum of 1
foot above the crest of the riset.
OPTION 1
Quo 4.57
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spilhway alitmment so that the control section and outlet section
are straight. The entrance width should be 1.-5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than 100.
Width of control section (ft) 6
Width of entrance (ft) 4
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillwa-v near where it intersects the
extension of the centerline of the dam
• Keep a level area to extend at least 14 R upstream from the outlet end of
the control section-to ensm•e a straight alignment_
• Side slopes should be 3:1
Step 12. Design spillway exit section_
• Spillwav exit should align with the control section and have the same

SB 2-22
1/5/23
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-22.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 4
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 4.6669
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 4.6669 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-22
• Slope should be sufficient to maintain supercritical flow.but make sure it 1/5/23
does act create erosive velocities for site conditions (Star within slope Page 6
ranges m appropriate design tables}
Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment_
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway.
• Constructed height should be 10°6 greater than the design to allow for
settlement_
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter_
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a nummum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill_
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards-and Specifications: 6.20, Temporaty Diversions).
• Select surface protection measures to control erosion(Practice Srandards
and Specifications. 6.10, Temporary Seeding; 6.14, Mulching;and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed.
Y:lJobs121-004 Mocksville(R210004)IDocumentsMeportslSB 2-22.xis

SEDIMENT BASIN DESIGN SB 2-23
6/22/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)IDocumentslReports1SB 2-23.xis
Designed By: PNJ Date: 6/Z 2/22-
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-23
Total Drainage Area (acres) 0.84
Step 1. Deterilune peal- fiOW� 0Ic- for the basin drainage area t-4DJei,,a'ix S.O3)
Q10 (cfs) 3.45
Step 2. Determine and site limitations for tine sediment pool elevation,enlergencN
spillway or top of the ctan1_
Minimum pool elevation (ft) 755
Maximum pool elevation (ft) 758.5
Step 3. Determine basul vohuues:
• Compute 11111llrmulm volume required (1800 fC acre disthlrbed)
• Specifi- sediment cleallout level to be marked on riser (one-half the desiall
ollume referenced to the top of the riser) and sediment storage area to be
cleared after the cLatu is built
Disturbed acreage (ac) 0.84
Min Volume (ft) 1512
Sediment cleanout elevation (ft) 756
Sediment Storage Area 546

YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-23.xis SB 2-23
Step 4. Determne area aid shape of basin- Page 2
• Check leii--th'width ratio (should be -'A to 6:1).
• Compute the basin surface area at pruicipal spilhva-'. elevation.
• Check the ratio of basin surface area to peak Inflow rate (should be greater
than or equal to 43; ft' cfs)_ Employ diversions with additional traps and
basuns to reduce area drained_
Deternnuie barrel capaciR'required for site conditions (nunitmuin capacity for 0-
is the ,-N ear peak runoff. Q,,.
Length/width ratio 2.07
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 1512
Ratio: basin surface area/Q10 438.26087
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spillway discharge capacity-.
• The combined capacities of the principal and emergency spillways must be
at least the 10-year peak flow for the entire watershed of the basin.
• The principal spillway is analyzed for three possible limiting flow ttipes:
Weir floe.•_ Orifice flow. and Pipe flow. The principal spilhvay discharge
capacity° is the smallest of these three flow rates. Discharges through a
skinuuer should be disregarded during this computation. IVVeir, orifice and
pipe flop-may be determined by the followma equations:
1. l eir Flow: Q = CLH'
twhere:
Q = discharge in cubic feet per second(cfs)
C =weir coefficient_ use 3."1 for corrugated metal pipe risers.
L=circumference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
Orifice Flow: Q = CA(2gH)'
where:
6/22/22

Q = discharge un cubic feet per second (cfs) SB 2-23
C = orifice coefficient. use C = 0.6 for cormRated metal pipe risers Page 3
A= cross-sectional area of the riser pipe iu square feet
g =acceleration due to gravity. 3 2.2 ft seer
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)"
i. Pipe Flo-,A- 1 - 1.+K; L
where:
Q =discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel ui square feet
g = acceleration due to gravity- i?.? ft.'sec'
h =head above the centerline of the outlet end of the barrel
Kn, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
K. =pipe friction coefficient:
_ 5037n' 8 07a- (fee Table for KF values for
di4,3 common size of pipe.)
n =Manning s coefficient of rottahness. use n = 0.0'S for
corrugated metal pipe
n =0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are Improved by
imaxiimiziug weir float- and mini n Q orifice flox . See Table 8.07b for
recommended riser.-barrel proportions
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-23
Inside diameter of barrel, d; (in) 0 6/22/22
Pipe friction coefficient, Kp #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select trail riser and barrel dinteu_•ious Use the eir. orifice and pipe 8onv
equations to determine if the year peak discharge is passed wIthcut acts,'ating
The emereeac_,` spill:ra_`. Determine riser size from Figure 8.07'b_ Check the
head and stage requirements. If the design -_tape is too high. chcose larger Table 8.07b
dlmerisions.and recalculate. As a minimum set the elevation of the riser at the
same elevation as the top of the sediment pool- A user height' to= times the
barrel diameter is recommended. Select the t,re of trash guard.
Select a dev.-atenng de-:ice. If a skimmer is used. refer to the manufacturers
dewaterina data_ or Table 6.64 b
Step 6. Design antrseep collar.
Ensure that antiseep collars are no cicset than , ft f_-:m a pipe jc-int. Collar
must project at least 1.= ft from the pipe Indicate watertight connections_
Step 7. Design antiflotation block_
Determine the weight of.hater displaced by the empty- riser. and design a
block with buovant weight 1.1 times the.'.-eight of water displaced.
Riser Height 1W
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design cutlet_
Determine discharge �:elocity from the barrel Design outlet protection to
assure stable conditions Riprap placement is usually necessai v (.-�ppendix
8.16)
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway
• Determine the required capacir=;for the emergenc.: spillway as
QE— Q.c—Q� (QF.'— Q')
• From Table®or Table®select the width and depth of the outlet. Table 8.07c
depending on soil conditions_ In general. the wider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
0 = CLHi

`here this option is used. the maxim m value of C should he _' 8. L SB 2-23
'
is the bottom width of the sp311 a:at the crest, and H is the depth of 6/22/22
flour above the spill, a-,•crest in fee:. \ote Manning's channel equattan
should not be used to size the spi11+.;-a_:crest. Howe-:er.it should be used Page 5
to design the outlet channel below the spillway crest
• The total of the emergency and prmctple spill:cav capacities must equal
or exceed the required 10 ear peal,discharge.
• Set the elevation of the crest of the emergency spillway a minimum of 1
foot above the crest of the riser
OPTION 1
Quo 3.45
QP #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
AdJust the spillway alignment so that the control section and outlet section
are straight The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the contrel section. Approach
channel should slope toward the reservoir no less than 10 0
Width of control section (ft) 6
Width of entrance (ft) 4
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillwa-v near where it intersects the
extension of the centerline of the dam
• Keep a level area to extend at least 20 ft upstream fiom the cutlet end of
the control section-to en-ure a straight aligrutnent.
• Side slopes should be 3:1.
Step 12. Desisn spillway exit section.
• Spiftwaz: exit should align with the control section and ha-ve the same

SB 2-23
6/22/22
YAJobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-23.xis
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 4
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 4.6669
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 4.6669 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-23
• Slope should be sufficient to maintain supercritical flow.but make sure it 6/22/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appiopriate design tables.)
• Extend the exit channel to a point where the water may be released without
damage
Step 13. Size the embankment_
• Set the design elevation of the top of the dam a minimum of 1 R above the
water surface for the design flow in the emergency spillway-
Constructed height should be 10°'u greater than the design to allow for
settlement.
• Base top width on the design height_
• Set side slopes 2.5:1 or flatter.
• Determine depth of cutoff trench from site bonags. It should extend to a
stable,tight soil layer(a minimum of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a siexaficant
amount of fill_
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Spectflcarions: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(P)-actice Standards
and Specifications: 6.10, Temporary Seeding; 6.14, 1lulching;and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions. Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 14. Safety.
• Construct a fence and install warning signs as needed.
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-23.xls

SEDIMENT BASIN DESIGN S B 2-24
8/25/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
Y:IJobs121-004 Mocksville(R210004)IDocuments\Reports1SB 2-24.xis
Designed By: PNJ Date: $12.51Z2Z
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-24
Total Drainage Area (acres) 2.29
Step 1. Determine peak flog. Q,,, for the basin drainage area C4DYe�,,d x S.03)
Q10 (cfs) 9.43
Step 2. Detern1i11e an-, site linutations for the sediment pool elevation,emergence
spillway or top of the dan1_
Minimum pool elevation (ft) 745
Maximum pool elevation (ft) 748.5
Step 3. Determine basui volumes:
• Compute 1111nrnlum volume reglllred(1800 f-,acre disturbed)
• Specifi- sediment cleanoult level to be marked on riser (one-half the design
olullne referenced to the top of the riser) and sediment storage area to be
cleared after the dam is built.
Disturbed acreage (ac) 2.29
Min Volume (ft) 4122
Sediment cleanout elevation (ft) 746
Sediment Storage Area 2418

Y:IJobs121-004 Mocksville(R210004)IDocuments\ReportslSB 2-24.xis SB 2-24
Step 4. Deternniue area and shape of baser: Page 2
• Check length width ratio (should be 2:1 to 6:1).
• Compute the basin surface area at principal spillway elevation.
• Check the ratio of basin surface area to peal. urflou rate (should be greater
than or equal to 435 ft' cfs). Employ diversions with additional traps and
basins to reduce area drained.
Determine barrel capacity required for site conditions (minimum capacity for 0,
is the '-year peak runoff, Qi.
Length/width ratio 2.04
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 4140
Ratio: basin surface area/Q10 439.02439
Is ratio >= 435 ft2/cfs? YES
Step -5. Determine the principal split- ay discharge capacity.
• The combined capacities of the principal and emergency spffl-ways must be
at least the 1 0-rear peak flow for the entire watershed of the basin.
• The principal spfflway is analyzed for three possible limiting flog' types:
NV'eir flow, Orifice flow. and Pipe flow. The principal spillway discharge
capacity is the smallest of these three flow rates. Discharges through a
skimmer should be disregarded during this computation. Weir, orifice and
pipe flog may be determined by the followmi c, equations:
1. Weir Flow: Q = CLH`-°
where:
Q =discharge ur cubic feet per second(cfs)
C =weir coefficient. use 3.1 for corrugated metal pipe risers.
L=circumference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
Q, (cfs) 0
?. Orifice Flow: Q = CA (29H)'0-5
where: 8/25/22

Q= discharge in cubic feet per second (cfs) SB 2-24
C = orifice coefficient. use C = 0.6 for comwated metal pipe risers Page 3
A=cross-Sectional area of the riser pipe in square feet
g =acceleration due to gratiity, 3-.? ft sec'
H =head above riser crest in feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)
,gh o:
3_ Pipe Floe: Q = a 1 + K.+1p L J
where:
Q = discharge iu cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration due to gravity, 3?2 ft'ser'
h =head above the centerline of the outlet end of the barrel
K,„ = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
Kr, =pipe friction coefficient:
_ 5087n2 (See Table 8.o7a for KR values for
0i 3 common size of pipe.)
n =Manning-s coefficient of roughness, use n =0.025 for
corrugated metal pipe
n = 0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are -unproved by
maximizing weir flow and minimizing orifice flow•. See Table 8.07b for
recommended risevbarrel proportions
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-24
Inside diameter of barrel, d; (in) 0 8/25/22
Pipe friction coefficient, KP #DIV/O!
Discharge, Qo (cfs) #DIV/O! 0
Page 4
RISER
Select nail riser and barrel dimensions. Use the weir, orifice and pipe ff mr
equations to determine if the' , ear peak discharge is passed without activating
the emergency spill-.ra_:. Determine riser size from Figure 8.01 b. Check the
head and stage requirements. If the design stage is too high. choose lamer Table 8.07b
dimensions and recalculate. As a minimum.set the elevation of the riser at the
same elevation as the top of the sediment pool_ A riser height 2 to= times the
barrel diameter r.s teccmmended. Select the Type of trash ward.
Select a dev.-aterina device. If a skimmer is used. refer to the manufacturers
dewaterine data, or Table 6 64.b.
Step 6. Design antiseep collar.
Ensure that antiseep collars are no closer than 2 ft from a pipe joint_ Collar
must project at least 15 ft from the pipe. Indicate watertight connections.
Step 7. Design antrflotation block_
Determine the weight of:rater displaced by the empty riser. and design a
block with buoyant weight 1 1 times the weight of water displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step S. Design outlet_
Determine discharge velocity, from the barrel. Design outlet protection to
assure stable conditions. Riprap placement is usually necessary (Appendix
8.06)
Discharge velocity, V (ft/s) #DIV/O! #DIV/O!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway.
• Determine the required capacity for the emereency spillway as
Qe= Q.0—Q; (QR Q2)
• From Table=or Table®select the width and depth of the outlet. Table 8.07c
depending on soil conditions. In general, the wider bottom widths and Table 8.07d
loner- slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
0 = CLH'

Where this option is used,the maximum value of C should be 2.3. L S B 2-24
is the bottom width of the spillway at the crest. and H is the depth of $/25/22
how above the spillway crest in feet. Note:Manning's channel equation
should not be used to size the spillway crest_ However,it should be used Page 5
to design the outlet channel below the spillway crest.
• The total of the emergency and principle spillway capacities must equal
or exceed the required 10-year peak discharge.
• Set the elevation of the crest of the emergency spillway a minimum of 1
foot above the crest of the riser.
OPTION 1
Q10 9.43
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
Qp + Qe #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment so that the control section and outlet section
are straight_ The entrance width should be 1.5 times the width of the control
section with a smooth transition to the width of the control section. Approach
channel should slope toward the reservoir no less than 20/0_
Width of control section (ft) 15
Width of entrance (ft) 10
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillway near where it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream from thee outlet end of
the control section_to ensure a straight alignment.
• Side slopes should be 3:1_
Step 12. Design spillway exit section_
• Spillway exit should align with the control section and have the same

SB 2-24
8/25/22
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-24.x1s
Page 5A
OPTION 2
Weir coefficient, C -
Bottom width of spillway crest, L (ft) 1�>
Depth of flow above spillway crest, H (ft)
Emergency spillway capacity, Qe (cfs) 11 .6673
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 11.6673 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-24
• Slope should be sufficient to maintain supercritical flow,but make sure it 8/25/22
does not create erosive velocities for site conditions. (Stay within slope Page 6
ranges in appropriate design tables_)
• Extend the exit channel to a point where the water may be released without
damage.
Step 13. Size the embankment_
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design Sow in the emergency spillway
• Constructed height should be 10% greater than the design to allow for
settlement.
• Base top width on the design height.
• Set side slopes 2.5:1 or flatter_
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a anniuium of 2 ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Temporary Seeding; 614,fulching;and 6.15,
Riprap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotextile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils_
Step 1-5. Safety_
• Construct a fence and install warning signs as needed.
Y:IJobM21-004 Mocksville(R210004)IDocumentslReportslSB 2-24.x1s

SEDIMENT BASIN DESIGN SB 2-25
6/23/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)1DocumentslReports\SB 2-25.x1s
Designed By: PNJ Date: 6/Z3lZ2-
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-25
Total Drainage Area (acres) 2.87
Step 1. Deterilune peak floe-, Q�- for the basin drainage area S.0 )
Q10 (cfs) 11.48
Step '_. Deteri22ine anv site hi22itations for the sediment pool elevation,emergency
spillway or top of the c!un-
Minimum pool elevation (ft) 779.75
Maximum pool elevation (ft) 783.5
Step 3. Deterilluie basi l volumes:
• Compute liiiiiinitim volume required(1800 f 3 acre disturbed)
• , ifl seclii22ent cleanout level to be marked on riser (one-half the design
L olu me referenced to the top of the riser) and sediment storage area to be
cleared after the clam is built
Disturbed acreage (ac) 2.73
Min Volume (ft) 4914
Sediment cleanout elevation (ft) 780.75
Sediment Storage Area 3132

YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-25.xis SB 2-25
Step 4. Deternuile area and shape of basin: Page 2
• Check length width ratio (should be 2:1 to 6:1)
• Compute the basin surface area at principal spilh�-a-' elevation_
• Check the ratio of basin surface area to peak infiow�- rate (:should be greater
than or equal to 435 ft',cfs). Employ diversions with additional traps and
basins to reduce area drained.
De reruline barrel capacity required for site conditions (I111nimuni capacity for 0-
is the 2-year peak runoff- Q`.
Length/width ratio 2.02
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 5050
Ratio: basin surface area/Q10 439.89547
Is ratio >= 435 ft2/cfs? YES
Step 5. Determine the principal spill-way-discharge capaeit-v
• The combined capacities of the principal and emergency spillways must be
at least the 10--%ear peak flow for the entire watershed of the basal.
• The principal spill-way is analyzed for three possible linutmg floe- t-,.Ws:
Weir flour, Orifice flow. and Pipe flow. The principal spills ay discharge
capacity is the smallest of these three flow rates. Discharges through a
skulimer should be disregarded during this computation Weir, orifice and
pipe floe-mati-be determined by the followu' lg equations:
1. � eir Flog-: Q = CLH'
wllere:
Q = discharge in cubic feet per second(cfs)
C =weir coefficient_ use 3.1 for corrugated metal pipe risers.
L = circuimtereIlce of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 4.71238898
Head above riser crest, H (ft) 0.75
Qw (cfs) 10.1005952
Orifice Flo,,. : Q = CA (2gH)=
where:
6/23/22

Q = d1wharge in cubic feet per second (cfs) SB 2-25
C = orifice coefficient. use C = 0.6 for comlaated metal pipe risers. Page 3
A = cross-sectional area of the riser pipe il1 square feet
g =acceleration due to aravin-_ 32' ft sec'
H = Bead above riser crest i11 feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 1.76714587
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft) 0.75
Discharge, Qo (cfs) 7.36880757
Riser Diameter (in.)L 18
'gh
3_ Pipe Floe 0 = a [1 _ lm+kr L
where:
Q =discharge ill cubic feet per second(cfs)
a =cross-sectional area of the barrel in square feet
g = acceleration clue to gravity. 32.2 ft'sec'
h =head above the centerline of the outlet end of the barrel
Km = coefficient of 111111or losses_ can be assumed to be 1.0 for
most principal spillway systems
L =barrel length u1 feet
K� =pipe friction coefficient:
_ 5087n2 (See Table s.o7a for K. values for
di43 common size of pipe_)
n coefficient of roughness_ use n =0.02 for
corrugated metal pipe
n = 0.015 for reinforced concrete pipe
di =inside diameter of the barrel in inches
Select riser and barrel dunensions so that the riser has a cross-sectional area
at least 1_5 times that of the barrel. Spillway hydraulics are improved by
maxu111Z1116 weir flow and mi'111nl171 11q orifice flow. See Table 8 07b for
recommended riserbarrel proportions.
Barrel diameter (ft) 2
Barrel cross-sectional area, a (ft2) 3.1
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft) 1
Minor loss coefficieint, Km 1.0
Barrel length, L (ft) 50

Mannings coeffienct of roughness, n 0.025 SB 2-25
Inside diameter of barrel, d; (in) 24 6/23/22
Pipe friction coefficient, KP 0.04593
Discharge, Qo (cfs) 12.1631234 17.8269813
Page 4
RISER
Select hail rise: and barrel drmen:�lons t*se the rei:_ orifice and pipe f z-1v
equations to determine if the 2=:ear peak discharge is passed w thcut ac:r•.atms
the emereenc> spilhra_._ Determine riser size from Figure 3.07b. Check-the
head and stage requirements. Ii the design stage is too high. choose larger Table 8.07b
d1mensicnS and recalculate- As a uunimlrm,set the elevation of the riser at the
same ele attcn as the top cf the sediment pool. Anger height 1 to f times the
barrel diameter is recommended. Select the rope of trash--rra.d_
Select a dewatermg de:-ice_ If a skimmer is used. refer to the manufacturers
dewaterinsr data, or Table 6 64 b
Step 6. Design anti-seep collar.
Ensure that auriseep collars are no closer than 21 tt fiom a pipe joint. Collar
must project at least L5 ft from the pipe. Indicate watertight connections
Step 7. Design autiflotation block.
Determine the weight of water displaced b,5,- the empty- riser. and de_.rgn a
block-with buoyant weight I.1 times the.-eight of i ater displaced.
Riser Height 3.5
Weight of water displaced by the empty riser 386.130208
Buoyant weight 424.743229
Step S. Design outlet.
Determine discharge telocir; from the barrel Design outlet arotection to
assure stable conditions. R.iprap placement is usuall-V necessar_s- (.AR endir
S.J6j
Discharge velocity, V (ft/s) 3.87164241 5.67450438
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spill„•ay.
• Determine the required capacir;for the emersenc-y spffl-,va;-as
Qe= Q,—Q� f QF•_> Q,)
• From Table=or Table®select the width and depth of the cutlet. Table 8.07c
depending cn soil conditions. In general_ the -, ider bertcm widths and Table 8.07d
lower- slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = CLHI`

'?.'here:his option is used. the max ini n value of C should be 2 3. L SB 2-25
is the bottom.width of the spill-xa-, at the crest. and;i is the depth of 6/23/22
Eo. above the spill;%-a; :rest in feet. Note: Nlanning's channel e,uattcn
should not be used to size the spillway;ctest Ho.ve-:er. it should be used Page 5
to deste_r the outlet channel below the 'spill•.4av crest
• The total of the emergency and ptmciple spill,.va_:capacities Must equal
cr exceed the required 10-year peak discharge.
• Set the elevation of the crest of the emergency: sprlh av a mintmum of _
foot abo,:e the crest of the riser.
OPTION 1
Quo 11.48
Qp 7.36880757
Emergency spillway capacity, Qe (cfs) 4.11119243
Qp + Qe 11.48
Does (Qp + Qe) equal or exceed Q10? YES, PROCEED
Step 10. Spillway;approach section.
Adjust the spiUwav alignment so that the control section and outlet section
are straight. The entrance width should be I.5 times the width of the control
section with a smooth transition to the width of the control section. Apptoach
channel should slope toward the reset:orr no less than_'0.
Width of control section (ft) 15
Width of entrance (ft) 10
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the SpillWaY near where it intersects the
extension of the centerline of the dam.
• Beep a level area to extend at least 20 8 upstream fiom the cutlet end of
the control section.to ensure a straight alignment_
• Side slopes should be 3:1.
Step 1-1. Design spillway exit section.
• Spilb.:-at; exit should alien with the control section and have the same

SB 2-25
6/23/22
Y:\Jobs\21-004 Mocksville(R210004)\Documents\Reports\SB 2-25.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 10
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 11.6673
19.0361
YES, PROCEED
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 19.0361 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom:width and side slopes. SB 2-25
• Slope should be sufficient tc maintain supercritical floe-,but make sure it 6/23/22
does nct create erosive velocities for site ccndinons (Stay-within slope Page 6
ianges in appropriate design tables.)
• Extend the exit channel to a point inhere the water may be released without
damage.
Step 13. Size the embankment.
• Set the design elevation of the tcp of the dam a minimum of 1 ft above the
water surface for the design flow in the emergency spillway-
Constructed height should be 10°•6 greater than the design to allow for
settlement
• Base tap width on the design height.
• Set side slopes 2.5:1 or flatter_
• Deteimine depth of cutoff trench from site borings_ It should extend to a
stable.tight soil layer(a minimum of?ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erasion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and.Specicadons: 6.20, Temporary Diversions).
• Select surface protection measures to control erosion(Practice Standards
and Specifications: 6.10, Temporan,Seeding; 6_14, Mulching: and 6.15,
Riprrap)-
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions_ Riprap stone over geotestile
fabric may be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 1-. Safety_
• Construct a fence and install learning signs as needed.
Y:1Jobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-25.xis

SEDIMENT BASIN DESIGN SB 2-26
6/23/22
This structure is intended for less than 3 years of use. Structures intended
for more than 3 years of use should be designed as permanent structures.
User Input Data
Calculated Value
Reference Data
YAJobs121-004 Mocksville(R210004)1DocumentslReportslSB 2-26.xis
Designed By: PNJ Date:
Checked By: Date:
Company: American EA
Project Name: Nelson's Creek
Project No.: 21-004
Site Location (City/Town) Mocksville
Sediment Basin Id. SB 2-26
Total Drainage Area (acres) 1.62
Step 1. Determine peal:fio-w- 0 1 C I for the basin drauia?e area (Azrpf?>;ciX S.03)
Q10 (cfs) 5.45
Step 2. Deternune amv site limitations for the sediment pool elevatiolz,emergency
spilhwwv or top of the darn_
Minimum pool elevation (ft) 745
Maximum pool elevation (ft) 748.5
Step 3. Deternurne basin vohunes:
• Counptrte nnlrnnuuun v olume required(1800 ft acre disturbed)
• Specrf�- sediment cleanout level to be marked on riser (one-half the design
v olunle referenced to the top of the riser) and sediment storage area to be
cleared after the darn is built
Disturbed acreage (ac) 1.17
Min Volume (ft) 2106
Sediment cleanout elevation (ft) 746
Sediment Storage Area 1120

YAJobM21-004 Mocksville(R210004)IDocuments%Reports1SB 2-26.xis SB 2-26
Step 4. Deternune area and shape of basin- Page 2
• Check length width ratio (should be 2:1 to 6:1.).
• Compute the basin surface area at pruicipal spillway elevation.
• Check the ratio of basin surface area to peak inflow rate t.should be Greater
than or equal to 435 ft cfs). Employ diversions with additional traps and
basins to reduce area drained
Determine barrel capacity required for site conditions (ninimuun capacitti' for Q,
is the 2-Fear peak runoff, Q.,.
Length/width ratio 2.06
Is length/width ratio between 2-6? YES, PROCEED
Basin surface area @ principal spillway (ft) 2380
Ratio: basin surface area/Q10 436.697248
Is ratio >= 435 ft2/cfs? YES
Step 5. Deternne the principal spillway discharge capacit;-.
• The combined capacities of the principal and emergency spillways must be
at least the 10--%ear peak flog' for the entire watershed of the basin.
• The principal spillway is analyzed for three possible limiting floe- vvpes-
l eir flow, Orifice ffo-,z-- and Pipe flow. The principal spillway discharge
capacity is the smallest of these three flocs- rates- Discharges through a
skinuner should be disregarded during this computation. Weir, orifice and
pipe floe- may-be detemuned by the followu' ig equations:
1. `Veir Floe,-: Q = C LH'-=
where:
Q = discharge in cubic feet per second(cfs)
C =weir coefficient. use 3--1 for corrugated metal pipe risers.
L=circ-uniference of the riser in feet
H =head above riser crest in feet
Weir coefficient, C 3.3
Riser circumference, L (ft) 0
Head above riser crest, H (ft)
QW (cfs) 0
'. Orifice Flow: Q = CA (2gH)
6/23/22

J = discharge - 1 cubic feet per second (cfs) SB 2-26
C = orifice coefficient_ use C _0.6 for corrugated inetal pipe risers Page 3
A= cross-sectional area of the riser pipe in square feet
g =acceleration due to gravity_ 32_2 ft-sec-
H =head above riser crest In feet
Orifice coefficient, Co 0.6
Riser cross-sectional area, A (ft2) 0
Accleration due to gravity, g (ft/s2) 32.2
Head above riser crest, H (ft)
Discharge, Qo (cfs) 0
Riser Diameter (in.)IL -
gh 11
3. Pipe Flow: O = a �1 = K, +ILL J
F
Z�'llere:
Q = discharge in cubic feet per second(cfs)
a =cross-sectional area of the barrel in sgwire feet
g = acceleration due to gravity. 32_2 ft'sec'-
h =head above the centerline of the outlet end of the barrel
K,,, = coefficient of minor losses, can be assumed to be 1.0 for
most principal spillway systems
L =barrel length in feet
K' =pipe friction coefficient:
_ 5,087n (See Table 8•o7a for KF t.ahles for
dig a common size of pipe.)
n =-Maiuiing-s coefficient of roughness. use n =0.0 5 for
corrtigated metal pipe
n = 0.01 for reinforced concrete pipe
di = inside diameter of the barrel in inches
Select riser and barrel dimensions so that the riser has a cross-sectional area
at least 1.5 times that of the barrel. Spillway hydraulics are improved bz
maximnizmg weir flox and ninimizii' orifice flow. See Table 8.07b for
recommended riser barrel proportions.
Barrel diameter (ft)
Barrel cross-sectional area, a (ft2) 0.0
Accleration due to gravity, g (ft/s2) 32.2
Head above outlet end of barrel, h (ft)
Minor loss coefficieint, Km 1.0
Barrel length, L (ft)

Mannings coeffienct of roughness, n 0.025 SB 2-26
Inside diameter of barrel, d; (in) 0 6/23/22
Pipe friction coefficient, KP #DIV/0!
Discharge, Qo (cfs) #DIV/0! 0
Page 4
RISER
Select %ail rise± and barrel d+men i.ns L'=e the :ei:. orifice and pipe fcov
equations to detetmrne rf the 2 ear peal:discharge is passed without acts:atrng
The emergenc_, spil!zyay. Determine r-et size from Figure 8.07;b_ Check the
head and stage requirements. If the design _tape is too high. choose larger
dinrensic.m_.and recalculate. As a mimmtuu gy,.set the ele ation ofthe riser at the Table 8.07b
same elevation as the top of the sediment pool A riser height' to` times the
barrel diameter i:;recommended. Select the rYpe of trash guard
Select a dewatering device. If a slimmer is used. refer to the manumctuters
dewatering data. or Table 6 64 b
Step 6. Design anti.seep collar.
Enstue that antiseep collars are no closer than 2 ft from a pipe joint_ Collar
must project at least I : R from the pipe Indicate waterright conmectious_
Step ?. Design an%flotation block
Determine the weight of water displaced by the emprY riser. and design a
block with buoyant weight 1.1 times the weight of i ater displaced.
Riser Height
Weight of water displaced by the empty riser 0
Buoyant weight 0
Step 8. Design outlet
Determine discharge -velacitv from the barrel. Design outlet protection to
assure stable conditi.ns Riprap placement is usuall necessar v i_4ppendix
S 06)
Discharge velocity, V (ft/s) #DIV/0! #DIV/0!
See Appendix 8.06 for riprap sizing, if necessary
Step 9. Design emergency spillway
• Determine the required capacirr fog the emergence;spillway as
Qe= 0.0—Q. (QF' Qa)
• From Tablf=oi Table®select the width and depth of the cutlet. Table 8.07c
depending on soil conditions. In general_ the hider bottom widths and Table 8.07d
lower slopes are preferred to minimize exit velocities at supercritical
flow
• An acceptable alternative is the use of the weir equation
Q = CLH'

'j.'here This option is used. the maxim:un value o:C should be_' 3 L SB 2-26
is the lloottom width of the spilhva-:at the crest, and r:is the depth of 6/23/22
f o.- a ove the sotlhva-,;crest in feet. dote: Manning's channel equattoa
should not be used to size the spill,.va-.crest_ However-it should be used Page 5
to de:ten the outlet channel below the .pill,v av crest.
• The total of the emergency- and principle ---pillwav capacities must equal
or exceed the requited 10-Near peak dischatge.
• Set the elevation of the crest of the emergencv spillwav a minimum of 1
foot above the crest of the riser.
OPTION 1
Quo 5.45
Qp #DIV/0!
Emergency spillway capacity, Qe (cfs) #DIV/0!
(gyp + (fie #DIV/0!
Does (Qp + Qe) equal or exceed Q10? #DIV/0!
Step 10. Spillway approach section.
Adjust the spillway alignment se that the control section and outlet section
are straight. The entrance width should be 1 5 times the :width of the control
section with a smooth transition to the width of the control section_ approach
channel should slope toward the resen-otr no less than 2"o-
W idth of control section (ft) 9
Width of entrance (ft) 6
Slope of approach channel (%) 2
Is width of the entrance section 1.5xcontrol section
width? YES, PROCEED
Is approach channel >/= 2%? YES, PROCEED
Step 11. Spillway control section
• Locate the control section in the spillcwa%. near ,there it intersects the
extension of the centerline of the dam.
• Keep a level area to extend at least 20 ft upstream from the cutlet end of
the control section. to ensure a straight alignment_
• Side slopes should be 3:1
Step 12. Design spillway exit section
• Spillway exit should align utth the control section and have the same

SB 2-26
6/23/22
Y:\Jobs121-004 Mocksville(R210004)\Documents\Reports\SB 2-26.x1s
Page 5A
OPTION 2
Weir coefficient, C 3.3
Bottom width of spillway crest, L (ft) 6
Depth of flow above spillway crest, H (ft) 0.5
Emergency spillway capacity, Qe (cfs) 7.00036
#DIV/0!
#DIV/0!
SPILLWAY IS ADEQUATE
Spillway + Riser Flow 7.00036 cfs
SPILLWAY + RISER IS ADEQUATE
(Print Page 16)

bottom width and side slopes. SB 2-26
• Slope should be sufficient to maintain supercritical flow-.but make sure it 6/23/22
does not create erosr:a velocities for site conditions (Star-within slope Page 6
ranges in appzopriate design tables.)
• Extend the exit charnel to a point where the water may be released w-ithour
damage.
Step 13. Size the embankment
• Set the design elevation of the top of the dam a minimum of 1 ft above the
water surface for the design floe;in the emergency spillway
• Constructed height should be 10°0 greater than the design to allow- for
settlement.
• Base top width on the design height.
• Set side slopes 2.5_1 or flatter.
• Determine depth of cutoff trench from site borings_ It should extend to a
stable,tight soil layer(a minimum of ft deep).
• Select borrow site—the emergency spillway cut will provide a significant
amount of fill.
Step 14. Erosion control
• Locate and design diversions to protect embankment and spillway
(Practice Standards and Specifications: 6.20, Te►npo►•ar y Diversion).
• Select surface protection measures to control erosion(Practice Standards
and Specifications. 6.10, Temporan,Seeding; 614, lizzlciiing;and 6.1.5.
Ripr•ap).
• Select groundcover for emergency spillway to provide protection for
design flow velocity and site conditions. R.iprap stone over geotextule
fabric ma}-be required in erodible soils or when the spillway is not in
undisturbed soils.
Step 15. Safety.
• Construct a fence and install warning signs as needed_
Y:IJobs121-004 Mocksville(R210004)1DocumentslReports1SB 2-26.xis

Major Stream Crossings and Permanent Rip-Rap Outlets
10

RIP-RAP PADS
Phases 1 & 2
Date: 3/13/23
Y:\Jobs\21-004 Mocksville(R210004)\documents\Schedules\Rip-Rap Pads.xlsx
Using NYSDOT Method
OUTLET PIPE DIA. VELOCITY ZONE STONE STONE WIDTH LENGTH DEPTH
NO. (IN.) (FPS) SIZE CLASS (FT.)* (FT.) (IN.)
A 72" &60" 9.06 4 13" 1 35.5 48 36
B
C 48" 5.01 2 6" B 16 24 18
A- Nelson Creek Dr.
B- Murphy Meadow Rd. (Crossing eliminated)
C- Frontiersman Dr.
*Downstream width, use 3 x pipe diameter upstream (single pipe), 3 x pipe diameter+center
to center distance between pipes upstream (multiple pipes).
FES 100 18" 5.98 1 3" A 5.5 6 12
FES 102 18" 8.8 2 6" B 6 9 18
FES 200 42" 9.29 3 13" 1 15.5 28 24
FES 400 15" 6.8 1 3" A 5 5 12
FES 450 18" 12.46 2 6" B 6 9 18
FES 500 42" 11.9 3 13" 1 15.5 28 24
FES 601 15" 6.5 1 3" A 5 5 12
FES 10 15" 16.38 3 13" 1 5.5 10 24
EW 11 54" 16.78 5 23" 2 21 45 36
FES 610 15" 4.65 1 3" A 5 5 12
FES 615 15" 5.99 1 3" A 5 5 12
FES 630 24" 11.53 3 13" 1 9 16 24
FES 700 24" 8.7 2 6" B 8 12 18
FES 750 18" 5.07 1 3" A 8 20 12
FES 760 15" 6.52 1 3" A 5 5 12
FES 800 24" 11.66 2 6" B 8 12 18
FES 820 36" 9.46 3** 13" 1 13 24 24
FES 810 18" 7.84 2 6" B 6 9 18
FES OS1 18" 3.1 1 3" A 5.5 6 12
**Next higher zone due to >10%grade on slope
#Plunge Pool, see detail for lowered bottom

Post-Construction Permitting Exhibit and Stream Buffer Requirement

Project Name: Nelson's Creek Job Number: 21-004
Project Manager: John MacDonald Project Engineer:
Owner: Richard Denzler—C2C Land Development LLC—rdenzler06130 a.road runner.co
PO Box 4628, Mooresville, NC 28117 Direct: 800.369.0120 Mobile: [phone] Fax: [phone]
Client: DR Horton
Marty Jones msiones(a)drhorton.com 336.847.0946
Brad Yoder bhvoder(cDdrhorton.com 336-307-5252
Ryan Moats rcmoats(a-drhorton.com 336-580-3905
Surveyor: Jordan Grant&ASS 704.928.8047 [e-mail] Contact- Gerald Grant
Aerial: WithersRavenel 919.238.0486 [e-mail] Contact- Karen Hancock
Enviro: ECS Southwest LLP 704.525.5152 [e-mail] Contact- Brandon Fulton
Architect: Phone#- Fax#- Contact-
Lighting: Phone#- Fax#- Contact-
Traffic: Ramey Kemp 336.813.9289 [e-mail] Contact- Chase Smith
Municipality: Davie County Phone#- Fax#-
Town of Mocksville contacts Direct Number Email Address
Brian Moore— PW Director 336.753.6739 [e-mail]
Amy Flyte— Planner 336.753.6050 atlyteiwdaviecountync.aov
Chuck Willis - Consultant 704.338.4668 [e-mail]
Zack Lentz— E.C. — DEQ 336.776.9116
Client Comments and Notes

4#
J'
Post-Construction Stormwater Permitting Information
County DAVIE
- 'Where am i? DAVIE CCD
Permitting None
h `
} T e None: Unincorporated
b area, County
Basis No Program Identified
ell
Notes, Verify ,,vith local authority
Contact DAVIE CO
-r-� DEQ Region Winston-Salem
QCategory No Stormwater Program
Zoom to
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SIT
Mocksville, North Carolina
1 September 7, 2022
. '1AMERICAN Page 1 of 1
Englr.eering
8008 Corporate Center Drive, Suite 110 j Charlotte, NC 28226 1 704.375.2438 Note: Conceptuar O?ans only, lot yield and layout subject to change based on,final design and approvals,

NC
Surface Classifications
4r c
0@
i _ S%01 Surface Water Classifications: � �1
�•r'`
Stream index: 12-102-15-1
A
Steam Name: Nelson Creek
Description: From source to Elisha Creel
r0-
t
Classification: C
? I
N
Q
Date of Class.: August 31, 1974
y
What does this Class. mean? View
River Basin: Yadkin Pee-Dee r
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61
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' T
A
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k6
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SITERich Park II l r
�jk' �ei''•,i r 1.'j �;� I
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Wilk 03b or, �rS�.'Jn
Ills
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• - -
Mocksville, North Carolina
September 7, 2022
AMERICAN Page 1 of 1
1 Engineering
Note: Conceptual plans only,lot yield and layout subject to change based on Final design and approvals
8008 Corporate Center Drive, Suite 110 Charlotte, NC 28226 1 704.375.2438