20210125 - Project Narrative and ESC

,.1
62S
ENGINEERING & ENVIRONMENTAL SCIENCE COMPANY
3008 ANDERSON DRIVE, SUITE 102
RALEIGH, NC 27609
[phone]
January 25, 2021
Mr. Tony Merritt
Tony Merritt's Gravel Pit
3200 Damascus Church Road
Chapel Hill, NC 27516
RE: Mine Erosion Control Evaluation RECEIVED
Tony Merritt's Gravel Pit
3200 Damascus Church Road JAN 2 5 2021
Chapel Hill, NC 27516
Permit No. 68-04 LAND QUALITY
MINING PROGRAM
Dear Mr. Merritt:
Engineering & Environmental Science Company (E2S) has completed the evaluation for the above
referenced mine. Following is a brief discussion of the mine and our evaluation.
1-11I,Z111-Kill Wilkle"I V [IIAN
The subject mine contains 26.12 acres of land. Modifications are proposed and include:
1. Relocation of the pump discharge basin.
2. Placement of fill in the northeast corner of the mine to develop the 25 ft. undisturbed buffer
(about 12,400 cubic yards of fill soil required).
3. Plant shrubs, trees, or bamboo along portions of the east undisturbed buffer (about 650
lineal feet of buffer area requires the vegetation for screening the mine).
4. Slope ground along the east side of the mine excavation toward the mine and a 1% slope
or steeper.
5. Install Culvert No. 1 down slope of the access/haul road to divert water into the mine.
6. Revegetate the sloped, undisturbed buffer along the west side of the mine limits.
The proposed mine modification also includes the addition of 0.71 acres of land where the
access/haul road is located. The permit limit is proposed at the west side of the 60 ft. easement to
form a 55 ft. wide unexcavated buffer. With the added land, the total permitted land will be 26.83
acres. Total disturbed land will be 23.73 acres for the life of the mine (about 20 years).
The mine is an excavation below the surrounding ground levels. No stormwater gravity flow is
allowed. Stormwater accumulates in the excavation and the water level generally reflects the

Page 2
Mine Erosion Control Evaluation
Tony Merritt's Gravel Pit
groundwater table. During heavy rains, and typically between late fall and early spring, pumping
is required. Pumping will be at a maximum rate of 1000 gpm. The pump discharge is through a
sediment basin that is sized to remove at least the 40-micron particle size. Total water pumped
daily will not exceed 10,000 gallons.
Concurrently with mining, beneficial fill will be used to fill the excavation and reclaim the mine
area. As the mine excavation is filled and before stormwater can no longer be contained in the
mine excavation, two sediment basins are required to accommodate gravity stormwater runoff.
Upon completion of mining, beneficial fill placement, and ground stabilization, the pump basin
and sediment basins will be removed and vegetated. However, the berm and outlet structure for
Basin No. 2 will remain in -place to convey the stormwater to the adjacent pond. The haul road
located in the easement and the office building will remain in -place.
EVALUATION
Attached are the erosion control calculations. For the water accumulation in the mine excavation,
the mine surface water will rise approximately 2.8 ft. for the 25-year rain event with a free board
of more than 1 ft. The surface area is assumed 3 acres.
Basin A (pump basin) will have the capability to settle at least the 15-micron particle size.
The TR-55 method was used to evaluate Basin Nos. 1 and 2, Culvert No. I and Ditch Nos. 1 and
2. The outlet for the basins, sizing the culvert and ditches was based on the 25-year rain event. The
10-year rain event was used to size the basin dimensions and stone outlet stabilization, and ditch
stabilization.
CLOSURE
We appreciate serving you on this project. Please contact me if you have any questions about this
evaluation.
Sincerely,
��
T. Patrick Shilli Pon E.
President
Attachment: Erosion Control Calculations
e2s

ATTACHMENT:
Erosion Control Calculations
M

Scale I" - 1000'

Scale 1" = 500'

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Precipitation Frequency Data Server
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage. htm I?lat=35.8...
NOAA Atlas 14, Volume 2, Version 3
Location name: Chapel Hill, North Carolina USA'
Latitude: 35, Longitude:-79.0861° Elevation:
{
Elevation: mlft"'
source: ESRI Maps y„tl
"source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, 0. Martin, 8. tin, T Parzybdc, M.Yekta, and D. Riley
NOAN National Weather Service, Silver Spring, Maryland
PF_tabular I PFyraphical I Mao_& aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)l
_Duration
-
recurrence interval (years)
FF
1
���-F-''��,
2
5
_Overage
_50
1 100
1 200
1 Soo
1000
0.412
0.486
0.560
0.617
0.678
0.720
0.758
0.790
0.824
0.851
5-min
(o.377-0.451)
(0.445-0.532)
(0..513-0.612)
(0.564-0.674)
(0 616-0 739)
(0 652 0 785).
(0.683-0.826)
(0 708-0.862)
(0 732-0.900)
(0 749 0 931)
0.777
0.896
0.987
1.08
1.16
1.20
1.25
1.30
1.34
n0.658
10-min(0.603-0720)
(07120.850)
(0821-0.980)
j (0903108)
(0982-118)',I
(1.D41.25).1
(109131)
1 (112-1_3J
(t.trr1.42)
(1.18-1.47)
1.45
L52
1.58
1.64
1.68
�15-min
(0.758-0900 )
( 0 95-1607)
(1.04324)
(1 42536).
(1.25-149)_..
(1.32-158)_
1 (1371.66)
1 (142-173)
1_(1,46-1.79).
(1.48-1.84)
L13
L35
1.61
1.81
2.03
2.19
2.33
2.46
2.61
2.72
30-min
(1.03-1.23)
(124-1.48)
(1 48-1.76)
1 (1 65-1 98)
1 (1.84-2.21) 11
(1.98 2 38)
1 (2.10-2.54)
1 (2.20-2.69)
1 (2.32-2.85)
1 (2.40-2.98)
1.41
1.69
2.07
2.36
2.70
2.96
3.21
3.45
3.75
3.98
60 -min
(1.29-1.54)
(1.55-1.85)
(1.89-2.26)
1 (215-257)
1 (246.2.94)
(269-3.23) ,1
(290.3.50)
(309377)
(3.33<.09)
1 (3.504.35)
1.68
F 2.03
F 2.50
F 2.87
F 3.33
3.70
F 4.05
4.41
4.86
F 5.23
2-hr
(1.53-1.85)
1 (1.85-2.23)
1 (2.28-2.74)
1 (2613.15).
(3.01-3.65)
(3.33-4.05)
1 (3.62-4.44)
(391-483)
(4.27-5.33)
1 (4.56-575)
1.79
2.16
2.67
3.09
3.61
4.04
4.46
4.89
5.46
5.94
3-hr
(1.64-1.96)
1 (1.98-2.37)
1 (2.44-2.93)
1 (282338)
(3.27-3.95) 11
(3.64-442)
(3.994.88)
1 (4.34-5.35)
1 (4.79-5.98)
1 (5.15-6.51)
(1 2-15
2.59
6.03
6.80
7.44
6-hr
( 98-2 35 )
( 2 38-2 84 )
(2.94 7050)_
(3. 0-0.OB) .
(3 97 4876 )
(4 445236 )
4. 9S?95
_( _ _)
(5 34-66.56)
(5 93-7.40) _
(6 41-8: 11)
2.54
3.06
3.61
-_
4.44
_
5.28
5.98
6.70
7.47
8.52
9.41
F12-hr
i
(2 34 2.77)
(2 82 3 34)
(3 49-4 15)
(4 06-4:84). ,
(4 79 5.73)
1 (5.39-6.48)
1 (5 98 7.25)
1 (6 58-8.06)
(7 37 9 20)
1 (8 02 10.2)
2.96
3.57
4.47
6.11
6.86
_
9.50
10.4
24-hr
(2 77-3 16)
(3 35-3.82 )
'
( 4.184.78
(4_3-551 )
(5 70 6.53.
'
( 8 38 7 34 )
(7078317)._
p78-9.03)
(8 73-10 2)
(9.48-11 2_)_
3.46
4.16
5.17
594
6.98
7.81
8.64
9.60
10.7
11.6
2-day
(3.24-3 70)
1 (3.90-4.46)
1 (4.845.53)_
(5 56.6.35) _
(6.51-7 47)
1 (7 25 8 36) ',.
(8 00-9.27)
(8 76-102)
(9.80-11.5)
(10.6-12.5)
4.40
6.43
6.24
7.33
8.19
9.07
9.97
11.2
12.2
3-day
r3.43 36s1 )
(4.13-4.70)
(509-581.
)
( 5846.67 )
( 6.83-7.84)
(760-877)',.
(8.39-9.73)
(819-10.7)
(10.3-12.1 )
( 11.1-13.2)
3.66
4.63
5.70
6.54
7.68
B.58
9.50
10.4
11.7
12.8
4-day
(3.63-4.13)
(4.35-4.95)
(5 34-6 09)
(6.12-6s9)
(7.15-8.22)
1 (7.95-9.19)
1 (8.78-102)
1 (9 62-11.2)
1 (10.8-12.7)
1 (11.6-13.8)
7-da
4.44
(4 19-4.73)
5.30
(5.00-5s l)
6.44 7 34
1 (6 07-6.86) (6 91 _7.82)_
8.57
(8.04-9.14)
9.55
1 (8.92-10.2)_
10.5
_ (9.82-11.3)
11.6
1 (10.7-12.4)
13.0
(12.0-13.9)
14.7
(12.9-15.2)
sm 5-7
F 6.00
7.2o 8.15
9.42
10.4
11.4
12.5
_
13.9
15.0
90-da
(477-5.37)
(5.66-6.37)
(679766)_ (767-866).,_
(884-10.0)
(9.75-11A)
(10.7-12.2)
(11e-13.3)
(12.8-149)
(13.8-16.1)
6.76
7.97
9.41 10.6
12.1
13.3
14.6
15.6
17.5
18.9
20-day
(6.39-7 15)
( 7 55-8.43).
1 (6.90-9.95) (9 97 11.2)_
1 (12.5-14.1)
1 (13.6-15.5)
1 (14.7-16.8)
1 (16.2-18.7)
1 (17.4-20.2)
�30-da
8.39
9.88
11.5 12.7
_(11.4-12.8)
14.4
15.6
19.8
212
1 -..
( 7 96 e 87 )
( 9 35-10 4 )
( 10 9 12 1 12 0 13 4 )'I
) (
(13 5-15..1)
(14.7-16.5)
.8-1
(15.8-17.8)
.0-1
(17.0-19.2)
(18 4 21 O)
(19 6 22.4)
45-day
17.5
18.9
20.3
21.7
23.4
�24.8
y
(10. 211.2)
(1119-13.1)
(1316-15.0)
(1510-16.5)
(167-18.4)
_
(17.9-199)
(182-21.4)
(20.422.8)
(220-248)
(23.2-26.2)
60-day
12.8
15.0
16.9
18.4
20.3
21.7 ''.
t2.3-13.4
( _ )
(14.3-15.7
-'
16.1-17.7)
I (6
(17519.2 ). _�,
_ (19.3-21 3 )
(20.7-22.8)
(21.9-24.3)
.9-2
.2-2
(23.2-25.7)
(24.8-276)
a-2
.9-2 )
(25.9-29.1
1 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.
Back to Top
PF graphical
l of 1/22/2021, 3:27 PM

Watershed 1
Subcat Reach on Llnk
Basin 1

Basin 1 Type 1124-hr 10 yr Rainfall=5.17"
Prepared by {enter your company name here) Printed 1/23/2021
HydroCAD®10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 2
Summary for Subcatchment 1S: Watershed 1
Runoff = 16.59 cfs @ 12.01 hrs, Volume= 0.884 af, Depth= 2.59"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 10 yr Rainfall=5.17"
Area (ac) CN Description
3.800
77 Fallow, bare soil, HSG A
0.300
43 Woods/grass comb., Fair, HSG A
4.100
75 Weighted Average
4.100
100.00% Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
7.8
100
0.0300
0.21
Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
1.2
471
0.1600
6.44
Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.2
316
0.1030
28.41
340.87 Channel Flow,
Area= 12.0 sf Perim= 8.0' r= 1.50'
n= 0.022 Earth. clean & straiaht
9.2 887 Total

Basin 1 Type // 24-hr 10 yr Rainfa11=5.17"
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD® 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 3
Summary for Pond 1 P: Basin 1
Inflow Area = 4.100 ac, 0.00% Impervious, Inflow Depth = 2.59" for 10 yr event
Inflow = 16.59 cfs @ 12.01 hrs, Volume= 0.884 of
Outflow = 3.84 cfs @ 12.23 hrs, Volume= 0.884 af, Atten= 77%, Lag= 13.2 min
Primary = 3.84 cfs @ 12.23 hrs, Volume= 0.884 of
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 102.85' @ 12.23 hrs Surf.Area= 9,552 sf Storage= 15,794 cf
Plug -Flow detention time= 562.5 min calculated for 0.884 of (100% of inflow)
Center -of -Mass det. time= 563.9 min (1,397.0 - 833.1 )
Volume Invert Avail.Storage Storage Description
#1 101.00, 27,430 cf Custom Stage Data (Prismatic) Listed below
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic -feet) (cubic -feet)
101.00 7,400 0 0
102.00 8,580 7,990 7,990
103.00 9,720 9,150 17,140
104.00 10,860 10,290 27,430
Device Routing Invert Outlet Devices
#1 Primary 100.00' 12.0" Round 12" Barrel
L= 50.0' CMP, projecting, no headwall, Ke= 0.900
Inlet / Outlet Invert= 100.00' / 99.00' S= 0.0200 'P Cc= 0.900
n= 0.025 Corrugated metal, Flow Area= 0.79 sf
#2 Device 1 102.00' 15.0" Horiz. 15" Riser C= 0.600 Limited to weir flow at low heads
#3 Device 1 101.00' 0.038 cfs 2" Skimmer
#4 Primary 103.00' Asymmetrical Weir, C= 3.27
Offset (feet) 0.00 4.50 14.50 19.00
Height (feet) 1.50 0.00 0.00 1.50
Primary Out low Max=3.83 cfs @ 12.23 hrs HW=102.85' (Free Discharge)
T2=15"
2" Barrel (Barrel Controls 3.83 cfs @ 4.88 fps)
Riser (Passes < 5.45 cfs potential flow)
3=2" Skimmer (Passes < 0.04 cfs potential flow)
=Asymmetrical Weir ( Controls 0.00 cfs)

Basin 1 Type 1124-hr 25 yr Rainfall=6. I I to
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD® 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 4
Summary for Subcatchment IS: Watershed 1
Runoff = 21.57 cfs @ 12.01 hrs, Volume= 1.153 af, Depth= 3.38"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 25 yr Rainfall=6.11"
Area (ac) CN Description
3.800 77 Fallow, bare soil, HSG A
0.300 43 Woods/grass comb., Fair, HSG A
4.100 75 Weighted Average
4.100 100.00% Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
min
(feet)
(ft/ft)
(ft/sec)
(cfs)
7.8
100
0.0300
0.21
Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
1.2
471
0.1600
6.44
Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.2
316
0.1030
28.41
340.87 Channel Flow,
Area= 12.0 sf Perim= 8.0' r= 1.50'
n= 0.022 Earth. clean & straiaht
9.2 887 Total

Basin 1 Type 1124-hr 25 yr Rainfall=6.11 "
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD® 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 5
Summary for Pond 1 P: Basin 1
Inflow Area = 4.100 ac, 0.00% Impervious, Inflow Depth = 3.38" for 25 yr event
Inflow = 21.57 cfs @ 12.01 hrs, Volume= 1.153 of
Outflow = 8.71 cfs @ 12.16 hrs, Volume= 1.153 af, Atten= 60%, Lag= 9.0 min
Primary = 8.71 cfs @ 12.16 hrs, Volume= 1.153 of
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 103.26' @ 12.16 hrs Surf.Area= 10,016 sf Storage= 19,815 cf
Plug -Flow detention time= 441.1 min calculated for 1.153 of (100% of inflow)
Center -of -Mass det. time= 442.5 min (1,268.0 - 825.5 )
Volume Invert Avail.Storage Storage Description
#1 101.00, 27,430 cf Custom Stage Data (Prismatic) Listed below
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic -feet) (cubic -feet)
101.00 7,400 0 0
102.00 8,580 7,990 7,990
103.00 9,720 9,150 17,140
104.00 10,860 10,290 27,430
Device Routing Invert Outlet Devices
#1 Primary 100.00' 12.0" Round 12" Barrel
L= 50.0' CMP, projecting, no headwall, Ke= 0.900
Inlet / Outlet Invert= 100.00' / 99.00' S= 0.0200'/' Cc= 0.900
n= 0.025 Corrugated metal, Flow Area= 0.79 sf
#2 Device 1 102.00' 15.0" Horiz. 15" Riser C= 0.600 Limited to weir flow at low heads
#3 Device 1 101.00' 0.038 cfs 2" Skimmer
#4 Primary 103.00' Asymmetrical Weir, C= 3.27
Offset (feet) 0.00 4.50 14.50 19.00
Height (feet) 1.50 0.00 0.00 1.50
Primary OutFlow Max=8.58 cfs @ 12.16 hrs HW=103.26' (Free Discharge)
h.
1=12" Barrel (Barrel Controls 4.10 cfs @ 5.22 fps)
t2=15" Riser (Passes < 6.62 cfs potential flow)
3=2" Skimmer (Passes < 0.04 cfs potential flow)
=Asymmetrical Weir (Weir Controls 4.49 cfs @ 1.52 fps)

2S � 2P
Watershed 2
Subcat Reach Aon Lin k
Basin 2

Basin 2 Type 11 24-hr 90 yr Rainfall=5.97"
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD® 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 2
Summary for Subcatchment 2S: Watershed 2
Runoff = 88.88 cfs @ 12.01 hrs, Volume= 4.872 af, Depth= 2.95"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 10 yr Rainfall=5.17"
Area (ac) CN Description
13.020
77
Fallow, bare soil, HSG A
1.010
43
Woods/grass comb., Fair,
HSG A
1.160
98
gravel/impery
4.640
86
Fallow, bare soil, HSG B
19.830
79
Weighted Average
18.670
94.15% Pervious Area
1.160
5.85% Impervious Area
Tc Length
Slope Velocity Capacity
Description
(min) (feet)
(ft/ft) (ft/sec) (cfs)
7.8 100
0.0300 0.21
Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
2.0 780
0.1600 6.44
Shallow Concentrated Flow,
U n paved Kv= 16.1 fps
9.8 880 Total

Basin 2 Type 1124-hr 10 yr Rainfall=5.97"
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD® 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 3
Summary for Pond 2P: Basin 2
Inflow Area = 19.830 ac, 5.85% Impervious, Inflow Depth = 2.95" for 10 yr event
Inflow = 88.88 cfs @ 12.01 hrs, Volume= 4.872 of
Outflow = 16.19 cfs @ 12.30 hrs, Volume= 4.770 af, Atten= 82%, Lag= 17.3 min
Primary = 16.19 cfs @ 12.30 hrs, Volume= 4.770 of
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 103.43' @ 12.30 hrs Surf.Area= 45,354 sf Storage= 102,621 cf
Plug -Flow detention time= 765.5 min calculated for 4.770 of (98% of inflow)
Center -of -Mass det. time= 752.8 min (1,576.2 - 823.4 )
Volume Invert Avail.Storage Storage Description
#1 101.00, 128,622 cf Custom Stage Data (Prismatic) Listed below
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic -feet) (cubic -feet)
101.00 38,700 0 0
102.00 41,616 40,158 40,158
103.00 44,232 42,924 83,082
104.00 46,848 45,540 128,622
Device Routing Invert Outlet Devices
#1 Primary 100.00' 12.0" Round 12" Barrel
L= 50.0' CMP, projecting, no headwall, Ke= 0.900
Inlet / Outlet Invert= 100.00' / 99.00' S= 0.0200 '/' Cc= 0.900
n= 0.025 Corrugated metal, Flow Area= 0.79 sf
#2 Device 1 102.00' 18.0" Horiz. 18" Riser C= 0.600 Limited to weir flow at low heads
#3 Device 1 101.00' 0.110 cfs 3" Skimmer
#4 Primary 103.00' Asymmetrical Weir, C= 3.27
Offset (feet) 0.00 4.50 16.50 21.00
Height (feet) 1.50 0.00 0.00 1.50
Primary OutFlow Max=16.17 cfs @ 12.30 hrs HW=103.43' (Free Discharge)
r=12" Barrel (Barrel Controls 4.20 cfs @ 5.35 fps)
2=18" Riser (Passes < 10.17 cfs potential flow)
3=3" Skimmer (Passes < 0.11 cfs potential flow)
-Asymmetrical Weir (Weir Controls 11.97 cfs @ 1.91 fps)

Basin 2 Type 1! 24-hr 25 yr Rainfall=6.11 "
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD® 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 4
Summary for Subcatchment 2S: Watershed 2
Runoff = 113.13 cfs @ 12.01 hrs, Volume= 6.243 af, Depth= 3.78"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 25 yr Rainfall=6.1 1 "
Area (ac) CN Description
13.020 77 Fallow, bare soil, HSG A
1.010 43 Woods/grass comb., Fair, HSG A
1.160 98 gravel/impery
4.640 86 Fallow, bare soil, HSG B
19.830 79 Weighted Average
18.670 94.15% Pervious Area
1.160 5.85% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
7.8 100 0.0300 0.21 Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
2.0 780 0.1600 6.44 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
9.8 880 Total

Basin 2 Type // 24-hr 25 yr Rainfall=6.19"
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD® 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 5
Summary for Pond 2P: Basin 2
Inflow Area = 19.830 ac, 5.85% Impervious, Inflow Depth = 3.78" for 25 yr event
Inflow = 113.13 cfs @ 12.01 hrs, Volume= 6.243 of
Outflow = 39.34 cfs @ 12.18 hrs, Volume= 6.138 af, Atten= 65%, Lag= 10.1 min
Primary = 39.34 cfs @ 12.18 hrs, Volume= 6.138 of
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 103.83' @ 12.18 hrs Surf.Area= 46,415 sf Storage=121,078 cf
Plug -Flow detention time= 610.3 min calculated for 6.138 of (98% of inflow)
Center -of -Mass det. time= 600.0 min ( 1,416.4 - 816.4)
Volume Invert Avail.Storage Storage Description
#1 101.00, 128,622 cf Custom Stage Data (Prismatic) Listed below
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic -feet) (cubic -feet)
101.00 38,700 0 0
102.00 41,616 40,158 40,158
103.00 44,232 42,924 83,082
104.00 46,848 45,540 128,622
Device Routing Invert Outlet Devices
#1 Primary 100.00' 12.0" Round 12" Barrel
L= 50.0' CMP, projecting, no headwall, Ke= 0.900
Inlet / Outlet Invert= 100.00' / 99.00' S= 0.0200 '/' Cc= 0.900
n= 0.025 Corrugated metal, Flow Area= 0.79 sf
#2 Device 1 102.00' 18.0" Horiz. 18" Riser C= 0.600 Limited to weir flow at low heads
#3 Device 1 101.00' 0.110 cfs 3" Skimmer
#4 Primary 103.00' Asymmetrical Weir, C= 3.27
Offset (feet) 0.00 4.50 16.50 21.00
Height (feet) 1.50 0.00 0.00 1.50
Primary OutFlow Max=38.99 cfs @ 12.18 hrs HW=103.83' (Free Discharge)
t=1=12" Barrel (Barrel Controls 4.44 cfs @ 5.66 fps)
2=18" Riser (Passes < 11.51 cfs potential flow)
3=3" Skimmer (Passes < 0.11 cfs potential flow)
=Asymmetrical Weir (Weir Controls 34.55 cfs @ 2.45 fps)

Watershed A
9 Reach Aon Link
24" Culvert

Culvert A Type 1124-hr 10 yr Rainfall=5.17"
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD® 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 2
Summary for Subcatchment IS: Watershed A
Runoff = 2.62 cfs @ 12.02 hrs, Volume= 0.147 af, Depth= 1.26"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 10 yr Rainfall=5.17"
Area (ac) CN Description
` 0.390 98 Gravel/Impervious
1.010 43 Woods/grass comb., Fair, HSG A
1.400 58 Weighted Average
1.010 72.14% Pervious Area
0.390 27.86% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
7.8 100 0.0300 0.21 Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
1.0 386 0.1500 6.24 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
8.8 486 Total

Culvert A Type /124-hr 10 yr Rainfal1=5.17"
Prepared by {enter your company name here} Printed 1/23/2021
HydroCADO 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 3
Summary for Pond 1 P: 24" Culvert
Inflow Area = 1.400 ac, 27.86% Impervious, Inflow Depth = 1.26" for 10 yr event
Inflow = 2.62 cfs @ 12.02 hrs, Volume= 0.147 of
Outflow = 2.62 cfs @ 12.02 hrs, Volume= 0.147 af, Atten= 0%, Lag= 0.0 min
Primary = 2.62 cfs @ 12.02 hrs, Volume= 0.147 of
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 100.77' @ 12.02 hrs
Device Routing Invert Outlet Devices
#1 Primary 100.00' 24.0" Round Culvert
L= 50.0' CPP, projecting, no headwall, Ke= 0.900
Inlet / Outlet Invert= 100.00' / 90.00' S= 0.2000 '/' Cc= 0.900
n= 0.013, Flow Area= 3.14 sf
Primary OutFlow Max=2.53 cfs @ 12.02 hrs HW=100.75' (Free Discharge)
L1=Culvert (Inlet Controls 2.53 cfs @ 2.33 fps)

Culvert A Type // 24-hr 25 yr Rainfall=6.1 I "
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD® 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page4
Summary for Subcatchment IS: Watershed A
Runoff = 3.93 cfs @ 12.01 hrs, Volume= 0.213 af, Depth= 1.83"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 25 yr Rainfall=6.11"
Area (ac) CN Description
0.390 98 Gravel/Impervious
1.010 43 Woods/grass comb., Fair, HSG A
1.400 58 Weighted Average
1.010 72.14% Pervious Area
0.390 27.86% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
7.8 100 0.0300 0.21 Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
1.0 386 0.1500 6.24 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fqs
8.8 486 Total

F
Culvert A Type 11 24-hr 25 yr Rainfall=6.11 "
Prepared by {enter your company name here} Printed 1/23/2021
HydroCADO 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 5
Summary for Pond 1 P: 24" Culvert
Inflow Area = 1.400 ac, 27.86% Impervious, Inflow Depth = 1.83" for 25 yr event
Inflow = 3.93 cfs @ 12.01 hrs, Volume= 0.213 of
Outflow = 3.93 cfs @ 12.01 hrs, Volume= 0.213 af, Atten= 0%, Lag= 0.0 min
Primary = 3.93 cfs @ 12.01 hrs, Volume= 0.213 of
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Peak Elev= 100.96' @ 12.01 hrs
Device Routing Invert Outlet Devices
#1 Primary 100.00' 24.0" Round Culvert
L= 50.0' CPP, projecting, no headwall, Ke= 0.900
Inlet / Outlet Invert= 100.00' / 90.00' S= 0.2000 '/' Cc= 0.900
n= 0.013, Flow Area= 3.14 sf
Primary OutFlow Max=3.82 cfs @ 12.01 hrs HW=100.95' (Free Discharge)
L1=Culvert (Inlet Controls 3.82 cfs @ 2.61 fps)

Watershed 1
Subcat Reach Pon Link

Ditch 1 Type 11 24-hr 2 yr Rainfall=3.57"
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD®10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 2
Summary for Subcatchment 1S: Watershed 1
Runoff = 8.59 cfs @ 12.01 hrs, Volume= 0.462 af, Depth= 1.35"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 2 yr Rainfall=3.57"
Area (ac) CN Description
3.800 77 Fallow, bare soil, HSG A
0.300 43 Woods/grass comb., Fair, HSG A
4.100 75 Weighted Average
4.100 100.00% Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
7.8
100
0.0300
0.21
Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
1.2
471
0.1600
6.44
Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.2
316
0.1030
28.41
340.87 Channel Flow,
Area= 12.0 sf Perim= 8.0' r= 1.50'
n= 0.022 Earth. clean & straiaht
9.2 887 Total

Ditch 1 Type 11 24-hr 10 yr Rainfall=5.17"
Prepared by {enter your company name here) Printed 1/23/2021
HydroCAD®10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 3
Summary for Subcatchment 1 S: Watershed 1
Runoff = 16.59 cfs @ 12.01 hrs, Volume= 0.884 af, Depth= 2.59"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 10 yr Rainfall=5.17"
Area (ac) CN Description
3.800 77 Fallow, bare soil, HSG A
0.300 43 Woods/grass comb., Fair, HSG A
4.100 75 Weighted Average
4.100 100.00% Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
7.8
100
0.0300
0.21
Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
1.2
471
0.1600
6.44
Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.2
316
0.1030
28.41
340.87 Channel Flow,
Area= 12.0 sf Perim= 8.0' r= 1.50'
n= 0.022 Earth. clean & straiaht
9.2 887 Total

a.
Ditch 1 Type 1124-hr 25 yr Rainfall=6. I I "
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD® 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 4
Summary for Subcatchment IS: Watershed 1
Runoff = 21.57 cfs @ 12.01 hrs, Volume= 1.153 aft Depth= 3.38"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 25 yr Rainfall=6.11"
Area (ac) CN Description
3.800
77 Fallow, bare soil, HSG A
0.300
43 Woods/grass comb., Fair, HSG A
4.100
75 Weighted Average
4.100
100.00% Pervious Area
Tc
Length
Slope
Velocity
Capacity Description
(min)
(feet)
(ft/ft)
(ft/sec)
(cfs)
7.8
100
0.0300
0.21
Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
1.2
471
0.1600
6.44
Shallow Concentrated Flow,
Unpaved Kv=16.1 fps
0.2
316
0.1030
28.41
340.87 Channel Flow,
Area= 12.0 sf Perim= 8.0' r= 1.50'
n= 0.022 Earth, clean & straight
9.2 887 Total

Watershed 2
Subcat Reach Aon Link

Ditch 2 Type // 24-hr 2 yr Rainfall=3.57"
Prepared by {enter your company name here) Printed 1/23/2021
HydroCAD® 10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 2
Summary for Subcatchment 2S: Watershed 2
Runoff = 41.45 cfs @ 12.02 hrs, Volume= 2.267 af, Depth= 1.55"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 2 yr Rainfall=3.57"
Area (ac) CN Description
12.350 77 Fallow, bare soil, HSG A
0.900 43 Woods/grass comb., Fair, HSG A
0.950 98 gravel/impery
3.340 86 Fallow, bare soil, HSG B
17.540 78 Weighted Average
16.590 94.58% Pervious Area
0.950 5.42% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
7.8 100 0.0300 0.21 Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
2.0 780 0.1600 6.44 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
9.8 880 Total

Ditch 2 Type 1124-hr 10 yr Rainfall=5.17"
Prepared by {enter your company name here} Printed 1/23/2021
HvdroCAD® 10.00-20 sln 07329 © 2017 HvdroCAD Software Solutions LLC Page 3
Summary for Subcatchment 2S: Watershed 2
Runoff = 76.29 cfs @ 12.01 hrs, Volume= 4.175 af, Depth= 2.86"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 10 yr Rainfall=5.17"
Area (ac) CN Description
12.350 77 Fallow, bare soil, HSG A
0.900 43 Woods/grass comb., Fair, HSG A
0.950 98 gravel/impery
3.340 86 Fallow, bare soil, HSG B
17.540 78 Weighted Average
16.590 94.58% Pervious Area
0.950 5.42% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
7.8 100 0.0300 0.21 Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
2.0 780 0.1600 6.44 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
9.8 880 Total

AC 4 • 1JL
Ditch 2 Type 1124-hr 25 yr Rainfall=6. I I "
Prepared by {enter your company name here} Printed 1/23/2021
HydroCAD®10.00-20 s/n 07329 © 2017 HydroCAD Software Solutions LLC Page 4
Summary for Subcatchment 2S: Watershed 2
Runoff = 97.62 cfs @ 12.01 hrs, Volume= 5.373 aft Depth= 3.68"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.05 hrs
Type II 24-hr 25 yr Rainfall=6.11"
Area (ac) CN Description
12.350 77 Fallow, bare soil, HSG A
0.900 43 Woods/grass comb., Fair, HSG A
0.950 98 gravel/impery
3.340 86 Fallow, bare soil, HSG B
17.540 78 Weighted Average
16.590 94.58% Pervious Area
0.950 5.42% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
7.8 100 0.0300 0.21 Sheet Flow,
Grass: Short n= 0.150 P2= 3.64"
2.0 780 0.1600 6.44 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
9.8 880 Total

r
Design storm 2-yr 10-yr 25-yr
Required Flow, Q (cfs) 8.59 16.59 21.57
Unit weight of water, y
(lb/ft3) 62.4
Channel slope, s (ft/ft) 0.103
Permissible shear
stress, Taud (lb/ft2) 5.00 Table 8.05a
Project Name Merritts
Ditch ID Number Ditch 1
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3.0
0.58
6.48
2.7492
6.67
0.41
0.078
3.40
9.3
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3.73
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10-yr
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3.0
0.78
7.68
1 4.1652
1 7.93
0.53
0.078
3.99
16.6
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5.01
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3.0
0.89
8.34
5.0463
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0.58
0.078
4.29
21.6
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5.72

11
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Design storm
Required Flow, Q (cfs)
Unit weight of water, y
(lb/ft')
Channel slope, s (ft/ft)
Permissible shear
stress, Taud (lb/ft2)
2-yr 1 0-yr 25-yr
41.45 76.29 97.62
62.4
0.026
4.00 Table 8.05g
Project Name Merritts
Ditch ID Number Ditch 2
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8.63
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42.4
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3
3.0
1.69
13.14
13.6383
13.69
1.00
0.078
3.07
41.9
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2.74
p
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3
3.0
2.22
16.32
21.4452
17.04
1.26
0.078
3.59
77.0
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3.60
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3
3.0
2.47
17.82
25.7127
18.62
1.38
0.078
3.82
98.2
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4.01