20121051 Ver 1_Stormwater Info_20131007

ketchem
engineering &
tU'SN►
DWQ # 12 -1051
NC Department of Environment and Natural Resources
Division of Water Resources
Wetlands, Buffers, Stormwater, Compliance and Permitting Unit (WeBSCaPe)
Attn: Karen Higgins
512 N. Salisbury Street (9h floor)
Raleigh, NC 27604
Re: DWQ # 12 -1051
Stormwater Management Plan Approval
Water Quality Certification Approval- Condition #3
Colvin Park Subdivision
Wake County, NC
To Ms. Higgins:
crowder
surveying
October 2, 2013
On December 21, 2012, we received a copy of the written 401 Water Quality Certification for the project known as Colvin
Park Subdivision (DWQ #:12- 1051). Condition #3 of this Approval required that a copy of the Approved Stormwater
Management Plan be submitted to your office once received from the Town of Apex. As such, please see attached
Stormwater Management Plan, the signed plans and details.
Sincerely,
KETCHEM- CROWDER & ASSOCIATES, PLLC
Brian Ketchem, P.E.
Attachments:
- SW Calculations, Plans, and Details
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AU�J LS
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Branch i
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4072 Barrett Dr. Raleigh, NC 27609 (919) 420 -7667

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
COLVIN PARK SUBDIVISION
Stormwater Calculations
3/15/2013
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getchem- Crowder & Associates, PLLC
4072 Barrett Dr
Raleigh, NC 27609
919- 420 -7667
Stormwater Management Report March 15, 2013

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
INTRODUCTION
Colvin Park Subdivision is a proposed residential development located in Apex
between Smith Rd and Stephenson Rd just south of Ten Ten. The project will be developed in
phases and totals approximately 63 acres and is proposing 148 total homes.
The site is located in the Neuse River Basin and ultimately drains to Middle Creek(C-
NSW). The site is subject to the North Carolina Division of Water Quality Neuse
River Basin rules for stormwater management. The development is also located in
the Town of Apex Secondary Water Protection Area and will be subject to the
stormwater management regulations of the Town of Apex. The purpose of
this report is to demonstrate the site's proposed compliance with all stormwater
regulations.
Figure 1. Colvin Park Subdivision
Stormwater Management Report March 15, 2013

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP DESIGN SUMMARY
BMP #_, 1 - Proposed Wet Pond
DRAINAGE AREA= 15.80 ACRES
PERCENT IMPERVIOUS AREA = 38 %
• 2.5" drawdown orifice @ 444.5
• 4' x 4' slab top cadet box, crest @ 446.7
• 36" RCP Outlet Barrel
• Top of Dam = 448.5
BMP #2 - Proposed Wet Pond
DRAINAGE AREA = 7.20 ACRES
PERCENT IIVIPERvtous AREA = 38%
• 1.5" drawdown onfice @ 449.50
• 4' x 4' slab top uilet box, crest @ 450.70
• 18" RCP Outlet Barrel
• Top of Dam = 452.00
Peak Water
vent
Surface
Freeboard
Qpeak Inflow
Qpeak Outflow
Elevation
F2-Year
446.19
2.31
40.98
0.21
ar
446.61
1.89
52.77
0.23
ear
447.12
1.38
72.32
11.5
BMP #2 - Proposed Wet Pond
DRAINAGE AREA = 7.20 ACRES
PERCENT IIVIPERvtous AREA = 38%
• 1.5" drawdown onfice @ 449.50
• 4' x 4' slab top uilet box, crest @ 450.70
• 18" RCP Outlet Barrel
• Top of Dam = 452.00
Stormwater Management Report
March 15, 2013
Peak Water
vent
Surface
Freeboard
Qpeak Inflow
Qpeak Outflow
Elevation
F?--Year
450.48
1.52
23.41
0.06
ar
450.70
1.30
29.34
0.07
ear
450.99
1.01
39.5
6.42
Stormwater Management Report
March 15, 2013

COLV'IN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
ST'EPHENSON ROAD APEX, NC
BMP #3 - ProRgsed Wet Pond
DRAINAGE AREA = 15.7 ACRES
PERCENT IMPERVIOUS AREA = 40%
• 2.3" drawdown onfice @ 451.5
• 4' x 4' slab top inlet box, crest @ 454
• 36" RCP Outlet Barrel
• Top of Dam = 456
BMP #4 - ProRosed Wet Pond
' DRAINAGE AREA = 3.0 ACRES
PERCENT IMPERVIOUS AREA = 43%
• 1.3" drawdown orifice @ 436.5
• 4' x 4' slab top inlet box, crest @ 437.75
• 18" RCP Outlet Barrel
• Top of Dam = 439
Peak Water
vent
Surface
F reeboard
Qpek Inflow
Qp..k Outflow
Elevation
FStorm
ar
453.29
2.71
43.68
0.18
ar
453.74
2.26
56.25
0.20
ear
454.33
1.67
77.08
8.08
BMP #4 - ProRosed Wet Pond
' DRAINAGE AREA = 3.0 ACRES
PERCENT IMPERVIOUS AREA = 43%
• 1.3" drawdown orifice @ 436.5
• 4' x 4' slab top inlet box, crest @ 437.75
• 18" RCP Outlet Barrel
• Top of Dam = 439
Stormwater Management Report
March 15, 2013
Peak Water
Storm Event
Surface
Freeboard
Qpe.k Inflow
Qpeak Outflow
Elevation
2 -Year
437.35
1.65
8.63
0.04
10 -Year
437.56
1.44
11.11
0.04
100 -Year
437.87
1.13
15.23
1.86
Stormwater Management Report
March 15, 2013

Stormwater Management Report
COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP # 1: Design Calculations
(Volume, Surface Area, and Orifice)
March 15, 2013

BMP Sizing Worksheet: BMP #1 - Wet Pond
Protect Name Colvin Park Protect #
' City /State Apex, NC Date 3/15/2013
Table 1.1 Surface Area to Drainage Area Ratio for Permanent Pool Sizing for 85% Pollutant
A..w.w..w/ Cfifwfwwwv fn thn Di0/#mnn*
% Impervious
Cover
Permanent
3.0 4.0 5.0
Pool Depth
6.0
(feet)
7.0 8.0 9.0
10
059
049
043
035
031
029
026
20
097
079
070
059
051
046
044
30
134
108
097
083
070
064
062
40
173
143
125
105
090
082
077
50
206
173
1 50
130
109
100
092
60
240
203
171
1 51
129
1 18
1 10
70
288
240
207
179
154
135
126
80
1 336
278
238
210
186
160
142
90
1 374
310
266
1 72 34-1
211
183
167
Source WDENROWQ stomnvater tsest Management rracuces, pg a, r,inn lnaa
STORMWATER BMP 1 - WET POND (25% TN Removal)
Land Use
Area
ac
% IA
Imp. Area
(ac)
Roadway & Sidewalk
220
100
22
Lots 47 @ 3,500sf ea
380
100
38
sq ft
Normal pool elevation = 4445
feet
Surface area provided = 0.271
Pervious Area
980
0
0 0
Totals
15.80
Rv = 0 05 + 0 009(1) where,
6.0
DA
-ieight(H) 355 ft
_ength(L) 1675 ft
tc (Kirpich) 10 min
Total % Impervious Surface Area =
38.0 %
Surface Area of Permanent Pool:
Calculated depth = 30
feet Rounded Down from Option 2
SA/DA ratio = 1.65
% From Table 10 1
Minimum pond surface area (SA) _ (DA' SA/DA ratio) /100
SA = 0.261
acres
11,356
sq ft
Normal pool elevation = 4445
feet
Surface area provided = 0.271
acres
11,822
sq ft
1 -inch Runoff Volume Calculation
Using the runoff volume calculations in the "Simple Method" as described by Schue/er (1987)
Rv = 0 05 + 0 009(1) where,
Rv = Runoff coefficient, in /in
I = Percent impervious
Rv = 039 in /in
Total runoff volume from 1 -inch precipitation
Runoff volume, S = (Design rainfall) (Rv)
(Drainage Area)
S = 0.516 acre-ft
22,470 cu ft
(Water Quality Volume)
WQ Head = 16
feet
Water quality pool elevation= 4461
feet

Colvin Park Subdivision - BMP 1
Detention Basin Volume Verification
FOREBAY
Frustrum Pyramid
440 707.51
C
441 1,031.65
864.50
442 1,412.34
1,217.02
443 1,849.58
1,626.05
444 2,343.37
2,091.61
444.5 2,718.02
1,264.19 Perm Pool
445 3,192.69
1,476.09
446 3,855.61
3,518.94
446.5 4,157.49
2,002.80
447.5 4,539.23
4,346.96
VOLUME ABOVE PP (ff3)
11,344.79
TOTAL VOLUME (ff3)
18,408.17
Forebay = 21%
Total Volume
SA @ Perm Pool = 11,822.28
SF
VOLUME ABOVE PP (113)
48.142.12
VOLUME AT PP (ff3)
33,122.25
TOTAL VOLUME (ft3)'
81,264.37
Water Quality Volume =
22,470
Water Quality Elevation =
446.1
Orifice Head =
1.6
Pre -Post Analysis
Drainage Area = 15.8 acres
1 -year 24 -hour rainfall event (i = 0.1'19 in /hr)
Pre - development: Q = CiA = 0.64 cfs
Post - development: BMP outflow = 0.06 cfs
10 -year 24 -hour rainfall event (i = 0.21 in /hr)
Pre - development: Q = CiA = 1.14 cfs
Post - development: BMP outflow = 0.10 cfs
3/15/2013
POND
C
Acreage
Totals
Frustrum
Pyramid
12.8
440
3,837.59
1.00
441
4,604.75
4,215.35
442
5,442.39
5,017.74
443
6,350.80
5,890.76
444
7,329.88
6,834.49
444.5
9,104.26
4,100.53 Perm Pool
445
11,035.80
5,027.28
446
12,270.113
11,647.51
446.5
13,165.37
6,357.56
447.5
14,373.41
13,764.97
VOLUME ABOVE
PP (113)
36,797.33
TOTAL VOLUME (ff3)
62,856.19
Aoottomshea =
9,673.25 ft
Apermpooi =
11,822.28 It
Aoottom pond =
4,545.10 ft
Depth =
4 ft
Calculated Avg Depth =
3.4 ft
Option 2
Pre - development Composite C:
Surface
C
Acreage
Totals
Unimproved Area:
0.35
12.8
4.48
Roof:
1.00
0.5
0.50
Wooded Area:
0.15
1.5
0.23
Lawns:
0.20
1.0
0.20
Composite C = 0.34

ORIFICE & LEVEL SPREADER WORKSHEET
STORMWATER BMP 1
WET POND (25% TN Removal)
Orifice Calculator
Q = Cd *A *(2gh)" (1/2)
1 Water Quality Volume Draw -down
Variables
WQ Volume 0 52 Acre -ft
Head 1 6 ft
Draw down time. 48 hrs
Orifice Area = 0 04 sq ft
Orifice Diameter = 2 60 in
2 Max Stage Draw -down
Variables
Volume
Head
Draw down time
Orifice Area =
Orifice Diameter =
USE 2.5" DIAMETER
Constants
22469 7 cf g =
0 53 ft (Ho /3) Cd=
172800s
5 33 sq in
Q= 013 cfs
Constants
1 11 Acre -ft 48142 12 cf g =
2 62 ft 0 87 ft (Ho /3) Cd=
87 5 hrs 315000s
0 03 sq ft 4 89 sq. in
2 50 in Q = 0 15 cfs
ORIFICE Onfice Area = 4 91 sq in
Level Spreader Sizing:
F Q at 10 -yr storm = 0 29 cfs
Level Spreader @ 20 ft/cfs (10' min) = 10 ft
2/11/2013
322 ft/s2
06
322 ft/s2
06

a COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP # 1: HydroCAD Routing
(Summary & Hydrographs)
Section 1: 2 -yr, 10-yr & 100 -yr Pond routing
Section 2: 1 -yr 24 -hr & 10 -yr 24 -hr Pre/Post Routing
Stormwater Management Report March 15, 2013

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
Section 1: 2 -yr, 10 -yr & 100 -yr Pond routing
Stormwater Management Report Mardi 15, 2013

BMP #1 -Post - rev 1 -2 -13 Rainfall Duration= 10 min, Inten =4 76 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/17/2013
HydroCADO 10 00 s/n 07807 0 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#1
Inflow Area = 15 800 ac, 37 97% Impervious, Inflow Depth = 0 44"
Inflow = 40.98 cfs @ 0 17 hrs, Volume= 0 574 of
' Outflow = 0 21 cfs @ 0 34 hrs, Volume= 0 015 af, Atten= 99 %, Lag= 10 4 min
Primary = 0 21 cfs @ 0 34 hrs, Volume= 0 015 of
Routing by Stor -Ind method, Time Span= 0 00-100 hrs, dt= 0 01 hrs
Peak Elev= 446 19'@ 0 34 hrs Surf Area= 16,587 sf Storage= 24,861 cf
Plug -Flow detention time= 32 1 min calculated for 0 015 of (3% of inflow)
Center -of -Mass det time= 23 9 min ( 33 9 - 10 0 )
F° Volume Invert Avail Storage Storage Description
#1 444 50' 48,116 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Perim Inc Store Cum Store Wet Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
44450 11,716 5645 0 0
11,716
44500 14,228 6058 6,476 6,476
15,573
446.00 16,126 6247 15,167 21,643
17,524
_ 44650 17,323 5205 8,360 30,003
27,024
44750 18,913 5390 18,112 48,116
28,671
Device Routing Invert Outlet Devices
#1 Primary 440 00' 36.0" Round Culvert
L= 55 0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert= 440 00'/437 50' S=00455? Cc= 0 900
n= 0 013, Flow Area= 7 07 sf
#2 Device 1 444 50' 2.5" Vert. Orifice C= 0 600
#3 Device 1 446 70' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 21 cfs @ 0 34 hrs HW=446 19' (Free Discharge)
t— = Culvert (Passes 0 21 cfs of 92 16 cfs potential flow)
17-Culvert
(Orifice Controls 0 21 cfs @ 6 07 fps)
3 Orifice /Grate ( Controls 0 00 cfs)

BMP #1 -Post - rev 1 -2 -13 Rainfall Duration =10 min, Inten =4.76 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCADO 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
44
42
40
38
36
34
32
30
28
26
24
3 22
0
LL 20
18
16
14
12
10
8
6
4
2
0
Pond 2P: BMP #1
Hydrograph
Time (hours)
� Inflow
® Primary

BMP #1 -Post - rev 1 -2 -13 Rainfall Duration= 10 min, inten =613 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD810 00 s/n 07807 02012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP #1
Inflow Area = 15 800 ac, 37 97% Impervious, Inflow Depth = 0 56"
Inflow = 52 77 cfs @ 0 17 hrs, Volume= 0 740 of
Outflow = 0 23 cfs @ 0 34 hrs, Volume= 0 017 af, Atten= 100 %,
Lag= 10 4 min
Primary = 0 23 cfs @ 0 34 hrs, Volume= 0 017 of
Routing by Stor -Ind method, Time Span= 0 00-100 hrs, dt= 0 01 hrs
Peak Elev= 446.61' @ 034 hrs Surf Area= 17,502 sf Storage= 32,038 cf
Plug -Flow detention time= 32 4 min calculated for 0 017 of (2% of inflow)
Center -of -Mass det time= 23.8 min ( 33.8 - 10 0 )
Volume Invert Avail Storage Storage Description
#1 444 50' 48,116 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Perim Inc Store Cum Store Wet Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
44450 11,716 5645 0 0
11,716
44500 14,228 6058 6,476 6,476
15,573
44600 16,126 6247 15,167 21,643
17,524
44650 17,323 5205 8,360 30,003
27,024
447.50 18,913 5390 18,112 48,116
28,671
Device Routing Invert Outlet Devices
#1 Primary 440 00' 36.0" Round Culvert
L= 55 0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert= 440 00'/ 437 50' S= 0.0455'f Cc= 0 900
n= 0 013, Flow Area= 7 07 sf
#2 Device 1 444 50' 2.5" Vert. Orifice C= 0 600
#3 Device 1 446 70' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 23 cfs @ 0 34 hrs HW =446 61' (Free Discharge)
t—J=Culvert (Passes 0 23 cfs of 96 19 cfs potential flow)
2= Orifce (Orifice Controls 0 23 cfs @ 6 82 fps)
3= Orifice /Grate ( Controls 0 00 cfs)

BMP #1 -Post - rev 1 -2 -13 Rainfall Duration =10 min, Inten =6.13 in /hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD® 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
55
50
45
40
35
y
V
30
3
O
LL 25
20
15
10
Pond 2P: BMP #1
Hydrograph
0
Time (hours)
3 inflow
8 Primary

BMP #1 -Post - rev 1 -2 -13 Rainfall Duration =10 min, Inten =8 40 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD®10 00 s/n 07807 @2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP #1
Inflow Area = 15 800 ac, 37 97% Impervious, Inflow Depth = 0 77"
Inflow = 72.32 cfs @ 0 17 hrs, Volume= 1 013 of
Outflow = 11.50 cis @ 0 31 hrs, Volume= 0 225 af, Atten= 84 %, Lag= 8 4 min
Primary = 11 50 cfs @ 0 31 hrs, Volume= 0 225 of
Routing by Stor -Ind method, Time Span= 0 00-100 hrs, dt= 0 01 hrs
Peak Elev= 447 12'@ 0 31 hrs Surf Area= 18,311 sf Storage= 41,254 cf
Plug -Flow detention time= 218 min calculated for 0 225 of (22% of inflow)
Center -of -Mass det time= 16 3 min ( 26 3 - 10 0 )
Volume Invert Avail Storage Storage Description
#1 444 50' 48,116 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Penm Inc Store Cum Store Wet Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
_
44450 11,716 5645 0 0
11,716
44500 14,228 6058 6,476 6,476
15,573
44600 16,126 6247 15,167 21,643
17,524
44650 17,323 520.5 8,360 30,003
27,024
44750 18,913 5390 18,112 48,116
28,671
Device Routing Invert Outlet Devices
#1 Primary 440 00' 36.0" Round Culvert
L= 55 0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert= 440.00'/437 50' S= 0.0455'f Cc= 0.900
n= 0 013, Flow Area= 7 07 sf
#2 Device 1 444 50' 2.6" Vert. Orifice C= 0 600
#3 Device 1 446 70' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =11 46 cfs @ 0 31 hrs HW=447 12' (Free Discharge)
= Culvert (Passes 1146 cfs of 100 86 cfs potential flow)
2= Orifice (Orifice Controls 0 26 cfs @ 7.64 fps)
3= Orifice /Grate (Weir Controls 11 20 cfs @ 2 12 fps)

BMP #1 -Post - rev 1 -2 -13 Rainfall Duration =10 min, lnten =8.40 in /hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD® 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
80
75
70
65
60
55
50
4 45
40
0
ti 35
30
25
20
15
10
5
0
0
Pond 2P: BMP #1
Hydrograph
Time (hours)
■ Inflow
Primary

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
Section 2: 1 -yr 24 -hr & 10 -yr 24 -hr Pre /Post Routing
Stormwater Management Report
March 15, 2013

BMP #1 -Post - rev 1 -2 -13 Rainfall Duration= 1, 440 min, Inten =0 12 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCADO 10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#1
Inflow Area = 15 800 ac, 37 97% Impervious, Inflow Depth > 0 06"
Inflow = 105 cis @ 0 17 hrs, Volume= 0 080 of
Outflow = 0.06 cfs @ 100 hrs, Volume= 0 002 af, Atten= 94 %, Lag= 49 8 min
Primary = 0.06 cfs @ 100 hrs, Volume= 0 002 of
Routing by Stor -Ind method, Time Span= 0 00-100 hrs, dt= 0 01 hrs
Peak Elev= 444.76' @ 100 hrs Surf Area= 13,024 sf Storage= 3,372 cf
Plug -Flow detention time= 40 3 min calculated for 0 002 of (3% of inflow)
Center -of -Mass det time= 115 min ( 44 1 - 32 6 )
Invert
Avail Storage Storage Description
_Volume
- #1 444 50'
48,116 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Perim Inc Store Cum.Store Wet Area
(feet)
(sq -ft)
(feet) (cubic -feet) (cubic -feet)
(sq -ft)
44450
11,716
5645 0 0
11,716
44500
14,228
6058 6,476 6,476
15,573
44600
16,126
6247 15,167 21,643
17,524
44650
17,323
5205 8,360 30,003
27,024
447.50
18,913
5390 18,112 48,116
28,671
Device Routing
Invert
Outlet Devices
#1 Primary
440 00'
36.0" Round Culvert
L= 55 0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert = 440.00'/437 50' S= 0.0455'/' Cc= 0 900
n= 0 013, Flow Area= 7 07 sf
#2 Device 1
444 50'
2.5" Vert. Orifice C= 0 600
#3 Device 1
446 70'
48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
rimary OutFlow Max =0 06 cfs @ 100 hrs HW =444 76' (Free Discharge)
= Culvert (Passes 0 06 cfs of 76 82 cfs potential flow)
2= Orifice (Orifice Controls 0 06 cfs @ 190 fps)
3= Orifice /Grate ( Controls 0 00 cfs)

BMP #1 -Post - rev 1 -2 -13 Rainfall Duration= 1, 440 min, lnten =0.12 in/hr
Prepared by Ketchem - Crowder & Associates Printed 3118/2013
HydroCAD ®10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
U
3
O
LL
a
0
Pond 2P: BMP #1
Hydrograph
Time (hours)
lnncw
Primary

BMP #1 -Post - rev 1 -2 -13 Rainfall Duration= 1, 440 min, Inten =0 21 in1hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCADO 10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#1
Inflow Area = 15 800 ac, 37 97% Impervious, Inflow Depth > 0 11"
Inflow = 184 cfs @ 0.17 hrs, Volume= 0 140 of
Outflow = 0 1Oafs @ 100 hrs, Volume= 0 004 af, Atten= 95 %, Lag= 49 8 min
Primary = 0 10 cfs @ 100 hrs, Volume= 0 004 of
Routing by Stor -Ind method, Time Span= 0 00-100 hrs, dt= 0 01 hrs
Peak Elev= 444 96'@ 100 hrs Surf Area= 14,004 sf Storage= 5,899 cf
Plug -Flow detention time= 38 3 min calculated for 0 004 of (3% of inflow)
Center -of -Mass det time= 9 5 min ( 42 1 - 32 6 )
Volume Invert
Avail Storage Storage Description
= #1 444 50'
48,116 cf Custom Stage Data (Irregular) Listed below
;^ Elevation Surf Area Penm Inc Store Cum Store Wet Area
(feet)
(sq -ft)
(feet) (cubic -feet) (cubic -feet)
(sq -ft)
44450
11,716
5645 0 0
11,716
44500
14,228
6058 6,476 6,476
15,573
` 446.00
16,126
6247 15,167 21,643
17,524
44650
17,323
5205 8,360 30,003
27,024
44750
18,913
539.0 18,112 48,116
28,671
Device Routing
Invert
Outlet Devices
#1 Primary
440 00'
36.0" Round Culvert
L= 55 0' RCP, groove end projecting, Ke= 0 200
Inlet / Outlet Invert= 440 00'/ 437 50' S= 0 0455? Cc= 0 900
n= 0 013, Flow Area= 7 07 sf
#2 Device 1
444 50'
2.5" Vert. Orifice C= 0 600
#3 Device 1
446 70'
48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 10 cfs @ 1 00 hrs HW =444 96' (Free Discharge)
t—
= Culvert (Passes 0 10 cfs of 79 08 cfs potential flow)
2 =Orifice (Orifice Controls 0 10 cfs @ 2 85 fps)
3 Orifice /Grate ( Controls 0 00 cfs)

BMP #1 -Post - rev 1 -2 -13 Rainfall Duration= 1, 440 min, Inten =0.21 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCADO 10-00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
VJ
V
3
O
LL
Pond 2P: BMP #1
Hydrograph
Time (hours)
i Inflow
■ Primary

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHWON ROAD APEX, NC
BMP # 1: DWQ Supplements
Supplement 1: Wet Detention Basin Supplement
Supplement 2: Wet Detention Basin O &M Agreement
Supplement 3: Required Items Checklist
Stormwater Management Report March 15, 2013

Permit
(to be provided by DWQ)
�.
WDENR = �I> -
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part tit) must be printed, filled out and submitted along with all of the required information.
jl PROJECT INFORMATION
Project name COLVIN PARK SUBDIVISION
Contact person BRIAN KETCHEM, PE
Phone number 919- 724 -0624
Date 3115/2013
Drainage area number 1
II. DESIGN INFORMATION
Site Characteristics
Drainage area 688,248 itz
Impervious area, post- development 261,360 fI2
°10 impervious 37.97 of �°
Design rainfall depth 1.0 in
Storage Volume: Non -SA Waters
Minimum volume required
Volume provided
Storage Volume: SA Waters
1.5" runoff volume
Pre - development 1 -yr, 24 -hr runoff
Post- deveiopment 1 -yr, 24 -hr runoff
Minimum volume required
Volume provided
Peak Flow Calculations
Is the pre /post control of the 1 y 24hr storm peak flow required?
1 -yr, 24-hr rainfall depth
Rational C, pre - development
Rational C, post - development
Rainfall intensity: 1 -yr, 24 -hr storm
Pre - development 1 -yr, 24 -hr peak flow
Post - development 1 -yr, 24 -hr peak flow
Pre /Post 1 -yr, 24 -hr peak flow control
Elevations
Temporary pool elevation
Permanent pool elevation
SHWT elevation (approx. at the perm. pool elevation)
Top of 1 Oft vegetated shelf elevation
Bottom of 1 Oft vegetated shelf elevation
Sediment cleanout, top elevation (bottom of pond)
Sediment cleanout, bottom elevation
Sediment storage provided
Is there additional volume stored above the state - required temp. pool?
Elevation of the top of the additional volume
22,470 ft3
48,142 ft3 OK, volume provided is equal to or in excess of volume required.
ft3
ft3
ft3
ft3
ft3
Y (Y or N)
2.9 in
0.34 (unitiess)
0.60 (unitless)
0.12 in /hr OK
0.64 ft3
/sec
0.07 ft3
/sec
-0.57 ft3 /sec
447.12 fmsi
444.50 fmsi
444.25 fmsl
445.00 frisl
444.00 fmsi
440.00 I'ms!
439.00 fmsi
1.00 ft
N (Y or N)
frnsi
Form SW401 -Wet Detention Basin- Rev.94PI8 112 Parts 1. u It. Design Summan), Page 'I of 2

II, DESIGN INFORMATION
Surface Areas
Area, temporary pool 18,913 ft'
Area REQUIRED, permanent pool 11,356 ft'
SAIDA ratio 1.65 (unitless)
Area PROVIDED, permanent pool, App,„_,.,
11,822 if
OK
Area, bottom of 1 Oft vegetated shelf, Abt_a,ar
9,673 ft
OK
Area, sediment cleanout, top elevation (bottom of pond), At,., p�d
4,545 ft`
1.8 :1
Volumes
Y (Y or N)
OK
Volume, temporary pool
48,142 ff
OK
Volume, permanent pool, Vpp,mj w
33,122 fe
OK
Volume, forebay (sum of forebays if more than one forebay)
7,063 fO
Orifice with manual valve control
Forebay % of permanent pool volume
21.3% %
OK
SAIDA Table Data
Design TSS removal
85 %
Coastal SAIDA Table Used?
N (Y or N)
Mountain/Piedmont SAIDA Table Used?
Y (Y or N)
SAIDA ratio
1.65 ( unitiess)
Average depth (used in SAIDA table):
Calculation option 1 used? (See Figure 10 -2b)
N (Y or N)
Volume, permanent pool, Vpp._,w
33,122 ft'
Area provided, permanent pool, A,._pw
11,822 ft
Average depth calculated
ft
Need 3 ft min.
Average depth used in SAIDA, dp„ (Round to nearest 0.5ft)
ft
Calculation option 2 used? (See Figure 10 -2b)
Y (Y or N)
Area provided, permanent pool, Ap,,_p,,
11,822 ft
Area, bottom of 10ft vegetated shelf, Abt_ ,w,
9,673 ft
Area, sediment deanout, top elevation (bottom of pond), Ate,,", d
4,545 fe
"Depth" (distance b/w bottom of 1Oft shelf and top of sediment)
4.00 ft
Average depth calculated
3.00 ft
OK
Average depth used in SAIDA, d.„ (Round to down to nearest 0.5ft)
3.0 ft
OK
Drawdown Calculations
Drawdown through orifice?
Y (Y or N)
Diameter of orifice (if circular)
2.50 in
Area of orifice (if- non - circular)
in
Coefficient of discharge (Co)
0.60 ( unitless)
Driving head (Ho)
2.62 ft
Drawdown through weir?
N (Y or N)
Weir type
(unitless)
Coefficient of discharge (CW)
( unitless)
Length of weir (L)
It
Driving head (H)
ft
Pre - development 1 -yr, 24 -hr peak flow
0.64 R3 /sec
Post - development 1 -yr, 24 -hr peak flow
1.05 ff3 /sec
Storage volume discharge rate (through discharge orifice or weir)
0.06 ft3 /sec
Storage volume drawdown time
3.65 days
OK, draws down in 2 -5 days.
Additional information
Vegetated side slopes
Vegetated shelf slope
Vegetated shelf width
Length of flowpath to width ratio
Length to width ratio
Trash rack for overflow & orifice?
Freeboard provided
Vegetated filter provided?
Recorded drainage easement provided?
Capures all runoff at ultimate build -out?
Drain mechanism for maintenance or emergencies is:
3 :1
OK
10 :1
OK
10.0 It
OK
3 :1
OK
1.8 :1
OK
Y (Y or N)
OK
1.0 ft
OK
Y (Y or N)
OK
Y (Y or N)
OK
Y (Y or N)
OK
Orifice with manual valve control
Permit
(to be provided by DWQ)
Form SW401 -Wet Detention Basin- Rev.9- 4/18/12 Parts 1. & II. Design Summary, Page 2 of 2

Permit Number
(to be provided by DWQ)
Drainage Area Number
Wet Detention Basin Operation and Maintenance Agreement
I will keep a maintenance record on this BUT. This maintenance record will be kept in a
log in a known set location. Any deficient BW elements noted in the inspection will be
corrected, repaired or replaced immediately. These deficiencies can affect the integrity
of structures, safety of the public, and the removal efficiency of the BW.
The wet detention basin system is defined as the wet detention basin,
pretreatment including forebays and the vegetated filter if one is provided.
This system (check one):
® does ❑ does not incorporate a vegetated filter at the outlet.
This system (check one):
❑ does ® does not incorporate pretreatment other than a forebay.
Important maintenance procedures:
- Immediately after the wet detention basin is established, the plants on the
vegetated shelf and perimeter of the basin should be watered twice weekly if
F needed, until the plants become established (commonly six weeks).
- No portion of the wet detention pond should be fertilized after the first initial
fertilization that is required to establish the plants on the vegetated shelf.
- Stable groundcover should be maintained in the drainage area to reduce the
sediment load to the wet detention basin.
- If the basin must be drained for an emergency or to perform maintenance, the
flushing of sediment through the emergency drawl should be minimized to the
maximum extent practical.
— Once a year, a dam safety expert should inspect the embankment.
After the wet detention pond is established, it should be inspected once a month and
within 24 hours after every storm event greater than 1.0 inches (or 1.5 inches if in a
Coastal County). Records of operation and maintenance should be kept in a known set
location and must be available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall
be repaired immediately.
BMP element:
Potential problem:
How I will remediate the problem:
The entire BMP
Trash /debris is present
Remove the trash/ debris
The perimeter of the wet
detention basin
Areas of bare soil and /or
erosive gullies have formed
Regrade the soil if necessary to
remove the gully, and then plant a
ground cover and water until it is
established Provide lime and a
one -time fertilizer application
Vegetation is too short or too
Maintain vegetation at a height of
long
approximately six inches
Form SW401 -Wet Detention Basin O &M -Rev 4 Page 1 of 4

Permit Number
(to be provided by DWQ)
Drainage Area Number
BMP element:
Potential problem:
How I will remediate the problem:
The inlet device: pipe or
The pipe is clogged
Unclog the pipe. Dispose of the
swale
sediment off -site.
The pipe is cracked or
Replace the pipe
otherwise damaged.
Erosion is occurring in the
Regrade the swale if necessary to
swale.
smooth it over and provide erosion
control devices such as reinforced
turf matting or nprap to avoid
future problems with erosion.
The forebay
Sediment has accumulated to
a depth greater than the
original design depth for
Search for the source of the
sediment and remedy the problem if
possible Remove the sediment and
sediment storage.
dispose of it in a location where it
will not cause impacts to streams or
the BMP.
Erosion has occurred.
Provide additional erosion
protection such as reinforced turf
matting or riprap if needed to
prevent future erosion problems
Weeds are present.
Remove the weeds, preferably by
hand. If pesticide is used, wipe it on
the plants rather than spraying
The vegetated shelf
Best professional practices
Prune according to best professional
show that pruning is needed
practices
to maintain optimal plant
health
Plants are dead, diseased or
Determine the source of the
dying
problem soils, hydrology, disease,
etc Remedy the problem and
replace plants Provide a one -time
fertilizer application to establish the
ground cover if a soil test indicates
it is necessary
Weeds are present.
Remove the weeds, preferably by
hand. If pesticide is used, wipe it on
the plants rather than spraying
The main treatment area
Sediment has accumulated to
a depth greater than the
original design sediment
Search for the source of the
sediment and remedy the problem if
possible. Remove the sediment and
storage depth
dispose of it in a location where it
will not cause impacts to streams or
the BMP.
Algal growth covers over
50% of the area
Consult a professional to remove
and control the algal growth
Cattails, phragnutes or other
Remove the plants by wiping them
invasive plants cover 50% of
with pesticide (do not spray).
the basin surface
Form SW401 -Wet Detention Basin O &M -Rev 4
Page 2 of 4

r
Permit Number
(to be provided by DWQ)
Drainage Area Number
BMP element:
Potential problem:
How I will remediate the roblem:
The embankment
Shrubs have started to grow
Remove shrubs munediately.
on the embankment
Evidence of muskrat or
Use traps to remove muskrats and
beaver activity is present
consult a professional to remove
beavers
A tree has started to grow on
Consult a dam safety specialist to
the embankment.
remove the tree
An annual inspection by an
Make all needed repairs
appropriate professional
shows that the embankment
needs repair if applicable)
The outlet device
Clogging has occurred
Clean out the outlet device Dispose
of the sediment off -site.
The outlet device is damaged
Repair or replace the outlet device.
The receiving water
Erosion or other signs of
Contact the local NC Division of
damage have occurred at the
Water Quality Regional Office, or
outlet.
the 401 Oversight Unit at 919 -733-
1786.
The measuring device used to determine the sediment elevation shall be such
that it will give an accurate depth reading and not readily penetrate into
accumulated sediments.
When the permanent pool depth reads 440 feet in the main pond, the sediment
shall be removed.
When the permanent pool depth reads 440 feet in the forebay, the sediment
shall be removed.
BASIN DIAGRAM
(fill in the blanks)
0 Permanent Pool Elevation 444 5
Sediment Removal 440 P anen Pool
- - - ----------- - - Volume Sediment Removal Elevation 440 Volume
Bottom Elevatio 439 ft Min.
-------------------------------------- - - - - -- - - - - --
Sedirment Bottom Elevation 439 1 -ft
Storage Sedimet
Storage
FOREBAY MAIN POND
Form SW401 -Wet Detention Basin O &M -Rev 4
Page 3 of 4

Permit Number
(to be provided by DWQ)
I acknowledge and agree by my signature below that I am responsible for the
performance of the maintenance procedures listed above. I agree to notify DWQ of any
problems with the system or prior to any changes to the system or responsible party.
Project name:COLVIN PARK
BW drainage area number:
Print name:Mitchell W Sanner, III - PARKER & ORLEANS HOMEBUILDERS. INC
Title:Division President
Address:211 James Jackson Ave Cry, NC 27513
Phone:[phone]
Signature:
Date:
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president.
1, , a Notary Public for the State of
County of , do hereby certify that
personally appeared before me this
day of , , and acknowledge the due execution of the
forgoing wet detention basin maintenance requirements. Witness my hand and official
seal,
SEAL
My commission expires
Form SW401 -Wet Detention Basin O &M -Rev.4 Page 4 of 4

Permit No
(to be provided by DWQ)
NIT, z�i L'',.+
a 4Yi1
��Y
Please Indicate the page or plan sheet numbers where the supporting documentation can be found An incomplete submittal package will
result in a request for additional Information. This will delay final review and approval of the project Initial in the space provided to
Indicate the following design requirements have been met If the applicant has designated an agent, the agent may Initial below H a
requirement has not been met, attach justification.
Pagel Plan
Initials Sheet No.
C-06 to 09 1 Plans (1" - 50' or larger) of the entire site showing
- Design at ultimate build -out,
- Off -site drainage (if applicable),
- Delineated drainage basins (include Rational C coefficient per basin),
- Basin dimensions,
- Pretreatment system,
- High flow bypass system,
- Maintenance access,
- Proposed drainage easement and public right of way (ROW),
- Overflow device, and
- Boundaries of drainage easement
C-41 2 Partial plan (1" = 30' or larger) and details for the wet detention basin showing
- Outlet structure with trash rack or similar,
- Maintenance access,
- Permanent pool dimensions,
- Forebay and main pond with hardened emergency spillway,
- Basin cross - section,
- Vegetation specification for planting shelf, and
- Filter strip
C-41 3 Section view of the wet detention basin (1" = 20' or larger) showing
- Slde slopes, 31 or lower,
- Pretreatment and treatment areas, and
- Inlet and outlet structures
C-41 4 If the basin Is used for sediment and erosion control during construction, clean out of the basin is specified
on the plans prior to use as a wet detention basin
SW Report 5 A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay,
to venfy volume provided
C-18 6 A construction sequence that shows how the wet detention basin will be protected from sediment until the
entire drainage area is stabilized
SW Report 7 The supporting calculations
SW Report 8 A copy of the signed and notarized operation and maintenance (O &M) agreement
NIA 9 A copy of the deed restrictions (If required)
SW Report 10 A soils report that is based upon an actual field investigation, sod bonngs, and Infiltration tests County
soil maps are not an acceptable source of sods Information
Form SW401 -Wet Detention Basin -Rev 9- 4/18/12 Part III Required Items Checklist, Page 1 of 1

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP #2: Design Calculations
(Volume, Surface Area, and Onfice)
Stormwater Management Report March 15, 2013

BMP Sizing Worksheet: BMP #2 - Wet Pond
Project Name Colvin Park Project #
City/State Apex, NC Date 3/15/2013
Table 11 Surface Area to Drainage Area Ratio for Permanent Pool Sizing for 85% Pollutant
n...........► car ........... ....tie cae.r...nn*
% Impervious
Cover
- Permanent Pool Depth (feet)
30 40 50 60
70 8.0 90
10
059
049
043
035
031
029
026
20
097
079
070
059
051
046
044
30
134
108
097
083
070
064
062
40
173
143
125
105
090
082
077
50
206
173
150
130
109
100
092
60
240
203
171
151
129
118
110
70
288
240
207
179
154
135
126
80
336
278
238
210
186
160
142
90
374
310
266
234
211
183
167
tiOUMO NUUGVK/UVVW Jj0rMWMUF OtM IIflFlfAf OU10lln Fu ., _F. ....
STORMWATER BMP 2 - WET POND (25% TN Removal)
Land Use
Area
ac
% IA
Imp. Area
ac
Roadway & Sidewalk
110
100
1 1
Lots 18 @ 3,500sf ea
160
100
16
4673
sq ft
Normal pool elevation = 4495
feet
Pervious Area
450
0
00
Totals
7.20
27
)A
ieight(H) 22 5 ft
- ength(L) 675 ft
c (Kirpich) 5 min
Total % Impervious Surface Area =
375 %
Surface Area of Permanent Pool-
Calculated depth = 35
feet
SA/DA ratio = 149
% From Supplemental Form SAIDA Tables (Piedmont 85 90')
Minimum pond surface area (SA) = (DA `
SA/DA ratio) /100
SA = 0.107
acres
4673
sq ft
Normal pool elevation = 4495
feet
Surface area provided = 0.137
acres
5949
sq ft
1 -Inch Runoff Volume Calculation
Using the runoff volume calculations in the "Simple Method" as described by Schueler (1987)
Rv = 0 05 + 0 009(1) where, Rv = Runoff coefficient, in /in
I = Percent impervious
Rv = 039 in /in
Total runoff volume from 1 -inch precipitation
Runoff volume, S = (Design rainfall) (Rv) (Drainage Area)
S = 0.233 acre -ft
10128 cu ft
WQ Head = 13 feet
Water quality pool elevation= 4508 feet

Colvin Park Subdivision - BMP 2
Detention Basin Volume Verification
2/1/2013
POND
Frustrum Pyramid
FOIZEBAY
Frustrum Pyramid
44
445
1,169.65
983.61
446 263.49
446
1,591.10
1,374.98
447 537.75
392.55
447
2,073.00
1,826.75
448 880.71
702.22
448
2,615.35
2,338.93
449 1,274.85
1,071.72
449
3,254.62
2,929.17
449.5 1,533.10
701.00
Perm Pool
449.5
4,415.48
1,910.16 Perm Pool
450 1,736.46
816.86
450
5,744.74
2,532.78
450.5 2,162.01
972.68
450.5
6.036.54
2,945.02
451 2,587.56
1,185.80
451
6,328.34
3,090.93
VOLUME ABOVE PP (ff3)
2,975.34
VOLUME ABOVE
PP (ff3)
8,568.73
TOTAL VOLUME (ff3)
5,842.83
TOTAL VOLUME (1113)
19,932.33
Forebay= 20%
Total Volume
Abonomshen =
4,529.47 ft
SA ^s Perm Pool = 5.948.58
SF
Aperm p_1 =
5,948.58 ft
VOLUME ABOVE PP (111113)
11,544.07
Abottompond =
1,072.14 ft
VOLUME AT PP (11113)
14,231.09
Depth =
5 ft
TOTAL VOLUME (ff3)'
25,775.16
Calculated Avg Depth =
3.5
Option 2
Water Quality Volume =
10,128
Water Quality Elevation =
450.8
Orifice Head =
1.3
Pre -Post Analysis
Drainage Area = 7.2 acres
1 -year 24 -hour rainfall event (i = 0.119
in /hr)
Pre - development Composite C:
Pre - development: Q = CiA =
0.23
cfs
Surface
C
Acreage
Totals
Post - development: BMP outflow =
0,05
cfs
Unimproved Area :
0.35
3.6
1.26
Roof:
1.00
0.1
0.10
" 10 -year 24 -hour rainfall event (i = 0.21
in/hr)
Wooded Area:
0.15
2.0
0.30
Pre - development: Q = CiA =
0.41
cfs
Lawns:
0.20
1.5
0.30
Post - development: BMP outflow =
0.06
cfs
Composite C =
0.27

ORIFICE & LEVEL SPREADER WORKSHEET
STORMWATER BMP 2
WET POND (25% TN Removal)
Orifice Calculator
Q = CdW(2gh) ^(112)
1 Water Quality Volume Draw -down
Variables
WQ Volume 0 23 Acre -ft
Head 1 3 ft
Draw down time 48 hrs
Orifice Area = 0 02 sq ft
Orifice Diameter = 1 83 in
2 Max Stage Draw -down
Variables
Volume 0.27 Acre -ft
Head 1 5 ft
Draw down time 77 hrs
Orifice Area = 0.01 sq ft
Orifice Diameter = 1.50 in
USE 1.5" DIAMETER ORIFICE Orifice Area =
Level Spreader Sizing:
Q at 10 -yr storm = 0.07 cfs
Level Spreader @ 50 ft/cfs (10' min) _
�—'
10127.7 cf
0 44 ft (Ho /3)
172800 s
2 63 sq in
11544.07 cf
0.50 ft (Ho /3)
277200s
1 77 sq in
Constants
9=
Cd=
Constants
9=
Cd=
Q = 0 04 cfs
1 77 sq in
10 ft
2/1/2013
322 ft/s2
06
322 ft/s2
06

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP #2: HydroCAD Routing
(Summary & Hydrographs)
Section 1: 2 -yr, 10 -yr & 100-yr Pond routing
Section 2: 1 -yr 24 -hr & 10-yr 24 -hr Pre/Post Routing
Stormwater Management Report March 15, 2013

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
Section 1: 2 -yr, 10 -yr & 100 -yr Pond routing
Stormwater Management Report
March 15, 2013

BMP #2 -Post - rev 1 -2 -13 Rainfall Duration =5 min, Inten =5 76 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD®10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#2
Inflow Area = 7 200 ac, 37 50% Impervious, Inflow Depth = 0.28"
Inflow = 23 41 cfs @ 0 08 hrs, Volume= 0 167 of
Outflow = 0 06 cfs @ 0 17 hrs, Volume= 0 013 af, Atten= 100 %,
Lag= 5.2 min
Primary = 0 06 cfs @ 0 17 hrs, Volume= 0 013 of
Routing by Stor -Ind method, Time Span= 0 00 -3 00 hrs, dt= 0 01 hrs
Peak Elev= 450 48' @ 0 17 hrs Surf Area= 8,166 sf Storage= 7,243 cf
Plug -Flow detention time= 90 2 min calculated for 0 013 of (8% of inflow)
Center -of -Mass det time= 86 5 min ( 91 5 - 5 0 )
Volume Invert Avail Storage Storage Description
#1 449 50' 11,521 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Perim Inc Store Cum Store Wet Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
44950 5,884 3950 0 0
5,884
45000 7,481 426.0 3,333 3,333
7,920
45100 8,916 3710 8,188 11,521
11,431
Device Routing Invert Outlet Devices
#1 Primary 449 50' 18.0" Round Culvert
L= 45 0' RCP, groove end projecting, Ke= 0 200
Inlet / Outlet Invert= 449 50'/ 447.50' S= 0 0444'/' Cc= 0 900
n= 0 013, Flow Area= 177 sf
#2 Device 1 449 50' 1.5" Vert Orifice C= 0.600
#3 Device 1 450 70' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max--O 06 cfs @ 0 17 hrs HW=450 48' (Free Discharge)
= Culvert (Passes 0 06 cfs of 5 13 cfs potential flow)
2 =Orifice (Orifice Controls 0 06 cfs @ 4 61 fps)
3=Orifice/Grate ( Controls 0 00 cfs)

BMP #2 -Post - rev 1 -2 -13 Rainfall Duration =5 min, Inten =5.76 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/1812013
HydroCAD®10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
26
24
22
20
18
16
N
14
0 12
LL
lit
8
6
4
2
0 3
0 1 2
Pond 2P: BMP #2
Hydrograph
Time (hours)
8 Inflow
as Primary

i
BMP #2 -Post - rev 1 -2 -13 Rainfall Duration =5 min, Inten =7 22 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3118/2013
HydroCAD010 00 s/n 07807 02012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP #2
Inflow Area = 7 200 ac, 37 50% Impervious, Inflow Depth = 0 35"
Inflow = 29 34 cfs @ 0 08 hrs, Volume= 0 209 of
Outflow = 0 07 cfs @ 0 17 hrs, Volume= 0 015 A Atten= 100 %,
Lag= 5 5 min
Primary = 0 07 cfs @ 017 hrs, Volume= 0.015 of
Routing by Stor -Ind method, Time Span= 0 00 -3 00 hrs, dt= 0 01 hrs
Peak Elev= 450 70'@0 17 hrs Surf Area= 8,488 sf Storage= 9,082 cf
Plug -Flow detention time= 90 1 min calculated for 0 015 of (7% of inflow)
Center -of -Mass det time= 86 4 min ( 914 - 5 0 )
Invert Avail Storage Storage Description
_Volume
#1 449 50' 11,521 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Perim Inc Store Cum Store Wet Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
44950 5,884 3950 0 0
5,884
45000 7,481 4260 3,333 3,333
7,920
45100 8,916 3710 8,188 11,521
11,431
Device Routing Invert Outlet Devices
#1 Primary 449 50' 18.0" Round Culvert
L= 45 0' RCP, groove end projecting, Ke= 0 200
Inlet / Outlet Invert= 449 50'/ 447.50' S= 0 0444T Cc= 0 900
n= 0 013, Flow Area= 177 sf
#2 Device 1 449 50' 1.5" Vert. Orifice C= 0 600
#3 Device 1 450 70' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 07 cfs @ 0 17 hrs HW =450 70' (Free Discharge)
1' = Culvert (Passes 0 07 cfs of 7 08 cfs potential flow)
17—Culvert
(Onfce Controls 0 06 cfs @ 5 14 fps)
3 Orifice /Grate (Weir Controls 0 00 cfs @ 0 15 fps)

BMP #2 -Post - rev 1 -2 -13 Rainfall Duration =5 min, Inten =7.22 in /hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD® 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
32
30
28
26
24
22
20
18
16
0
LL 14
12
10
8
6
4
2
0
0
Pond 2P: BMP #2
Hydrograph
1 2 3
Time (hours)
Inflow
Primary

BMP #2 -Post - rev 1 -2 -13 Rainfall Duration =5 min, Inten =9 72 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD010 00 s/n 07807 @2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#2
Inflow Area = 7 200 ac, 37 50% Impervious, Inflow Depth = 0 47"
Inflow = 39 50 cfs @ 0 08 hrs, Volume= 0 281 of
Outflow = 6 42 cfs @ 0.15 hrs, Volume= 0 083 af, Atten= 84 %, Lag= 4 3 min
Primary = 6 42 cfs @ 0 15 hrs, Volume= 0 083 of
Routing by Stor -Ind method, Time Span= 0.00 -3 00 hrs, dt= 0 01 hrs
Peak Elev= 450 99'@ 015 hrs Surf Area= 8,899 sf Storage= 11,424 cf
Plug -Flow detention time= 26 2 min calculated for 0 083 of (30% of inflow)
Center -of -Mass det. time= 23.7 min ( 28 7 - 5 0 )
' Invert
Avail Storage Storage Description
_Volume
#1 449 50'
11,521 cf Custom Stage Data (Irregular) Listed below
Elevation Surf
Area Perim Inc Store Cum Store Wet Area
(feet)
(sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
_ 44950
5,884 3950 0 0
5,884
45000
7,481 4260 3,333 3,333
7,920
45100
8,916 3710 8,188 11,521
11,431
Device Routing
Invert Outlet Devices
#1 Primary
449 50' 18.0" Round Culvert
L= 45 0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert= 449 50'/447 50' S=00444? Cc= 0 900
n= 0.013, Flow Area= 177 sf
#2 Device 1
449 50' 1.5" Vert. Orifice C= 0 600
#3 Device 1
450.70' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =6 33 cfs @ 0 15 hrs HW =450 99' (Free Discharge)
t-- = Culvert (Passes 6 33 cfs of 9 15 cfs potential flow)
=Orifice (Orifice Controls 0 07 cfs @ 5 74 fps)
3 Orifice /Grate (Weir Controls 6 26 cfs @ 175 fps)

BMP #2 -Post - rev 1 -2 -13 Rainfall Duration =5 min, Inten =9.72 in /hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD® 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
t/1
V
3
O
LL
Pond 2P: BMP #2
Hydrograph
Time (hours)
F Inflow
Primary

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
Section 2: 1 -yr 24 -hr & 10 -yr 24 -hr Pre/Post Routing
Stormwater Management Report Mardi 15, 2013

BMP #2 -Post - rev 1 -2 -13 Rainfall Duration= 1, 440 min, Inten =0 12 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/1812013
HydroCAD810 00 s/n 07807 02012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#2
Inflow Area = 7.200 ac, 37 50% Impervious, Inflow Depth > 0 21"
Inflow = 0.51 cis @ 0 09 hrs, Volume= 0 124 of
Outflow = 0 05 cfs @ 3 00 hrs, Volume= 0 007 af, Atten= 91%, Lag= 174 6 min
Primary = 0 05 cfs @ 3 00 hrs, Volume= 0 007 of
Routing by Stor -Ind method, Time Span= 0 00 -3.00 hrs, dt= 0 01 hrs
Peak Elev= 450 21' @ 3 00 hrs Surf Area= 7,783 sf Storage= 5,057 cf
Plug -Flow detention time= 105 6 min calculated for 0 007 of (6% of inflow)
Center -of -Mass det time= 22.0 min ( 113 4 - 914 )
Volume Invert
Avail Storage Storage Description
#1 449 50'
11,521 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Penm Inc Store Cum Store Wet Area
(feet)
(sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
44950
5,884 3950 0 0
5,884
45000
7,481 4260 3,333 3,333
7,920
45100
8,916 3710 8,188 11,521
11,431
Routing
Invert Outlet Devices
_Device
#1 Primary
449 50' 18.0" Round Culvert
L= 45 0' RCP, groove end projecting, Ke= 0.200
Inlet/ Outlet Invert= 449 50'/447 50' S= 0 0444 T Cc= 0 900
n= 0 013, Flow Area= 177 sf
#2 Device 1
449 50' 1.5" Vert. Orifice C= 0 600
#3 Device 1
450.70' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 05 cfs @ 3 00 hrs HW=450 21' (Free Discharge)
t—J=Culvert (Passes 0 05 cfs of 2 96 cfs potential flow)
2= Orifice (Orifice Controls 0 05 cfs @ 3 88 fps)
3= Orifice /Grate ( Controls 0 00 cfs)

BMP #2 -Post - rev 1 -2 -13 Rainfall Duration= 1,440 min, lnten =0.92 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD® 10-00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
0.55
0.5
0.45
0.4
0.35
0.3
3
LL 0.25
0.2
0.15
0.1
0.05
0
0 1 2 3
Pond 2P: BMP #2
Hydrograph
Time (hours)
■ Inflow
■ Primary

BMP #2 -Post - rev 1 -2 -13 Rainfall Duration= 1,440 min, Inten =0 21 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCADO 10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP #2
Inflow Area = 7 200 ac, 37 50% Impervious, Inflow Depth > 0 36"
Inflow = 0 88 cfs @ 0 09 hrs, Volume= 0 217 of
Outflow = 0 06 cfs @ 3 00 hrs, Volume= 0 010 af, Atten= 93 %, Lag= 174 6 min
Primary = 0 06 cfs @ 3 00 hrs, Volume= 0 010 of
Routing by Stor -Ind method, Time Span= 0 00 -3 00 hrs, dt= 0 01 hrs
Peak Elev= 450 69' @ 300 hrs Surf Area= 8,470 sf Storage= 8,975 cf
Plug -Flow detention time= 104 3 min calculated for 0 010 of (5% of inflow)
Center -of -Mass det time= 19 4 min ( 110 8 - 914 )
Volume Invert
Avail Storage Storage Description
#1 449 50'
11,521 cf Custom Stage Data (Irregular) Listed below
Elevation Surf.Area Perim Inc Store Cum Store Wet Area
(feet)
(sq -ft)
(feet) (cubic -feet) (cubic -feet)
(sq -ft)
44950
5,884
3950 0 0
5,884
45000
7,481
4260 3,333 3,333
7,920
45100
8,916
3710 8,188 11,521
11,431
Device Routina
Invert
Outlet Devices
#1 Primary
449 50'
18.0" Round Culvert
L= 45.0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert= 449 50'/447 50' S= 0 0444 'P Cc= 0 900
n= 0.013, Flow Area= 177 sf
#2 Device 1
449 50'
1.5" Vert. Orifice C= 0 600
#3 Device 1
450.70'
48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 06 cfs @ 3 00 hrs HW =450 69' (Free Discharge)
1-1= Culvert (Passes 0 06 cfs of 6 97 cfs potential flow)
= Orifice (Orifice Controls 0 06 cfs @ 5 11 fps)
� ( Controls 0 00 cfs)

BMP #2 -Post - rev 1 -2 -13 Rainfall Duration= 1, 440 min, lnten =0.21 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD® 10.00 sin 07807 © 2012 HydroCAD Software Solutions LLC
w
3
0
LL
Pond 2P: BMP #2
Hydrograph
Time (hours)
fnfiow
® Primary

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP #2: DWQ Supplements
Supplement 1: Wet Detention Basin Supplement
Supplement 2: Wet Detention Basin O &M Agreement
Supplement 3: Required Items Checklist
Stormwater Management Report March 15, 2013

Permit No.
(to be provided by DWQ)
MA
WDENR
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part Ill) must be printed, filled out and submitted along with all of the required information.
I. PROJECT INFORMATION
Project name
CO LVIN PARK SUBDIVISION
Contact person
BRIAN KETCHEM, PE
Phone number
919- 724 -0624
Date
3/15/2013
Drainage area number
2
IN. DESHW INFORMATION
Site Characteristics
Drainage area
313,632 fe
Impervious area, post - development
117,612 fe
°k impervious
0
37.5 0
Design rainfall depth
1.0 in
Storage Volume: Non-SA Waters
Minimum volume required
Volume provided
Storage Volume: SA Waters
1.5" runoff volume
Pre - development 1 -yr, 24-hr runoff
Post - development 1 -yr, 24 -hr runoff
Minimum volume required
Volume provided
Peak Flow Calculations
Is the prelpost control of the 1 yr 24hr stone peak flow required?
1 -yr, 24 -hr rainfall depth
Rational C, pre - development
Rational C, post- development
Rainfall intensity: 1 -yr, 24 -hr storm
Pre - development 1 -yr, 24-hr peak flow
Post - development 1 -yr, 24-hr peak flow
Pre/Post 'I -yr, 24 -hr peak flow control
Elevations
Temporary pool elevation
Permanent pool elevation
SHWT elevation (approx. at the perm. pool elevation)
Top of 1 Oft vegetated shelf elevation
Bottom of 1 Oft vegetated shelf elevation
Sediment cleanout, top elevation (bottom of pond)
Sediment cleanout, bottom elevation
Sediment storage provided
Is there additional volume stored above the state- required temp. pool?
Elevation of the top of the additional volume
10,128 ft3
11,544 ft3 OK, volume provided is equal to or in excess of volume required.
ft3
ft3
ft3
ft3
ft3
Y (Y or N)
2.9 in
0.27 (unitless)
0.55 (unitless)
0.12 in /hr OK
0.23 ft?/sec
0.51 fe /W
0.28 ft?/sec
450.99 fmsl
449.50 fmsl
449.50 fmsl
450.00 fmsl
449.00 fmsl
444.00 fmsl
443.00 fmsl
1.00 it
N (Y or N)
fmsl
Form SW401 -Wei Detention Basin- Rev.9- 4118112 Parts i. & il. Design Summary, Page 1 of 2

Surface Areas
Area, temporary pool
Area REQUIRED, permanent pool
SAIDA ratio
Area PROVIDED, permanent pool, Ap.,w
Area, bottom of 1 Oft vegetated shelf, Aw- h,jf
Area, sediment cleanout, top elevation (bottom of pond), A,at ond
8,916 ft3
4,673 ft
1.49 (unitless)
5,949 OK
4,529
1,072 ft'
Volumes
Volume, temporary pool 11,544 ft3
Volume, permanent pool, V,._p , 14,231 ft3
Volume, forebay (sum of forebays if more than one forebay) 2,867 ft3
Forebay % of permanent pool volume 20.1% %
SAIDA Table Data
Design TSS removal
Coastal SAIDA Table Used?
Mountain/Piedmont SAIDA Table Used?
SAIDA ratio
Average depth (used in SAIDA table):
Calculation option 1 used? (See Figure 10 -2b)
Volume, permanent pool, Vl,.-pool
Area provided, permanent pool, Ap,„_,,,d
Average depth calculated
Average depth used in SAIDA, d.„ (Round to nearest 0.5ft)
Calculation option 2 used? (See Figure 10-2b)
Area provided, permanent pool, Ap,._pod
Area, bottom of 1 Oft vegetated shelf, Abc1- .11.11
Area, sediment cleanout, top elevation (bottom of pond), Abot.PlId
85 %
N (Y or N)
Y (Y or N)
1.49 (unitless)
N (Y or N)
14,231 ft'
5,949 ft`
ft
ft
Y (Y or N)
5,949 ft`
4,529 fe
1,072 ft
"Depth" (distance b/w bottom of 1Oft shelf and top of sediment) 5.00 ft
Average depth calculated 3.50 ft
Average depth used in SAIDA, d.„ (Round to down to nearest 0.5ft) 3.5 ft
Drawdown Calculations
Drawdown through orifice?
Diameter of orifice (if circular)
Area of orifice (if- non - circular)
Coefficient of discharge (CD)
Driving head (H,)
Drawdown through weir?
Weir type
Coefficient of discharge (C",)
Length of weir (L)
Driving head (H)
Pre - development 1 -yr, 24 -hr peak flow
Post - development 1 -yr, 24 -hr peak How
Storage volume discharge rate (through discharge orifice or weir)
Storage volume drawdown time
Additional Information
Vegetated side slopes
Vegetated shelf slope
Vegetated shelf width
Length of flowpath to width ratio
Length to width ratio
Trash rack for overflow & orifice?
Freeboard provided
Vegetated filter provided?
Recorded drainage easement provided?
Capures all runoff at ultimate build -out?
Drain mechanism for maintenance or emergencies is:
Y (Y or N)
1.50 in
in'
0.60 (unitless)
1.49 ft
N (Y or N)
(unitless)
(unilless)
ft
ft
0.23 ft?/sec
0.51 felsec
0.05 ft3 /sec
3.21 days
Wz
OK
Need 3 ft min.
OK
OK
OK, draws down in 2 -5 days.
3 :1 OK
i-0:1 OK
10.0 ft
OK
3 :1
OK
2.0 :1
OK
Y (Y or N)
OK
1.0 It
OK
Y (Y or N)
OK
Y (Y or N)
OK
Y (Y or N)
OK
Orifice with manual valve control
Permit
(to be provided by DWQ)
Form SW401 -Wet Detention Basin- Rev.9- 4/18/12 Parts I. & It. Design Summary, Page 2 of 2

Permit Number:
(to be provided by DWQ)
Drainage Area Number
Wet Detention Basin Operation and Maintenance Agreement
I will keep a maintenance record on this BMP. This maintenance record will be kept in a
log in a known set location. Any deficient BMP elements noted in the inspection will be
corrected, repaired or replaced immediately. These deficiencies can affect the integrity
of structures, safety of the public, and the removal efficiency of the BMP.
The wet detention basin system is defined as the wet detention basin,
pretreatment including forebays and the vegetated filter if one is provided.
This system (check one):
® does ❑ does not incorporate a vegetated filter at the outlet.
This system (check one):
❑ does ® does not incorporate pretreatment other than a forebay.
Important maintenance procedures:
- Immediately after the wet detention basin is established, the plants on the
vegetated shelf and perimeter of the basin should be watered twice weekly if
needed, until the plants become established (commonly six weeks).
- No portion of the wet detention pond should be fertilized after the first initial
fertilization that is required to establish the plants on the vegetated shelf.
- Stable groundcover should be maintained in the drainage area to reduce the
sediment load to the wet detention basin.
- If the basin must be drained for an emergency or to perform maintenance, the
flushing of sediment through the emergency drain should be mmiin -dzed to the
maximum extent practical.
- Once a year, a dam safety expert should inspect the embankment.
After the wet detention pond is established, it should be inspected once a month and
within 24 hours after every storm event greater than 1.0 inches (or 1.5 inches if in a
Coastal County). Records of operation and maintenance should be kept in a known set
location and must be available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall
be repaired immediately.
BMP element:
Potential problem:
How I will remediate the problem:
The entire BMP
Trash/ debris is present
Remove the trash debris
The perimeter of the wet
detention basin
Areas of bare soil and/or
erosive gullies have formed
Regrade the soil if necessary to
remove the gully, and then plant a
ground cover and water until it is
established Provide lone and a
one -time fertilizer application.
Vegetation is too short or too
Maintain vegetation at a height of
long
approximately six inches
Form SW401 -Wet Detention Basin O &M -Rev.4 Page 1 of 4

Permit Number
(to be provided by DWQ)
Drainage Area Number*
BMP element:
Potential problem:
How I will remediate the problem:
The inlet device: pipe or
The pipe is clogged
Unclog the pipe Dispose of the
Swale
sediment off -site
The pipe is cracked or
Replace the pipe
otherwise damaged.
Erosion is occurring in the
Regrade the swale if necessary to
swale
smooth it over and provide erosion
control devices such as reinforced
turf matting or riprap to avoid
future problems with erosion
The forebay
Sediment has accumulated to
a depth greater than the
Search for the source of the
sediment and remedy the problem if
original design depth for
possible Remove the sediment and
sediment storage
dispose of it in a location where it
will not cause impacts to streams or
the BUT.
Erosion has occurred
Provide additional erosion
protection such as reinforced turf
matting or riprap if needed to
prevent future erosion problems
Weeds are present
Remove the weeds, preferably by
hand. If pesticide is used, wipe it on
the plants rather than spraying
The vegetated shelf
Best professional practices
Prune according to best professional
show that pruning is needed
practices
to maintain optimal plant
health.
Plants are dead, diseased or
Determine the source of the
dying.
problem: soils, hydrology, disease,
etc Remedy the problem and
replace plants. Provide a one -tine
fertilizer application to establish the
ground cover if a soil test indicates
it is necessary
Weeds are present
Remove the weeds, preferably by
hand. If pesticide is used, wipe it on
the plants rather than spraying
The main treatment area
Sediment has accumulated to
a depth greater than the
original design sediment
Search for the source of the
sediment and remedy the problem if
possible. Remove the sediment and
storage depth.
dispose of it in a location where it
will not cause impacts to streams or
the BMT
Algal growth covers over
Consult a professional to remove
50% of the area
and control the algal growth
Cattails, phragmites or other
Remove the plants by wiping them
invasive plants cover 50% of
with pesticide (do not spray).
the basm surface
Form SW401 -Wet Detention Basin O &M -Rev 4 Page 2 of 4

Permit Number:
(to be provided by DWQ)
Drainage Area Number:
BMP element:
Potential problem:
How I will remediate the prob, lem:
The embankment
Shrubs have started to grow
Remove shrubs immediately
on the embankment.
Evidence of muskrat or
Use traps to remove muskrats and
beaver activity is present
consult a professional to remove
beavers
A tree has started to grow on
Consult a dam safety specialist to
the embankment.
remove the tree
An annual inspection by an
Make all needed repairs
appropriate professional
shows that the embankment
needs repair if applicable)
The outlet device
Clogging has occurred
Clean out the outlet device Dispose
of the sediment off -site.
The outlet device is damaged
Repair or replace the outlet device
The receiving water
Erosion or other signs of
damage have occurred at the
Contact the local NC Division of
Water Quality Regional Office, or
outlet
the 401 Oversight Unit at 919 -733-
1786
The measuring device used to determine the sediment elevation shall be such
that it will give an accurate depth reading and not readily penetrate into
accumulated sediments.
When the permanent pool depth reads 444 feet in the main pond, the sediment
shall be removed.
When the permanent pool depth reads 446 feet in the forebay, the sediment
shall be removed.
BASIN DIAGRAM
(dill in the blanks)
Permanent Pool Elevation 449 5
Sediment Removal 446 Pe anen Pool
----------------- Volume Sediment Removal Elevation 444 Volume
Bottom Elevatio 445 ft Mm ------------------------------ ---- -- - - - - -- - - - - --
Sediment Bottom Elevation 443 1 -ft
Storage Sedimei
Storage
FOREBAY MAIN POND
Form SW401 -Wet Detention Basin O &M -Rev.4
Page 3 of 4

M
Permit Number
(to be provided by DWQ)
I acknowledge and agree by my signature below that I am responsible for the
performance of the maintenance procedures listed above. I agree to notify DWQ of any
problems with the system or prior to any changes to the system or responsible party.
Project name:COLVIN PARK
BMP drainage area number: 2
Print name:Mitchell W Sanner, III - PARKER & ORLEANS HOMEBUILDERS, INC
Title:Division President
Address:211 James Jackson Ave Cary NC 27513
Phone:[phone]
Signature:
Date:
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president.
a Notary Public for the State of
County of , do hereby certify that
personally appeared before me this
day of , and acknowledge the due execution of the
forgoing wet detention basin maintenance requirements. Witness my hand and official
seal,
SEAL
My commission expires
Form SW401 -Wet Detention Basin O &M -Rev 4 Page 4 of 4

Permit No
(to be provided by DWQ)
Please indicate the page or plan sheet numbers where the supporting documentation can be found An incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project Initial in the space provided to
indicate the following design requirements have been met If the applicant has designated an agent, the agent may initial below If a
requirement has not been met, attach justification.
Pagel Plan
Initials Sheet No.
C-06 to 09 1 Plans (1" - 50' or larger) of the entire site showing
- Design at ultimate build -out,
- Off -site drainage (if applicable),
- Delineated drainage basins (Include Rational C coefficient per basin),
- Basin dimensions,
- Pretreatment system,
- High flow bypass system,
- Maintenance access,
- Proposed drainage easement and public right of way (ROW),
- Overflow device, and
- Boundaries of drainage easement
C41 2 Partial plan (1" = 30' or larger) and details for the wet detention basin showing
- Outlet structure with trash rack or similar,
- Maintenance access,
- Permanent pool dimensions,
- Forebay and main pond with hardened emergency spillway,
- Basin cross- section,
- Vegetation specification for planting shelf, and
- Fitter strip
C-41 3 Section view of the wet detention basin 0" = 20' or larger) showing
- Side slopes, 31 or lower,
- Pretreatment and treatment areas, and
- Inlet and outlet structures
C-41 4 If the basin is used for sediment and erosion control during construction, dean out of the basin is specified
on the plans prior to use as a wet detention basin
SW Report 5 A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay,
to verify volume provided
C -18 6 A construction sequence that shows how the wet detention basin will be protected from sediment until the
entire drainage area is stabilized
SW Report 7 The supporting calculations
SW Report 8 A copy of the signed and notarized operation and maintenance (O &M) agreement
N/A 9 A copy of the deed restrictions (if required)
SW Report 10 A soils report that is based upon an actual field investigation, soil borings, and infiltration tests County
soil maps are not an acceptable source of soils information
Form SW401 -Wet Detention Basin -Rev 9- 4/18/12 Part III Required Items Checklist, Page 1 of 1

Stormwater Management Report
COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP #3: Design Calculations
(Volume, Surface Area, and Orifice)
March 15, 2013

BMP Sizing Worksheet: BMP #3 - Wet Pond
Proiect Name Colvin Park Project #
Cily/State Apex, NC Date 3/15/2013
Table 10.1 Surface Area to Drainage Area Ratio for Permanent Pool Sizing for 85% Pollutant
C#iwinnnv in the piotimAnt
% Impervious
Cover
Permanent Pool Depth
3.0 4.0 5.0 6.0
(feet)
7.0 8.0 9.0
10
059
049
043
035
031
029
026
20
097
079
070
059
051
046
044
30
134
108
097
083
070
064
062
40
1 73
143
125
105
090
082
077
50
206
173
1 50
130
1 09
100
092
60
240
203
171
151
129
118
1 10
70
288
240
207
1 79
154
135
126
80
336
278
238
210
186
160
142
90
374
310
266
234
1 211
183
1 167
Source NC1JENR/1JVVQ btormwater best Management rracuces, pg a, „p111 1 m
STORMWATER BMP 3 - WET POND (25% TN Removal)
Land Use
Area
ac
% IA
Imp. Area
ac
Roadway 8r Sidewalk
200
100
20
Lots 50 + 2 ex @ 3,500s
415
100
42
Pervious Area
955
0
00
Totals
15.7
1
6.2
DA
Height(H) 35 ft
Length(L) 1450 ft
.c (Kirpich) 10 min
Total % Impervious Surface Area = 39.5 %
Surface Area of Permanent Pool:
Assumed depth = 30 feet
SA/DA ratio = 1.71 % From Table 10 1
Minimum pond surface area (SA) _ (DA " SA/DA ratio) /100
SA = 0.268 acres
11695 sq ft
Normal pool elevation = 4515 feet
Surface area provided = 0.269 acres
11726 sq ft
1 -Inch Runoff Volume Calculation
Using the runoff volume calculations in the "Simple Method" as described by Schueler (1987)
Rv = 0 05 + 0 009(1) where, Rv = Runoff coefficient, in /in
I = Percent impervious
Rv = 041 in /in
Total runoff volume from 1 -inch precipitation
Runoff volume, S = (Design rainfall) (Rv) (Drainage Area)
S = 0.530 acre -ft
23105 cu ft
WQ Head = 16 feet
Water quality pool elevation= 4531 feet

Colvin Park Subdivision - BMP 3
Detention Basin Volume Verification
FOREBAY
Frustrum Pyramid
_,`� "E;
*_W�4a W� EMS
448 733.45
'11 . -
449 1,195.80
955.25
450 1,738.05
1,458.50
451 2,354.99
2,038.73
451.5 2,687.43
1,259.69 Perm Pool
452 3,034.93
1,429.71
453 3,775.25
3,398.36
454 4,576.21
4,169.31
455 5,550.21
5.055.38
VOLUME ABOVE PP (ff3)
14,052.77
TOTAL VOLUME (ff3)
19,764.94
Forebay = 21%
Total Volume
SA @ Perm Pool = 11,726.20
SF
VOLUME ABOVE PP (ff3)
58,308.40
VOLUME AT PP (1113)
26,602.79
TOTAL VOLUME (ff3)'
86,895.59
Water Quality Volume =
23,105
Water Quality Elevation =
453.1
Orifice Head =
1.6
Pre -Post Analysis
Drainage Area = 7.2 acres
1 -year 24 -hour rainfall event (i = 0.119 in /hr)
Pre - development Q = CiA = 0.59 cfs
Post- developmei BMP outflow = 0.12 cfs
" 10 -year 24 -hour rainfall event (i = 0.21 in /hr)
Pre - development Q = CiA = 1,04 cfs
Post- developmei BMP outflow = 0.16 cfs
3/15/2013
POND
Surface C
Frustrum
Pyramid
Unimproved Area: 0.35
2.0
0.70
17.
0.1
447.5
3,753.32
4.4
448
4,188.24
1,984.40
449
5,109.00
4,641.00
450
6,097.07
5,595.76
451
7,149.10
6,616.11
451.5
9,038.77
4,037.74 Perm Pool
452
11,092.16
5,023.98
453
12,402.29
11,741.13
454
13, 770.30
13, 080.33
455
15,059.68
14, 410.18
VOLUME ABOVE PP (ff3)
44,255.63
TOTAL VOLUME (ff3)
67,130.64
Aoottom shelf =
9,504.09 It
Ap,m pooh =
11,726.20 ft
Aeottom oond °
4,486.77 ft
Depth =
3.5 ft
Calculated Avg Depth =
3.0 ft
Option 2
Pre - development Composite C:
Surface C
Acreage
Totals
Unimproved Area: 0.35
2.0
0.70
Roof. 1.00
0.1
0.10
Wooded Area: 0.15
4.4
0.66
Lawns: 0.20
0.7
0.14
Composite C = 0.22

ORIFICE & LEVEL SPREADER WORKSHEET
STORMWATER BMP 3
WET POND (25% TN Removal)
Orifice Calculator
Q = CdW(2gh) ^(112)
1 Water Quality Volume Draw -down
Variables
WQ Volume 0 53 Acre -ft 23104 95 cf
Head 16 ft 0.53 ft (Ho/3)
Draw down time 48 hrs 172800s
Orifice Area = 0 04 sq ft 5 50 sq in
Orifice Diameter = 2 65 in
1 Max Stage Draw -down-
Variables
Volume 1 34 Acre -ft
Head 3 5 ft
Draw down time 108 hrs
Orifice Area = 0 03 sq ft
Orifice Diameter = 2 30 in
USE 2.3" DIAMETER ORIFICE Orifice Area =
Level Spreader Sizing:
Q at 10 -yr storm = 0 20 cis
Level Spreader @ 50 ft/cfs (10' min) _
Constants
9=
Cd=
Constants
58308 4 cf g =
1.17 ft (Ho /3) Cd=
388800s
4 15 sq in
Q= 015cfs
4 15 sq in
10 ft
3/15/2013
322 ft/s2
06
322 ft/s2
06

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP #3: HydroCAD Routing
(Summary & Hydrographs)
Section 1: 2 -yr, 10 -yr & 100 -yr Pond routing
Section 2: 1 -yr 24 -hr & 10 -yr 24 -hr Pre/Post Routing
Stormwater Management Report March 15, 2013

COLV IN PARK SUBDIVMION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
Section 1: 2 -yr, 10 -yr & 100 -yr Pond routing
Stormwater Management Report March 15, 2013

BMP #3 -Post - rev 1 -2 -13 Rainfall Duration= 10 min, Inten =4 76 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCADO 10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP #3
Inflow Area = 15 700 ac, 39 49% Impervious, Inflow Depth = 0 47"
Inflow = 43 68 cfs @ 0 17 hrs, Volume= 0 612 of
Outflow = 0 18 cfs @ 0 34 hrs, Volume= 0 042 af, Atten= 100 %,
Lag= 10 4 min
Primary = 0 18 cfs @ 0 34 hrs, Volume= 0 042 of
Routing by Stor -Ind method, Time Span= 0 00 -3.00 hrs, dt= 0 01 hrs
Peak Elev= 453 29' @ 0 34 hrs Surf Area= 16,921 sf Storage= 26,527 cf
Plug -Flow detention time= 910 min calculated for 0 042 of (7% of inflow)
Center -of -Mass det time= 83 5 min (93 5 - 10 0 )
Volume Invert Avail Storage Storage Description
#1 451 50' 58,292 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Perim Inc Store Cum Store Wet Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
45150 10,718 6200 0 0
10,718
45200 14,170 6930 6,202 6,202
18,352
45300 16,281 7140 15,213 21,415
20,807
45400 18,453 7340 17,356 38,771
23,222
45500 20,610 6440 19,522 58,292
33,116
Device Routing Invert Outlet Devices
#1 Primary 447 50' 36.0" Round Culvert
L= 60 0' RCP, groove end projecting, Ke= 0 200
Inlet / Outlet Invert= 447 50' / 447.00' S= 0 00837 Cc= 0 900
n= 0 013, Flow Area= 7 07 sf
#2 Device 1 45150' 2.3" Vert. Orifice C= 0 600
#3 Device 1 454 00' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 18 cfs @ 0 34 hrs HW =453 29' (Free Discharge)
L
= Culvert (Passes 0 18 cfs of 80.51 cfs potential flow)
, 2_Orifice (Orifice Controls 0 18 cfs @ 6 28 fps)
3 Orifice /Grate ( Controls 0 00 cfs)

BMP #3 -Post - rev 1 -2 -13 Rainfall Duration =10 min, Inten =4.76 in /hr
Prepared by Ketchem - Crowder & Associates Printed 3/18/2013
HydroCAD ®10 00 s/n 07807 @2012 HydroCAD Software Solutions LLC
w
J
3
0
LL
Pond 2P: BMP #3
Hydrograph
Time (hours)
F Inflow
Primary

BMP #3 -Post - rev 1 -2 -13 Rainfall Duration =10 min, Inten =6 13 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD®10 00 s/n 07807 @2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP #3
Inflow Area = 15.700 ac, 39 49% Impervious, Inflow Depth = 0 60"
Inflow = 56 25 cfs @ 0 17 hrs, Volume= 0 788 of
Outflow = 0 20 cfs @ 0 34 hrs, Volume= 0 048 af, Atten= 100 %,
Lag= 10 4 min
Primary = 0 20 cfs @ 0 34 hrs, Volume= 0 048 of
Routing by Stor -Ind method, Time Span= 0 00 -3 00 hrs, dt= 0 01 hrs
Peak Elev= 453 74'@ 0 34 hrs Surf Area= 17,879 sf Storage = 34,183 cf
Plug -Flow detention time= 91 1 min calculated for 0 048 of (6% of inflow)
Center -of -Mass det time= 83 5 min ( 93 5 - 10 0 )
Volume Invert Avail Storage Storage Description
#1 451 50' 58,292 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Perim Inc Store Cum Store Wet Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
45150 10,718 6200 0 0
10,718
452.00 14,170 6930 6,202 6,202
18,352
45300 16,281 7140 15,213 21,415
20,807
45400 18,453 7340 17,356 38,771
23,222
45500 20,610 6440 19,522 58,292
33,116
Device Routing Invert Outlet Devices
#1 Primary 447 50' 36.0" Round Culvert
L= 60 0' RCP, groove end projecting, Ke= 0 200
Inlet / Outlet Invert= 447 50'/ 447 00' S= 0 0083'/' Cc= 0 900
n= 0 013, Flow Area= 7 07 sf
#2 Device 1 45150' 2.3" Vert. Orifice C= 0 600
#3 Device 1 454 00' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
rimary OutFlow Max =O 20 cfs @ 0 34 hrs HW =453 74' (Free Discharge)
= Culvert (Passes 0 20 cfs of 85 73 cfs potential flow)
2= Orifce (Onfce Controls 0 20 cfs @ 7 04 fps)
3= Orifice /Grate ( Controls 0 00 cfs)

BMP #3 -Post - rev 1 -2 -13 Rainfall Duration =90 min, lnten =6.93 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD® 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
60
55
50
45
40
35
U
c 30
LL
25
20
15
10
5
0
0 i 2 3
Pond 2P; BMP#3
Hydrograph
Time (hours)
Inflow
a Primary

BMP #3 -Post - rev 1 -2 -13 Rainfag Duration =10 min, Inten =8 40 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD ®10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#3
Inflow Area = 15 700 ac, 39 49% Impervious, Inflow Depth = 0 83"
Inflow = 77 08 cfs @ 0 17 hrs, Volume= 1 080 of
Outflow = 8.08 cfs @ 0 32 hrs, Volume= 0 214 af, Atten= 90 %, Lag= 8 9 min
Primary = 8 08 cfs @ 0 32 hrs, Volume= 0 214 of
Routing by Stor -Ind method, Time Span= 0.00 -3 00 hrs, dt= 0 01 hrs
Peak Elev= 454 33' @ 032 hrs Surf Area= 19,169 sf Storage= 45,247 cf
Plug -Flow detention time= 40 0 min calculated for 0 213 of (20% of inflow)
Center -of -Mass det time= 34 6 min ( 44 7 - 10 0 )
Invert Avail Storage Storage Description
_Volume
#1 451 50' 58,292 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Penm Inc Store Cum.Store Wet Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
45150 10,718 6200 0 0
10,718
45200 14,170 6930 6,202 6,202
18,352
45300 16,281 7140 15,213 21,415
20,807
45400 18,453 7340 17,356 38,771
23,222
45500 20,610 644.0 19,522 58,292
33,116
Device Routing Invert Outlet Devices
#1 Primary 447 50' 36.0" Round Culvert
L= 60 0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert= 447 50'/447 00' S= 0 0083 'f Cc= 0 900
n= 0 013, Flow Area= 7 07 sf
#2 Device 1 451 50' 2.3" Vert. Orifice C= 0 600
#3 Device 1 454 00' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =8 05 cfs @ 0 32 hrs HW=454 33' (Free Discharge)
t-17—culvert (Passes 8 05 cfs of 92 30 cfs potential flow)
2 =10rifce (Orifice Controls 0 23 cfs @ 7 96 fps)
3 Orifice /Grate (Weir Controls 7 82 cfs @ 188 fps)

BMP #3 -Post - rev 1 -2 -13 Rainfall Duration =90 min, Inten =8.40 in /hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD® 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
85
80
75
70
65
60
55
50
45
o 40
LL
35
30
25
20
15
10
5
0
0 1 2 3
Pond 2P: BMP #3
Hydrograph
Time (hours)
TInflow
M Primary

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
Section 2: 1 -yr 24 -hr & 10 -yr 24 -hr Pre/Post Routing
Stormwater Management Report March 15, 2013

BMP #3 -Post - rev 1 -2 -13 Rainfall Duration= 1, 440 min, Inten =0 12 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD810 00 s/n 07807 02012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#3
Inflow Area = 15 700 ac, 39 49% Impervious, Inflow Depth > 0 21"
Inflow = 1.12 cfs @ 0 17 hrs, Volume= 0 271 of
Outflow = 0 12 cfs @ 3 00 hrs, Volume= 0.018 af, Atten= 89 %, Lag= 169 8 min
Primary = 0 12 cfs @ 3 00 hrs, Volume= 0 018 of
Routing by Stor -Ind method, Time Span= 0 00 -3 00 hrs, dt= 0 01 hrs
Peak Elev= 452 31' @ 300 hrs Surf.Area= 14,835 sf Storage= 10,992 cf
Plug -Flow detention time= 104 8 min calculated for 0 018 of (7% of inflow)
Center -of -Mass det time= 22 8 min ( 115 4 - 92 6 )
Invert
Avail Storage Storage Description
_Volume
#1 451 50'
58,292 cf Custom Stage Data (Irregular) Listed below
Elevation Surf-Area Penm Inc Store Cum.Store Wet Area
(feet)
(sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
451.50
10,718 6200 0 0
10,718
452.00
14,170 693.0 6,202 6,202
18,352
" 45300
16,281 7140 15,213 21,415
20,807
45400
18,453 7340 17,356 38,771
23,222
45500
20,610 6440 19,522 58,292
33,116
Device Routing
Invert Outlet Devices
#1 Primary
447 50' 36.0" Round Culvert
L= 60 0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert= 447 50'/447 00' S=000837 Cc= 0 900
n= 0 013, Flow Area= 7.07 sf
#2 Device 1
45150' 2.3" Vert Orifice C= 0 600
#3 Device 1
454 00' 48.0" Horiz Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 12 cfs @ 3 00 hrs HW =452 31' (Free Discharge)
t— = Culvert (Passes 0 12 cfs of 67 48 cfs potential flow)
2= Orifice (Orifice Controls 0 12 cfs @ 4 08 fps)
3 Orifice /Grate ( Controls 0 00 cfs)

BMP #3 -Post - rev 1 -2 -13 Rainfall Duration= 1, 440 min, Inten =0.12 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCADO 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
N
V
O
LL
Pond 2P; BMP #3
Hydrograph
Time (hours)
a Inflow
B Primary

BMP #3 -Post - rev 1 -2 -13 Rainfall Duration= 1,440 min, lnten =0 21 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCADO 10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP #3
Inflow Area = 15 700 ac, 39 49% Impervious, Inflow Depth > 0.36"
Inflow = 196 cfs @ 0 17 hrs, Volume= 0 474 of
Outflow = 0.16 cfs @ 3 00 hrs, Volume= 0 025 af, Atten= 92 %, Lag= 169 8 min
Primary = 0 16 cfs @ 3 00 hrs, Volume= 0 025 of
Routing by Stor -Ind method, Time Span= 0 00 -3 00 hrs, dt= 0 01 hrs
Peak Elev= 452 88' @ 3 00 hrs Surf Area= 16,018 sf Storage= 19,519 cf
Plug -Flow detention time= 103 4 min calculated for 0 025 of (5% of inflow)
Center -of -Mass det time= 20 0 min ( 112 6 - 92 6 )
Volume Invert Avail Storage Storage Description
#1 45150' 58,292 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Perim Inc Store Cum Store Wet Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
45150 10,718 6200 0 0
10,718
45200 14,170 6930 6,202 6,202
18,352
45300 16,281 7140 15,213 21,415
20,807
45400 18,453 7340 17,356 38,771
23,222
45500 20,610 6440 19,522 58,292
33,116
Device Routing Invert Outlet Devices
#1 Primary 447.50' 36.0" Round Culvert
L= 60 0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert= 447 50'/447 00' S= 0 0083 '/' Cc= 0 900
n= 0 013, Flow Area= 7 07 sf
#2 Device 1 45150' 2.3" Vert. Orifice C= 0 600
#3 Device 1 454 00' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 16 cfs @ 3 00 hrs HW =452 88' (Free Discharge)
= Culvert (Passes 0 16 cfs of 75 21 cfs potential flow)
2= Orifice (Orifice Controls 0 16 cfs @ 5 45 fps)
3= Orifice /Grate ( Controls 0 00 cfs)

BMP #3 -Post - rev 1 -2 -13 Rainfall Duration =1, 440 min, lnten =0.21 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD® 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
a
U
0
0 1
LL
Pond 2P: BMP #3
Hydrograph
Time (hours)
! Inflow
■ Primary

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP #3: DWQ Supplements
Supplement 1: Wet Detention Basin Supplement
Supplement 2: Wet Detention Basin O &M Agreement
Supplement 3: Required Items Checklist
Stormwater Management Report March 15, 2013

Permit
(to be provided by DWQ)
I. PROJECT INFORMATION
Project name COLVIN PARK SUBDIVISION
Contact person BRIAN KETCHEM, PE
Phone number 919- 724 -0624
Date 3/15/2013
Drainage area number
II. DESIGN INFORMATION
WDENR
Drainage area
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
Impervious area, post - development
401 CERTIFICATION APPLICATION FORM
% impervious
WET DETENTION BASIN SUPPLEMENT
Design rainfall depth
This form must be filled out, printed and submitted.
The Required Items Checklist (Part III) must be printed, filled out and submitted along with all of the required information.
I. PROJECT INFORMATION
Project name COLVIN PARK SUBDIVISION
Contact person BRIAN KETCHEM, PE
Phone number 919- 724 -0624
Date 3/15/2013
Drainage area number
II. DESIGN INFORMATION
Site Characteristics
Drainage area
683,892 f?
Impervious area, post - development
270,072 ftz
% impervious
39.49 %
Design rainfall depth
1.0 in
Storage Volume: Non -SA Waters
Minimum volume required
Volume provided
Storage Volume: SA Waters
1.5" runoff volume
Pre- development 1 -yr, 24 -hr runoff
Post - development 1 -yr, 24 -hr runoff
Minimum volume required
Volume provided
Peak Flow Calculations
Is the pre /post control of the 1yr 24hr storm peak flow required?
1 -yr, 24 -hr rainfall depth
Rational C, pre - development
Rational C, post- development
Rainfall intensity: 1 -yr, 24 -hr storm
Pre - development 1 -yr, 24 -hr peak Ilow
Post - development 1 -yr, 24 -hr peak flow
PrelPost 1 -yr, 24 -hr peak flow control
Elevations
Temporary pool elevation
Permanent pool elevation
SHWT elevation (approx. at the perm. pool elevation)
Top of 'I Oft vegetated shelf elevation
Bottom of 1 Oft vegetated shelf elevation
Sediment cleanout, top elevation (bottom of pond)
Sediment cleanout, bottom elevation.
Sediment storage provided
Is there additional volume stored above the state - required temp. pool?
Elevation of the top of the additional volume
23,105 ft3
58,308 ft3 OK, volume provided is equal to or in excess of volume required.
ft3
ft3
ft3
ft3
ft3
Y (Y or N)
2.9 in
0.20 (unitless)
0.52 (unitless)
0.12 in /hr OK
0.59 ft3 /sec
1.12 ft3 /sec
0.53 ft3 /sec
454.33 fmsl
451.50 fmsl
451.25 fmsl
452.00 fmsl
451.00 fmsl
447.50 fmsl
446.50 fmsl
1.00 ft
N (Y or N)
fmsl
Forrn SW40I -Wet Detention Basin- Rev.9- 4118/12 Parts I. & 11. Design Summary, Page 1 of 2

Permit
(to be provided by DWQ)
1II DESIGN INFORMATION
3 :1
Surface Areas
85 %
Area, temporary pool
20,610 ftz
Area REQUIRED, permanent pool
11,695 flz
SAIDA ratio
1.71 (unitless)
Area PROVIDED, permanent pool, Apenn�od
11,726 ft` OK
Area, bottom of 10ft vegetated shelf, Ab, shI„
9,504 ft
Area, sediment cleanout, top elevation (bottom of pond), Abotyond
4,487 ft'
Volumes
11,726 ftz
Volume, temporary pool
58,308 ft' OK
Volume, permanent pool, VP,. P.,
26,603 ft3
Volume, forebay (sum of forebays if more than one forebay)
5,712 ft3
Foeebay % of permanent pool volume
21.5% % OK
SAIDA Table Data
3 :1
Design TSS removal
85 %
Coastal SAIDA Table Used?
N (Y or N)
Mountain/Piedmont SAIDA Table Used?
Y (Y or N)
SAIDA ratio
1.71 (unidess)
Average depth (used in SAIDA table):
OK
Calculation option 1 used? (See Figure 10 -2b)
N (Y or N)
Volume, permanent pool, Vpe<,,,yw,
2503 ft'
Area provided, permanent pool, Apes, -Poo,
11,726 ftz
Average depth calculated
ft Need 3 ft min.
Average depth used in SA /DA, dov, (Round to nearest 0.5ft)
ft
Calculation option 2 used? (See Figure 10 -2b)
Y (Y or N)
Area provided, permanent pool, Ape _pwj
11,726 ft`
Area, bottom of 10ft vegetated shelf, Awl shelf
9,504 ftz
Area, sediment cleanout, top elevation (bottom of pond), Aborpond
4,487 ftz
"Depth" (distance b/w bottom of 1Oft shelf and top of sediment)
3.50 It
Average depth calculated
3.00 ft OK
Average depth used in SAIDA, dav, (Round to down to nearest 0.5ft)
3.0 ff OK
Drawdown Calculations
Drawdown through orifice?
Y (Y or N)
Diameter of orifice (if circular)
2.30 in
Area of orifice (if- non - circular)
in
Coefficient of discharge (Co)
0.60 (unitless)
Driving head (Ho)
2.83 ft
Drawdown through weir?
N (Y or N)
Weir type
(unitless)
Coefficient of discharge (C,v)
( unitless)
Length of weir (L)
ft
Driving head (H)
ft
Pre - development 1 -yr, 24 -hr peak flow
0.59 ft3 /sec
Post- development 1 -yr, 24 -hr peak flow
1.12 ft3 /sec
Storage volume discharge rate (through discharge orifice or weir)
0.12 ft3 /sec
Storage volume drawdown time
4.50 days OK, draws down in 2 -5 days.
Additional Information
Vegetated side slopes
Vegetated shelf slope
Vegetated shelf width
Length of flowpath to width ratio
Length to width ratio
Trash rack for overflow 8. orifice?
Freeboard provided
Vegetated filter provided?
Recorded drainage easement provided?
Capures all runoff at ultimate build out?
Drain mechanism for maintenance or emergencies is:
Form SW40I -Wei Detention Basin- Rev.9- 4/18/12 Parts I. 3 !I. Design Summary, Page 2 of 2
3 :1
OK
10 :1
OK
10.0 ft
OK
3 :1
OK
3.0 :1
OK
Y
C( or N)
OK
1.5 ft
OK
Y
(Y or N)
OK
`(
(Y or N)
OK
Y
(Y or N)
OK
Orifice with manual valve control
Form SW40I -Wei Detention Basin- Rev.9- 4/18/12 Parts I. 3 !I. Design Summary, Page 2 of 2

Permit Number-
(to be provided by DWQ)
Drainage Area Number
Wet Detention Basin Operation and Maintenance Agreement
I will keep a maintenance record on this BMP. This maintenance record will be kept in a
log in a known set location. Any deficient BMP elements noted in the inspection will be
corrected, repaired or replaced immediately. These deficiencies can affect the integrity
of structures, safety of the public, and the removal efficiency of the BMP.
The wet detention basin system is defined as the wet detention basin,
pretreatment including forebays and the vegetated filter if one is provided.
This system (check one):
® does ❑ does not
This system (check one):
❑ does ® does not
incorporate a vegetated filter at the outlet.
incorporate pretreatment other than a forebay.
Important maintenance procedures:
- Immediately after the wet detention basin is established, the plants on the
vegetated shelf and perimeter of the basin should be watered twice weekly if
needed, until the plants become established (commonly six weeks).
- No portion of the wet detention pond should be fertilized after the first initial
fertilization that is required to establish the plants on the vegetated shelf.
- Stable groundcover should be maintained in the drainage area to reduce the
sediment load to the wet detention basin.
- If the basin must be drained for an emergency or to perform maintenance, the
flushing of sediment through the emergency drain should be m,nin- zed to the
maximum extent practical.
- Once a year, a dam safety expert should inspect the embankment.
After the wet detention pond is established, it should be inspected once a month and
within 24 hours after every storm event greater than 1.0 inches (or 1.5 inches if in a
Coastal County). Records of operation and maintenance should be kept in a known set
location and must be available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall
be repaired immediately.
BMP element:
Potential problem:
How I will remediate the problem:
The entire BMP
Trash/ debris is present
Remove the trash debris
The perimeter of the wet
detention basin
Areas of bare soil and/or
erosive gullies have formed
Regrade the soil if necessary to
remove the gully, and then plant a
ground cover and water until it is
established. Provide hme and a
one -time fertilizer application
Vegetation is too short or too
long
Maintain vegetation at a height of
approximately six inches
Form SW401 -Wet Detention Basin O &M -Rev 4 Page 1 of 4

Permit Number
(to be provided by DWQ)
Drainage Area Number
BMP element:
Potential problem:
How I will remediate the problem:
The inlet device: pipe or
The pipe is clogged
Unclog the pipe. Dispose of the
swale
sediment off -site
The pipe is cracked or
Replace the pipe
otherwise damaged
Erosion is occurring in the
Regrade the swale if necessary to
swale
smooth it over and provide erosion
control devices such as reinforced
turf matting or nprap to avoid
future problems with erosion.
The forebay
Sediment has accumulated to
a depth greater than the
Search for the source of the
sediment and remedy the problem if
original design depth for
possible Remove the sediment and
sediment storage
dispose of it in a location where it
will not cause impacts to streams or
the BMP.
Erosion has occurred
Provide additional erosion
protection such as reinforced turf
matting or nprap if needed to
prevent future erosion problems.
Weeds are present.
Remove the weeds, preferably by
hand If pesticide is used, wipe it on
the plants rather than s ra
The vegetated shelf
Best professional practices
Prune according to best professional
show that pruning is needed
practices
to maintain optimal plant
health
Plants are dead, diseased or
Determine the source of the
dying
problem soils, hydrology, disease,
etc. Remedy the problem and
replace plants Provide a one -time
fertilizer application to establish the
ground cover if a soil test indicates
it is necessary.
Weeds are present
Remove the weeds, preferably by
hand If pesticide is used, wipe it on
the plants rather than spraying
The main treatment area
Sediment has accumulated to
a depth greater than the
original design sediment
Search for the source of the
sediment and remedy the problem if
possible. Remove the sediment and
storage depth
dispose of it in a location where it
will not cause impacts to streams or
the BMP
Algal growth covers over
50% of the area
Consult a professional to remove
and control the algal growth
Cattails, phragmites or other
Remove the plants by wiping them
invasive plants cover 50% of
with pesticide (do not spray).
the basin surface
Form SW401 -Wet Detention Basin O &M -Rev 4 Page 2 of 4

Permit Number.
(to be provided by DWQ)
Drainage Area Number
BMP element:
Potential problem:
How I will remediate the problem;
The embankment
Shrubs have started to grow
Remove shrubs immediately
on the embankment.
Evidence of muskrat or
Use traps to remove muskrats and
beaver activity is present
consult a professional to remove
beavers.
A tree has started to grow on
Consult a dam safety specialist to
the embankment.
remove the tree.
An annual inspection by an
Make all needed repairs.
appropriate professional
shows that the embankment
needs repair. if applicable)
The outlet device
Cloggmg has occurred
Clean out the outlet device. Dispose
of the sediment off -site.
The outlet device is damaged
Repair or replace the outlet device
The receiving water
Erosion or other signs of
Contact the local NC Division of
damage have occurred at the
Water Quality Regional Office, or
outlet.
the 401 Oversight Unit at 919 -733-
1786.
The measuring device used to determine the sediment elevation shall be such
that it will give an accurate depth reading and not readily penetrate into
accumulated sediments.
When the permanent pool depth reads 447.5 feet in the main pond, the
sediment shall be removed.
When the permanent pool depth reads 448 feet in the forebay, the sediment
shall be removed.
BASIN DIAGRAM
(fill in the blanks)
V Permanent Pool Elevation 4515
Sediment Removal 448 Pe anen Pool
-------------- - - Volume Sediment Removal Elevation 447 5 Volume
Bottom Elevatio 447 ft Mm. ------------------------------------ - - - - -- - - - - --
Sediment Bottom Elevation 446 5 1 -ft
Storage Sedimei
Storage
FOREBAY MAIN POND
Form SW441 -Wet Detention Basin O &M -Rev 4 Page 3 of 4

r
Permit Number-
(to be provided by DWQ)
I acknowledge and agree by my signature below that I am responsible for the
performance of the maintenance procedures listed above. I agree to notify DWQ of any
problems with the system or prior to any changes to the system or responsible party.
Project name:COLV IN PARK
BMP drainage area number: 3
Print name:Mitchell W Sanner, III - PARKER & ORLEANS HOMEBUILDERS, INC
Tttle:Division President
Address:21 I James Jackson Ave Cary NC 27513
Phone:[phone]
S ignature:
Date:
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president
1, , a Notary Public for the State of
County of , do hereby certify that
personally appeared before me this _
day of , and acknowledge the due execution of the
forgoing wet detention basin maintenance requirements. Witness my hand and official
seal,
SEAL
My commission expires,
Form SW401 -Wet Detention Basin O &M -Rev 4 Page 4 of 4

Permit No
(to be provided by DWQ)
��# ?I � ° ' ! `� fy �, , , v Jk2Y. �s{3 .F- �`. y i77`+.?�'r ' -� � a lw;�!I . � u� �� a� � ����.. ,. �, " s � .�,.�, •�
....�r�.:.c#�.:�*�fa����� �!v..s.>����2� *r+, ^ "�i:��+�.,'.,����`_3.. �.� us: �.su�,.y_,...��::,.�'�'# �..3.c._���,s��..=�.Es.. .a,:,. ,_.+��a.�•r:.� � ..
Please indicate the page or plan sheet numbers where the supporting documentation can be found An Incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to
Indicate the following design requirements have been met If the applicant has designated an agent, the agent may Initial below If a
requirement has not been met, attach justification.
Pagel Plan
Initials Sheet No.
C-06 to 09 1 Plans (1" - 50' or larger) of the entire site showing
- Design at ultimate build -out,
- Off -site drainage (if applicable),
- Delineated drainage basins (include Rational C coefficient per basin),
- Basin dimensions,
- Pretreatment system,
- High flow bypass system,
- Maintenance access,
- Proposed drainage easement and public right of way (ROW),
- Overflow device, and
- Boundaries of drainage easement
C-42 2 Partial plan (1" = 30' or larger) and details for the wet detention basin showing
- Outlet structure with trash rack or similar,
- Maintenance access,
- Permanent pool dimensions,
- Forebay and main pond with hardened emergency spillway,
- Basin cross- section,
- Vegetation specification for planting shelf, and
- Fitter strip
C42 3 Section view of the wet detention basin (1" = 20' or larger) showing
- Side slopes, 31 or lower,
- Pretreatment and treatment areas, and
- Inlet and outlet structures
C42 4 If the basin is used for sediment and erosion control during construction, clean out of the basin Is specified
on the plans prior to use as a wet detention basin
SW Report 5 A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay,
to verify volume provided
C-18 6 A construction sequence that shows how the wet detention basin will be protected from sediment until the
entire drainage area is stabilized
SW Report 7 The supporting calculations
SW Report 8 A copy of the signed and notarized operation and maintenance (0 &M) agreement
N/A 9 A copy of the deed restrictions (If required)
SW Report 10 A soils report that is based upon an actual field Investigation, soil bonngs, and Infiltration tests County
soil maps are not an acceptable source of soils information
Form SW401 -Wet Detention Basin -Rev 9- 4/18/12 Part III Required Items Checklist, Page 1 of 1

Stormwater Management Report
COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP #4: Design Calculations
(Volume, Surface Area, and Orifice)
March 15, 2013

BMP Sizing Worksheet: BMP #4 - Wet Pond
Proiect Name Colvin Park Proiect #
City /State Apex, NC Date 3/15/2013
Table 10.1 Surface Area to Drainage Area Ratio for Permanent Pool Sizing for 85% Pollutant
0 w _i C#fwlnnwv in }he Didu4mnnt
% Impervious
Cover
Permanent Pool Depth (feet)
3.0 4.0 5.0 6.0 7.0 8.0 9.0
10
059
049
043
035
031
029
026
20
097
079
070
059
051
046
044
30
134
108
097
083
070
064
062
40
1 73
143
125
105
090
082
077
50
206
173
150
130
1 09
100
092
60
240
203
171
1 51
129
118
1 10
70
288
240
207
179
154
135
126
80
336
278
238
210
186
160
142
90
374
310
1 266
234
211
183
167
Source NCDENR/DWQ Stormwater Best Management rracnces, pg o, /Apni i aaa
STORMWATER BMP 4 - WET POND (25% TN Removal)
Land Use
Area
ac
% IA
Imp. Area
ac
Roadway & Sidewalk
080
100
08
Lots 4 + 2ex @ 3,500s
050
100
05
2405
sq ft
Normal pool elevation = 4365
feet
Pervious Area
170
0
00
Totals
3.00
Using the runoff volume calculations in the "Simple Method" as described by Schueler (1987)
1.3
DA
Height(H) 46 ft
Length(L) 1450 ft
tc (Kirpich) 10 min
Total % Impervious Surface Area =
43.3 %
' Surface Area of Permanent Pool:
Calculated depth = 30
feet Rounded Down from Option 2
SA/DA ratio = 1.84
% From Table 10 1
Minimum pond surface area (SA) _ (DA "
SA/DA ratio) /100
SA = 0.055
acres
2405
sq ft
Normal pool elevation = 4365
feet
Surface area provided = 0.114
acres
4973
sq ft
1 -Inch Runoff Volume Calculation
Using the runoff volume calculations in the "Simple Method" as described by Schueler (1987)
Rv = 0 05 + 0 009(1) where,
Rv = Runoff coefficient, in /in
I = Percent impervious
Rv = 044 in /in
Total runoff volume from 1 -inch precipitation
Runoff volume, S = (Design rainfall) (Rv) (Drainage Area)
S = 0.110 acre -ft
4792 cu ft
WQ Head = 08 feet
Water quality pool elevation= 4373 feet

Colvin Park Subdivision - BMP 4
Detention Basin Volume Verification
POND
FOREBAY
Frustrum Pyramid
Frustrum Pyramid
432 616.58
433 274.92
433 951.82
778.16
434 522.15
391.98
434 1,359.07
1,149.42
435 820.81
665.87
435 1,838.32
1,592.67
436 1,177.42
993.77
436 2,389.56
2,107.93
436.5 1,424.94
649.61
Perm Pool
436.5 3,547.89
1,47436
Perm Pool
437 1,590.02
753.36
437 4,678.91
2,050.19
438 2,060.57
1,820.22
438 5,507.39
5,087.53
VOLUME ABOVE NWL (03)
2,573.58
VOLUME ABOVE NWL (ff3)
7,137.72
TOTAL VOLUME (ff3)
5,274.82
TOTAL VOLUME (ff3)
14,240.75
Forebay= 22%
Total Volume
Aboffomsh.f = 3,566.98 ft
SA @ Perm Pool = 4,972.83
SF
Aperm pool = 4,972.83 ft
VOLUME ABOVE PP (ff3)
9.711.30
Abon mpond = 1,138.73 ft
VOLUME AT PP (ff3)
12,514.96
Depth = 4 ft
TOTAL VOLUME (ft3)-
19,515.56
Calculated Avg Depth = 3.1 ft
Option 2
Water Quality Volume =
4,792
Water Quality Elevation =
437.3
Orifice Head =
0.8
Pre -Post Analysis
Drainage Area = 7.2 acres
" 1 -year 24 -hour rainfall event (i =
0.119 in /hr)
Pre - development Composite C:
Pre - development Q = CiA =
0.17
cfs
Surface C
Acreage
Totals
Post - developmef BMP outflow =
0.03
cfs
Unimproved Area: 0.35
0.0
0.00
Roof: 1.00
0.1
0.10
* 10 -year 24 -hour rainfall event (i = 0.21 in /hr)
Wooded Area: 0.15
1.7
0.26
Pre - development Q = CiA =
0,30
cfs
Lawns: 0.20
1.2
0.24
Post - developmef BMP outflow =
0.03
cfs
Composite C =
0.20

ORIFICE & LEVEL SPREADER WORKSHEET
STORMWATER BMP 4
WET POND (25% TN Removal)
Orifice Calculator
Q = Cd *A *(2gh) "(1/2)
1 Water Quality Volume Draw -down
Variables
WQ Volume 0 11 Acre -ft
47916 cf
Head 0 8 ft
0.26 ft
Draw down time 48 hrs
172800s
Orifice Area = 0 01 sq ft
162 sq in
Orifice Diameter = 144 in
1 Max Stage Draw -down
Variables
Volume 0 22 Acre -ft 9711 298 cf
Head 15 ft
0 50 ft
Draw down time 86 hrs
309600s
Orifice Area = 0 01 sq ft
1 33 sq in
Orifice Diameter = 1 30 in
Q =
USE 1.3" DIAMETER ORIFICE Orifice Area =
4 15 sq. in
Level Spreader Sizing:
Q at 10 -yr storm = 0 04 cfs
Level Spreader @ 50 ft/cfs (10' min) =
10 ft
3/15/2013
Constants
g = 322 ft/s2
Cd= 06
Constants
g = 322 ft/s2
Cd= 06
0 03 cfs

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP #4: HydroCAD Routing
(summary & xydrographs)
Section 1: 2 -yr, 10 -yr & 100 -yr Pond routing
Section 2: 1 -yr 24 -hr & 10 -yr 24 -hr Pre/Post Routing
Stormwater Management Report March 15, 2013

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
Section 1: 2 -yr, 10 -yr & 100 -yr Pond routing
Stormwater Management Report March 15, 2013

BMP #4 -Post - rev 1 -2 -13 Rainfall Duration =10 min, Inten =4 76 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCADO 10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#4
Inflow Area = 3 000 ac, 43 33% Impervious, Inflow Depth = 0 48"
Inflow = 8 63 cfs @ 0 17 hrs, Volume= 0 121 of
Outflow = 0 04 cfs @ 0.34 hrs, Volume= 0 009 af, Atten= 100 %,
Lag= 10 4 min
Primary = 004 cfs @ 034 hrs, Volume= 0 009 of
Routing by Stor -Ind method, Time Span= 0 00 -3 00 hrs, dt= 0 01 hrs
Peak Elev= 437 35'@ 0 34 hrs Surf Area= 6,798 sf Storage= 5,238 cf
Plug -Flow detention time= 90.9 min calculated for 0 009 of (8% of inflow)
Center -of -Mass det. time= 83 5 min ( 93 5 - 10 0 )
Volume Invert Avail Storage Storage Descnption
#1 436 50' 9,810 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Perim Inc Store Cum Store Wet.Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
_
43650 4,973 3716 0 0
4,973
43700 6,367 4004 2,828 2,828
6,753
43800 7,615 4220 6,982 9,810
8,225
Device Routing Invert Outlet Devices
#1 Primary 432 00' 18.0" Round Culvert
L= 48 0' RCP, groove end projecting, Ke= 0 200
Inlet / Outlet Invert= 432.00'/ 430 00' S= 0.0417'/' Cc= 0 900
n= 0.013, Flow Area= 1 77 sf
#2 Device 1 436 50' 1.3" Vert. Orifice C= 0 600
#3 Device 1 437 75' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 04 cfs @ 0 34 hrs HW =437 35' (Free Discharge)
t- = Culvert (Passes 0 04 cfs of 22 80 cfs potential flow)
2_Orifice (Onfce Controls 0 04 cfs @ 4 28 fps)
3 Orifice /Grate ( Controls 0 00 cfs)

BMP #4 -Post - rev 1 -2 -13 Rainfall Duration =90 min, Inten =4.76 in /hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD ®10.00 s/n 07807 O 2012 HydroCAD Software Solutions LLC
N
V
3
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Pond 2P; BMP#4
Hydrograph
Time (hours)
Inflow
® Primary

BMP #4 -Post - rev 1 -2 -13 Rainfall Duration= 10 min, Inten =6 13 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD010 00 s/n 07807 02012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#4
Inflow Area = 3 000 ac, 43 33% Impervious, Inflow Depth = 0 62"
Inflow = 11 11 cfs @ 0 17 hrs, Volume= 0 156 of
Outflow = 0 04 cfs @ 0 34 hrs, Volume= 0 010 af, Atten= 100 %,
Lag= 10 4 min
Primary = 0.04 cfs @ 0 34 hrs, Volume= 0 010 of
Routing by Stor -Ind method, Time Span= 0 00 -3 00 hrs, dt= 0 01 hrs
Peak Elev= 437 56'@0 34 hrs Surf Area= 7,068 sf Storage= 6,750 cf
Plug -Flow detention time= 91 1 min calculated for 0 010 of (7% of inflow)
Center -of -Mass det. time= 83 5 min ( 93 5 - 10 0 )
Volume Invert Avail Storage Storage Description
#1 436 50' 9,810 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Penm Inc Store Cum Store Wet Area
(feet) (sq -ft) (feet) (cubic-feet) (cubic -feet)
(sq -ft)
43650 4,973 3716 0 0
4,973
437.00 6,367 4004 2,828 2,828
6,753
43800 7,615 4220 6,982 9,810
8,225
Device Routing Invert Outlet Devices
#1 Primary 432 00' 18.0" Round Culvert
L= 48 0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert= 432 00' /430 00' S=00417? Cc= 0 900
n= 0 013, Flow Area= 177 sf
#2 Device 1 436 50' 1.3" Vert. Orifice C= 0 600
#3 Device 1 437 75' 48.0" Horiz. Orifice /Grate C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max =O 04 cfs @ 0 34 hrs HW =437 56' (Free Discharge)
= Cuivert (Passes 0 04 cfs of 23 33 cfs potential flow)
2=Orifice (Orifice Controls 0 04 cfs @ 4 83 fps)
3=Orifice/Grate ( Controls 0 00 cfs)

BMP #4 -Post - rev 1 -2 -13 Rainfall Duration =10 min, Inten =6.13 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD® 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
a�
U
3
0
LL
Pond 2P: BMP#4
Hydrograph
Time (hours)
■ Inflow
■ Primary

BMP #4 -Post - rev 1 -2 -13 Rainfall Duration =10 min, Inten =8 40 in/hr
Prepared by Ketchem - Crowder & Associates Printed 3/18/2013
HydroCADO 10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#4
Inflow Area = 3 000 ac, 43 33% Impervious, Inflow Depth = 0 85"
Inflow = 15 23 cfs @ 0 17 hrs, Volume= 0 213 of
Outflow = 1 86 cfs @ 0 31 hrs, Volume= 0 036 af, Atten= 88 %, Lag= 8 8 min
Primary = 186 cfs @ 0 31 hrs, Volume= 0 036 of
Routing by Stor -Ind method, Time Span= 0.00 -3 00 hrs, dt= 0 01 hrs
Peak Elev= 437 87' @ 0 31 hrs Surf Area= 7,459 sf Storage= 8,935 cf
Plug -Flow detention time= 42 2 min calculated for 0 036 of (17% of inflow)
Center -of -Mass det time= 36 5 min ( 46 5 - 10.0 )
Volume Invert Avail Storage Storage Description
#1 436 50' 9,810 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Penm Inc Store Cum Store Wet Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
43650 4,973 3716 0 0
4,973
43700 6,367 4004 2,828 2,828
6,753
43800 7,615 4220 6,982 9,810
8,225
Device Routing Invert Outlet Devices
#1 Primary 432 00' 18.0" Round Culvert
L= 48 0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert= 432 00'/430 00' S= 0 0417 T
Cc= 0 900
n= 0 013, Flow Area= 177 sf
#2 Device 1 436 50' 1.3" Vert. Orifice C= 0 600
#3 Device 1 437 75' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =1 85 cfs @ 0 31 hrs HW =437 87' (Free Discharge)
= Culvert (Passes 185 cfs of 24 08 cfs potential flow)
2 =Orifice (Orifice Controls 0 05 cfs @ 5 53 fps)
3 =Orifice /Grate (Weir Controls 180 cfs @ 1 15 fps)

BMP #4 -Post - rev 1 -2 -13 Rainfall Duration =10 min, Inten =8.40 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCADO 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
17
16
15
14
13
12
11
10
N
9
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LL 7
6
5
4
3
2
1
0
0
Pond 2P; BMP#4
Hydrograph
1 2 3
Time (hours)
3 Inflow
M Primary

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
Section 2: 1 -yr 24 -hr & 10 -yr 24 -hr Pre /Post Routing
Stormwater Management Report Mardi 15, 2013

BMP #4 -Post - rev 1 -2 -13 Rainfall Duration= 1, 440 min, Inten =0 12 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD®10 00 s/n 07807 4 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#4
Inflow Area = 3 000 ac, 43 33% Impervious, Inflow Depth > 0 21"
Inflow = 0 22 cfs @ 0 17 hrs, Volume= 0 053 of
Outflow = 0 03 cfs @ 3 00 hrs, Volume= 0 004 af, Atten= 89 %, Lag= 169 8 min
Primary - 0 03 cfs @ 3 00 hrs, Volume= 0 004 of
Routing by Stor -Ind method, Time Span= 0 00 -3 00 hrs, dt= 0.01 hrs
Peak Elev= 436 88'@ 3 00 hrs Surf Area= 6,041 sf Storage= 2,167 cf
Plug -Flow detention time= 107 2 min calculated for 0 004 of (7% of inflow)
Center -of -Mass det time= 25 2 min ( 117 8 - 92 6 )
Volume Invert Avail Storage Storage Description
#1 436 50' 9,810 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Perim Inc Store Cum Store Wet Area
(feet) (sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
43650 4,973 3716 0 0
4,973
43700 6,367 4004 2,828 2,828
6,753
43800 7,615 4220 6,982 9,810
8,225
Device Routing Invert Outlet Devices
#1 Primary 432 00' 18.0" Round Culvert
L= 48 0' RCP, groove end projecting, Ke= 0 200
Inlet/ Outlet Invert= 432 00'1430 00' S= 0 0417 '/'
Cc= 0 900
n= 0 013, Flow Area= 177 sf
#2 Device 1 436 50' 1.3" Vert. Orifice C= 0 600
#3 Device 1 437 75' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 03 cfs @ 3 00 hrs HW =436 88' (Free Discharge)
t- Culvert (Passes 0 03 cfs of 21.62 cfs potential flow)
2= 0rifice (Orifice Controls 0 03 cfs @ 2 76 fps)
r
3 Orifice /Grate ( Controls 0 00 cfs)

BMP #4 -Post - rev 1 -2 -13 Rainfall Duration =1,440 min, Inten =0.12 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD® 10.00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
N
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Pond 2P: BMP#4
Hydrograph
Time (hours)
Inflow
® Primary

BMP #4 -Post - rev 1 -2 -13 Rainfall Duration= 1, 440 min, Inten =0 21 in/hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCADO 10 00 s/n 07807 C 2012 HydroCAD Software Solutions LLC
Summary for Pond 2P: BMP#4
Inflow Area = 3 000 ac, 43.33% Impervious, Inflow Depth > 0 37"
Inflow = 0 39 cfs @ 0.17 hrs, Volume= 0 094 of
Outflow = 0 03 cfs @ 3 00 hrs, Volume= 0 005 af, Atten= 91 %, Lag= 169 8 min
Primary = 0 03 cfs @ 3 00 hrs, Volume= 0 005 of
Routing by Stor -Ind method, Time Span= 0 00 -3 00 hrs, dt= 0.01 hrs
Peak Elev= 437 14'@ 3 00 hrs Surf Area= 6,548 sf Storage= 3,840 cf
Plug -Flow detention time= 104 8 min calculated for 0 005 of (6% of inflow)
Center -of -Mass det time= 217 min ( 114 4 - 92 6 )
Volume Invert
Avail Storage Storage Description
#1 436.50'
9,810 cf Custom Stage Data (Irregular) Listed below
Elevation Surf Area Penm Inc Store Cum Store Wet Area
(feet)
(sq -ft) (feet) (cubic -feet) (cubic -feet)
(sq -ft)
43650
4,973 3716 0 0
4,973
43700
6,367 4004 2,828 2,828
6,753
43800
7,615 4220 6,982 9,810
8,225
Device Routing
Invert Outlet Devices
#1 Primary _
432 00' 18.0" Round Culvert
L= 48 0' RCP, groove end projecting, Ke= 0.200
Inlet/ Outlet Invert= 432.00'/430 00' S= 0 0417'/'
Cc= 0 900
n= 0.013, Flow Area= 177 sf
#2 Device 1
436 50' 1.3" Vert. Orifice C= 0 600
#3 Device 1
437 75' 48.0" Horiz. Orifice /Grate C= 0 600
Limited to weir flow at low heads
Primary OutFlow Max =O 03 cfs @ 3 00 hrs HW =437 14' (Free Discharge)
t— = Culvert (Passes 0 03 cis of 22 30 cfs potential flow)
2 =Orifice (Onfice Controls 0 03 cfs @ 3 70 fps)
3 Orifice /Grate ( Controls 0 00 cfs)

BMP #4 -Post - rev 1 -2 -13 Rainfall Duration= 1, 440 min, Inten =0.21 in /hr
Prepared by Ketchem- Crowder & Associates Printed 3/18/2013
HydroCAD ®10 00 s/n 07807 © 2012 HydroCAD Software Solutions LLC
0
a
0
0
0
0.
0.
0.
U
V.
0
U. 0.
0.
0.
0
0
0
0.
0
Pond 2P; BMP#4
Hydrograph
VO 1 2 3
Time (hours)
Inflow
® Primary

COLVIN PARK SUBDIVISION
STORMWATER MANAGEMENT REPORT
STEPHENSON ROAD APEX, NC
BMP #4: DWQ Supplements
Supplement 1: Wet Detention Basin Supplement
Supplement 2: Wet Detention Basin O &M Agreement
Supplement 3: Required Items Checklist
Stormwater Management Report March 15, 2013

Permit No.
(to be provided by DWQ)
NCDENR
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part III) must be printed, filled out and submitted along with all of the required information.
I. PROJECT INFORMATION
Project name
COLVIN PARK SUBDIVISION
Contact person
BRIAN KETCHEM, PE
Phone number
919- 724-0624
Date
3/15/2013
Drainage area number
4
II. DESIGN INFORMATION
Site Characteristics
Drainage area
130,680 fe
Impervious area, post- development
56,628 ft
% impervious
43.33 %
Design rainfall depth
1.0 in
Storage Volume: Non-SA Waters
Minimum volume required
Volume provided
Storage Volume: SA Waters
1.5" runoff volume
Pre- development 1 -yr, 24 -hr runoff
Post - development 1 -yr, 24 -hr runoff
Minimum volume required
Volume provided
Peak Flow Calculations
Is the pre /post control of the lyr 24hr storm peak flow required?
1 -yr, 24 -hr rainfall depth
Rational C, pre - development
Rational C, post - development
Rainfall intensity: 1 -yr, 24 -hr storm
Pre- development 1 -yr, 24 -hr peak flow
Post - development 1 -yr, 24 -hr peak flow
Pre /Post 1 -yr, 24 -hr peak flow control
Elevations
Temporary pool elevation
Permanent pool elevation
SHWT elevation (approx. at the perm. pool elevation)
Top of 10ft vegetated shelf elevation
Bottom of I Oft vegetated shelf elevation
Sediment deanou4, top elevation (bottom of pond)
Sediment cleanout, bottom elevation
Sediment storage provided
Is there additional volume stored above the state - required temp. pool?
Elevation of the Lop of the additional volume
4,792 ft3
9,711 ft3
OK, volume provided is equal to or in excess of volume required.
ft3
ft3
ft3
ft3
ft3
(Y or N)
2.9 in
0.20 (unitless)
0.56 (unidess)
0.12 in /hr OK
0.17 ft3 /sec
0.22 ft3 /sec
0.05 ft3
/sec
437.87 fmsl
436.50 fmsl
436.00 fmsl
437.00 fmsl
436.00 fmsl
432.00 fmsl
431.00 fmsl
'1.00 ft
N (Y or N)
fmsi
Form SW401 -Wet Detention Basin- Rev.9- 4/1 811 2 Parts I. 3, II. Design Summary, Page 'I of 2

II. DESIGN INFORMATION
Surface Areas
Area. temporary pool
Area REQUIRED, permanent pool
SAIDA ratio
Area PROVIDED, permanent pool, Apempool
Area, bottom of 1 Oft vegetated shelf, Abot shell
Area, sediment cleanout, top elevation (bottom of pond), Ab t ,.d
Volumes
Volume, temporary pool
Volume, permanent pool, Voef11,_pd
Volume, forebay (sum of forebays if more than one forebay)
Forebay % of permanent pool volume
SAIDA Table Data
Design TSS removal
Coastal SAIDA Table Used?
Mountain /Piedmont SAIDA Table Used?
SAIDA ratio
Average depth (used in SAIDA table):
Calculation option 1 used? (See Figure 10 -2b)
Volume, permanent pool, Vpem _pool
Area provided, permanent pool, Ap,. -P ,
Average depth calculated
Average depth used in SAIDA, day, (Round to nearest 0.5ft)
Calculation option 2 used? (See Figure 10 -2b)
Area provided, permanent pool, Ap ,_pwl
Area, bottom of 1 Oft vegetated shelf, Abo, shelf
Area, sediment cleanout, top elevation (bottom of pond), Aboayond
7,568 ft3
2,405 ft'
1.84 ( unitless)
4,973 ft` OK
3,567 ft`
1,139 ft`
9,711 ft3 OK
12,515 ft3
2,701 ft3
21.6% % OK
85 %
N (Y or N)
Y (Y or N)
1.84 ( unifless)
N (Y or N
12,515 ft'
4,973 W
It
It
Y (Y or N)
4,973 ft
3,567 ft
1,139 ft2
"Depth" (distance b/w bottom of 1 Oft shelf and top of sediment) 4.00 It
Average depth calculated 3.10 It
Average depth used in SAIDA, dam„ (Round to down to nearest 0.5ft) 3.0 it
Drawdown Calculations
Drawdown through orifice?
Diameter of orifice (if circular)
Area of orifice (if- non - circular)
Coefficient of discharge (Co)
Driving head (Ho)
Drawdown through weir?
Weir type
Coefficient of discharge (C,y)
Length of weir (L)
Driving head (H)
Pre- development 1 -yr, 24 -hr peak Flow
Past - development 1 -yr, 24-hr peak flow
Storage volume discharge rate (through discharge orifice or weir)
Storage volume drawdown time
Additional Information
Vegetated side slopes
Vegetated shelf slope
Vegetated shelf width
Length of flowpath to width ratio
Length to width ratio
Trash rack for overflow & orifice?
Freeboard provided
Vegetated filter provided?
Recorded drainage easement provided?
Capures all runoff at ultimate build -our?
Drain mechanism for maintenance or emergencies is:
_ Y (Y or N)
1.30 in
in'
0.60 ( unifless)
1.37 It
N (Y or N)
(unitless)
(unidess)
ft
It
0.17 ft3/sec
0.22 ft3lsec
0.03 ft'/sec
3.58 days
Need 3 It min.
OK
OK
OK, draws down in 2 -5 days.
Permit
(to be provided by DWQ)
Form SW401 -Wet Detention Basin- Rev.9- 4/18/12 Parts I. & II. Design Summary, Page 2 of 2
3 :1
OK
10 :1
OK
10.0 ft
OK
3 J
OK
2.2 :1
OK
Y
(Y or N)
OK
1.0 It
OK
Y
(Y or N)
OK.
Y
(Y or N)
OK.
Y
(Y or N)
OK
Orifice with
manual valve control
Permit
(to be provided by DWQ)
Form SW401 -Wet Detention Basin- Rev.9- 4/18/12 Parts I. & II. Design Summary, Page 2 of 2

Permit Number-
(to be provided by DWQ)
Drainage Area Number
Wet Detention Basin Operation and Maintenance Agreement
I will keep a maintenance record on this BUF. This maintenance record will be kept in a
log in a known set location. Any deficient BNT elements noted in the inspection will be
corrected, repaired or replaced immediately. These deficiencies can affect the integrity
of structures, safety of the public, and the removal efficiency of the BMF.
The wet detention basin system is defined as the wet detention basin,
pretreatment including forebays and the vegetated filter if one is provided.
This system (check one):
® does ❑ does not incorporate a vegetated filter at the outlet.
This system (check one):
❑ does ® does not incorporate pretreatment other than a forebay.
Important maintenance procedures:
- Immediately after the wet detention basin is established, the plants on the
vegetated shelf and perimeter of the basin should be watered twice weekly if
needed, until the plants become established (commonly six weeks).
- No portion of the wet detention pond should be fertilized after the first initial
fertilization that is required to establish the plants on the vegetated shelf.
- Stable groundcover should be maintained in the drainage area to reduce the
sediment load to the wet detention basin.
- If the basin must be drained for an emergency or to perform maintenance, the
flushing of sediment through the emergency drain should be minimized to the
maximum extent practical.
- Once a year, a dam safety expert should inspect the embankment.
After the wet detention pond is established, it should be inspected once a month and
within 24 hours after every storm event greater than 1.0 inches (or 1.5 inches if in a
Coastal County). Records of operation and maintenance should be kept in a known set
location and must be available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall
be repaired immediately.
BMP element:
Potential problem:
How I will remediate the problem:
The entire BMP
Trash debris is present
Remove the trash/ debris
The perimeter of the wet
Areas of bare soil and /or
Regrade the soil if necessary to
detention basin
erosive gullies have formed
remove the gully, and then plant a
ground cover and water until it is
established Provide lime and a
one -time fertilizer application.
Vegetation is too short or too
Maintam vegetation at a height of
long
approximately six inches
Form SW401 -Wet Detention Basin O &M -Rev 4 Page 1 of 4

Permit Number
(to be provided by DWQ)
Drainage Area Number
BMP element:
Potential problem:
How I will remediate the problem:
The inlet device: pipe or
The pipe is clogged.
Unclog the pipe Dispose of the
swale
sediment off -site.
The pipe is cracked or
Replace the pipe
otherwise damaged.
Erosion is occurring in the
Regrade the swale if necessary to
swale.
smooth it over and provide erosion
control devices such as reinforced
turf matting or nprap to avoid
future problems with erosion.
The forebay
Sedunent has accumulated to
Search for the source of the
a depth greater than the
sediment and remedy the problem if
original design depth for
sediment storage.
possible. Remove the sediment and
dispose of it m a location where it
will not cause impacts to streams or
the BMP
Erosion has occurred
Provide additional erosion
protection such as reinforced turf
matting or riprap if needed to
prevent future erosion problems.
Weeds are present.
Remove the weeds, preferably by
hand If pesticide is used, wipe it on
the plants rather than spraying.
The vegetated shelf
Best professional practices
Prune according to best professional
show that pruning is needed
practices
to maintain optimal plant
health.
Plants are dead, diseased or
Determine the source of the
dying
problem- soils, hydrology, disease,
etc. Remedy the problem and
replace plants Provide a one -time
fertilizer application to establish the
ground cover if a soil test indicates
it is necessary.
Weeds are present.
Remove the weeds, preferably by
hand. If pesticide is used, wipe it on
the plants rather than spraying
The main treatment area
Sediment has accumulated to
Search for the source of the
a depth greater than the
sediment and remedy the problem if
ongunal design sediment
possible Remove the sediment and
storage depth
dispose of it in a location where it
will not cause impacts to streams or
the BMP
Algal growth covers over
Consult a professional to remove
500 of the area
and control the algal growth
Cattails, phragmutes or other
Remove the plants by wiping them
invasive plants cover 50% of
with pesticide (do not spray).
the basin surface
Form SW401 -Wet Detention Basin O &M -Rev 4 Page 2 of 4

Permit Number
(to be provided by DWQ)
Drainage Area Number*
BMP element:
Potential problem:
How I will remediate the problem:
The embankment
Shrubs have started to grow
Remove shrubs immediately
on the embankment
Evidence of muskrat or
Use traps to remove muskrats and
beaver activity is present
consult a professional to remove
beavers
A tree has started to grow on
Consult a dam safety specialist to
the embankment
remove the tree.
An annual inspection by an
Make all needed repairs.
appropriate professional
shows that the embankment
needs repair. if applicable)
The outlet device
Clogging has occurred
Clean out the outlet device. Dispose
of the sediment off -site.
The outlet device is damaged
Repair or replace the outlet device
The receiving water
Erosion or other signs of
damage have occurred at the
Contact the local NC Division of
Water Quality Regional Office, or
outlet
the 401 Oversight Unit at 919 -733-
1786
The measuring device used to determine the sediment elevation shall be such
that it will give an accurate depth reading and not readily penetrate into
accumulated sediments.
When the permanent pool depth reads 432 feet in the main pond, the sediment
shall be removed.
When the permanent pool depth reads 433 feet in the forebay, the sediment
shall be removed.
BASIN DIAGRAM
ill in the blanks)
Permanent Pool Elevation 436 5
- Sediment Removal .4 33 Pe anen Pool
-------------- - - Volume Sediment Removal Elevation 432 Volume
Bottom Elevatio 432 ft Min
Sediment Bottom Elevation 431 1 f
Storage Sednmei
Storage
FOREBAY MAIN POND
Form SW401 -Wet Detention Basin O &M -Rev 4 Page 3 of 4

Permit Number
(to be provided by DWQ)
I acknowledge and agree by my signature below that I am responsible for the
performance of the maintenance procedures listed above. I agree to notify DWQ of any
problems with the system or prior to any changes to the system or responsible party.
Project name:COLVIN PARK
BMP drainage area number: 4
Print name:Mitchell W Sanner, III - PARKER & ORLEANS HOMEBUILDERS INC
Title:Division President
Address:21 I James Jackson Ave Cary, NC 27513
Phone:[phone]
Signature:
Date:
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president
I, , a Notary Public for the State of
County of , do hereby certify that
personally appeared before me this
day of , and acknowledge the due execution of the
forgoing wet detention basin maintenance requirements. Witness my hand and official
seal,
SEAL
My commission expires
Form SW401 -Wet Detention Basin O &M -Rev 4
Page 4 of 4

Permit No
(to be provided by DWQ)
Please Indicate the page or plan sheet numbers where the supporting documentation can be found An incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project Initial In the space provided to
Indicate the following design requirements have been met If the applicant has designated an agent, the agent may Initial below ff a
requirement has not been met, attach justification.
Pagel Plan
Initials Sheet No.
C-06 to 09 1 Plans (1" - 50' or larger) of the entire site showing
- Design at ultimate build -out,
- Off -site drainage (if applicable),
- Delineated drainage basins (include Rational C coefficient per basin),
- Basin dimensions,
- Pretreatment system,
- High flow bypass system,
- Maintenance access,
- Proposed drainage easement and public right of way (ROW),
- Overflow device, and
- Boundaries of drainage easement
C42 2 Partial plan (1" = 30' or larger) and details for the wet detention basin showing
- Outlet structure with trash rack or similar,
- Maintenance access,
- Permanent pool dimensions,
- Forebay and main pond with hardened emergency spillway,
- Basin cross - section,
- Vegetation specification for planting shelf, and
- Filter strip
C42 3 Section view of the wet detention basin (1" = 20' or larger) showing
- Side slopes, 31 or lower,
- Pretreatment and treatment areas, and
- Inlet and outlet structures
C-42 4 If the basin is used for sediment and erosion control during construction, clean out of the basin is specified
on the plans prior to use as a wet detention basin
SW Report 5 A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay,
to verify volume provided
C-18 6 A construction sequence that shows how the wet detention basin well be protected from sediment until the
- entire drainage area is stabilized
SW Report 7 The supporting calculations
SW Report 8 A copy of the signed and notarized operation and maintenance (0 &M) agreement
N/A 9 A copy of the deed restrictions (if required)
SW Report 10 A soils report that is based upon an actual field investigation, soil bonngs, and infiltration tests County
soil maps are not an acceptable source of soils information
Form SW401 -Wet Detention Basin -Rev 9.4/18112 Part III Required Items Checklist, Page 1 of 1