20050732 Ver 28_Stormwater Info Ph 9_20130910

C>S -0�3 a U a.g
401 NARRATIVE &
SUPPORTING CALCULATIONS
Briar Chapel Development
Phase 9
Chatham County, North Carolina
September 8, 2013
Prepared for:
BRIAR CHAPEL'S
by
Newland commmm
NNP Briar Chapel, LLC
16 Windy Knoll Circle
Chapel Hill, North Carolina 27516
Prepared By:
MCMM&CREED
1730 Varsity Drive, Suite 500
Raleigh, North Carolina 27606
Phone: [phone]
Fax: [phone]
M&C Project No. 02735 -0096
12@19MM N
SEP 1 0 2013
036348
�:, 0910812013 4

"R=
MCKM&C
TO. NCDENR — Division of Energy, Mineral and
Land Resources, North Carolina Stormwater
1612 Mail Service Center
Raleigh, NC 27604
ATTENTION- Ms. Annette Lucas
Z) 5 - 0-13a. L) aS
LETTER OF TRANSMITTAL
DATE September 4, 2013
PROJECT NO: 2735 -0096
TASK NO EXP
RE. Briar Chapel — Phase 9
TRANSMTTTAL NO 1
PAGE 1 OF 1
WE ARE SENDING: ❑ Originals ® Prints ❑ Shop Drawings ❑ Samples
❑ Specifications ® Calculations ❑ Other -
Quantity
Dwg
No.
Rev.
Description
Status
2
Stormwater Design Plans
G
2
Narrative & Supporting Calculations
G
2
BMP #14 O &M Agreement and Design Supplements (1 Original, 1 copy)
G
2
BMP #15 O &M Agreement and Design Supplements (1 Original, 1 copy)
G
2
BMP #16 O &M Agreement and Design Supplements (1 Original, 1 copy)
G
Issue Status Code: A. Preliminary B. Fabrication Only C. For Information D. Bid
E. Construction F. For Review & Comments G. For Approval H. See Remarks
REMARKS:
Annette,
Please find the enclosed documents for your review. Please let us know if you have any questions or
comments. Thank you.
1730 Varsity Drive, Suite 500 Raleigh, NC 27606 919233 -8091 Fax [phone]
Cc: McKIM & CREED INC.
.-. r-, r. r� n'c1 n r= r1 ,
Gareth Avant, PE

IPROJECT DESCRIPITON
' The purpose of the project is to construct water, sewer and roadway infrastructure to support
114 residential lots within the Briar Chapel development. This will be the third of several phases of
construction in this proximity.
Based on the conditions of the approved 401 Water Quality Certification, NCDENR -DWQ will
require runoff from the roads to be captured and treated for 85% TSS removal before being
' discharged into existing stream buffers. To meet this requirement, the runoff from the northern
portion of this phase of construction will be directed to Wet Detention Pond # 14. The runoff from
the southern portion of this phase will be directed to a new BMP, Wet Detention Pond # 15. To
capture drainage from the existing portion of Boulder Point Drive that currently drains to a
' previously approved temporary LS /VFS measure (NCDENR -DWQ Project #05- 0732v21), a
stormwater wetland will be constructed to ensure the site meets the requirements of the 401
certification. Calculations for these new facilities are included in this package.
1 Upon completion of the project's construction, the proposed public roads will be turned over to
and maintained by NCDOT.
' SITE DESCRIPTION
' The project area is approximately 30 acres of disturbed area located within the BC South
development area, adjacent to Boulder Point Drive and north of Margaret B Pollard Middle
School.
' This portion of the site drains to the north on the north side of Boulder Point Drive and south on
the south side of road.
' SOILS
' According to the Chatham County Generalized Soil Survey, the soils located on the site are
classified as Wedowee sandy loam, 2% to 15% slopes (WeB, , WeD) and Wedowee sandy loam,
2% to 15% slopes, bouldery (WdC).
' The following soil descriptions are associated with the soils found on the site:
We(X) - Wedowee sandy loam soils are often found in piedmont uplands, along ridges
' and side slopes. Permeability is moderate and the soils are well drained. Soils have a low
shrink /swell potential. The seasonal high water is generally more than 6.0 feet below the
surface.
' WdC - Wedowee sandy loam, boulder soils carry the same characteristics of Wedowee
We(X) soils, listed above, with the exception that large boulders are more commonly
found.
' WET DETENTION DESIGN
The wet detention pond on this site has been designed to remove 907o of the total suspended
solids entering from the surrounding impervious drainage areas before discharging into the
adjacent stream. The calculations provided with this package include all projected future

drainage areas that might be captured by the pond. Treated runoff will be dissipated by a
riprap outlet protection device before entering any stream buffers.
' Design parameters were taken from the BMP manual and from DWQ's design supplement forms.
' STORMWATER WETLAND DESIGN
The stormwater wetland on this site has been designed to remove 85% of the total suspended
solids entering from the surrounding impervious drainage areas before discharging into the
' adjacent stream. The calculations provided with this package include all projected future
drainage areas that might be captured by the wetland. Treated runoff will be dissipated by a
riprap outlet protection device before entering any stream buffers.
Design parameters were taken from the BMP manual and from DWQ's design supplement forms.
I MAINTENANCE CONSIDERATIONS
' The property owner shall be responsible for periodic inspection and maintenance of all
temporary erosion control measures devices. Any measure that fails to function as intended
shall be repaired immediately.
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BMP #14 DESIGN

1S 2S
Pre - Development Post -De elopment
3P
BMP #14
Subcat Reach on Link Routing Diagram for 2013.08.19.BMP #14
Prepared by McKim & Creed, Printed 9/8/2013
HydroCAD®10.00 s/n 04927 0 2011 HydroCAD Software Solutions LLC

' 2013.08.19.BMP #14 Type// 24 -hr 1 -Yr Rainfall= 2.96"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD ®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 12
' Summary for Subcatchment 1 S: Pre - Development
' Runoff = 7.12 cfs @ 12.15 hrs, Volume= 0.544 af, Depth> 0.61"
Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Type II 24 -hr 1 -Yr Rainfall= 2.96"
Area (ac) CN Description
10.710 70 Woods, Good, HSG C
' 10.710 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
' (min) (feet) (ft/ft) (ft/sec) (cfs)
20.0 Direct Entry,
' Subcatchment 1S: Pre - Development
Hydrograph
' 7.12 cfs Runoff
7.
Type II 24 -hr
6 1 -Yr Rainfall= 2.96"
Runoff Area = 10.710 ac
5 Runoff Volume =0.544 of
A
- - - - - - - - - - - - - - - Runoff - Depth >0:61-" -
... 4
LL Tc =20.0 min
' 3 CN =70
1 a
1
1
1
1
1
10 11 12 13 14 15 16 17 18 19 20
Time (hours)

' 2013.08.19.BMP #14 Type 11 24 -hr 1 -Yr Rainfall= 2.96"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD®10.00 s/n 04927 C 2011 HydroCAD Software Solutions LLC Page 14
' Summary for Pond 3P: BMP #14
Inflow Area =
10.710 ac, 61.62% Impervious, Inflow Depth > 1.73" for 1 -Yr event
'
Inflow
29.86 cfs @ 12.01 hrs, Volume= 1.545 of
Outflow =
6.79 cfs @ 12.25 hrs, Volume= 0.927 af, Aften= 77 %, Lag= 14.4 min
Primary =
6.79 cfs @ 12.25 hrs, Volume= 0.927 of
' Secondary =
0.00 cfs @ 5.00 hrs, Volume= 0.000 of
Routing by Stor -Ind
method, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Peak Elev= 491.20'@ 12.25 hrs Surf.Area= 22,936 sf Storage= 35,921 cf
Plug -Flow detention time= 157.7 min calculated for 0.924 of (60% of inflow)
Center -of -Mass det. time= 85.8 min ( 862.0 - 776.1 )
Volume Invert Avail.Storage Storage Description
#1 489.50' 136,442 cf Custom Stage Data (Prismatic)Listed below (Recalc)
Elevation
Surf.Area Inc.Store Cum.Store
(feet)
(sq -ft) (cubic -feet) (cubic -feet)
489.50
18,132 0 0
490.00
20,871 9,751 9,751
491.00
22,590 21,731 31,481
492.00
24,366 23,478 54,959
493.00
26,198 25,282 80,241
494.00
28,086 27,142 107,383
495.00
30,031 29,059 136,442
tDevice Routing
Invert Outlet Devices
#1 Primary
484.00' 18.0" Round Culvert
L= 105.1' RCP, square edge headwall, Ke= 0.500
Inlet/ Outlet Invert= 484.00'/482.00' S=0.01907 Cc= 0.900
n=0.013 Concrete pipe, bends & connections, Flow Area= 1.77 sf
#2 Device 1
489.50' 2.7" Vert. Orifice /Grate C= 0.600
#3 Device 1
490.65' 20.0" W x 3.0" H Vert. Orifice /Grate C= 0.600
#4 Device 1
490.90' 30.0" x 30.0" Horiz. Orifice /Grate C= 0.600
Limited to weir flow at low heads
#5 Secondary 493.00' 20.0' long x 10.0' breadth Broad - Crested Rectangular Weir
'
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
' Primary OutFlow Max =6.77 cfs @ 12.25 hrs HW= 491.19' (Free Discharge)
t- E3=Orifice/Grate ulvert (Passes 6.77 cfs of 21.27 cfs potential flow)
= Orifice /Grate (Orifice Controls 0.24 cfs @ 6.06 fps)
(Orifice Controls 1.29 cfs @ 3.11 fps)
= Orifice /Grate (Weir Controls 5.23 cfs @ 1.78 fps)
econdary OutFlow Max =0.00 cfs @ 5.00 hrs HW= 489.50' (Free Discharge)
= Broad - Crested Rectangular Weir( Controls 0.00 cfs)

2013.08.19.BMP #14 Type// 24 -hr 1 -Yr Rainfall= 2.96"
Prepared by McKim & Creed Printed 9/8/2013
HydroCADO 10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 15
Pond 3P: BMP #14
Hydrograph
N
v
3
0
a_
301 I
Inflow Area = 10.710 ac
Peak Elev= 491.20'
- - - - - - - - - - - - Storage =35,921 cf -
LV
18 -- - - - - - - - - - - ----- - - - - --
16 - - - - - - - - - - - ----- - - - - --
14
12 - - - --
10 --- 6.79 cfs
8]
0.00 cfs
0
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
■ Inflow
C Outflow
El Primary
❑ Secondary

' 2013.08.19.BMP #14 Type 1124 -hr 10 -Yr Rainfall = 5.17"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD ®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 17
Summary for Subcatchment 1S: Pre - Development
Runoff = 25.22 cfs @ 12.14 hrs, Volume= 1.753 af, Depth> 1.96"
Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Type II 24 -hr 10 -Yr Rainfall =5.17"
Area (ac) CN Description
10.710 70 Woods, Good, HSG C
' 10.710 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
20.0 Direct Entry,
Subcatchment IS: Pre - Development
Hydrograph
28
26
25.22 Cfs O Runoff
- - - - --- -------- - - - - --
24 - -- -
- - - - Type 1124 -h r -
- -- -- ---- - - - - -- - -- -- -
10 -Yr Rainfall= 5.17" -
2o Runoff Area = 10.710 ac
18- Runoff Volume =1.753 of
16 Runoff Depth >1.96"
14 - -- -
LL 12 - - - Tc =20.0 m i n-
101 -- - -- - - - - - -- ---- - - - - -- ----------------------- CN=70-
6
4
2
0
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)

' 2013.08.19.BMP #14 Type 11 24 -hr 10 -Yr Rainfall = 5.17"
Prepared by McKim & Creed Printed 9/8/2013
HydroCADS 10.00 s/n 04927 C 2011 HydroCAD Software Solutions LLC Page 19
Summary for Pond 3P: BMP #14
[82] Warning: Early inflow requires earlier time span
Inflow Area = 10.710 ac, 61.62% Impervious, Inflow Depth > 3.69" for 10 -Yr event
Inflow = 60.90 cfs @ 12.01 hrs, Volume= 3.289 of
' Outflow _ 22.79 cfs @ 12.17 hrs, Volume= 2.624 af, Atten= 63 %, Lag= 9.6 min
Primary 22.79 cfs @ 12.17 hrs, Volume= 2.624 of
Secondary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 of
' Routing by Stor -Ind method, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Peak Elev= 492.34' @ 12.17 hrs Surf.Area= 24,984 sf Storage= 63,281 cf
Plug -Flow detention time= 104.2 min calculated for 2.615 of (80% of inflow)
Center -of -Mass det. time= 50.7 min ( 809.6 - 758.9 )
Volume Invert Avail.Storage Storage Description
#1 489.50' 136,442 cf Custom Stage Data (Prismatic)Listed below (Recalc)
' Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq -ft) (cubic -feet) (cubic -feet)
489.50 18,132 0 0
490.00 20,871 9,751 9,751
491.00 22,590 21,731 31,481
492.00 24,366 23,478 54,959
493.00 26,198 25,282 80,241
' 494.00 28,086 27,142 107,383
495.00 30,031 29,059 136,442
Device Routing Invert Outlet Devices
#1 Primary 484.00' 18.0" Round Culvert
L= 105.1' RCP, square edge headwall, Ke= 0.500
Inlet/ Outlet Invert= 484.00'/482.00' S=0.01907 Cc= 0.900
n=0.013 Concrete pipe, bends & connections, Flow Area= 1.77 sf
#2 Device 1 489.50' 2.7" Vert. Orifice /Grate C= 0.600
#3 Device 1 490.65' 20.0" W x 3.0" H Vert. Orifice /Grate C= 0.600
#4 Device 1 490.90' 30.0" x 30.0" Horiz. Orifice /Grate C= 0.600
Limited to weir flow at low heads
#5 Secondary 493.00' 20.0' long x 10.0' breadth Broad - Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max =22.78 cfs @ 12.17 hrs HW= 492.33' (Free Discharge)
t = Culvert (Barrel Controls 22.78 cfs @ 12.89 fps)
2= Orifice /Grate (Passes < 0.32 cfs potential flow)
3= Orifice /Grate (Passes < 2.50 cfs potential flow)
= Orifice /Grate (Passes < 35.95 cfs potential flow)
econdary OutFlow Max =0.00 cfs @ 5.00 hrs HW= 489.50' (Free Discharge)
= Broad - Crested Rectangular Weir( Controls 0.00 cfs)

2013.08.19.BMP #14
Type 1124 -hr 10 -Yr Rainfall= 5.17"
Prepared by McKim & Creed
Printed 9/8/2013
HydroCADO 10.00 s/n 04927 © 2011
HydroCAD Software
Solutions LLC
Page 20
Pond 3P: BMP #14
Hydrograph
60.90 cfs
® Inflow
_ ._
C outflow
Inflow Area = 10.710 ac
El Primary
-- - - - - -- - -- - --
- -- _ _
❑Secondary
65
Peak Elev= 492.34'
60
Storage= 63,281 cf
55
50
45
N 40
w ,
35
3
99 70 e-f
30
22.79 cfs
25
20 .
15
10
7"
0.00 c
5 6
7 8 9 10
11 12 13 14
15 16 17 18 19 20
Time (hours)

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
t
1
1
1
2013.08.19.131YIP #14 Type 11 24 -hr 100 -Yr Rainfall= 7.62"
Prepared by McKim & Creed Printed 9/8/2013
HvdroCAD ®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 22
Summary for Subcatchment 1 S: Pre - Development
Runoff = 49.00 cfs @ 12.13 hrs, Volume= 3.397 af, Depth> 3.81"
Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Type II 24 -hr 100 -Yr Rainfall= 7.62"
Area (ac) CN Description
10.710 70 Woods, Good, HSG C
10.710 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ftift) (ft/sec) (cfs)
20.0 Direct Entry,
Subcatchment 1 S: Pre - Development
Hydrograph
40
30
3
25
LL
20
15
10
1 149.00 cfs
Type 11 24-hr
100 -Yr Rainfall= 7.62"
Runoff Area = 10.710 ac
Runoff Volume =3.397 of.
Runoff Depth >3.81"
Tc =20.0 min
CN =70
NeO4 rZZZZZOZ�
Time (hours)
p Runoff

1
2013.08.19.BMP #14 Type 11 24 -hr 100 -Yr Rainfafl= 7.62"
Prepared by McKim & Creed Printed 9/8/2013
HydroCADO 10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 24
Summary for Pond 3P: BMP #14
' [82] Warning: Early inflow requires earlier time span
Inflow Area = 10.710 ac, 61.62% Impervious, Inflow Depth > 5.91" for 100 -Yr event
Inflow = 95.02 cfs @ 12.01 hrs, Volume= 5.277 of
Outflow 42.75 cfs @ 12.15 hrs, Volume= 4.590 af, Atten= 55 %, Lag= 8.7 min
Primary 24.24 cfs @ 12.15 hrs, Volume= 4.293 of
Secondary = 18.51 cfs @ 12.15 hrs, Volume= 0.297 of
Routing by Stor -Ind method, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Peak Elev= 493.50' @ 12.15 hrs Surf.Area= 27,139 sf Storage= 93,528 cf
Plug -Flow detention time= 90.4 min calculated for 4.574 of (87% of inflow)
Center -of -Mass det. time= 49.3 min ( 799.0 - 749.7 )
Volume Invert Avail.Storage Storage Description
#1 489.50' 136,442 cf Custom Stage Data (Prismatic)Listed below (Recalc)
Elevation
Surf.Area
Inc.Store
Cum.Store
(feet)
(sq -ft)
(cubic -feet)
(cubic -feet)
489.50
18,132
0
0
490.00
491.00
20,871
22,590
9,751
21,731
9,751
31,481
492.00
24,366
23,478
54,959
493.00
26,198
25,282
80,241
' 494.00 28,086 27,142 107,383
495.00 30,031 29,059 136,442
' Device Routing Invert Outlet Devices
#1 Primary 484.00' 18.0" Round Culvert
L= 105.1' RCP, square edge headwall, Ke= 0.500
Inlet/ Outlet Invert= 484.00'/482.00' S=0.0190? Cc= 0.900
n=0.013 Concrete pipe, bends & connections, Flow Area= 1.77 sf
#2 Device 1 489.50' 2.7" Vert. Orifice /Grate C= 0.600
#3 Device 1 490.65' 20.0" W x 3.0" H Vert. Orifice /Grate C= 0.600
#4 Device 1 490.90' 30.0" x 30.0" Horiz. Orifice /Grate C= 0.600
Limited to weir flow at low heads
#5 Secondary 493.00' 20.0' long x 10.0' breadth Broad - Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64
Primary OutFlow Max =24.23 cfs @ 12.15 hrs HW= 493.49' (Free Discharge)
' t = Culvert (Barrel Controls 24.23 cfs @ 13.71 fps)
2= Orifice /Grate (Passes < 0.38 cfs potential flow)
3= Orifice /Grate (Passes < 3.31 cfs potential flow)
= Orifice /Grate (Passes < 48.47 cfs potential flow)
econdary OutFlow Max =18.25 cfs @ 12.15 hrs HW= 493.49' (Free Discharge)
= Broad - Crested Rectangular Weir (Weir Controls 18.25 cfs @ 1.85 fps)

2013.08.19.BMP #14 Type 1124 -hr 100 -Yr Rainfall= 7.62 "
Prepared by McKim & Creed Printed 9/8/2013
HydroCADO 10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 25
Pond 3P: BMP #14
Hydrograph
95.02 cfs
■ Inflow
E, outflow
Inflow Area = 10.710 ac
0 Primary
105
❑ Secondary
100
- - - - - - - - - - - - - Peak Elev= 493.50'
95
-- -- - - - - -- - - - -- - -
90
Storage =93,628
85
- - - -- - -- _ _cf
80
- - -- - --
75
70
" 60
42.76 C& -- - - - - -- -----------------
55
3
-- --
LL45
- - -- - - - - - - - - - - - - - - - - - - - - - - - - - - - -
40
35
24.24 cfs: - -- - - - -- - - - - -- ---- - - - - --
30
- -- - --- - -- - - - - - - - - - - - - - - - - --
25
18.51 cfs -
20
15
10
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)

1
1
1
1
1
1
1
1
1
r
WATER QUALITY POND #14 CALCULATIONS
Project Name
Briar Chapel - Phase 9 - Section 1
Project Number
02735 -0096
Date
August 6, 2013
3rd revision
2nd revision
1 st revision

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t
Water Quality Pond Drainage Area Data
Project Briar Chapel - Phase 9 - Section 1
Project No. 02735 -0096
Date August 6, 2013
Total site area 466,607 square feet = 10.71 acres
Impervious areas
Drainage
area to and
Other Drainage
Area
Existing
s
Proposed
s
Change
s
Existing
s
Proposed
[Sfl
On -site buildings BUA
0
192,000
192,000
0
0
On -site streets
0
44,537
44,537
0
0
On -site alleys
0
23,182
23,182
0
0
On -site sidewalks
0
13,072
13,072
0
0
On -site future (open space)
0
1,000
1,000
0
0
Off -site streets
0
0
0
0
0
5% Contingency
0
13,690
13,690
0
0
Total Impervious
1 0
287,481
287,481
0
0
Non-impervious areas
Draina
a area to and
Other Drainage
Area
Existing
s
Proposed
s
Change
1sfl
Existing
[Sfl
Proposed
s
On -site grass/landscape
0
179,126
179,126
0
0
On -site woods
466,607
0
- 466,607
0
0
Other undeveloped
0
0
0
0
0
Total off -site non-impervious
0
0
0
0
0
Total non-impervious
466,607
179,126
- 287,481
1 0
0
Total Drainage Area
466,607
466,607
0
3,167,850
3,167,850
Percent Impervious
0.0
61.6
61.6
0.0
0.0
Notes:
2013.08.06.Wet Detention Pond #14.Gareth.xis
Site Drainage Area Data Page 2 of 18
Printed 9/8/2013 5:36 PM

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Water Quality Pond Surface Area Calculations
Project Briar Chapel - Phase 9 - Section 1
Project No. 02735 -0096
Date August 6, 2013
Total on -site drainage area to pond 466,607 square feet
Total impervious area in drainage area 287,481 square feet
Average water depth of basin at normal pool 3.0
Location of site Chatham County
Site region Piedmont
% Impervious cover 61.6 percent
If the site is in a coastal area, will a vegetative filter be used?
Surface Area /Drainage Area Ratios:
feet
n/a
For a site in the Piedmont (85 %) 2.5 percent
For a site in the Piedmont (90 %) 3.6 percent
For a site in a Coastal County w/ Vegetative Filter 5.2 percent
For a site in a Coastal County w /out Vegetative Filter 7.2 percent
Required surface area of pond:
For a site in the Piedmont (85 %) 11,560.0 square feet
For a site in the Piedmont (90 %) 16,710.0 square feet
For a site in a Coastal County w/ Vegetative Filter 24,090.0 square feet
For a site in a Coastal County w /out Vegetative Filter 33,490.0 square feet
Notes:
2013.08.06.Wet Detention Pond #14.Gareth.xis
Pond Surface Area Calcs Page 3 of 18
Printed 9/8/2013 5:36 PM

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Water Quality Pond Stormwater Runoff Volume Calculations
Project Briar Chapel - Phase 9 - Section 1
Project No. 02735 -0096
Date August 6, 2013
Drainage area 466,607 square feet
Impervious area 287,481 square feet
Rainfall depth 1.00 inches
Percent Impervious 61.6 percent
R(v) =0.05 +0.009 *(Percent impervious)
Runoff coefficient - R(v) 0.60 in /in
Runoff volume = (Design rainfall) *(R(v)) *(Drainage area)
Runoff volume 23,505.2 cubic feet
Notes:
2013.08.06.Wet Detention Pond #14.Gareth.xls
Runoff Volume Calcs Page 4 of 18
Printed 9/8/2013 5:36 PM

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Water Quality Pond Volume Calculations
Stage - Storage Data for Pond - Temporary Pool
Project Briar Chapel - Phase 9 - Section 1
Project No. 02735 -0096
Date August 6, 2013
Contour ID
Stage
Area
ft.
Area
acres ]
Incremental
Area
[sq ft.
Incremental
Area
acres
Incremental
volume
cu ft
Incremental
volume
acre -ft
Cumulative
volume
ICU. ft
Cumulative
volume
acre -ft
489.5
0
18,131.9
0.416
18,131.9
0.4
00
0.0
00
0.0
490
0.5
20,871.1
0.479
20,871.1
0.1
9,750.8
0.2
9,750.8
0.2
490.65
1 15
21,982.0
0.505
21,9820
00
13,927.3
03
23,6780
05
491
1.5
22,590.1
0.519
22,590.1
0.0
7,800.1
0.2
31,478.2
0.5
492
2.5
24,365.6
0 559
24,365.6
0.0
23,477.8
0.5
54,956.0
07
493
3.5
26,197.6
0.601
26,197.6
0.0
25,281.6
0.6
80,237.6
1.1
494
4.5
28,086.2
0.645
28,086.2
0.0
27,141.9
0.6
107,379.5
12
495
5.5
30,031.4
0.689
30,031.4
0.0
29,058.8
0.7
136,438.3
1.3
2013.08.06 Wet Detention Pond #14.Gareth As
' Stage Storage (Temp Pool) Page 5 of 18 Printed 9/8/2013 5.36 PM

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Water Quality Pond Volume Calculations
Stage -Storage Data for Pond - Permanent Pool
Project Briar Chapel - Phase 9 - Section 1
Project No. 02735 -0096
Date August 6, 2013
Contour ID
Stage
Area
ft.
Area
acres ]
Incremental
Area
[sq ft
Incremental
Area
acres
Incremental
volume
cu. ft
Incremental
volume
acre -ft
Cumulative
volume
cu. ft
Cumulative
volume
acre -ft
484
0
6,021.5
0.138
6,021.5
01
0.0
0.0
00
0.0
485
1
7,553.4
0.173
1,5319
0.0
6,787.5
0.2
6,7875
0.2
486
2
9,218.0
0212
1,664.6
0.0
8,385.7
0.2
15,173.2
0.3
487
3
10,983.7
0 252
1,765.7
0.0
10,1009
02
25,274.0
0.4
488
4
12,862.4
0295
1,878.8
0.0
11,923.1
0.3
37,197.1
0.5
489
5
14,854.3
0.341
1,991.9
0.0
13,8584
0.3
51,055.4
0.6
489.5
5.5
18,131.9
0.416
3,277.6
0.1
8,246.5
0.2
59,302.0
0.5
2013.08.06.Wet Detention Pond #14.Gareth.xis
' Stage Storage (Perm Pool) Page 6 of 18 Printed 9/8/2013 5.36 PM

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Water Quality Pond Volume Calculations
Stage - Storage Data for Pond - Forebays
Project Briar Chapel - Phase 9 - Section 1
Project No 02735 -0096
Date August 6, 2013
Contour ID
Stage
Area
ft.
Area
acres
Incremental
Area
. ft.
Incremental
Area
acres
Incremental
volume
cu. ft
Incremental
volume
acre -ft
Cumulative
volume
cu. ft
Cumulative
volume
acre -ft
484
0
749.2
0.017
7492
0.0
0.0
0.0
0.0
00
485
1
1,139.6
0.026
390.4
0.0
944.4
00
944.4
0.0
486
2
1,603.2
0.037
463.5
00
1,371.4
00
2,315.8
0.1
487
3
2,114.0
0.049
510.9
0.0
1,858.6
0.0
4,1744
0.1
488
4
2,681.5
0.062
567.4
0.0
2,397.7
0.1
6,572.2
0.1
489
5
3,305.4
0 076
624.0
0.0
2,993.4
0.1
9,5656
0.1
489.5
5.5
4,471.0
0.103
1,165.6
0.0
1,944.1
0.0
11,5097
0.1
2013.08.06.Wet Detention Pond #14.Gareth.xis
' Stage Storage (Forebays) Page 7 of 18 Printed 9/8/2013 5:36 PM

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Water Quality Basin Dewatering Time Calculations
Project Briar Chapel - Phase 9 - Section 1
Project No. 02735 -0096
square feet
5.9
Date August 6, 2013
0.041
Water quality treatment volume
23,502
square feet
Total treatment volume
23,678
square feet
Maximum head of water above dewatering hole
1.15
feet
Driving head
0.38
feet
Orifice coefficient
0.60
Diameter of each hole
2.75
inches
Number of holes
1
Cross sectional area of each hole =
Cross sectional area of each hole =
Cross sectional area of dewatering hole(s) _
Cross sectional area of dewatering hole(s) _
Dewatering time for water quality volume =
Dewatering time for total volume =
0.041
square feet
5.9
square inches
0.041
square feet
5.9
square inches
2.2
days
2.2 days
Notes:
Dewatering time formula: t (days) = V / (Cd *A *Sgrt (2 *32.2 *H) *86,400)
t = drawdown time
V = treatment volume
Cd = orifice coefficient
A = cross sectional area of orifice
H = driving head (1/3 max. head)

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IWater Quality Pond Summary Information
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2013.08.06.Wet Detention Pond #14.Gareth.xls
' Summary Data Page 10 of 18 Printed 9/8/2013 5:36 PM
Project Briar Chapel - Phase 9 - Section 1
Project No. 02735 -0096
'
Date August 6, 2013
Drainage area to pond
466,607
square feet= 10.71 acres
'
Impervious area in drainage area
287,481
square feet = 6.60 acres
Bottom of pond elevation
484.00
feet
Normal pool elevation
489.50
feet
Pond volume at normal pool
59,302
cubic feet
'
Required volume for design rainfall
23,505
cubic feet
Required surface area for pond
16,710
square feet
'
Volume provided for storage of design
rainfall =
23,678 cubic feet at elevation 490.65
Surface area provided at normal pool
18,132
square feet
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2013.08.06.Wet Detention Pond #14.Gareth.xls
' Summary Data Page 10 of 18 Printed 9/8/2013 5:36 PM

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rf[VJCV I IY/11VI G. DIlal VIlapul - rlla3w v
PROJECT LOCATION: Chatham County, NC
Storm Outlet Structure
Structure= BMP #14 Out
Size= 18 in
Q10 = 22.79 cfs
Qfull = 14.45 cfs
Vfull = 8.18 fps
From Fig. 8.06.b.1:
TE: 9/3/2013 DESIGNED BY:
IDJB
Q10 /Qfull = 1.58
V/Vfull = MAX
V = #VALUE! fps
Zone = 5
D50
= 14 in
_
DMAx
= 21 in
Riprap Class
= 2
Apron Thickness
= 36 in
—'
Apron Length
= 15.0 ft
�ngt"
Apron Width = 3 x Dia
= 5.0 ft

(PROJECT LOCATION: Chatham Countv, NC
Pond Name= BMP #14
Riser Outer Width =
3.5 ft
Riser Outer Length =
3.5 ft
Riser Inner Width =
2.5 ft
Riser Inner Length =
2.5 ft
Riser Height =
6.9 ft
Concrete Base Length =
4.5 ft
Concrete Base Width =
4.5 ft
Concrete Base Depth =
12 in
DATE: 8/23/2013
02735 -0096
Riser Resisting Force =
Base Resisting Force =
Total Resisting Force =
Riser Buoyant Force =
Base Buoyant Force =
Total Buoyant Force =
Factor of Safety
DESIGNED BY: GCA
6,210 lb
3,038 lb
9,248 lb
5,274 lb
1,264 lb
6,538 lb
4.41 Design Acceptable

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1
Permit No.
(to be provided by DWQ)
III. REQUIRED ITEMS CHECKLIST
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.
GCA C3.3 -C3.4 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.
GCA D4.1 -D4.3 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.
GCA D4.1 -D4.3 3. Section view of the wet detention basin 0" = 20' or larger) showing:
- Side slopes, 3:1 or lower,
- Pretreatment and treatment areas, and
- Inlet and outlet structures.
GCA N/A 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.
1
1
5. A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay,
to verify volume provided.
6. A construction sequence that shows how the wet detention basin will be protected from sediment until the
entire drainage area is stabilized.
7. The supporting calculations.
8. A copy of the signed and notarized operation and maintenance (0 &M) agreement.
GCA Included 9. A copy of the deed restrictions (f required).
N/A 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.8- 9/17/09 Part III Required Items Checklist, Page 1 of 1
GCA
Calc Booklet
GCA
C3.1
'
GCA
Calc Booklet
GCA
Included
1
1
5. A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay,
to verify volume provided.
6. A construction sequence that shows how the wet detention basin will be protected from sediment until the
entire drainage area is stabilized.
7. The supporting calculations.
8. A copy of the signed and notarized operation and maintenance (0 &M) agreement.
GCA Included 9. A copy of the deed restrictions (f required).
N/A 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.8- 9/17/09 Part III Required Items Checklist, Page 1 of 1

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Permit No
(to be provded by DWG)
Red triangles at the upper right hand comer indicate design comments
Please complete the yellow shaded items.
ot VVATF9O�
MEW '
o <
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This form must be Alled out printed and submitted.
The Required Items Checklist (Part Ill) must be printed, filled out and submitted along w/th all of the required information
I. PROJECT INFORMATION
Y (Y or N)
Project name
Briar Chapel Development - Great Ndge Parkway Extension
Contact person
Gareth Avant, PE
Phone number
919 233 8091
Date
30- Aug -2013
Drainage area number
1- Wet Pond #14
II. DESIGN INFORMATION
0.12 1rdhr
Site Characteristics
Pre - development 1 -yr, 24 -hr peak flow
Drainage area
466,528 fe
Impervious area, post- development
287,496 f?
% impervious
61.62%
Design rainfall depth
1.0 in
Storage Volume: Non-SA Waters
Minimum volume required 23,506 ft3 OK
Volume provided 23,678 ft3
OK, volume provided is equal to or in excess of volume required.
Storage Volume: SA Waters
1.5' runoff volume ft"
Pre-development 1 -yr, 24 -hr runoff ft3
Post - development 1 -yr, 24-hr runoff ft"
Minimum volume required ft"
Volume provided ft3
Peak Flow Calculations
Is the pre/post control of the 1 yr 24hr storm peak flow required?
Y (Y or N)
1 -yr, 24-hr rainfall depth
3.0 in
Rational C, pre - development
0.40 (undless)
Rational C, post-development
0.86 (unitless)
Rainfall intensity, 1 -yr, 24-hr stone
0.12 1rdhr
Insufficient Check intensity calculation.
Pre - development 1 -yr, 24 -hr peak flow
12.87 f3/sec
Post - development 1 -yr, 24-hr peak flow
47.65 ft3 /sec
Pre/Post 1 -yr, 24-hr peak flow control
34.78 f3 /sec
Elevations
Temporary pool elevation
495.00 fmsl
Permanent pool elevation
489.50 fmsl
SHWT elevation (approx. at the pens. pool elevation)
fmsl
Top of 1Oft vegetated shelf elevation
490.00 imsl
Bottom of 1Oft vegetated shelf elevation
489 00 fmsl
Data not needed for calculation option #1, but OK if provided.
Sediment deanout, top elevation (bottom of pond)
485.00 frnsl
Sediment deanout, bottom elevation
484.00 fmsl
Data not needed for calculation option #1, but OK if provided.
Sediment storage provided
1.00 ft
Is there additional volume stored above the state - required temp pool?
N (Y or N)
Elevation of the top of the additional volume
find
Form SW401 -Wet Detention Basin -Rev 8. 9/17/09
Parts I & 11 Design Summary. Page 1 of 2

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1
1
1
Permit No
(to be provided by DWQ)
11. DESIGN INFORMATION
Surface Areas
Area, temporary pool
30,031 fe
Area REQUIRED, permanent pool
11,663 ft
SAIDA ratio
2.50 (unitless)
Area PROVIDED, permanent pool, A�rm_p d
18,132 fe
OK
Area, bottom of 10fl vegetated shelf, Aye uw
14,854 ft'
Area, sediment deanout, top elevation (bottom of pond), Ab„_pow
6,022 fe
Volumes
Volume, temporary pool
23,678 ft3
OK
Volume, permanent pool, V,,,,,_,w
59,302 ft3
Volume, forebay (sum of forebays N more than one forebay)
11,510 ft3
Forebay % of permanent pool volume
19.4%%
OK
SAIDA Table Data
Design TSS removal
90%
Coastal SAIDA Table Used?
N (Y or N)
MountairdPiedmont SAIDA Table Used?
Y (Y or N)
SAIDA ratio
2.50 (unitless)
Average depth (used in SAIDA table):
Calculation option 1 used? (See Figure 10-2b)
Y (Y or N)
Volume, permanent pool, V,,,,_pw
59,302 ft3
Area provided, permanent pool, Av,, _pw
18,132 fe
Average depth calculated
3.27 It
OK
Average depth used in SAIDA, da,,, (Round to nearest 0.5ft)
3.5 ft
OK
Calculation option 2 used? (See Figure 10-2b)
N (Y or N)
Area provided, permanent pool, Ate,,, w
18,132 fe
Area, bottom of 10ft vegetated shelf, Abo dvr
14,854 ft'
Area, sediment deanout, top elevation (bottom of pond), A
6,022 fe
'Depth' (distance b1w bottom of 1Oft shelf and top of sediment)
4.00 ft
Average depth calculated
ft
Average depth used in SAIDA, dam„ (Round to nearest 0.5ft)
ft
Drawdown Calculations
Drawdown through orifice?
Y (Y or N)
Diameter of orifice (if circular)
2.70 in
Area of orifice (d- non-circular)
in2
Coefficient of discharge (Co)
0.60 (unitless)
Driving head (Ho)
1.15 It
Drawdown through weir?
N (Y or N)
Weir type
(unitless)
Coefficient of discharge (C.,)
(unitless)
Length of weir (L)
ft
Driving head (H)
ft
Pre-development 1 -yr, 24 -hr peak flow
712 ft3 /sec
Post-development 1 -yr, 24-hr peak flow
6.79 g3 /sec
Storage volume discharge rate (through discharge orifice or weir)
0.24 f3 /sec
Storage volume drawdown time
2.20 days
OK, draws down in 2 -5 days.
Additional Information
Vegetated side slopes
3-1
OK
Vegetated shelf slope
10 :1
OK
Vegetated shelf width
10.0 ft
OK
Length of flowpath to width ratio
3 :1
OK
Length to width ratio
1.5 :1
OK
Trash rack for overflow & orifice?
Y (Y or N)
OK
Freeboard provided
1.5 It
OK
Vegetated filter provided?
N (Y or N)
OK
Recorded drainage easement provided?
Y (Y or N)
OK
Capures all runoff at ultimate build -out?
Y (Y or N)
OK
Drain mechanism for maintenance or emergencies is:
8' DIP with gate valve
Form SW401 -Wet Detention Basin-Rev 8-9/17/09
Parts I & 11 Design Summary, Page 2 of 2

' Permit Number:
(to be provided by DWQ)
' Drainage Area Number:
Wet Detention Basin Operation and Maintenance Agreement
fl
1
1
1
1
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 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
Maintain vegetation at a height of
long.
approximately six inches.
Form SW401 -Wet Detention Basin O &M -Rev.4
Page 1 of 4

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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
Search for the source of the
a depth greater than 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 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
original 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
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 basin surface.
Form SW401 -Wet Detention Basin O &M -Rev.4 Page 2 of 4

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1
1
1
1
1
1
1
1
1
1
1
1
1
1
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
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 4.50 feet in the main pond, the
sediment shall be removed.
When the permanent pool depth reads 4.50 feet in the forebay, the sediment
shall be removed.
BASIN DIAGRAM
(fill in the blanks)
Permanent Pool Elevation 489.50
Sediment Removal EX. 485.00 - - - - - - - 1 Pe anen Pool
L8� Volume Sediment Removal Elevation 485.00 Volume
ottom E evatio ft Mm.
Sediment Bottom Elevation 484.00 1 -ft r.
Storage Se imei
Storage
FOREBAY
Form SW401 -Wet Detention Basin O &M -Rev.4
MAIN POND
Page 3 of 4

I, G. I-Cool Alowote t , a Notary Public for the State of
A'
' ! / C , County of ch'11(4 , do hereby certify that
� fy
:�'► iFm personally appeared before me this
' day of _ k a� , �! /, and acknowledge the due execution of the
forgoing wet detention basin maintenance requirements. Witness my hand and official
seal,
SEAL
My commission expires ytv�
Form SW401 -Wet Detention Basin O&M -Rev.4 Page 4 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 parry.
Project name:Briar Chapel - Phase 9
BAP drainage area number: l - Wet Detention Pond # 14
Print name:Kevin Graham
Title:Vice President, Operations
Address:16 Windt/ Knoll Circle, Chapel Hill, NC 27516
'
Phone; 919 951 -0709
Signature• ,." c
'Date:
z
Note: The legally responsible party should not be a homeowners association unless more than 50016 of
the lots have been sold and a resident of the subdivision has been named the president.
I, G. I-Cool Alowote t , a Notary Public for the State of
A'
' ! / C , County of ch'11(4 , do hereby certify that
� fy
:�'► iFm personally appeared before me this
' day of _ k a� , �! /, and acknowledge the due execution of the
forgoing wet detention basin maintenance requirements. Witness my hand and official
seal,
SEAL
My commission expires ytv�
Form SW401 -Wet Detention Basin O&M -Rev.4 Page 4 of 4

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BMP #15 DESIGN

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1S 2S
Pre - Development Post -Development
3P
BMP #15
Subcat Reach on Link Routing Diagram for 2013.08.21.BMP 915
Prepared by McKim & Creed, Printed 9/8/2013
HydroCAD®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC

1
2013.08.21.BMP #15 Type 11 24 -hr 1 -Yr Rainfall= 2.96"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 7
Summary for Subcatchment 1 S: Pre - Development
Runoff = 10.18 cfs @ 12.15 hrs, Volume= 0.778 af, Depth> 0.61"
Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Type II 24 -hr 1 -Yr Rainfall= 2.96"
' Area (ac) CN Description
15.310 70 Woods, Good, HSG C
15.310 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
' (min) (feet) (ft/ft) (ft/sec) (cfs)
20.0 Direct Entry,
Subcatchment IS: Pre - Development
Hydrograph
10.18 cfs O Runoff
10 Type e 1 124 -h r
9 1 -Yr
8'
Runoff Area= 15.10 ac
- -- ----------- - - - - -- - -
Runoff Volume =0.778 of
6 Runoff Depth >0.61"
LL 5 Tc =20.0 min
-
4 CN =70

2013.08.21.BMP #15 Type 1124 -hr 1 -Yr Rainfall= 2.96"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 9
Summary for Pond 3P: BMP #15
' Inflow Area = 15.310 ac, 60.16% Impervious, Inflow Depth > 1.65" for 1 -Yr event
Inflow 41.01 cfs @ 12.01 hrs, Volume= 2.109 of
Outflow - 8.93 cfs @ 12.26 hrs, Volume- 1.259 af, Atten= 78 %, Lag= 14.9 min
Primary = 8.93 cfs @ 12.26 hrs, Volume= 1.259 of
Secondary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 of
Routing by Stor -Ind method, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Peak Elev= 466.55' @ 12.26 hrs Surf.Area= 25,732 sf Storage= 48,489 cf
Plug -Flow detention time= 155.8 min calculated for 1.255 of (60% of inflow)
Center -of -Mass det. time= 83.3 min ( 862.7 - 779.4 )
Volume Invert Avail.Storage Storage Description
#1 464.50' 182,141 cf Custom Stage Data (Prismatic)Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq -ft) (cubic -feet) (cubic -feet)
464.50 20,017 0 0
465.00 22,898 10,729 10,729
466.00 24,702 23,800 34,529
467.00 26,562 25,632 60,161
468.00 28,479 27,521 87,681
469.00 30,453 29,466 117,147
470.00 32,483 31,468 148,615
471.00 34,569 33,526 182,141
Device Routing Invert Outlet Devices
#1 Primary 458.00' 18.0" Round Culvert
L= 108.0' RCP, square edge headwall, Ke= 0.500
Inlet/ Outlet Invert= 458.00'/456.00' S=0.01857 Cc= 0.900
n=0.013 Concrete pipe, bends & connections, Flow Area= 1.77 sf
' #2 Device 1 464.50' 3.2" Vert. Orifice /Grate C= 0.600
#3 Primary 465.95' 24.0" W x 3.0" H Vert. Orifice /Grate C= 0.600
#4 Device 1 466.20' 30.0" x 30.0" Horiz. Orifice /Grate C= 0.600
Limited to weir flow at low heads
#5 Secondary 468.50' 30.0' long x 12.0' breadth Broad - Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.57 2.62 2.70 2.67 2.66 2.67 2.66 2.64
Primary OutFlow Max - 8.86 cfs @ 12.26 hrs HW= 466.55' (Free Discharge)
= Culvert (Passes 7.20 cfs of 22.89 cfs potential flow)
' 2= Orifice /Grate (Orifice Controls 0.37 cfs @ 6.67 fps)
= Orifice /Grate (Weir Controls 6.83 cfs @ 1.94 fps)
3= Orifice /Grate (Orifice Controls 1.66 cfs @ 3.32 fps)
' econdary OutFlow Max =0.00 cfs @ 5.00 hrs HW= 464.50' (Free Discharge)
= Broad - Crested Rectangular Weir( Controls 0.00 cfs)

2013.08.21.BMP #15 Type 1124 -hr 1- YrRainfa& 2.96"
Prepared by McKim & Creed Printed 9/8/2013
HydroCADO 10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 10
Pond 3P: BMP #15
Hydrograph
141. U I
44
42 - - -- -- --- - - - ---
40
38 - - - -- -- - - - - - -- - -- - --
36
34 -------------------------
32 -------------------------
30
28 - -- - -- - - - - - --
w 26
v 24
3 22
LL 20
18
16
14 - - 8.93 cfs
12
10 -- - - - - --
8
6
■ Inflow
� � Outflow
Inflow Area= 15.310 ac ■Primary
® Secondary
Peak -Elev= 466.55'- -
Storage= 48,489 cf
------------------------
- --
0.00 cfs
0
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)

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2013.08.21.13MP #15 Type 11 24 -hr 10 -Yr Rainfall =5.17"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 12
Summary for Subcatchment IS: Pre - Development
Runoff = 36.06 cfs @ 12.14 hrs, Volume= 2.506 af, Depth> 1.96"
Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Type II 24 -hr 10 -Yr Rainfall =5.17"
Area (ac) CN Description
15.310 70 Woods, Good, HSG C
15.310 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
20.0 Direct Entry,
Subcatchment IS: Pre - Development
Hydrograph
40 O Runoff
38 36.06 cfs - -- - - - -- --- - - - - -- -- -- -
36 Type II 24 -hr
-- - -- -------- -- - - - - -- - - - - - -- -
32 10 -Yr Rainfall = 5.17"
26 _ - Rulnoff Area =_15.310 ac -
24 - - - - - - - - Runoff Volume =2.506 of
22 Runoff Depth >1.96"
20 - - - —
LL 18 Tc =20.0 min
16 -------- ---- ----------- - - - - -- ------------------
14 - -- CW70 -
12 -
8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)

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2013.08.21.BMP #15 Type 1124 -hr 10 -Yr Rainfall= 5.17"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD ®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 14
Summary for Pond 3P: BMP #15
Inflow Area = 15.310 ac, 60.16% Impervious, Inflow Depth > 3.59" for 10 -Yr event
Inflow =
85.34 cfs @
12.01 hrs,
Volume=
4.574 of
Outflow =
28.13 cfs @
12.19 hrs,
Volume=
3.668 af, Atten= 67 %, Lag= 10.6 min
Primary =
28.13 cfs @
12.19 hrs,
Volume=
3.668 of
Secondary =
0.00 cfs @
5.00 hrs,
Volume=
0.000 of
Routing by Stor -Ind method, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Peak Elev= 468.07' @ 12.19 hrs Surf.Area= 28,618 sf Storage= 89,691 cf
Plug -Flow detention time= 103.2 min calculated for 3.656 of (80% of inflow)
Center -of -Mass det. time= 50.3 min ( 811.9 - 761.6 )
Volume Invert
Avail.Storage Storage Description
#1 464.50'
182,141 cf Custom Stage Data (Prismatic)Listed below (Recalc)
Elevation Surf.Area
Inc.Store Cum.Store
(feet)
(sq -ft)
(cubic -feet) (cubic -feet)
464.50
20,017
0 0
465.00
22,898
10,729 10,729
466.00
24,702
23,800 34,529
467.00
26,562
25,632 60,161
468.00
28,479
27,521 87,681
469.00
30,453
29,466 117,147
470.00
32,483
31,468 148,615
471.00
34,569
33,526 182,141
Device Routing
Invert
Outlet Devices
#1 Primary
458.00'
18.0" Round Culvert
L= 108.0' RCP, square edge headwall, Ke= 0.500
Inlet/ Outlet Invert= 458.00'/456.00' S= 0.0185 'f Cc= 0.900
n=0.013 Concrete pipe, bends & connections, Flow Area= 1.77 sf
#2 Device 1
464.50'
3.2" Vert. Orifice /Grate C= 0.600
#3 Primary
465.95'
24.0" W x 3.0" H Vert. Orifice /Grate C= 0.600
#4 Device 1
466.20'
30.0" x 30.0" Horiz. Orifice /Grate C= 0.600
Limited to weir flow at low heads
#5 Secondary
468.50'
30.0' long x 12.0' breadth Broad - Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.57 2.62 2.70 2.67 2.66 2.67 2.66 2.64
Primary OutFlow Max =28.12 cfs @ 12.19 hrs HW= 468.06' (Free Discharge)
= Culvert (Barrel Controls 24.73 cfs @ 13.99 fps)
2= Orifice /Grate (Passes < 0.50 cfs potential flow)
= Orifice /Grate (Passes < 4 1. 10 cfs potential flow)
3= Orifice /Grate (Orifice Controls 3.40 cfs @ 6.79 fps)
econdary OutFlow Max =0.00 cfs @ 5.00 hrs HW= 464.50' (Free Discharge)
= Broad - Crested Rectangular Weir( Controls 0.00 cfs)

2013.08.21.BMP #15 Type 1124 -hr 10 -Yr Rainfall = 5.17"
Prepared by McKim & Creed Printed 9/8/2013
HydroCADO 10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 15
Pond 3P: BMP #15
Hydrograph
60
w 55
50
0 45
" 40 28.13 cfs
35
30
25 - - - -- - -- - -- - - --
20
15
0.00 Cfs
0
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
85.34 cfs
■ Inflow
[ -, outflow
Inflow Area = 15.310 ac
E3 Primary
95
DSecondary
go
Peak Elev= 468.07'
85
80
-- - - - - - -- ---- - - - - -- -------- Storage= 89;691 -c# -
.
75
- - - - - -- ---------------------
70
------------ ..----- - - - - -- --------------------------------
65
60
w 55
50
0 45
" 40 28.13 cfs
35
30
25 - - - -- - -- - -- - - --
20
15
0.00 Cfs
0
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)

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2013.08.21.BMP #15 Type// 24 -hr 100 -Yr Rainfall = 7.62"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD ®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 17
Summary for Subcatchment IS: Pre - Development
Runoff = 70.05 cfs @ 12.13 hrs, Volume= 4.856 af, Depth> 3.81"
Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Type II 24 -hr 100 -Yr Rainfall= 7.62"
Area (ac) CN Description
15.310 70 Woods, Good, HSG C
15.310 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
20.0 Direct Entry,
Subcatchment IS: Pre - Development
Hydrogmph
- - - - — - - -
' 75
70
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170.05 cfs
�^ 4b
40
u35 - - - - - - - -- - - - - -- - - - - - - - -
J- --- - - - - - -- - -- -- - - - - - -- --
Type 1124 -h r
100 -Yr Rainfall= 7.62"
Runoff Area = 15.310 ac
Runoff Volume =4.856 of
Runoff Depth >3.81"
Tc =20.0 m1n
CN =70
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
p Runoff

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' 2013.08.21 AMP #15 Type // 24 -hr 100 -Yr Rainfall= 7.62"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 19
' Summary for Pond 3P: BMP #15
' [82] Warning: Early inflow requires earlier time span
Inflow Area = 15.310 ac, 60.16% Impervious, Inflow Depth > 5.81" for 100-Yr event
Inflow = 134.27 cfs @ 12.01 hrs, Volume= 7.407 of
Outflow 81.77 cfs @ 12.12 hrs, Volume= 6.473 af, Atten= 39 %, Lag= 6.6 min
Primary 30.35 cfs @ 12.12 hrs, Volume= 5.645 of
Secondary = 51.42 cfs @ 12.12 hrs, Volume= 0.828 of
' Routing by Stor -Ind method, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Peak Elev= 469.24' @ 12.12 hrs Surf.Area= 30,947 sf Storage= 124,619 cf
Plug -Flow detention time= 87.5 min calculated for 6.472 of (87% of inflow)
Center -of -Mass det. time= 46.7 min ( 798.5 - 751.8 )
' Volume Invert Avail.Storage Storage Description
#1 464.50' 182,141 cf Custom Stage Data (Prismatic)Listed below (Recalc)
Elevation
Surf.Area
Inc.Store
Cum.Store
'
(feet)
(sq -ft)
(cubic -feet)
(cubic -feet)
464.50
20,017
0
0
' 465.00
466.00
22,898
24,702
10,729
23,800
10,729
34,529
467.00
26,562
25,632
60,161
468.00
28,479
27,521
87,681
' 469.00 30,453 29,466 117,147
470.00 32,483 31,468 148,615
471.00 34,569 33,526 182,141
'
Device
Routing
Invert
Outlet Devices
#1
Primary
458.00'
18.0" Round Culvert
L= 108.0' RCP, square edge headwall, Ke= 0.500
'
Inlet/ Outlet Invert= 458.00'/456.00' S=0.01857 Cc= 0.900
n= 0.013 Concrete pipe, bends & connections, Flow Area= 1.77 sf
#2
Device 1
464.50'
3.2" Vert. Orifice /Grate C= 0.600
#3
Primary
465.95'
24.0" W x 3.0" H Vert. Orifice /Grate C= 0.600
'
#4
Device 1
466.20'
30.0" x 30.0" Horiz. Orifice /Grate C= 0.600
Limited to weir flow at low heads
'
#5
Secondary
468.50'
30.0' long x 12.0' breadth Broad - Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.57 2.62 2.70 2.67 2.66 2.67 2.66 2.64
' Primary OutFlow Max =30.30 cfs @ 12.12 hrs HW= 469.21' (Free Discharge)
= Culvert (Barrel Controls 26.04 cfs @ 14.73 fps)
2= Orifice /Grate (Passes < 0.58 cfs potential flow)
' = Orifice /Grate (Passes < 52.25 cfs potential flow)
3= Orifice /Grate (Orifice Controls 4.27 cfs @ 8.53 fps)
econdary OutFlow Max =48.62 cfs @ 12.12 hrs HW= 469.21' (Free Discharge)
' = Broad - Crested Rectangular Weir (Weir Controls 48.62 cfs @ 2.27 fps)

2013.08.21.BMP #15 Type 1124 -hr 100 -Yr Rainfall= 7.62"
Prepared by McKim & Creed Printed 9/8/2013
HydroCADO 10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 20
Pond 3P: BMP #15
Hydrograph
N
V
3
O
LL
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
® Inflow
L: Outflow
E3 Primary
❑ Secondary

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WATER QUALITY POND #15 CALCULATIONS
Project Name
Briar Chapel - Phase 9 - Section 2 - BMP #15
Project Number
02735 -0096
Date
August 6, 2013
3rd revision
2nd revision
1 st revision

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Water Quality Pond Drainage Area Data
Project Briar Chapel - Phase 9 - Section 2 - BMP #15
Project No. 02735 -0096
Date August 6, 2013
Total site area 666,950 square feet = 15.31 acres
Impervious areas
Drainage
area to and
Other Drainage
Area
Existing
s
Proposed
s
Change
s
Existing
s
Proposed
s
On -site buildings BUA
0
238,000
238,000
0
0
On -site streets
0
104,466
104,466
0
0
On -site alleys
0
6,701
6,701
0
0
On -site sidewalks
0
31,922
31,922
0
0
On -site future (open space)
0
1,000
1,000
0
0
Off -site streets
0
0
0
0
0
5% Contingency
0
19,104
19,104
0
0
Commercial building
0
10,000
10,000
0
0
Commercial pavement
0
25,000
25,000
0
0
Total Impervious
0
401,193
401,193
0
0
Non-impervious areas
Drainage
area to and
Other Draina
a Area
Existing
s
Proposed
[Sfl
Change
Isf]
Existing
s
Proposed
s
On -site grass/landscape
0
265,757
265,757
0
0
On -site woods
666,950
0
- 666,950
0
0
Other undeveloped
0
1 0
1 0
0
0
Total off -site non-impervious
0
1 0
0
0
0
Total non-impervious
666,950
1 265,757
1 - 401,193
0
0
Total Drainage Area
666,950
666,950
0
3,167,850
3,167,850
Percent Impervious
0.0
60.2
60.2
0.0
0.0
Notes:
2013.08.06.Wet Detention Pond #15.xis
Site Drainage Area Data Page 2 of 18
Printed 9/8/2013 5:58 PM

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Water Quality Pond Surface Area Calculations
Project Briar Chapel - Phase 9 - Section 2 - BMP #15
Project No. 02735 -0096
Date August 6, 2013
Total on -site drainage area to pond 666,950 square feet
Total impervious area in drainage area 401,193 square feet
Average water depth of basin at normal pool 4.0 feet
Location of site Chatham County
Site region Piedmont
% Impervious cover
60.2 percent
If the site is in a coastal area, will a vegetative filter be used? n/a
Surface Area /Drainage Area Ratios:
For a site in the Piedmont (85 %)
2.0 percent
For a site in the Piedmont (90 %)
2.8 percent
For a site in a Coastal County w/ Vegetative Filter
3.8 percent
For a site in a Coastal County w /out Vegetative Filter
5.3 percent
Required surface area of pond:
For a site in the Piedmont (85 %) 13,580.0 square feet
For a site in the Piedmont (90 %) 18,730.0 square feet
For a site in a Coastal County w/ Vegetative Filter 25,420.0 square feet
For a site in a Coastal County w /out Vegetative Filter 35,420.0 square feet
Notes:
2013.08.06.Wet Detention Pond #15.xls
Pond Surface Area Calcs Page 3 of 18
Printed 9/8/2013 5:58 PM

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Water Quality Pond Stormwater Runoff Volume Calculations
Project Briar Chapel - Phase 9 - Section 2 - BMP
Project No. 02735 -0096
Date August 6, 2013
Drainage area 666,950 square feet
Impervious area 401,193 square feet
Rainfall depth 1.00 inches
Percent Impervious 60.2 percent
R(v) =0.05 +0.009 *(Percent impervious)
Runoff coefficient - R(v) 0.59 in /in
Runoff volume = (Design rainfall) *(R(v)) *(Drainage area)
Runoff volume 32,868.5 cubic feet
Notes:
2013.08.06.Wet Detention Pond #15.xis
Runoff Volume Calcs Page 4 of 18
Printed 9/8/2013 5:58 PM

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Water Quality Pond Volume Calculations
Stage -Storage Data for Pond - Temporary Pool
Project Briar Chapel - Phase 9 - Section 2 - BMP #15
Project No. 02735 -0096
Date August 6, 2013
Contour ID
Stage
Area
[sq ft.
Area
acres
Incremental
Area
ft.
Incremental
Area
acres
Incremental
volume
cu ft
Incremental
volume
acre-ft
Cumulative
volume
cu ft
Cumulative
volume
acre -ft
464.5
0
20,017.0
0.460
20,0170
05
00
00
00
00
465
0.5
22,898.0
0.526
2,881.0
01
10,728.8
02
10,728.8
02
465.95
1.45
24,610.3
0.565
1,7123
00
22,5664
0.5
33,2952
0.8
466
1.5
24,702.0
0.567
91.8
00
1,232.8
0.5
34,528.0
0.8
467
2.5
26,562.0
0.610
1,860.0
0.0
25,632.0
0.6
60,160.0
1.1
468
35
28,479.0
0.654
1,917.0
0.0
27,520.5
0.6
87,680.5
1.2
469
4.5
30,453.0
0.699
1,974.0
0.0
29,466.0
0.7
117,146.5
1.3
470
55
32,483.0
0.746
2,030.0
0.0
31,4680
0.7
148,614.5
1.4
2013.08 06 Wet Detention Pond #15 As
' Stage Storage (Temp Pool) Page 5 of 18 Printed 9/8/2013 5.58 PM

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Water Quality Pond Volume Calculations
Stage - Storage Data for Pond - Permanent Pool
Project Briar Chapel - Phase 9 - Section 2 - BMP #15
Project No 02735 -0096
Date August 6, 2013
Contour ID
Stage
Area
[sq ft.
Area
acres
Incremental
Area
. ft.
Incremental
Area
acres
Incremental
volume
cu. ft
Incremental
volume
acre -ft
Cumulative
volume
cu. ft
Cumulative
volume
acre -ft
394
0
6,007.0
0.138
6,007.0
0.1
0.0
0.0
0.0
0.0
395
1
7,474.0
0.172
1,467.0
00
6,7405
0.2
6,740.5
0.2
396
2
9,071.0
0208
1,597.0
0.0
8,272.5
0.2
15,013.0
0.3
397
3
10,770.0
0.247
1,6990
0.0
9,9205
0.2
24,933.5
04
398
4
12,583.0
0.289
1,813.0
0.0
11,676.5
0.3
36,6100
05
399
5
14,509.0
0 333
1,926.0
0.0
13,546.0
0.3
50,156.0
0.6
400
6
16,547.0
0 380
2,038.0
0.0
15,5280
0.4
65,684.0
07
400.5
65
20,017.0
0 460
3,470.0
0.1
9,141.0
0.2
74,825.0
06
2013.08 06 Wet Detention Pond #15.x1s
' Stage Storage (Perm Pool) Page 6 of 18 Printed 9/8/2013 5:58 PM

1
Water Quality Pond Volume Calculations
Stage -Storage Data for Pond - Forebays
Project Briar Chapel - Phase 9 - Section 2 - BMP #15
Project No. 02735 -0096
Date August 6, 2013
Contour ID
Stage
Area
ft
Area
acres
Incremental
Area
. ft.
Incremental
Area
acres
Incremental
volume
cu. ft
Incremental
volume
acre -ft
Cumulative
volume
cu. ft
Cumulative
volume
acre -ft
458
0
636.0
0.015
6360
00
00
00
0.0
0.0
459
1
1,005.0
0 023
369.0
0.0
820.5
0.0
820.5
0.0
460
2
1,442.0
0 033
437.0
0.0
1,223.5
0.0
2,0440
0.0
461
3
1,927.0
0.044
485.0
0.0
1,684.5
00
3,728.5
0.1
462
4
2,469.0
0.057
542.0
0.0
2,198.0
0.1
5,926.5
0.1
463
5
3,068.0
0 070
599.0
0.0
2,768.5
0.1
8,695.0
0.1
464
6
3,723.0
0.085
655.0
0.0
3,395.5
0.1
12,090.5
0.1
464.5
6.5
4,940.0
0.113
1,217.0
0.0
2,165.8
0.0
14,256.3
0.1
2013 08.06.Wet Detention Pond #15.x1s
Stage Storage (Forebays) Page 7 of 18 Printed 9/8/2013 5:58 PM

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Water Quality Basin Dewatering Time Calculations
Project Briar Chapel - Phase 9 - Section 2 - BMP #15
Project No. 02735 -0096
Date August 6, 2013
Water quality treatment volume
32,869
square feet
Total treatment volume
33,295
square feet
Maximum head of water above dewatering hole
1.45
feet
Driving head
0.48
feet
Orifice coefficient
0.60
Diameter of each hole
3.25
inches
Number of holes
1
Cross sectional area of each hole =
Cross sectional area of each hole =
Cross sectional area of dewatering hole(s) _
Cross sectional area of dewatering hole(s) _
Dewatering time for water quality volume =
Dewatering time for total volume =
0.058 square feet
8.3 square inches
0.058 square feet
8.3 square inches
2.0 days
2.0 days
Notes:
Dewatering time formula: t (days) = V / (Cd *A *Sgrt (2"32.2 *H) *86,400)
t = drawdown time
V = treatment volume
Cd = orifice coefficient
A = cross sectional area of orifice
H = driving head (1/3 max. head)

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v
v
v
a
A
Water Quality Pond Summary Information
Project Briar Chapel - Phase 9 - Section 2 -
Project No. 02735 -0096
Date August 6, 2013
Drainage area to pond
666,950
square feet = 15.31 acres
Impervious area in drainage area
401,193
square feet = 9.21 acres
Bottom of pond elevation
457.00
feet
Normal pool elevation
562.50
feet
Pond volume at normal pool
178,071
cubic feet
Required volume for design rainfall
32,868
cubic feet
Required surface area for pond
18,730
square feet
Volume provided for storage of design rainfall = 71,862 cubic feet at elevation 463.9
Surface area provided at normal pool 46,957 square feet
2013.08.06.Wet Detention Pond #15.xis
Summary Data Page 10 of 18 Printed 9/8/2013 5:58 PM

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Storm Outlet Structure
Structure= BMP #15 Out
= 14 in
Size= 18
in
Q10 = 24.93
cfs
Qfull = 14.45
cfs
Vfull = 8.18
fps
From Fig. 8.06.b.1:
Apron Length
Apron Width = 3 x Dia
Q10 /Qfull = 1.72
VNfull = MAX
V = 10.9 fps
Zone = 5
D50
= 14 in
DMAx
21 in
Riprap Class
Apron Thickness
2
= 36 in
Apron Length
Apron Width = 3 x Dia
= 15.0 ft
= 5.0 ft

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rrw -JF-%.. i onai %ol WPM - ot. aUuui
PROJECT LOCATION: Chatham County, NC
Storm Outlet Structure
Structure= BMP #16 Out
Size= 12 in
Quo= 7.19 cfs
Qfull = 3.98 cfs
Vfull = 5.06 fps
From Fig. 8.06.b.1:
I
Length
TE: 9/3/2013
NO:
DESIGNED BY:
DJB
GCA
Quo / Qfull = 1.81
V/Vfull = MAX
V = #VALUE! fps
Zone = 5
D5o
= 14 in
DMax
= 21 in
Riprap Class
= 2
Apron Thickness
= 36 in
Apron Length
= 10.0 ft
Apron Width = 3 x Dia
= 3.0 ft

M M M M M M M M M M M w M s s M M M M
ECT LOCATION: Chatham County, NC
Pond Name= BMP #15
Riser Outer Width =
3.5 ft
Riser Outer Length =
3.5 ft
Riser Inner Width =
2.5 ft
Riser Inner Length =
2.5 ft
Riser Height =
8.62 ft
Concrete Base Length =
4.5 ft
Concrete Base Width =
4.5 ft
Concrete Base Depth =
12 in
DATE: 8/23/2013
02735 -0096
Riser Resisting Force =
Base Resisting Force =
Total Resisting Force =
Riser Buoyant Force =
Base Buoyant Force =
Total Buoyant Force =
Factor of Safety
GNED BY: GCA
7,758 lb
3,038 lb
10,796 lb
6,589 lb
1,264 lb
7,853 lb
Design Acceptable

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Permit No.
(to be provided by DWQ)
III. REQUIRED ITEMS CHECKLIST
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.
Page/ Plan
Initials Sheet No.
GCA C3.3 -C3.4 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 (ROM,
- Overflow device, and
- Boundaries of drainage easement.
GCA D4.1 -D4.3 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.
GCA D4.1 -D4.3 3. Section view of the wet detention basin (1" = 20' or larger) showing:
- Side slopes, 3:1 or lower,
- Pretreatment and treatment areas, and
- Inlet and outlet structures.
GCA N/A 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.
GCA Calc Booklet 5. A table of elevations, areas, incremental volumes & accumulated volumes for overall pond and for forebay,
to verify volume provided.
GCA C3.1 6. A construction sequence that shows how the wet detention basin will be protected from sediment until the
entire drainage area is stabilized.
GCA Calc Booklet 7. The supporting calculations.
GCA Included 8. A copy of the signed and notarized operation and maintenance (0 &M) agreement.
GCA Included 9. A copy of the deed restrictions (if required).
N/A 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.8- 9/17/09 Part III. Required Items Checklist, Page 1 of 1

IPermit No
' Red triangles at the upper right hand comer indicate design comments
Please complete the yellow shaded items.
EWA
A �
=7AA
MOM
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 he pnnied, filled out and submitted along with all of the required Information
(to be provided by DWQ)
1. PROJECT INFORMATION
' Project name Bnar Chapel Development - Great Ridge Parkway Extension
Contact person Gareth Avant, PE
Phone number 919 233 8091
Date 30 -Aug -2013
1
a
1
r
1
1
Drainage area number
2 - Wet Pond #15
O ?OF W A Z ;q
1
II. DESIGN INFORMATION
Site Characteristics
Drainage area
666,904 ft2
Impervious area, post -development
401,188 fe
% impervious
60.16%
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 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 1 -yr, 24 -hr peak flow control
Elevations
Temporary pool elevation
Permanent pool elevation
SHWT elevation (approx at the pens. pool elevation)
Top of 1Oft vegetated shelf elevation
Bottom of 1 Oft vegetated shelf elevation
Sediment deanout, top elevation (bottom of pond)
Sediment deanout, bottom elevation
Sediment storage provided
Is there additional volume stored above the state - required temp. pool?
Elevation of the top of the additional volume
Form SW401 -Wet Detention Basin -Rev &9/17/09
32,869 ft3 OK
33,295 ft3 OK, volume provided is equal to or in excess of volume required.
ft3
ft3
ft"
ft3
tt3
Y (Y or N)
3.0 In
0 40 (unitless)
0.86 (undless)
0.13 inthr OK
12.87 f3 /sec
47.65 ft"/sec
345 ft3 /sec
471.00 fmsl
464.50 imsl
fmsl
465.001ms1
464.00 fmsl Data not needed for calculation option #1, but OK I provided.
459.00 fmsl
458 00 fmsl Data not needed for calculation option #1, but OK If provided.
1.00 ft
N (Y or N)
Mid
Parts I & 11 Design Summary. Page 1 of 2

I Permit No
(to be provided by DWQ)
1
1
1
II, DESIGN INFORMATION
Surface Areas
Area, temporary pool
Area REQUIRED, permanent pool
SAIDA ratio
Area PROVIDED, permanent pool, Ace,,,,
Area, bottom of 1 Oft vegetated shelf, Abo swf
Area, sediment cleanout, top elevation (bottom of pond), Ab„_mw
ft2
16,673 ft2
2.50 (unitless)
74,689 ff2 OK
16,547 ff
7,474 ft2
Volumes
Volume, temporary pool 33,295 ft3
Volume, permanent pool, Vpe, _pw 74,689 ft3
Volume, forebay (sum of forebays If more than one forebay) 14,256 fti
Forebay % of permanent pool volume 19.1%%
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, Vce,,,,yw
' Area provided, permanent pool, A,_pw
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, Ace,,,,
Area, bottom of 1 Oft vegetated shelf, Ab di
Area, sediment cleanout, top elevation (bottom of pond), Abo_p.d
90%
N (Y or N)
Y (Y or N)
2.50 (umdess)
Y (Y or N)
74,689 ft3
74,689 fy
3.73 ft
3.5 It
N (Y or N)
74,689 ft2
16,547 ft2
7,474 ft2
' 'Depth' (distance b/w bottom of 1Oft shelf and top of sediment) 5.00 It
Average depth calculated ft
Average depth used in SAIDA, d.„ (Round to nearest 0.5ft) ft
1
0
1
r
1
Drawdown Calculations
Drawdown through orifice?
Diameter of orifice (if circular)
Area of orifice (if- nonciroular)
Coefficient of discharge (Co)
Driving head (Ho)
Drawdown through weir?
Weir type
Coefficient of discharge (Q
Length of weir (L)
Driving head (H)
Pre-development 1 -yr, 24 -hr peak flow
Post -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-out?
Drain mechanism for maintenance or emergencies is:
Forth SW401 -Wet Detenhon Basin -Rev 8- 9117/09
Y (Y or N)
3.50 in
in
0.60 ( unitess)
1.50 ft
N (Y or N)
( unitless)
( unitless)
It
It
10.18 fe /sec
5.92 fP /sec
0 38 fP /sec
2.23 days
OK
OK
OK
OK
OK, draws down in 2 -5 days.
3 :1
OK
10 :1
OK
10.0 It
OK
3 :1
OK
1.5 :1
OK
Y (Y or N)
OK
1.5 It
OK
N (Y or N)
OK
Y (Y or N)
OK
Y (Y or N)
OK
8' DIP with gate valve
Paris I & 11 Design Summary, Page 2 of 2

' Permit Number:
(to be provided by DWQ)
Drainage Area Number:
Wet Detention Basin Operation and Maintenance Agreement
'
Potential problem:
How I will remediate the problem:
I will keep a maintenance record on this BMP. This maintenance record will be kept in a
Trash debris is present.
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
Regrade the soil if necessary to
of structures, safety of the public, and the removal efficiency of the BMP.
erosive gullies have formed.
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.
'
one -time fertilizer application.
This system (check one):
Vegetation is too short or too
does ® does not incorporate pretreatment other than a forebay.
lon
approximately six inches.
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.
t
— 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
Maintain vegetation at a height of
lon
approximately six inches.
Form SW401 -Wet Detention Basin O &M -Rev.4
Page 1 of 4

1
1
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1
1
1
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
Search for the source of the
a depth greater than 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 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 spray in .
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
original 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
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 basin surface.
IForm SW401 -Wet Detention Basin O &M -Rev.4 Page 2 of 4

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1
1
1
1
1
1
1
1
1
1
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
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 5.50 feet in the main pond, the
sediment shall be removed.
When the permanent pool depth reads 5.50 feet in the forebay, the sediment
shall be removed.
BASIN DIAGRAM
ill in the blanks)
Permanent Pool Elevation 464.50
Sediment Removal 459.00--- - - - - -- Pe amen Pool
- - - -- -- Volume Sediment Removal Elevation 459.00 Volume
Bottom E evatio 458.00 ft Mm.
-------------------------------------- - - - - -- --- - --
Sediment Bottom Elevation 458.00 1 -ft n
Storage Sedimei
Storage
FOREBAY MAIN POND
Form SW401 -Wet Detention Basin O &M -Rev.4
Page 3 of 4

F-
I
i
Permit Number:_ _
' (to be provided by DWQ)
I acknowledge and agree by my signature below that 1 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.
1
1
Project name:Briar Chapel - Phase 9
BMP drainage area number: l - Wet Detention Pond # 15
Print name:Kevin Graham
Title:Vice President, Operations
Address:16 Windy Knoll Circle, Chapel Hill. NC 27516
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.
&w~ , a Notary Public for the State of
/VC,. . , County of GWrrh[ts• , do hereby certify that
JL{hoh &1144M personally appeared before me this
day of 4 st I• t and acknowledge the due execution of the
forgoing wet detention basin maintenance requirements. Witness my hand and official
seal,
SEAL
My commission expires R "10 r�
Form SW401 -Wet Detention Basin O&M -Rev.4
Page 4 of 4

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BMP #16 DESIGN

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1S
Pre - Development
Subcat Reach on Link
2S
Post- Devjelopment
3P
BMP #16

' BMP #16.Gareth Type 11 24 -hr 1 -Yr Rainfall= 2.96"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD ®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 7
' Summary for Subcatchment 1 S: Pre - Development
Runoff = 2.23 cfs @ 12.09 hrs, Volume= 0.144 af, Depth> 0.61"
Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Type II 24 -hr 1 -Yr Rainfall= 2.96"
' Area (ac) CN Description
2.820 70 Woods, Good, HSG C
' 2.820 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
' (min) (feet) (ft/ft) (ft/sec) (cfs)
15.0 Direct Entry,
1
1
1
0
LL
Subcatchment IS: Pre - Development
Hydrograph
2.23 cfs
- -- - - - - --
Type II 24 -hr
1 -Yr Rainfall= 2.96"
Runoff Area =2.820 ac
Runoff Volume =0.144 of
Runoff Depth >0.61"
-- -- ----------- Tc =15.0 min -
CN=70
Time (hours)
18 19 20
O Runoff

' BMP #16.Gareth Type 1124 -hr 1- YrRainfall= 296"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD ®10.00 s/n 04927 C 2011 HydroCAD Software Solutions LLC Page 9
' Summary for Pond 3P: BMP #16
' Inflow Area = 2.820 ac, 49.65% Impervious, Inflow Depth > 1.50" for 1 -Yr event
Inflow 6.94 cfs @ 12.02 hrs, Volume= 0.353 of
Outflow = 1.97 cfs @ 12.22 hrs, Volume= 0.225 af, Atten= 72 %, Lag= 12.2 min
Primary = 1.97 cfs @ 12.22 hrs, Volume= 0.225 of
' Secondary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 of
Routing by Stor -Ind method, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Peak Elev= 492.37' @ 12.22 hrs Surf.Area= 6,711 sf Storage= 7,607 cf
Plug -Flow detention time= 144.6 min calculated for 0.225 of (64% of inflow)
Center -of -Mass det. time= 72.1 min ( 857.5 - 785.4 )
' Volume Invert Avail.Stora a Storage Description
#1 491.00' 29,289 cf Custom Stage Data (Prismatic)Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq -ft) (cubic -feet) (cubic -feet)
' 491.00 4,139 0 0
492.00 6,302 5,221 5,221
493.00 7,418 6,860 12,081
494.00 8,590 8,004 20,085
495.00 9,819 9,205 29,289
_Device Routing Invert Outlet Devices
' #1 Primary 489.00' 12.0" Round Culvert
L= 40.0' RCP, square edge headwall, Ke= 0.500
Inlet/ Outlet Invert= 489.00'/488.50' S=0.01257 Cc= 0.900
n=0.013 Concrete pipe, bends & connections, Flow Area= 0.79 sf
#2 Device 1 491.00' 1.3" Vert. Orifice /Grate C= 0.600
#3 Device 1 492.00' 18.0" W x 3.0" H Vert. Orifice /Grate C= 0.600
#4 Device 1 492.25' 24.0" x 24.0" Horiz. Orifice /Grate C= 0.600
Limited to weir flow at low heads
#5 Secondary 493.25' 10.0' long x 15.0' breadth Broad - Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
Primary OutFlow Max =1.93 cfs @ 12.22 hrs HW= 492.36' (Free Discharge)
L = Culvert (Passes 1.93 cfs of 6.40 cfs potential flow)
' 2= Orifice /Grate (Orifice Controls 0.05 cfs @ 5.51 fps)
3= Orifice /Grate (Orifice Controls 0.87 cfs @ 2.33 fps)
= Orifice /Grate (Weir Controls 1.01 cfs @ 1.10 fps)
econdary OutFlow Max =0.00 cfs @ 5.00 hrs HW= 491.00' (Free Discharge)
= Broad - Crested Rectangular Weir( Controls 0.00 cfs)

BMP #16.Gareth Type 1124 -hr 1 -Yr Rainfall = 2.96"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD® 10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 10
Pond 3P: BMP #16
Hydrograph
6.94 CfS ■ Inflow
G Outflow
Inflow Area =2.820 ac ® Primary
❑ Secondary
7f// Peak Elev= 492.37'
Storage =7,607 cf
6
5
N_ _ _ _ _ _ - _ _ - _ .. _ _ _ _ _ _ _ _ _ _ _ _ _
u
4
3
0
LL
s 1.97 cfs
2

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BMP #16.Gareth Type 1124 -hr 10 -Yr Rainfall = 5.17"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 12
Summary for Subcatchment 1 S: Pre - Development
Runoff = 7.75 cfs @ 12.08 hrs, Volume= 0.462 af, Depth> 1.97'
Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Type II 24 -hr 10 -Yr Rainfall = 5.17'
Area (ac) CN Description
2.820 70 Woods, Good, HSG C
2.820 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
15.0 Direct Entry,
Subcatchment IS: Pre - Development
Hydrograph
7.75 cfs
5
a4-------------------
- - - - -- - --
LL
Type II 24 -hr
10 -Yr Rainfall = 5.17"
uno ff A rid a =2. 92 0 -ac-
Runoff Volume =0.462 of
Runoff_ _ Depth >1.97"
TC =15.0 min
-
-- - - - - -- - - - - -- -------- CN =70-
wiii� i���ii�i���. �Z'Zzww"Ovsov'
� Runoff

BMP #16.Gareth Type 1124 -hr 10 -Yr Rainfall = 5.17"
Prepared by McKim & Creed Printed 9/8/2013
HydroCADS 10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 14
' Summary for Pond 3P: BMP #16
' Inflow Area = 2.820 ac, 49.65% Impervious, Inflow Depth > 3.39" for 10 -Yr event
Inflow 15.05 cfs @ 12.01 hrs, Volume= 0.796 of
Outflow = 7.19 cfs @ 12.14 hrs, Volume= 0.661 af, Atten= 52 %, Lag= 8.0 min
Primary = 7.19 cfs @ 12.14 hrs, Volume= 0.661 of
' Secondary = 0.00 cfs @ 5.00 hrs, Volume= 0.000 of
Routing by Stor -Ind method, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
' Peak Elev= 493.11' @ 12.14 hrs Surf.Area= 7,552 sf Storage= 12,935 cf
Plug -Flow detention time= 90.5 min calculated for 0.661 of (83% of inflow)
Center -of -Mass det. time= 41.3 min ( 808.3 - 767.0 )
Volume Invert Avail.Storage Storage Description
#1 491.00' 29,289 cf Custom Stage Data (Prismatic)Listed below (Recalc)
' Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq -ft) (cubic -feet) (cubic -feet)
' 491.00 4,139 0 0
492.00 6,302 5,221 5,221
493.00 7,418 6,860 12,081
' 494.00 8,590 8,004 20,085
495.00 9,819 9,205 29,289
Device Routing Invert Outlet Devices
' #1 Primary 489.00' 12.0" Round Culvert
L= 40.0' RCP, square edge headwall, Ke= 0.500
Inlet/ Outlet Invert= 489.00'/488.50' S= 0.0125 '/' Cc= 0.900
'
n=0.013 Concrete pipe, bends & connections, Flow Area= 0.79 sf
#2 Device 1 491.00' 1.3" Vert. Orifice /Grate C= 0.600
#3 Device 1 492.00' 18.0" W x 3.0" H Vert. Orifice /Grate C= 0.600
#4 Device 1 492.25' 24.0" x 24.0" Horiz. Orifice /Grate C= 0.600
Limited to weir flow at low heads
#5 Secondary 493.25' 10.0' long x 15.0' breadth Broad - Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
' Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
Primary OutFlow Max =7.19 cfs @ 12.14 hrs HW= 493.11' (Free Discharge)
L = Culvert (Inlet Controls 7.19 cfs @ 9.15 fps)
2= Orifice /Grate (Passes < 0.06 cfs potential flow)
3= Orifice /Grate (Passes < 1.79 cfs potential flow)
= Orifice /Grate (Passes < 17.87 cfs potential flow)
' econdary OutFlow Max =0.00 cfs @ 5.00 hrs HW= 491.00' (Free Discharge)
5= Broad - Crested Rectangular Weir( Controls 0.00 cfs)

BMP #16.Gareth Type// 24 -hr 10 -Yr Rainfall= 5.17"
Prepared by McKim & Creed Printed 9/8/2013
HydroCADO 10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 15
Pond 3P: BMP #16
Hydrograph
® Inflow
15.05 cfs outflow
Inflow Area =2.820 ac Else Secondary
- - -
15 ,. Peak Elev= 493.11'
13 Storage= 12,935 cf
12 - - - - - -- - -- - - - -- - - - - - -- --
10
9 1 7.19 cfs I[
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)

1
' BMP #16.Gareth Type 1124 -hr 100 -Yr Rainfall= 7.62"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD ®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 17
' Summary for Subcatchment 1S: Pre - Development
' Runoff = 14.99 cfs @ 12.07 hrs, Volume= 0.896 af, Depth> 3.81"
Runoff by SCS TR -20 method, UH =SCS, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Type II 24 -hr 100 -Yr Rainfall= 7.62"
' Area (ac) CN Description
2.820 70 Woods, Good, HSG C
' 2.820 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
' (min) (feet) (ft/ft) (ft/sec) (cfs)
15.0 Direct Entry,
' Subcatchment IS: Pre - Development
Hydrogimph
' 16
- - 14.99 cfs
Runoff
15
Type 11 24-hr
14
13
1
-
100 -Yr Rainfall= 7.62"
-- - - - - - -- ------ - - - - -- - - -- - -- - - - --
12
Runoff Area =2.820 ac
11
10
Runoff Volume =0.896 of
9
- - - - -- - -- - --
- - - -- ------ - - - - -- -- - -- - - ._Runoff Depth >3.81" _
° 8
Tc =15.0 min
6
- -- --- - - - - -- - - - - -- - - - - - -- - --- -
5
1
0
1
1
5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
Time (hours)

' BMP #16.Gareth Type 1124 -hr 100 -Yr Rainfall= 7.62"
Prepared by McKim & Creed Printed 9/8/2013
HydroCAD®10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 19
' Summary for Pond 3P: BMP #16
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[82] Warning: Early inflow requires earlier time span
Inflow Area = 2.820 ac, 49.65% Impervious, Inflow Depth > 5.59" for 100-Yr event
Inflow =
24.11 cfs @
12.01 hrs,
Volume=
1.313 of
Outflow =
16.71 cfs @
12.10 hrs,
Volume=
1.172 af, Atten= 31 %, Lag= 5.6 min
Primary =
7.78 cfs @
12.10 hrs,
Volume=
1.040 of
Secondary =
8.93 cfs @
12.10 hrs,
Volume=
0.133 of
Routing by Stor -Ind method, Time Span= 5.00 -20.00 hrs, dt= 0.05 hrs
Peak Elev= 493.73' @ 12.10 hrs Surf.Area= 8,271 sf Storage= 17,793 cf
Plug -Flow detention time= 73.2 min calculated for 1.172 of (89% of inflow)
Center -of -Mass det. time= 36.9 min ( 792.9 - 756.0 )
Volume Invert
Avail.Storage Storage Description
#1 491.00'
29,289 cf Custom Stage Data (Prismatic)Listed below (Recalc)
Elevation Surf.Area
Inc.Store Cum.Store
(feet)
(sq -ft)
(cubic -feet) (cubic -feet)
491.00
4,139
0 0
492.00
6,302
5,221 5,221
493.00
7,418
6,860 12,081
494.00
8,590
8,004 20,085
495.00
9,819
9,205 29,289
Device Routing
Invert
Outlet Devices
#1 Primary
489.00'
12.0" Round Culvert
L= 40.0' RCP, square edge headwall, Ke= 0.500
Inlet /Outlet Invert= 489.00'/488.50' S=0.01257 Cc= 0.900
n= 0.013 Concrete pipe, bends & connections, Flow Area= 0.79 sf
#2 Device 1
491.00'
1.3" Vert. Orifice /Grate C= 0.600
#3 Device 1
492.00'
18.0" W x 3.0" H Vert. Orifice /Grate C= 0.600
#4 Device 1
492.25'
24.0" x 24.0" Horiz. Orifice /Grate C= 0.600
Limited to weir flow at low heads
#5 Secondary
493.25'
10.0' long x 15.0' breadth Broad - Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
Primary OutFlow Max =7.77 cfs @ 12.10 hrs HW= 493.72' (Free Discharge)
L = Culvert (Inlet Controls 7.77 cfs @ 9.90 fps)
2= Orifice /Grate (Passes < 0.07 cfs potential flow)
3= Orifice /Grate (Passes < 2.28 cfs potential flow)
= Orifice /Grate (Passes < 23.38 cfs potential flow)
econdary OutFlow Max =8.82 cfs @ 12.10 hrs HW= 493.72' (Free Discharge)
= Broad - Crested Rectangular Weir (Weir Controls 8.82 cfs @ 1.86 fps)

BMP #16.Gareth Type 11 24 -hr 100 -Yr Rainfall= 7.62 "
Prepared by McKim & Creed Printed 9/8/2013
HydroCADO 10.00 s/n 04927 © 2011 HydroCAD Software Solutions LLC Page 20
Pond 3P: BMP #16
Hydrograph
N
V
3
O
LL
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Time (hours)
■ Inflow
G Outflow
■ Primary
■ Secondary

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BMP SIZING - SIMPLE METHOD
Briar Chapel Phase 9
BMP #16
Stormwater Wetland
Project:
02735-0096
Prepared by:
GCA
Date:
8/19/2013
Drainage area:
122,794
sf
Impervious area:
61,033
sf
Volume to Catch The First 1.0 Inches of Runoff:
Runoff :
Rv = 0.05 +
0 9 * la Simple Method, Schueler
la (actac)=
0.497
Rv =
0.497
Volume.
V = 3630 *
P * Rv * A
P =
1.00
in
Rv =
0 497
A =
2.82
ac
V =
5,089
cf
Surface Area:
SA = Volume / Depth
Depth =
12
in
SA =
5,089
sf

STORMWATER WETLAND #16 CALCULATIONS
Project Name
Briar Chapel Phase 9
Project Number
2735 -0096
Date
August 19, 2013
3rd revision
2nd revision
1 st revision

Water Quality Pond Drainage Area Data
Project Briar Chapel Phase 9
Project No. 2735 -0096
Date August 19, 2013
Total site area 122,794 square feet = 2.82 acres
Impervious areas
Draina
a area to and
Other Drainage
Area
Existing
s
Proposed
s
Change
s
Existing
s
Proposed
s
On -site buildings lots
0
33,400
33,400
0
0
On -site streets
0
20,672
20,672
0
0
On -site sidewalks
0
6,961
6,961
0
0
On -site future (open space)
0
0
0
0
0
Off -site buildings
0
0
0
0
0
Off -site streets
0
0
0
0
0
Off -site sidewalks
0
1 0
1 0
0
1 0
Total Impervious
0
61,033
61,033
0
0
Non-impervious areas
Drainage
area to and
Other Drainage
Area
Existing
s
Proposed
s
Change
s
Existing
s
Proposed
s
On -site grass/landscape
0
785,984
785,984
0
0
On -site woods
1,639,768
30,917
- 1,608,851
0
0
Other undeveloped
0
1 0
1 0
0
0
Total off -site non-impervious
0
1 0
0
0
0
Total non-impervious
1,639,768
1 816,901
- 822,867
0
0
Total Drainage Area
122,794
122,794
0
3,167,850
3,167,850
Percent Impervious
0.0
49.7
49.7
0.0
0.0
Notes:
2013.08.19.Wetland #16 Design Worksheet.Stage Storage.xls
Site Drainage Area Data Page 2 of 5 Printed 9/8/2013 6:06 PM

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F
Stormwater Wetland Volume Calculations
Stage -Storage Data for Wetland - Temporary Pool
Project Briar Chapel Phase 9
Project No. 2735 -0096
Date August 19, 2013
Contour ID
Stage
Area
[s q. ft.
Area
acres
Incremental
Area
. ft.
Incremental
Area
acres
Incremental
volume
cu. ft
Incremental
volume
acre -ft
Cumulative
volume
cu. ft
Cumulative
volume
acre-ft
491
0
4,139.0
0.095
4,1390
0.1
0.0
0.0
00
0.0
492
1
6,302.0
0.145
2,1630
0.0
5,220.5
0.1
5,2205
0.1
493
2
7,418.0
0.170
1,116.0
0.0
6,860.0
0.2
12,080.5
0.3
494
3
8,590.0
0.197
1,172.0
0.0
8,0040
0.2
20,084.5
03
495
4
9,819.0
0 225
1,229.0
0.0
9,204 5
0.2
29,289.0
0.4
IF
2013.08.19.Wetiand #16 Design Worksheet Stage Storage.xls
' Stage Storage (Temp Pool) Page 3 of 5 Printed 9/8/2013 6:06 PM

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Water Quality Basin Dewatering Time Calculations
Project Briar Chapel Phase 9
Project No. 2735 -0096
Date August 19, 2013
Water quality treatment volume
5,089
square feet
Total treatment volume
5,221
square feet
Maximum head of water above dewatering hole
1.00
feet
Driving head
0.33
feet
Orifice coefficient
0.60
Diameter of each hole
1.33
inches
Number of holes
1
Cross sectional area of each hole =
Cross sectional area of each hole =
Cross sectional area of dewatering hole(s) _
Cross sectional area of dewatering hole(s) _
Dewatering time for water quality volume =
Dewatering time for total volume =
0.010 square feet
1.4 square inches
0.010 square feet
1.4 square inches
2.2 days
2.3 days
Notes:
Dewatering time formula: t (days) = V / (Cd *A *Sgrt (2 *32.2 *H) *86,400)
t = drawdown time
V = treatment volume
Cd = orifice coefficient
A = cross sectional area of orifice
H = driving head (1/3 max. head)

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@MMMM@UM DATE: 9/3/2013 DESIGNED BY:
BEAM 1DJ13
PROJECT NAME: Briar Chapel - BC South PROJECT NO: CHECKED BY
PROJECT LOCATION: Chatham County, NC 102735-0096 GCA
Storm Outlet Structure
Structure= BMP #16 Out Q10 /Qfull = 1.81
Size= 12 in VNfull = MAX
Q10 = 7.19 cfs V = #VALUE! fps
Qfull = 3.98 cfs
Vfull = 5.06 fps
From Fig. 8.06.b.1: Zone = 5
r — D50 = 14 in
DmAx = 21 in
i' Riprap Class = 2
Apron Thickness = 36 in
i—' Apron Length = 10.0 ft
Lengtn Apron Width = 3 x Dia = 3.0 ft

I Permit No.
(to be provided by DWQ)
III. REQUIRED ITEMS CHECKLIST
' 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.
' Initials Page/ Plan
Sheet No.
' GCA D4.7 -D4.8 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),
' - Wetland dimensions (and length to width ratio),
- Pretreatment system,
- Maintenance access,
' - Proposed drainage easement and public right of way (ROW),
- Overflow device, and
- Boundaries of drainage easement.
GCA D4.7 -D4.8 2. Plan details (1" = 50' or larger) for the wetland showing:
- Wetland dimensions (and length to width ratio)
' - Pretreatment system,
- Maintenance access,
- Proposed drainage easement and public right of way (ROW),
' - Design at ultimate build -out,
- Off -site drainage (if applicable),
- Overflow device, and
- Boundaries of drainage easement.
GCA D4.7 3. Section view of the wetland (1" = 20' or larger) showing:
- Side slopes, 3:1 or lower
' - Wetland layers
All wetlands: Shallow land depth, shallow water depth, deep pool depth
Option 1, no clay liner: SLWT depth
' Option 2, clay liner: Depth of topsoil on top of liner, liner specifications
GCA
D4.7
4. A detailed planting plan (1" = 20' or larger) prepared by a qualified individual showing:
'
- A variety of several suitable species (not including cattails),
- Sizes, spacing and locations of plantings,
- Total quantity of each type of plant specified,
- A planting detail,
'
- The source nursery for the plants, and
- Fertilizer and watering requirements to establish vegetation.
GCA
C3.1
5. A construction sequence that shows how the wetland will be protected from sediment until the entire
drainage area is stabilized.
' GCA
Calc Book
6. The supporting calculations (including drawdown calculations).
GCA
Included
7. A copy of the signed and notarized operation and maintenance (0 &M) agreement.
' GCA
N/A
8. A copy of the deed restrictions (if required).
GCA
N/A
9. A soils report that is based upon an actual field investigation and soil borings. County soil maps are not an
acceptable source of soils information.
SW401- Wetland -RPv 6- 11/16/09
Part III nacre 1 of 1

1
pF WA le;9
pG
1 T
HOM
' STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WETLAND SUPPLEMENT
1 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 the required information.
I. PROJECT INFORMATION
'Project name Briar Chapel Development - Phase 9
Contact name Gareth Avant, PE
Phone number 9193233.809
1 Date September 8, 2013
Drainage area number 3 - BMP #16
DESIGN INFORMATION
'II.
Site Characteristics
Drainage area
122,794.00 fe
Impervious area
61,033.00 fe
Percent impervious
1
49.7%%
Design rainfall depth
1.00 inch
Peak Flow Calculations
1 -yr, 24 -hr rainfall depth
1
3.00 in
1 -yr, 24 -hr intensity
0.12 in/hr
Pre - development 1 -yr, 24-hr runoff
2.23 ft3 /sec
1 Post - development 1 -yr, 24 -hr runoff
6.94 ft3/sec
Pre/Post 1 -yr, 24-hr peak control
4.71 ft3 /sec
Storage Volume: Non -SA Waters
Minimum required volume
1
5,089.00 ft
Volume provided (temporary pool volume)
5,221.00 ft3 OK
1 Storage Volume: SA Waters Parameters
1.5" runoff volume
ft3
Pre - development 1 -yr, 24 -hr runoff volume
ft3
Post - development 1 -yr, 24 -hr runoff volume
ft3
Minimum volume required
ft3
'Volume provided
ft3
Outlet Design
Depth of temporary pool/ponding depth (DPI)
12.00 in OK
Drawdown time
2.20 days OK
Diameter of orifice
1.33 in OK
1 Coefficient of discharge (CD) used in orifice diameter
calculation
0.60 (unitless)
Driving head (Ho) used in the orifice diameter calculation 0.33 ft Provide calculations to support this driving head.
Forth SW401- Wetland -Rev 6- 11/16/09 Parts I and 11 Project Design Summary, Page 1 of 3

1
'Surface Areas of Weiland Zones
Surface Area of Entire Wetland
Shallow Land
The shallow land percentage is:
'Shallow Water
The shallow water percentage is:
Deep Pool
'Forebay portion of deep pool (pretreatment)
The forebay surface area percentage is:
Non - forebay portion of deep pool
'The non - forebay deep pool surface area percentage is:
Total of wetland zone areas
Add or subtract the following area from the zones
' Topographic Zone Elevations
Temporary Pool Elevation (TPE)
Shallow Land (top)
'Permanent Pool Elevation (PPE)
Shallow Water/Deep Pool (top)
Shallow Water bottom
'Most shallow point of deep pool's bottom
Deepest point of deep pool's bottom
Design must meet one of the following two options:
'This design meets Option #1,
Top of PPE is within 6" of SHWT, If yes:
SHWT (Seasonally High Water Table)
This design meets Option #2,
' Wetland has liner with permeability < 0.01 in/hr, If yes:
Depth of topsoil above impermeable liner
Topographic Zone Depths
Temporary Pool
Shallow Land
Permanent Pool
'Shallow Water
Deep Pool (shallowest)
Deep Pool (deepest)
'Planting Plan
Are cattails included in the planting plan?
Number of Plants recommended in Shallow Water Area:
' Herbaceous (4'cubic -inch container)
Number of Plants recommended in Shallow Land Area:
Herbaceous (4'cubic -inch container), OR
' Shrubs (1 gallon or larger), OR
Trees (3 gallon or larger) and Herbaceous (4+ cubic -inch)
Number of Plants provided in Shallow Water Area:
Herbaceous (4'cubic -inch container)
' Number of Plants provided in Shallow Land Area:
Herbaceous (4'cubic -inch container)
Shrubs (1 gallon or larger)
' Trees (3 gallon or larger) and
Grass -like Herbaceous (4+ cubic -inch)
IForm SW401- Wetland -Rev 6- 11/16/09
6,301.00 f? OK
2,215.00 fe OK
35%%
2,602.00 fe OK
41 %%
648.00 fe OK
10%%
836.00 f? OK
13%%
6,301.00 fe OK
0.00 fe
492.00 ft amsl
491.00 ft amsl
490.50 ft amsl
489.50 ft amsl
489.00 ft amsl
(Y or N)
ft amsl OK
Y (Y or N)
4.00 in OK
12.00 in OK
6.00 in OK
18.00 in OK
24.00 in OK
N (Y or N) OK
700
600
96
12
and
480
700
OK
600 OK
Parts I and 11 Pro ject Design Summary, Page 2 of 3

1
Form SW401- Wetland -Rev 6- 11/16/09 Parts I and II Project Design Summary, Page 3 of 3
9 N 9
Additional Information
'Can
the design volume be contained?
Y
(Y or N)
OK
Does project drain to SA waters? ff yes,
N
(Y or N)
Excess volume must pass through filter.
What is the length of the vegetated filter?
N/A
ft
'Are
calculations for supporting the design volume provided in the
Y
(Y or N)
OK
application?
Is BMP sized to handle all runoff from ultimate build -out?
Y
(Y or N)
OK
Is the BMP located in a recorded drainage easement with a
recorded access easement to a public Right of Way (ROW)?
Y
(Y or N)
OK
The length to width ratio is:
2.85 :1
OK
Approximate wetland length
137.00 ft
'Approximate
wetland width
48.00 ft
Approximate surface area using length and width provided
6,576.00 �
This approx. surface area is within this number of square feet
of the entire wetland surface area reported above:
Will the wetland be stabilized within 14 days of construction?
Y
(Y or N)
OK
1
Form SW401- Wetland -Rev 6- 11/16/09 Parts I and II Project Design Summary, Page 3 of 3
9 N 9

' Permit Number:
(to be provided by DWQ)
tDrainage Area Number:
Stormwater Wetland 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.
Important maintenance procedures:
' — Immediately following construction of the stormwater wetland, bi- weekly inspections will be
conducted and wetland plants will be watered bi- weekly until vegetation becomes established
(commonly six weeks).
L— No portion of the stormwater wetland will be fertilized after the first initial fertilization that is
required to establish the wetland plants.
— Stable groundcover will be maintained in the drainage area to reduce the sediment load to the
wetland.
— Once a year, a dam safety expert should inspect the embankment.
After the stormwater wetland is established, I will inspect it monthly 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 will be kept in a known set location and will 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 problenr
Entire BMP
Trash debris is present.
Remove the trash debris.
Perimeter of wetland
Areas of bare soil and /or erosive
Regrade the soil if necessary to remove the
gullies have formed.
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 long.
Maintain vegetation at an appropriate
height.
Inlet device: pipe or
The pipe is clogged (if applicable).
Unclog the pipe. Dispose of the sediment
swale
offsite.
The pipe is cracked or otherwise
Replace the pipe.
-damaged if applicable).
Erosion is occurring in the swale (if
Regrade the swale if necessary to smooth
applicable).
it over and provide erosion control
devices such as reinforced turf matting or
riprap to avoid future problems with
erosion.
IForm SW401-Wetland O &M -Rev.4 Page 1 of 3

1
1
n
L
Permit Number:
(10 be provided by DWQ)
BMP element:
Potential problem:
How I will remediate the problem:
Forebay
Sediment has accumulated in the
Search for the source of the sediment and
forebay to a depth that inhibits the
remedy the problem if possible. Remove
forebay from functioning well.
the sediment and 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
roblems.
Weeds are present.
Remove the weeds, preferably by hand. If
a pesticide is used, wipe it on the plants
rather than spraying.
Deep pool, shallow water
Algal growth covers over 50% of the
Consult a professional to remove and
and shallow land areas
deep pool and shallow water areas.
control the algal growth.
Cattails, phragmites or other invasive
Remove invasives by physical removal or
plants cover 50% of the deep pool and
by wiping them with pesticide (do not
shallow water areas.
spray) - consult a professional.
Shallow land remains flooded more
Unclog the outlet device immediately.
than 5 days after a storm event.
Plants are dead, diseased or dying.
Determine the source of the problem:
soils, hydrology, disease, etc. Remedy the
problem and replace plants. Provide a
one -time fertilizer application to establish
the ground cover if necessary.
Best professional practices show that
Prune according to best professional
pruning is needed to maintain optimal
practices.
plant health.
Sediment has accumulated and
Search for the source of the sediment and
reduced the depth to 75% of the
remedy the problem if possible. Remove
original design depth of the deep
the sediment and dispose of it in a location
pools.
where it will not cause impacts to streams
or the BMP.
Embankment
A tree has started to grow on the
Consult a dam safety specialist to remove
embankment.
the tree.
An annual inspection by appropriate
Make all needed repairs.
professional shows that the
embankment needs repair
Evidence of muskrat or beaver activity
Consult a professional to remove muskrats
is present.
or beavers.
Micropool
Sediment has accumulated and
Search for the source of the sediment and
reduced the depth to 75% of the
remedy the problem if possible. Remove
original design depth.
the sediment and dispose of it in a location
where it will not cause impacts to streams
or the BMP.
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.
Receiving water
Erosion or other signs of damage have
Contact the NC Division of Wafter Quality
occurred at the outlet.
401 Oversight Unit at 919 - 733 -1786.
IForm SW401-Wetland O &M -Rev.4 Page 2 of 3

' Permit Number.
(lobe provided by DWQ)
I acknowledge and agree by my signature below that I am responsible for the performance of the
' maintenance procedures listed above. 1 agree to notify DWQ of any problems with the system or prior
to any changes to the system or responsible party.
1
Project name:Briar Chapel - Phase 9
BMP drainage area number:3 - Stormwater Wetland # 16
Print name:Kevin Graham
Title:Vice President, Operations
Address: 16 Windy Knoll Circle, Chapel Hill, NC 27516
Phone:[phone]
Signature: T e
Date: � 3
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, G, Leh'+ djwmo, a Notary Public for the State of
NL , County of CAIAf M , do hereby certify that
%LG►i)l personally appeared before me this P? day of
i4fteW ,'[3 , and acknowledge the due execution of the forgoing stormwater wetland
1 41
maintenance requirements. Witness my hand and official seal,
SON 60W
%%OTARV
AU9LIG
SEAL
My commission expires
Form SW401- Wetland O &M -Rev.4
Page 3 of 3