20050732 Ver 47_Stormwater Site Plans_20190220

v�MCIQNI&cREED
TO NCDENR — Division of Water Resources
401 & Buffer Permitting Unit
512 N. Salisbury St.
Archdale Building - 9th floor
Raleigh, NC 27604
ATTENTION: Ms. Karen Higgins
'�) cOSG T?,L- V /- {-
LETTER OF TRANSMITTAL
DATE: February 8, 2019
PROJECT NO: 2735-0214
TASK NO: REIMB
RE: Modification to DWQ 05-0732v17
TRANSMITTAL NO: 1
PAGE 1 OF 1
WE ARE SENDING: ❑ Originals ® Prints ❑ Shop Drawings ❑ Samples
❑ Specifications ® Calculations ❑ Other -
Quantity
Dwg
No.
Rev.
Description
Status
1
Cover Letter Requesting Stormwater Management Plan Approval
C
2
Stormwater Design Plans
G
2
Narrative & Supporting Calculations
G
2
Granite Mill Wetland Design Supplements
G
2
Granite Mill Wetland O&M Agreements
G
Issue Status Code:
REMARKS:
A. Preliminary B. Fabrication Only C. For Information D. Bid
E. Construction F. For Review & Comments G. For Approval H. See Remarks
Ms. Higgins,
Please find the enclosed documents for your review and approval. Please let us know if you have any
questions or comments.
Thank you.
1730 Varsity Drive, Suite 500 Raleigh, NC 27606 919/2338091 Fax [phone]
Cc:
McKIM &CREED, INC.
I�
1 19 + Signed
Gareth Avant, PE

v. MCKIM&CREED
February 8th, 2019
Ms. Karen Higgins
512 N. Salisbury St.
Archdale Building - 9th floor
Raleigh, NC 27604
RE: DWQ 05-0732v17
Ms. Higgins,
E N G I N E E R S
S U R V E Y O R S
P L A N N E R S
R @
uu ray 2 0 2019
Please find enclosed the plans, caclulations, supplement forms and operation and
maintenance agreements for the Granite Mill Blvd. Wetland at Briar Chapel.
This letter is to formally request approval for modifying the previously approved
stormwater management program per Water Quality Certification June 28, 2010
as issued by the Division of Water Resources 05-0732v17
Please let me know if you have any questions on this. Thank you for your
assistance.
Sincerely,
McKIM & CREED, INC.
Venture IV Building ✓&46e-4 {.If�l -
Suit. 500 Gareth Avant, PE
Project Engineer
1730 Varsity Drive
Raleigh, NC 27606
919.233.8091
Fax [phone]
www.mckimcreed.com

Operation & Maintenance Agreement
Project Name:
Project Location:
Briar Chapel - Granite Mill Wetland
East of Andrews Store Rd and Granite Mill Blvd Intersection
Cover Page;
Maintenance records shall be kept on the following BMP(s). This maintenance record shall 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 pollutant removal efficiency of the BMP(s).
The BMP(s) on this project include (check all that apply & correspc
Bioretention Cell
Quantity:
Dry Detention Basin
Quantity:
Grassed Swale
Quantity:
Green Roof
Quantity:
Infiltration Basin
Quantity:
Infiltration Trench
Quantity:
Level Spreader/VFS
Quantity:
Permeable Pavement
Quantity:
Proprietary System
Quantity:
Rainwater Harvesting
Quantity:
Sand Filter
Quantity:
Stormwater Wetland
Quantity:
1
Wet Detention Basin
Quantity:
Disconnected Impervious Area
Present:
No
User Defined BMP
Present:
No
O&M tables wil
Location(s)
Location(s)
Location(s)
Location(s)
Location(s)
Location(s)
Location(s)
Location(s).
Location(s)
Location(s)
Location(s)
Location(s)
Location(s)
Location(s):
Location(s):
iixtllx•
I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed
for each BMP above, and attached O&M tables. I agree to notify NCDENR of any problems with the system or prior to any
changes to the system or responsible party.
* Responsible Party:
Title & Organization:
Street address:
City, state, zip:
Phone number(s):
Email:
Lee Bowman
Senior Project Manager, NNP -Briar Chapel, LLC
1342 Briar Chapel Parkway
Chapel Hill, NC 27516
[phone]
(bowman newlandco.com
Signature: ASM, Date: -211F13 J�Zj
I, LA,( }(-nnY`CCA a Notary Public for the State of t1)0Y iC-,Lr 11 it/1A.
County of y\0-YYs do hearby certify that (� W ,n�,•�T
personally appeared before me this day of PbY (ACLX and
acknowledge the due execution of the Operations and Maintenance Agreement .
Witness my hand and official seal,
Kin
1NIIf
CP
aotary
Pub�xo U
ham Co�� �`�
a l usWL My commission expires
Version 1.4
Ce / Z-3 /a 6 20
2/7/2019
Page 1 of 3

Stormwater Wetland Maintenance Requirements
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).
_ 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, it shall be inspected 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:
Potentialproblem:
How I will remediate theproblem:
Entire BMP
Trash/debris is present.
Remove the trash/debris.
The perimeter of the BMP
Areas of bare soil and/or
Regrade the soil if necessary to remove the gully, and then plant a
erosive gullies have formed.
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 approximately six inches.
long.
Forebay
Sediment has accumulated in
Search for the source of the sediment and remedy the problem if
the forebay to a depth that
possible. Remove the sediment and dispose of it in a location where it
inhibits the forebay from
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 a pesticide is used, wipe it
on the plants rather than spraying.
The inlet device
The pipe is clogged.
Unclog the pipe. Dispose of the sediment off-site.
The pipe is cracked or
Replace the pipe.
otherwise damaged.
Erosion is occurring in the
Regrade the swale if necessary to smooth it over and provide erosion
swale.
control devices such as reinforced turf matting or riprap to avoid future
problems with erosion.
Stone verge is clogged or
Remove sediment and replace with clean stone.
covered in sediment (if
applicable).
STORM -EZ 2/7/2019
Version 1.4 O&M Manual Page 2 of 3

Stormwater Wetland Maintenance Requirements (Continued)
Deep pool, shallow water
Algal growth covers over 50%
Consult a professional to remove and control the algal growth.
and shallow land areas
of the deep pool and shallow
water areas.
Cattails, phragmites or other
Remove invasives by physical removal or by wiping them with
invasive plants cover 50% of
pesticide (do not spray) — consult a professional.
the deep pool and shallow
Shallow land remains flooded
Unclog the outlet device immediately.
more than 5 days after a
storm event.
Plants are dead, diseased or
Determine the source of the problem: soils, hydrology, disease, etc.
dying.
Remedy the problem and replace plants. Provide a one-time fertilizer
application to establish the ground cover if necessary.
Best professional practices
Prune according to best professional practices.
show that pruning is needed
to maintain optimal plant
Sediment has accumulated
Search for the source of the sediment and remedy the problem if
and reduced the depth to 75%
possible. Remove the sediment and dispose of it in a location where it
of the original design depth of
will not cause impacts to streams or the BMP.
Embankment
A tree has started to grow on
Consult a dam safety specialist to remove the tree.
the embankment.
An annual inspection by
Make all needed repairs.
appropriate professional
shows that the embankment
Evidence of muskrat or
Consult a professional to remove muskrats or beavers.
beaver activity is present.
Micropool
Sediment has accumulated
Search for the source of the sediment and remedy the problem if
and reduced the depth to 75%
possible. Remove the sediment and dispose of it in a location where it
of the original design depth.
will not cause impacts to streams or the BMP.
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 Department of Environment and Natural
damage have occurred at the
Resources Regional Office.
outlet.
STORM -EZ 2/7/2019
Version 1.4 O&M Manual Page 3 of 3

Operation & Maintenance Agreement
Project Name:
Project Location:
Briar Chapel - Granite Mill Wetland
East of Andrews Store Rd and Granite Mill Blvd Intersection
Maintenance records shall be kept on the following BMP(s). This maintenance record shall 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 pollutant removal efficiency of the BMP(s).
The BMP(s) on this project include (check all that apply & a
Bioretention Cell
Quantity:
Dry Detention Basin
Quantity:
Grassed Swale
Quantity:
Green Roof
Quantity:
Infiltration Basin
Quantity:
Infiltration Trench
Quantity:
Level SpreaderNFS
Quantity:
Permeable Pavement
Quantity:
Proprietary System
Quantity:
Rainwater Harvesting
Quantity:
Sand Filter
Quantity:
Stormwater Wetland
Quantity:
Wet Detention Basin
Quantity:
Disconnected Impervious Area
Present:
User Defined BMP
Present:
ing O&M tables wil
Location(s):
Location(s):
Location(s):
Location(s):
Location(s):
Location(s):
Location(s):
Location(s):
Location(s):
Location(s):
Location(s):
Location(s):
Location(s):
Location(s):
Location(s):
oe aaoeo
I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance procedures listed
for each BMP above, and attached O&M tables. I agree to notify NCDENR of any problems with the system or prior to any
changes to the system or responsible party.
Responsible Party:
Title & Organization:
Street address:
City, state, zip:
Phone number(s):
Email:
Lee Bowman
Senior Project Manager, NNP -Briar Chapel, LLC
1342 Briar Chapel Parkway
Chapel Hill, NC 27516
919)951-0700
P40�[e-mail]
o
Signature: Z-- Date: .2113
1, %Yy1'u I.. �( � 010 Y -Cr a Notary Public for the State of i')Or CCAY711 i0o�
County of QQDL&yyxo-yyi do hearby certify that (-�, L G W
personally appeared before me this day of )-PbY (ACLJ L�, and
acknowledge the due execution of the Operations and Maintenance Agreement .
Witness my hand and official seal,
�altf
``�, K ngCP e e
notary
Pubs'° U:
O $
�..`
,,/ham
vac My commission expires
Version 1.4
(g / Z3 /a 62.-o
2/7/2019
Page 1 of 3

Stcrrnwater Wettand Milnten ' a Requirements
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).
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, it shall be inspected 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:
Potentialproblem:
How I will remediate theproblem:
Entire BMP
Trash/debris is present.
Remove the trash/debris.
The perimeter of the BMP
Areas of bare soil and/or
Regrade the soil if necessary to remove the gully, and then plant a
erosive gullies have formed.
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 approximately six inches.
long.
Forebay
Sediment has accumulated in
Search for the source of the sediment and remedy the problem if
the forebay to a depth that
possible. Remove the sediment and dispose of it in a location where it
inhibits the forebay from
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 a pesticide is used, wipe it
on the plants rather than spraying.
The inlet device
The pipe is clogged.
Unclog the pipe. Dispose of the sediment off-site.
The pipe is cracked or
Replace the pipe.
otherwise damaged.
Erosion is occurring in the
Regrade the swale if necessary to smooth it over and provide erosion
swale.
control devices such as reinforced turf matting or riprap to avoid future
problems with erosion.
Stone verge is clogged or
Remove sediment and replace with clean stone.
covered in sediment (if
applicable).
STORM -EZ 2/7/2019
Version 1.4 O&M Manual Page 2 of 3

Stormwater Wetland Maintenance Requirements (Continued)
Deep pool, shallow water
Algal growth covers over 50%
Consult a professional to remove and control the algal growth.
and shallow land areas
of the deep pool and shallow
water areas.
Cattails, phragmites or other
Remove invasives by physical removal or by wiping them with
invasive plants cover 50% of
pesticide (do not spray) — consult a professional.
the deep pool and shallow
Shallow land remains flooded
Unclog the outlet device immediately.
more than 5 days after a
storm event.
Plants are dead, diseased or
Determine the source of the problem: soils, hydrology, disease, etc.
dying.
Remedy the problem and replace plants. Provide a one-time fertilizer
application to establish the ground cover if necessary.
Best professional practices
Prune according to best professional practices.
show that pruning is needed
to maintain optimal plant
Sediment has accumulated
Search for the source of the sediment and remedy the problem if
and reduced the depth to 75%
possible. Remove the sediment and dispose of it in a location where it
of the original design depth of
will not cause impacts to streams or the BMP.
Embankment
A tree has started to grow on
Consult a dam safety specialist to remove the tree.
the embankment.
An annual inspection by
Make all needed repairs.
appropriate professional
shows that the embankment
Evidence of muskrat or
Consult a professional to remove muskrats or beavers.
beaver activity is present.
Micropool
Sediment has accumulated
Search for the source of the sediment and remedy the problem if
and reduced the depth to 75%
possible. Remove the sediment and dispose of it in a location where it
of the original design depth.
will not cause impacts to streams or the BMP.
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 Department of Environment and Natural
damage have occurred at the
Resources Regional Office.
outlet.
STORM -EZ 2/7/2019
Version 1.4 O&M Manual Page 3 of 3

SUPPLEMENT -EZ FORM COVER PAGE
Please indicate the types, quantities and locations of SCMs that will be used on this project:
Quantity Location(s)
Infiltration System
Bioretention Cell
Wet Pond
Stormwater Wetland 1 East of Andrews Store Road and Granite Mill Blvd Intersection
Permeable Pavement
Sand Filter
Rainwater Harvesting
Green Roof
Level Spreader -Filter Strip
Disconnected Impervious Surface
Treatment Swale
Dry Pond
Designer information for this project:
Name and Title:
Gareth C. Avant
Organization:
McKim and Creed, Inc.
Street address:
1730 Varsity Drive, Suite 500
City, State, Zip:
Raleigh, NC 27606
Phone number(s):
[phone]
Email:
[e-mail]
Designer
�•'P�\A CARCi,,
�CC ES 3lp�V�'L9 2
Q 9�
Gr_AL =
036348 =
C99FH� I NES yP��
lot
Signature of Designer
_1cllzoly
Date
Applicant:
Project Name:
Briar Chapel - Granite Mill Wetland
Address
N/A
City / Town
Pittsboro, NC
Company:
NNP -Briar Chapel, LLC
Contact:
Lee Bowman, Senior Project Manager
Mailing Address:
1342 Briar Chapel Parkway
City, State, Zip:
Chapel Hill, NC 27516
Phone number(s):
[phone]
Email
[e-mail]
Certification Statement:
I certify, under penalty of law: that this Supplement -EZ form and all supporting
information were prepared under my direction or supervision;
- that the information provided in the form is, to the best of my knowledge
and belief, true, accurate, and complete; and
- that the engineering plans, specifications, operation and maintenance
agreements and other supporting information are consistent with
the information provided here.
I am aware that there are significant penalties for submitting false
information including the possibility of fines and imprisonment for knowing
violations as well as a report being made to my professional board.
Cover Page
1 2:17 PM 2/7/2019

STORMWATER WETLAND
Briar Chanel - Granite Mill Wetland
THE DRAINAGE AREA
I
Drainage area number
NIA
Break down of BUA in the drainage area both new and existing):
Total coastal wetlands area (sq R)
sf
- Parking I driveway (sq R)
sf
Total surface water area (sq R)
of
- Sidewalk (sq ft)
sf
Total drainage area (sq R)
303(101 sf
- Roof (sq ft)
49899 sf
BUA associated with existing development (sq R)
sf
- Roadway (sq R)
87399 sf
Proposed new BUA (sq R)
151028 sf
- Other. please specify in the comment box below (sq R)
13730 id
Percent BUA of drainage area
50%
Total BUA (sq R)
151028 sf
COMPLIANCE WITH THE APPUCAINA STOR19WATM PROGRAM
Stormwater program(s) that a easespecify).
Desgn rainfall depth (in)
1.0 in
Minimum volume required (cu R)
Design volume of SCM (cu ft)
12592 cf
17422 cf
91 Is the SCM sized to treat the SW from all surfaces at build o ?
Yes
#7 If a -ble, wM the SCM be cleaned out after construction?
Yes
#2 Is the SCM located on or mar contaminated soils?
No
#8 Does the maintenance access comply with General MDC 8)?
Yes
#3 What are the side slopes of to SCM (H:V)?
3:1
#9 Does the drainage easement comply with General MDC (9)?
Yes
#3 Does the SCM have missing walls. gabion walls or other engineered side slopes?
No
#10 If the SCM is on a single family lot, does the plat comply with Genral MDC (10)?
#4 Are the inlets, outlets, and receiving stream protected from erosion (10 -year storm)?
Yee
911 Is there an O&M Agreement that complies with General MDC 11)?
Yes
#5 Is Imre a a bypass for flows in excess of the design Row?
No
#12 Is there an O&M Plan that complies with General MDC 12)?
Yes
#6 What is the method for devartering the SCM for maintennce7 I
Pump (Preferred)
1#13 Was Bre SCM designed by an NC licensedprofessional?
Yes
#1 Permanent pool elevation ((mil)
439 R
#8 Total surface area of the shallow water zone at temporary pool (square feet)
7912 sf
#1 Temporary pool elevation (fmsi)
44D R
#8 SW wetland surface area comprised of shallow water zone at temporary %
57.6%
#1 Ponding depth (inches)
12 in
#8 Depth of the shallow water zone below permanent pool Inches
12 in
#2 Is the SW warlord designed for peak attenuation?
yes
#8 Elevation of bottom of the shatlow water zone (fms4
439 It
#2 If so, peak attenuation depth inches
16.2 in
#9 Total surface area of the temporary inundation zone at temporary 1 square feet)
2110.3 sf
#3 Surface area of SW wetland at temporary (square feel
13740 sf
#9 SW wetland sudace area Comprised of temp inundation zone at temp pool %)
34.9%
#4 Depth of soil amendment inches
6 in
#9 Height of the temporary inundation zone above permanent pool (inches)
12n
#4 Describe how the soil is being amended to promote plantgrowth:
#9 Elevation of bottom of the temporary inundation zone fmsl
439 ft
Topsoil all be added so anstae edeNale militants while plants are being established.
#10 Drawdown time for the temporary pool (hours)
#10 Does the orifice drawdown from below the top surface off�rmanent pool? _
#11 Does the pond minimize impacts In the receiving channelfrom the 1 -yr. 24 -hr storm?
84.5 hos
Yes
Yes
#6 Are the inlet(s) and outlet located in a manner that avoids short-circuiting?
Yes
#12 Has a landscaping plan that meets SW Wetland MDC (12) been provided? _
Yin
06 Describe any measures, such as berms or bafRes, that will be taken to improve the flow path:
#13 of plants per 200 square feel (#) In Bre shallow water zone:
—---- ._.._..--
50
_Number
The wetland was in a ('rear manner to increase th distance from doe inlet to the outlet The inbt and outlet are
d � #13 Describe the planting plan for the shallow water zone:
located on opposite sides of the basin and as far as possible from each other in the space 50 plants per 200 all. plants chosen as outlined in C-4 of NCDEQ Stortmwater Design Manual
— --------------
_—_ #6 Surface area of the forebay at temporary pool (square feet) 2840 sf
#6
#6 Overall SW wetland surface area comprised of forebay at temporary pool (%) 20.6%
#6 Depth of forebay below pertnannt pool (inches)
42 in
#14 Does planting for the temporary inundation zone comply with SW Welland MDC_ (14)?
Yes
06 Elevation of bottom of forebay (fmsl)
435.5 R
#14 Describe the planting plan for the temporary inundation zone:
#6 Will the foretbay be cleaned out when depth Is reduced to 15 inches or less?
#7 Total surface area of the non-forebay deep pools at temporary pool (square feet)
Yes
2989 sf
_
50 plants per 200 at, plards chosen as outlined in C4 of NCDEQ Stamwater Design Manual
#7 SW wetland surface area comprised of nn-forebay deep pools at temporary pool (%
21.8%
Are the dam structure and temporary fill slopes planted in nom -clumping lurfgmss?
#15 n
Yes
#7 Depth of non-forebay deep pools below permanent pool (inches)
42 in
#16 Will cattails be planted in the wetland?
No
#70—hon of bottom of non-forebay deep Pods (fmsl)
435.5 R
#t 7 Is a trash rack or other device provided to protect the outlet system?
Yes
ADDITIONAL INFORMATION
Please use this s ace to provide an mformation about this slormwaler wetland that you think is relevant to the review:
Other BUA impervious is a 10% contingency Included In our design
Wetland 2 1:33 PM 2/13/2019

SUPPLEMENT -EZ FORM COVER PAGE
Please indicate the types, quantities and locations of SCMs that will be used on this project:
Quantity. Location(s)
Infiltration Svstem
Bioretention Cell
Wet Pond
Stormwater Wetland 1 East of Andrews Store Road and Granite Mill Blvd Intersection
Permeable Pavement
Sand Filter
Rainwater Harvesting
Green Roof
Level Spreader -Filter Strip
Disconnected Impervious Surface
Treatment Swale
Dry Pond
Designer information for this project:
Name and Title:
Gareth C. Avant
Organization:
McKim and Creed, Inc.
Street address.
1730 Varsity Drive, Suite 500
City, State, Zip:
Raleigh, NC 27606
Phone number(s):
[phone]
Email:
gavantQmkcimcreed.com
Designer
'00%H CAR�Z'�.,�,
�CPC� E�31prv.!29
.Q
Sr.AL
066.8 =
C'yRFq'GINEtiP��
�FTH P,`'`��;
i
44"4 " /�
Signature of Designer
Date
Applicant:
Project Name:
Briar Chapel - Granite Mill Wetland
Address
N/A
City / Town
Pittsboro, NC
Company:
NNP -Briar Chapel, LLC
Contact:
Lee Bowman, Senior Project Manager
Mailing Address:
1342 Briar Chapel Parkway
City, State, Zip:
Chapel Hill, NC 27516
Phone number(s):
[phone]
Email:
Ibowman n&Mandco.com
Certification Statement:
I certify, under penalty of law: that this Supplement -EZ form and all supporting
information were prepared under my direction or supervision;
- that the information provided in the form is, to the best of my knowledge
and belief, true, accurate, and complete; and
- that the engineering plans, specifications, operation and maintenance
agreements and other supporting information are consistent with
the information provided here.
I am aware that there are significant penalties for submitting false
information including the possibility of fines and imprisonment for knowing
violations as well as a report being made to my professional board.
Cover Page 1 2:17 PM 2/7/2019

STORMWATER WETLAND
Briar Chanel - Granite Mill Wetland
E DRAINAGE AREA
Drainage area rwmber _ _ _ _ _ _
WA
Break down of BUA in the drainage area (both new and existing):__
Total coastal wetlands area (sq fl)
d-
Parlong / Ur vi sway (sq 0)
d
Total surface water area (sq fl)
d
- Sidewalk (sq ft)
d
Total drainage area (sq ft)
BUA associated win existing development (sq ft) '
Proposed new BUA (sq h)
303601 d
sf
151028 sf
Root (sq ft) - -�
- Roadway (sq 111
- Other. please specify in the comment box below (sq ftl
49899 at
87399 d
13730 d
Percent BUA of drainage area
50%
Total BUA (sq ft)
151028 d
COMPLIANCE WITH THE APPLICABLE STORINWATER PROGRAM
Sbrmw-sten ams Oat a ase s if ).Design
rainfall depth (in)
1.0 n
Minimum volume required (cu ft)
Design volume of SCM (cu ft)
12592 cf
17422 d
#1 Is the SCM sized to treat the SW from all surfaces at build -outs
Yes
#7 O applicable. with the SCM be cleaned out after construction?
Yes
#2 Is the SCM located on or near contaminated soils?
No
#8 Does the mainetanance access ce wtlh Gerorel MDC B ?
Yes
93 What are the side slopes of the SCM (H: V )?
3:1
#9 Does the drains easement cont with General MDC 9 ?
Yea
#3 Does Ute SCM have retaini walls, bion walls or Omer a peered side slopes?
No
#10 O the SCM is on a Singlefamilylel, does Ore at cam with General MDC 10 ?
#4 Are the inlets. outlets, and receiving sVeam protected from erosion (10 -year storm)?
Yet
11 Is there an 08th Agreement that complies with General MDC 11)?
Yes
#5 Is there a a bypass for flows in excess of the design 11-1
No
#12 Is mere an O8M Plan that m ies went General MDC 12 ?
Yes
#6 W hat is the meOtod for dewaten the SCM for maintenance?
Pump (prafened)
13 Was IM SCM desi reed an NC licensed /essional?
Yes
#1 Permanent pool elevation (hmsp
439 It
#8 Total surface area of the shallow water zone at ttmieorruy pool (,I, -e leer
7912 9f
#1 Temporary pool elevation (fmsl)
440 ft
#8 SW wetland surface area composed of shallow water zone, at temporary %
57.6%
#1 Ponding depth (inches)
12 In
De of me shallow water zone below rmanent riches
12.
2 Is the S W wetland designed for ale attenuation?
Yea
Elevation of bottom of me shallow water zone fmsl
439 ft
#2O so, ak attenuation depth inches
16.2 n
#9 Total surface area of me tem re inundation zone at tem I (square feet
21103 sf
#3 Surface area of SW wetland at temporary (square feel)
13740 of=
and surface area -sed of tem inundation zone at tem %
34.9%
#4 Depth of soil amendment inches
8 in
He of the temporary inundation zone above permument inches
121n
#4 Descnbe how the soil is being amended W promote plantgrowth:
#9 Elevation of bottom of the tem rot inundation zone imsl
439 ft
opeol will be added b ensurer adequate nutrients while planar are bekg established.
#10 Drawdown time for the temporary pool (hours)
10 Does Use onfice drawdown from below the top surface of this permanent
11 Does the pond minimize impacts In the receiving channel from his 1 -yr, 244r storm?
84.5 his
Yes
Yes
#6 Are the inlet(s) and oullel located In a manner that avoids shod-rircuifirg?
Yes
12 Has a landscape plan that meets SW Welland MDC (12) been provided?
Yes
. _
#6 Describe any measures, such as benne a bathes, mat will be taken to memve the flow path:
13 Number of plants per 200 square feel (#) in the shallow water mne:
50
The wretleM well designed In e user cheerer to increase the distance from the ktlM to ms outlet, The ft," and ou"are13
krcaled on opposis sides of ms bean and r for as possiN from each other n the space.
06 Surface area of the forebay M temporary pool (square feet) 2840 of
06 Overall SW wetland surface area comprised of forebay, at temporary pod (%) 20.6%
Descnbe the plantingplan for the shallow water zone: —_
plans per 200 d, parMs (mtlsan as owned in C4 of NCDEO Sbmwaler Design Manfred
#6 Depth of lorebay, below permanent pool (inches) _
42 n
#1d Does planting far the temporary enundatlon zone ce mply with SW Wetiared MDC (14)?
Yea
#6 Elevation of bottom of forebay (fmsl)
435.5 R
_
#14 Describe the planting plan for the temporaryinundation zone:
#6 Will the /orebay be cleaned ora when depth is reduced to 15 inches or less?
7 To1a1 surface area of the non-forebaytl pools M tempora pool (square feet)
Yes
2989 d
Diems Der 200 d, plates Imoewl ea outlksdn Gil ot NCDEO Saamtwaarr Design Mahal
#7 SW wetland surface area comprised of non-forebay deep Is at tempora 11%
21.8%
#15 Are the dam structure and temporary fill slopes planted in non -dumping turfgmss?
Yee
07 Depth d non-foreba deep pools below permanent pool (inches)
42 n
16 Will cattails be planted in the wetland?
No
#7 Elevation of bosom of non tomboy deep pools (frost)
435.511
17 Is a trash rack or other device provided to protect me outlet system?
Yes
ADDITIONAL BIFORMATIDM
Plea s, this s ce to provide an information about this slow le, wetland that u think is relevant to the review.
Omer BUA impetvkxls b a 10%contingency In�Aded in our design
Wetland 2 1.33 PM 2/13/2019

401 NARRATIVE &
SUPPORTING CALCULATIONS
Briar Chapel Development
Granite Mill Blvd. Wetland
Chatham County, North Carolina
February 8, 2019
Prepared for:
BRIAR.S CHAPEL'S
Newland COMMUMMS
NNP Briar Chapel, LLC
1342 Briar Chapel Parkway
Chapel Hill, North Carolina 27516
Prepared By:
v MCIUM&CREED
v
1730 Varsity Drive, Suite 500
Raleigh, North Carolina 27606
Phone: [phone]
`\\aul+Illi+r�ai,,,
Fax: [phone]
�.0``�Z ..••••.....
,.
+
M&C Project No. 02735-0214
148
�9'•Z ?~
fMQ11E�.
H• � :
//1111111111111\\

PROJECT DESCRIPITON
The purpose of the project is to convert the existing Granite Mill bioretention cell into a
stormwater wetland to improve its ability to sustainably function as a BMP.
Based on monitoring the basin over time, and multiple attempts at corrective action, it appears
that, at this time, it will be more effective to convert the previously installed bioretention to a
stormwater wetland.
Based on other developments in the relative vicinity, and changes over time to the proposed
area layouts, stormwater that was originally intended to drain to the BMP are draining to
alternative measures. Therefore, the originally approved drainage and impervious areas are
somewhat reduced. Refer to drainage area map included with this package for clarification on
those drainage areas.
However, the proposed BMP is designed to treat runoff from the current drainage area.
Based on the conditions of the approved 401 Water Quality Certification, NCDENR-DWR 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 Granite Mill
Blvd. and connected lots currently treated by the bioretention cell will be treated by a
stormwater wetland designed per the latest version of NC DEQ's Minimum Design Criteria.
Calculations for this new facility is included in this package.
SITE DESCRIPTION
The project area is east of the intersection of Andrews Store Rd. and Granite Mill Blvd. The
existing bioretention cell serves as a stormwater BMP for approximately 6.97 acres of developed
land.
SOILS
The following soil description is a copy from the original narrative for the construction of Granite
Mill Boulevard, dated February 16, 2010:
According to the Chatham County Generalized Soil Survey, the majority of uplands within the
site are classified as Wedowee sandy loam, 2% to 6% slopes (WeB). Along the banks of the
stream, soils are classified as Wedowee sandy loam, 6% to 10% slopes (WeC). On the far eastern
portion of the site, the development encroaches into an area of Helena sandy loam, 2% to 6%
slopes (HeB).
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.
He(B) - Helena sandy loam soils are often found in piedmont uplands, along ridges,
through drainageways and at the heads of drainageways. Permeability is slow and the
soils are moderately well drained. Soils have a high shrink/swell potential. The seasonal

high water is perched and generally 1.5 to 2.5 feet below the surface from January
through April.
WETLAND DESIGN
The wetland for this project has been designed to remove 85% of the total suspended solids
entering from the surrounding drainage areas before discharging into the adjacent stream
buffers. The calculations provided with this package includes the area that is currently being
treated by the bioretention area. Treated runoff will be dissipated by a riprap outlet protection
device before entering any stream buffers.
Design parameters were taken from the BMP manual, DEQ's design supplement forms, and the
latest version of NC DEQ's Minimum Design Criteria for stormwater Control Measures.
BMP SUMMARY OF RESULTS
In order to meet the requirements of the development, the wetland has been designed based
on the existing conditions plus a 10% contingency to account for any increase in impervious
area in the drainage area.
MAINTENANCE CONSIDERATIONS
The property owner shall be responsible for periodic inspection and maintenance of all
permanent stormwater management devices and shall adhere to conditions agreed upon by
the executed Operation and Maintenance agreements included with this submittal. Any
measure that fails to function as intended shall be repaired immediately.
Granite
Mill Wetland
1 -yr
10 -yr
100 -yr
Pre -Development
5.51
19.22
37.42
Discharge cfs
Post-Development
Controlled
0.79
18.12
36.36
Discharge cfs
Peak Water
Surface
440.35'
441.06'
441.61 '
Elevation tt
MAINTENANCE CONSIDERATIONS
The property owner shall be responsible for periodic inspection and maintenance of all
permanent stormwater management devices and shall adhere to conditions agreed upon by
the executed Operation and Maintenance agreements included with this submittal. Any
measure that fails to function as intended shall be repaired immediately.

Maps

u 6
t

-'s
6—, " 00
SITE
ZA
jol-
' S
4
��
�' �C1� .,r �`Y'`_--r•--_� i.,�i, -.'4. ,,.� � ,` j �. `tip ,� �\ _�i�•-''f y� !f�(""" �....F
r 1 '--� i � ! _ _� _ � � �� `"'`„ � I �,,lr ' t rte'•,.., -
r
1✓ �I , , a r— �v S ..t
Copyright (C) 1998, Maptech. Inc.

'♦ -
\ APPROVED GRANITE MILL SIORETENTION AREA
(NCO WQ PROJECT Y05 -771v17)
- ) i POP 835- 8o ® APPROVED BIDREFENPON DRAINAW AREA
5-j � eeAcox RwceeLw 4V►
'♦ b / l - PROPOSED SrORMIrATER W nAND
`f \ \ DRAINACE AREA
s
/ I
\- \ ' APPROVED PHASE 11 WET FOND DR—AGE
\ s w Y� Y� im m m m ` Y� m � �� m m m�:iiii1im \ _ �, " AREA
—V v ✓IV / /' �\ l
CARDINAL RIDGE ROAD
op
_ -- r--- , - _ J _
♦ I I 1—J I-- t _ —� WAIL—CE TRAR- --� )`--/,��,
♦ �,—' — —
40
4W f
we
anB
`JII
.►�
�,�
DRAINAGE AREA , 1 I
33.10 ACRES
�b (NCDWQ PROJECT $05-732,19) / '•'� ,, i 5-'I ( » \
� J
) I , BMPY17 � 1
GRANITE MILL STORMWATER WETLAND , 1,
1 \ V \ NEW DRAINAGE AREA
I V 1 6.97 ACRES `� 'A , ,
i \ ,
—
1 GRANITE MILL STORMWATER WETLAND
_ -
to�
---- - - - aN�
--------
NORTH
��_�_ - _______ ______ - I \1
i
A& BRIAR CHAPEL DATE: FEBRUARY 8, 2019 SCALE
�`v>> 'IVl`�C7CIWL,D GRANITE MILL BLVD. STORMWATER WETLAND p� NO)., D2735 -Dass
4 HOM
CHATHAM COUNTY, NORTH CAROLINA DESIGNED 855 AS NOTED
1730 Varsity Drive, Suite 500 � cMECKFD GU VERTICAL:
(
Raleigh, North Carolina 27606 BRIAR C H A P E L PRO). MGR. CH, N/A
Phone: [phone], Fax: [phone] STORMWATER WETLAND
F-1222 by DRAINAGE AREA S,NrOSi PRELIMINARY DRAWING
.mcximcreed.com NMand COro MUNInFs NOT FOR CONSTRUCTION a ��

Granite Mill Stormwater
Wetland Design

STORMWATER WETLAND SIZING CALCULATIONS
Project Name
Briar Chapel - Granite Mill Wetland
Project Number
02735-0214
Date
February 6, 2019
3rd revision
2nd revision
1st revision

Stormwater Wetland Drainage Area Data
Project Briar Chapel - Granite Mill Wetland
Project No. 02735-0214
Date February 6, 2019
Total site area 303,601 square feet = 6.97 acres
Impervious areas
Drainage area to
Existing Proposed
s s
and
Change
s
Other Drainage
Existing
s
Area
Proposed
s
On-site buildings
0
49,899
49,899
0
0
On-site streets/parking
0
87,399
87,399
0
0
On-site Sidewalk
0
0
0
0
0
On-site Equipment
0
0
0
0
0
Contingency
0
13,730
13,730
0
0
Total Impervious
0
151,028
151,028
0
0
Non -impervious areas
Drainage
area to and Other Drainage Area
Existing
s
Proposed
s
Change Existing
s s
Proposed
s
On-site grass/landscape
0
152,573
152,573 0
0
On-site woods
303,601
0
-303,601 1 0
0
Total non -impervious
303,601
152,573
1 -151,028 1 0
10
Total Drainage Area 303,601 303,601 0
Percent Impervious 1 0.0 49.7 49.7
Notes:
2019.02.08.GMB Wetland Conversion.xls
BMP Drainage Area Data Page 2 of 5 Printed 2/7/2019 2:39 PM

Stormwater Wetland Runoff Volume Calculations
Project
Project No
Date
Drainage area
Impervious area
Rainfall depth
Percent Impervious
Briar Chapel - Granite Mill Wetland
02735-0214
February 6, 2019
303,601 square feet
151,028 square feet
1.00 inches
49.7 percent
R(v)=0.05+0.009*(Percent impervious)
Runoff coefficient - R(v) 0.50 in/in
Runoff volume=(Design rainfall)*(R(v))*(Drainage area)
Runoff volume 12.592.1 cubic feet
Notes:
2019.02.08.GMB Wetland Conversion.xls
Runoff Volume Calcs Page 3 of 5 Printed 2/7/2019 2:39 PM

Project
Project No.
Date
Stormwater Wetland Volume Calculations
Stage -Storage Data for Wetland - Temporary Pool
Briar Chapel - Granite Mill Wetland
02735-0214
February 6, 2019
Contour ID
Stage
Area
s . 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
439
0
13,740.0
0.315
13,740.0
0.3
0.0
0.0
0.0
0.0
440
1
21,103.0
0.484
21,103.0
0.2
17,421.5
0.4
17,421.5
0.4
440.62
1.62
22 310.0
0.512
22,310.0
0.0
13,458.0
0.3
30,879.5
0.7
441
2
23,098.0
0.530
23,098.0
0.0
8,627.5
0.2
39,507.1
0.5
442
3
25 127.0
0.577
25,127.0
0.0
24,112.5
0.6
63,619.6
0.8
443
4
27,191.0
0.624
27191.0
0.0
26159.0
0.6
89,778.6
1.2
2019.02.08.GMB Wetland Conversion.xls
Stage Storage (Temp Pool) Page 4 of 5 Printed 2/7/2019 2:39 PM

Stormwater Wetland Dewatering Time Calculations
Project Briar Chapel - Granite Mill Wetland
Project No. 02735-0214
Date February 6, 2019
Water quality treatment volume
Total treatment volume
Maximum head of water above dewatering hole
Driving head
Orifice coefficient
Diameter of each hole
Number of holes
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 =
12,592
cubic feet
17,421
cubic feet
1.00
feet
0.33
feet
0.60
2.25
inches
1
0.028 square feet
4.0 square inches
0.021 square feet
3.0 square inches
2.5 days
61.1 hours
3.5 days
84.5 hours
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)

Granite Mill Stormwater
Wetland Design

1S
Pre -Development
OSubcat Reach on Link1
J
2S
Post- Devk lopment
New Wetland Design

2019.02.08.GMB Wetland Routing Type 1124 -hr 1 -Inch Rainfall=1.00"
Prepared by McKim & Creed Printed 2/7/2019
HydroCAD@ 10.00-15 s/n 03870 @2015 HydroCAD Software Solutions LLC Page 6
Summary for Pond 3P: New Wetland Design
Inflow Area = 6.970 ac, 49.75% Impervious, Inflow Depth= 0.20" for 1 -Inch event
Inflow = 1.82 cfs @ 12.04 hrs, Volume= 0.115 of
Outflow = 0.05 cfs @ 19.91 hrs, Volume= 0.098 af, Atten= 97%, Lag= 472.2 min
Primary = 0.05 cfs @ 19.91 hrs, Volume= 0.098 of
Routing by Stor-Ind method, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs
Peak Elev= 439.22'@ 19.91 hrs Surf.Area= 15,370 sf Storage= 3,223 cf
Plug -Flow detention time= 878.2 min calculated for 0.097 of (85% of inflow)
Center -of -Mass det. time= 808.4 min ( 1,701.7 - 893.3 )
Volume Invert Avail.Storage Storage Description
#1 439.00' 89,794 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq -ft) (cubic -feet) (cubic -feet)
439.00 13,740 0 0
440.00 21,103 17,422 17,422
441.00 23,098 22,101 39,522
442.00 25,127 24,113 63,635
443.00 27,191 26,159 89,794
Device Routing Invert Outlet Devices
#1 Primary 434.83' 24.0" Round Culvert
L= 60.6' RCP, square edge headwall, Ke= 0.500
Inlet/ Outlet Invert= 434.83'/434.00' S=0.0137'/' Cc= 0.900
n=0.013 Concrete pipe, bends & connections, Flow Area= 3.14 sf
#2 Device 1 439.00' 2.2" Vert. Orifice/Grate C= 0.600
#3 Device 1 440.00' 12.0" W x 7.4" H Vert. Orifice/Grate C= 0.600
#4 Device 1 440.62' 48.0" x 48.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=0.05 cfs @ 19.91 hrs HW=439.22' (Free Discharge)
L =Culvert (Passes 0.05 cfs of 27.86 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.05 cfs @ 1.73 fps)
3--Orifice/Grate ( Controls 0.00 cfs)
=Orifice/Grate ( Controls 0.00 cfs)

2019.02.08.GMB Wetland Routing Type 1124 -hr 1 -Inch Rainfall=1.00"
Prepared by McKim & Creed Printed 2/7/2019
HydroCADO 10.00-15 s/n 03870 0 2015 HydroCAD Software Solutions LLC Page 7
2
0
Pond 3P: New Wetland Design
Hydrograph
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60
Time (hours)
■ Inflow
■ Primary

2019.02.08.GMB Wetland Routing Type 1124 -hr 1 -Yr Rainfall=2.96"
Prepared by McKim & Creed Printed 2/7/2019
HydroCAD® 10.00-15 s/n 03870 @2015 HydroCAD Software Solutions LLC Paae 8
Time span=5.00-60.00 hrs, dt=0.05 hrs, 1101 points
Runoff by SCS TR -20 method, UH=SCS, Weighted -CN
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Subcatchment 1S: Pre -Development Runoff Area=303,601 sf 0.00% Impervious Runoff Depth=0.69"
Tc=15.0 min CN=70 Runoff=5.51 cfs 0.402 of
Subcatchment 2S: Post -Development Runoff Area=303,601 sf 49.75% Impervious Runoff Depth=1.63"
Tc=10.0 min CN=86 Runoff=17.15 cfs 0.946 of
Pond 313: New Wetland Design Peak Elev=440.35' Storage=24,831 cf Inflow=17.15 cfs 0.946 of
Outflow=0.79 cfs 0.802 of
Total Runoff Area =13.939 ac Runoff Volume =1.348 of Average Runoff Depth =1.16"
75.13% Pervious =10.472 ac 24.87°/6 Impervious = 3.467 ac

2019.02.08.GMB Wetland Routing Type 1124 -hr 1 -Yr Rainfall=2.96"
Prepared by McKim & Creed Printed 2/7/2019
HydroCAD@ 10.00-15 s/n 03870 @2015 HydroCAD Software Solutions LLC Paae 9
Summary for Subcatchment 1S: Pre -Development
Runoff = 5.51 cfs @ 12.09 hrs, Volume= 0.402 af, Depth= 0.69"
Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs
Type II 24 -hr 1 -Yr Rainfall=2.96"
Area (sf) CN Description
303,601 70 Woods, Good, HSG C
303,601 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
15.0 Direct Entry,
Subcatchment IIS: Pre -Development
Hydrograph
61 I I ■Runoff
Type II 24 -hr
5 1 -Yr Rainfall -2.96"
Runoff Area=303,601 sf
4 Runoff Volume=0.402 of
Runoff Depth=0.69"
LL 3 Tc=15.0 min
CN=70
2
6 8 10 12 14 16 18 20 22 '214'"'216'"'218'"'310'"'312'"'314'"'316 318'"4'10 42 44-'4'16-'4''8-'5'10'''5-2 54 56 58 60
Time (hours)

2019.02.08.GMB Wetland Routing Type 1124 -hr 1 -Yr Rainfall=2.96"
Prepared by McKim & Creed Printed 2/7/2019
HydroCADO 10.00-15 s/n 03870 © 2015 HydroCAD Software Solutions LLC Page 10
Summary for Subcatchment 2S: Post -Development
Runoff = 17.15 cfs @ 12.02 hrs, Volume= 0.946 af, Depth= 1.63"
Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs
Type II 24 -hr 1 -Yr Rainfall=2.96"
Area (sf) CN Description
152,573
74 >75% Grass cover, Good, HSG C
151,028
98 Paved parking, HSG C
303,601
86 Weighted Average
152,573
50.25% Pervious Area
151,028
49.75% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.0 Direct Entry,
19
18
17
16
15
14
13
12
� 11
10
3 9
0
LL
7
5-
Subcatchment 2S: Post -Development
Hydrograph
Type II 24 -hr
1 -Yr Rainfall=2.96"
Runoff Area=303,601 sf
Runoff Volume=0.946 of
Runoff Depth=1.63"
Tc=10.0 min
CN=86
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60
Time (hours)
■ Runoff

2019.02.08.GMB Wetland Routing Type 1124 -hr 1 -Yr Rainfall=2.96"
Prepared by McKim & Creed Printed 2/7/2019
HydroCAD®10.00-15 s/n 03870 © 2015 HydroCAD Software Solutions LLC Page 11
Summary for Pond 3P: New Wetland Design
Inflow Area = 6.970 ac, 49.75% Impervious, Inflow Depth= 1.63" for 1 -Yr event
Inflow = 17.15 cfs @ 12.02 hrs, Volume= 0.946 of
Outflow = 0.79 cfs @ 13.64 hrs, Volume= 0.802 af, Atten= 95%, Lag= 97.5 min
Primary = 0.79 cfs @ 13.64 hrs, Volume= 0.802 of
Routing by Stor-Ind method, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs
Peak Elev= 440.35'@ 13.64 hrs Surf.Area= 21,792 sf Storage= 24,831 cf
Plug -Flow detention time= 789.9 min calculated for 0.801 of (85% of inflow)
Center -of -Mass det. time= 721.8 min ( 1,548.4 - 826.6)
Volume Invert Avail.Storage Storage Description
#1 439.00' 89,794 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq -ft) (cubic -feet) (cubic -feet)
439.00 13,740 0 0
440.00 21,103 17,422 17,422
441.00 23,098 22,101 39,522
442.00 25,127 24,113 63,635
443.00 27,191 26,159 89,794
Device Routing Invert Outlet Devices
#1 Primary 434.83' 24.0" Round Culvert
L= 60.6' RCP, square edge headwall, Ke= 0.500
Inlet/ Outlet Invert= 434.83'/ 434.00' S=0.0137'/' Cc= 0.900
n=0.013 Concrete pipe, bends & connections, Flow Area= 3.14 sf
#2 Device 1 439.00' 2.2" Vert. Orifice/Grate C= 0.600
#3 Device 1 440.00' 12.0" W x 7.4" H Vert. Orifice/Grate C= 0.600
#4 Device 1 440.62' 48.0" x 48.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=0.79 cfs @ 13.64 hrs HW=440.35' (Free Discharge)
L=Culvert (Passes 0.79 cfs of 32.14 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.14 cfs @ 5.39 fps)
3=Orifice/Grate (Orifice Controls 0.65 cfs @ 1.89 fps)
=Orifice/Grate ( Controls 0.00 cfs)

2019.02.08.GMB Wetland Routing Type 1124 -hr 1-YrRainfall=2.96"
Prepared by McKim & Creed Printed 2/7/2019
HydroCADO 10.00-15 s/n 03870 © 2015 HydroCAD Software Solutions LLC Page 12
1
1
1
1
1
1
1
1
H 1
1
3
O
LL
Pond 3P: New Wetland Design
Hydrograph
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60
Time (hours)
■ Inflow
■ Primary

2019.02.08.GMB Wetland Routing Type Il 24 -hr 10 -Yr Rainfall=5.18"
Prepared by McKim & Creed Printed 2/7/2019
HydroCAD® 10.00-15 s/n 03870 02015 HydroCAD Software Solutions LLC Page 13
Time span=5.00-60.00 hrs, dt=0.05 hrs, 1101 points
Runoff by SCS TR -20 method, UH=SCS, Weighted -CN
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Subcatchment 1S: Pre -Development Runoff Area=303,601 sf 0.00% Impervious Runoff Depth=2.17"
Tc=15.0 min CN=70 Runoff=19.22 cfs 1.261 of
Subcatchment 2S: Post -Development Runoff Area=303,601 sf 49.75% Impervious Runoff Depth=3.64"
Tc=10.0 min CN=86 Runoff=37.30 cfs 2.111 of
Pond 3P: New Wetland Design Peak Elev=441.06' Storage=40,957 cf Inflow=37.30 cfs 2.111 of
Outflow=18.12 cfs 1.957 of
Total Runoff Area = 13.939 ac Runoff Volume = 3.372 of Average Runoff Depth = 2.90"
75.13% Pervious =10.472 ac 24.87% Impervious = 3.467 ac

2019.02.08.GMB Wetland Routing Type Il 24 -hr 10 -Yr Rainfall=5.18"
Prepared by McKim & Creed Printed 2/7/2019
HydroCADO 10.00-15 s/n 03870 © 2015 HydroCAD Software Solutions LLC Paae 14
Summary for Subcatchment 1S: Pre -Development
Runoff = 19.22 cfs @ 12.08 hrs, Volume= 1.261 af, Depth= 2.17"
Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs
Type II 24 -hr 10 -Yr Rainfall=5.18"
Area (sf) CN Description
303,601 70 Woods, Good, HSG C
303,601 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
15.0 Direct Entry,
Subcatchment 1S: Pre -Development
Hydrograph
21-
20- 19 zz crs
19 Type II 24 -hr
18
17- 10 -Yr Rainfall=5.18"
15 Runoff Area=303,601 sf
13 Runoff Volume=1.261 of
Runoff Depth=2.17"
° '°
LL y. Tc=15.0 min
CN=70
1
0
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60
Time (hours)
■ Runoff

2019.02.08.GMB Wetland Routing Type 1124 -hr 10 -Yr Rainfall=5.18"
Prepared by McKim & Creed Printed 2/7/2019
HydroCADO 10.00-15 s/n 03870 © 2015 HydroCAD Software Solutions LLC Page 15
Summary for Subcatchment 2S: Post -Development
Runoff = 37.30 cfs @ 12.01 hrs, Volume= 2.111 af, Depth= 3.64"
Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs
Type II 24 -hr 10 -Yr Rainfall=5.18"
Area (sf) CN Descriotion
152,573
74 >75% Grass cover, Good, HSG C
151,028
98 Paved parking, HSG C
303,601
86 Weighted Average
152,573
50.25% Pervious Area
151,028
49.75% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.0 Direct Entry,
Subcatchment 2S: Post -Development
Hydrograph
40
38 37.30 cts
36- Type II 24 -hr
32 10 -Yr Rainfall=5.18"
30Runoff Area=303,601 sf
28-
26- Runoff Volume=2.111 of
24
22 --Runoff Depth=3.64"
20
U. 18
Tc=10.0 min
IL
16 CN=86
14
12
10
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60
Time (hours)
■ Runoff

2019.02.08.GMB Wetiand Routing Type Il 24 -hr 10 -Yr Rainfall=5.18"
Prepared by McKim & Creed Printed 2/7/2019
HydroCAD® 10.00-15 s/n 03870 @2015 HydroCAD Software Solutions LLC Page 16
Summary for Pond 3P: New Wetland Design
Inflow Area = 6.970 ac, 49.75% Impervious, Inflow Depth= 3.64" for 10 -Yr event
Inflow = 37.30 cfs @ 12.01 hrs, Volume= 2.111 of
Outflow = 18.12 cfs @ 12.15 hrs, Volume= 1.957 af, Atten= 51 %, Lag= 8.2 min
Primary = 18.12 cfs @ 12.15 hrs, Volume= 1.957 of
Routing by Stor-Ind method, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs
Peak Elev= 441.06'@ 12.15 hrs Surf.Area= 23,224 sf Storage= 40,957 cf
Plug -Flow detention time= 384.9 min calculated for 1.956 of (93% of inflow)
Center -of -Mass det. time= 347.0 min ( 1,150.7 - 803.7)
Volume Invert Avail.Storage Storage Description
#1 439.00' 89,794 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq -ft) (cubic -feet) (cubic -feet)
439.00 13,740 0 0
440.00 21,103 17,422 17,422
441.00 23,098 22,101 39,522
442.00 25,127 24,113 63,635
443.00 27,191 26,159 89,794
Device Routing Invert Outlet Devices
#1 Primary 434.83' 24.0" Round Culvert
L= 60.6' RCP, square edge headwall, Ke= 0.500
Inlet/ Outlet Invert= 434.83'/ 434.00' S=0.0137'/' Cc= 0.900
n=0.013 Concrete pipe, bends & connections, Flow Area= 3.14 sf
#2 Device 1 439.00' 2.2" Vert. Orifice/Grate C= 0.600
#3 Device 1 440.00' 12.0" W x 7.4" H Vert. Orifice/Grate C= 0.600
#4 Device 1 440.62' 48.0" x 48.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=18.02 cfs @ 12.15 hrs HW=441.06' (Free Discharge)
t- =Culvert (Passes 18.02 cfs of 34.59 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.18 cfs @ 6.76 fps)
3=Orifice/Grate (Orifice Controls 2.56 cfs @ 4.15 fps)
=Orifice/Grate (Weir Controls 15.29 cfs @ 2.17 fps)

2019.02.08.GMB Wetland Routing Type 1124 -hr 10 -Yr Rainfall=5.18"
Prepared by McKim & Creed Printed 2/7/2019
HydroCADO 10.00-15 s/n 03870 © 2015 HydroCAD Software Solutions LLC Page 17
Pond 3P: New Wetland Design
Hydrograph
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60
Time (hours)
FE -1 n —fI o -w
■ Primary

2O19.O2.08.GMB Wetland Routing Type Il 24 -hr 100 -Yr Rainfall=7.67"
Prepared by McKim & Creed Printed 2/7/2019
HydroCAD® 10.00-15 s/n 03870 © 2015 HydroCAD Software Solutions LLC Page 18
Time span=5.00-60.00 hrs, dt=0.05 hrs, 1101 points
Runoff by SCS TR -20 method, UH=SCS, Weighted -CN
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Subcatchment 1S: Pre -Development Runoff Area=303,601 sf 0.00% Impervious Runoff Depth=4.18"
Tc=15.0 min CN=70 Runoff=37.42 cfs 2.429 of
Subcatchment 2S: Post -Development Runoff Area=303,601 sf 49.75% Impervious Runoff Depth>6.00"
Tc=10.0 min CN=86 Runoff=60.04 cfs 3.486 of
Pond 3P: New Wetland Design Peak Elev=441.61' Storage=53,905 cf Inflow=60.04 cfs 3.486 of
Oufflow=36.36 cfs 3.326 of
Total Runoff Area =13.939 ac Runoff Volume = 5.915 of Average Runoff Depth = 5.09"
75.13% Pervious =10.472 ac 24.870/6 Impervious = 3.467 ac

2019.02.08.GMB Wetland Routing Type Il 24 -hr 100 -Yr Rainfall=7.67"
Prepared by McKim & Creed Printed 2/7/2019
HydroCAD®10.00-15 s/n 03870 @2015 HydroCAD Software Solutions LLC Page 21
Summary for Pond 3P: New Wetland Design
[82] Warning: Early inflow requires earlier time span
Inflow Area = 6.970 ac, 49.75% Impervious, Inflow Depth > 6.00" for 100 -Yr event
Inflow = 60.04 cfs @ 12.01 hrs, Volume= 3.486 of
Outflow = 36.36 cfs @ 12.11 hrs, Volume= 3.326 af, Atten= 39%, Lag= 6.2 min
Primary = 36.36 cfs @ 12.11 hrs, Volume= 3.326 of
Routing by Stor-Ind method, Time Span= 5.00-60.00 hrs, dt= 0.05 hrs
Peak Elev= 441.61'@ 12.11 hrs Surf.Area= 24,329 sf Storage= 53,905 cf
Plug -Flow detention time= 254.9 min calculated for 3.326 of (95% of inflow)
Center -of -Mass det. time= 227.8 min ( 1,018.3 - 790.5 )
Volume Invert Avail.Storage Storage Description
#1 439.00' 89,794 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq -ft) (cubic -feet) (cubic -feet)
439.00 13,740 0 0
440.00 21,103 17,422 17,422
441.00 23,098 22,101 39,522
442.00 25,127 24,113 63,635
443.00 27,191 26,159 89,794
Device Routing Invert Outlet Devices
#1 Primary 434.83' 24.0" Round Culvert
L= 60.6' RCP, square edge headwall, Ke= 0.500
Inlet/ Outlet Invert= 434.83'/434.00' S=0.0137'/' Cc= 0.900
n= 0.013 Concrete pipe, bends & connections, Flow Area= 3.14 sf
#2 Device 1 439.00' 2.2" Vert. Orifice/Grate C= 0.600
#3 Device 1 440.00' 12.0" W x 7.4" H Vert. Orifice/Grate C= 0.600
#4 Device 1 440.62' 48.0" x 48.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
Primary OutFlow Max=36.32 cfs @ 12.11 hrs HW=441.60' (Free Discharge)
-=Culvert (Inlet Controls 36.32 cfs @ 11.56 fps)
2=Orifice/Grate (Passes < 0.20 cfs potential flow)
3=Orifice/Grate (Passes < 3.36 cfs potential flow)
=Orifice/Grate (Passes < 50.43 cfs potential flow)

2019.02.08.GMB Wetland Routing Type Il 24 -hr 100 -Yr Rainfall=7.67'
Prepared by McKim & Creed Printed 2/7/2019
HydroCADO 10.00-15 s/n 03870 © 2015 HydroCAD Software Solutions LLC Page 22
q
v
3
0
LL
Pond 3P: New Wetland Design
Hydrograph
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60
Time (hours)
■ Inflow
■ Primary

• ' " • •
DATE: 2/06/2019
DESIGNED BY:
ENS
PROJECT NAME: Briar Chapel - Granite Mill Wetland
PROJECT NO:
CHECKED BY
PROJECT LOCATION: Chatham County, NC
12735-0214
GCA
Storm Outlet Structure
Structure= GMB Wet Out
Quo/Qfull =
0.69
Size= 24 in
V/Vfull =
1.07
Qio = 18.12 cfs
V =
9.0
fps
Qfull = 26.43 cfs
Vfull = 8.41 fps
From Fig. 8.06.b.1:
Zone
=
2
From Fig. 8.06.b.2:
D5o
=
8
in
DMAx
=
12
in
Riprap Class
=
B
Apron Thickness
=
22
in
3
Apron Length
=
12.0
ft
Length
Apron Width = 3 x Dia
=
6.0
ft
Storm Outlet Structure
Structure= GMB Wet In
Q10/Qfull =
0.83
Size= 36 in
V/Vfull =
1.12
Q 1 o = 37.30 cfs
V =
7.1
fps
Qfull = 45.16 cfs
Vfull = 6.39 fps
From Fig. 8.06.b.1:
Zone
=
2
From Fig. 8.06.b.2:
D50
=
8
in
DMAx
=
12
in
Riprap Class
=
B
_
Apron Thickness
=
22
in
J
Apron Length
=
18.0
ft
Length
Apron Width = 3 x Dia
=
9.0
ft