20050732 Ver 19_Stormwater Info_20110119

I I
EcoEngineering
A division of The Joh ams Company, Inc.
LETTER OF TRANSMITTAL b5
t
To: Ms. Laurie Dennison/Mr. Joseph Gyarafi, PE Date
NC DENR/Division of Water Qualitv
401 Express Permitting Unit
512 N. Salisbury Street (Archdale Building)
9m Floor. Room #942W
Raleigh, North Carolina 27604
Re: Briar Chapel - Phase 4
am sendina you the followina item(s)-
COPIES DATE NO. DESCRIPTION
1 Express Revew Application Fee - Check for $1,000
2 Express Review SW Management Plan Application
2 Bioretention Area Final Design Calculations Booklet
2 Bioretention Area Construction Drawings
2 BMP Supplement Forms and O&M Agreements
1 Data CD of full size plans in TIFF format
These are transmitted as checked below:
? As requested ? For your use
® For approval ?
? For review and comment ? o "71 n
Remarks: Please call with any questions/comments.
JAN 11 4
MIG•WATEK Tf
$YOW AMfllliA11G1
Job No.
4
Januarv 19. 2011
E Y-9 o 5- Dl 3 a. U11
** HAND DELIVER **
NEW-09002
Copy to:
Signed:
? Finch, PE
anager
FOR INTERNAL USE ONLY
® Copy Letter of Transmittal Only to File
? Copy Entire Document to File
2905 Meridian Parkway, Durham, North Carolina 27713
PO Box 14005, RTP, North Carolina 27709

OFFICE USE ONLY
Date Received Fee Paid Permit Number(s)
State of North Carolina
Department of Environment and Natural Resources
Division of Water Quality 401/Wetlands Unit
EXPRESS REVIEW PROGRAM STORMWATER MANAGEMENT APPLICATION FORM
This form may be photocopied for use as an original
1. GENERAL INFORMATION
1. APPLICANT'S NAME (specify the name of the corporation, individual, etc. who owns the project):
NNP - Briar Chapel, LLC
2. OWNER/SIGNING OFFICIAL'S NAME AND TITLE (person legally responsible for facility and
compliance): Mr. William Mumford, PE
3. OWNER MAILING ADDRESS (for person listed in item 2 above):
16 Windy Knoll Circle
Chapel Hill, NC 27516
4. OWNER ADDITIONAL CONTACT INFORMATION:
Phone: [phone] Fax: [phone] Email: [e-mail]
5. PROJECT NAME (subdivision, facility, or establishment name - should be consistent with project name
on plans, specifications, letters, inspection and maintenance agreements, etc.):
Briar Chapel - Phase 4
6. PROJECT LOCATION:
Street Address: US HWY 15-501 (west side) between Manns Chapel Rd & Andrews Store Rd
City: County: Chatham State: NC Zip Code:
Latitude: 35'49'29" Longitude: 79°05' 51
7. DIRECTIONS TO PROJECT SITE (from nearest major intersection):
From intersection of US HWY 15-501 and US HWY 64, go north on US HWY 15-501. Approximately 5,000 feet
north of the intersection of US HWY 15-501 and Andrews Store Road, the project entrance will be on the left.
8. CONTACT PERSON (who can answer stormwater-related questions about the project):
Name: Jeremy Finch, PE Company: EcoEngineering
Phone: [phone] Fax: [phone] Email: jfinchgecoengr.com
1/2009 Version 1.1 Page 1 of 5
H. PERMIT INFORMATION
1. THE PROJECT IS (check one): ? NEW ? A RENEWAL A MODIFICATION
2. OTHER JURISDICTIONS:
Which local government(s) has jurisdiction over the project (e.g. Town of Cary or Johnston County)?:
Chatham County
3. STORMWATER MANAGEMENT PROGRAM
Check all of the state-approved stormwater management programs (implemented by either the State or
local government) that apply to your project:
?X Phase It Post Construction ?X Water Supply Watershed ? Neuse or Tar-Pamlico NSW
? Randleman WSWS ? USMP ? Coastal Counties ? HQW ? ORW
4. PERMIT HISTORY (renewal or modification requests must complete this item):
Existing DWQ Permit Number:EXP 05-0732v18 Date issued: 10/08/10
5. PROJECT TYPE (check one): ? Low Density* ?X High Density*
* Low Density projects shall be under 24% Impervious with only vegetated stormwater conveyances. A
curb and gutter or pipe system for stormwater conveyance shall result in reclassification of project as
High Density even if below 24%, except when pipes are used for road or driveway crossing purposes.
6. ADDITIONAL PROJECT REQUIREMENTS (check all that apply):
? CAMA Major ?X Sedimentation/Erosion Control ?X NPDES Stormwater
?X 404/401 Permit ? Non-404 Jurisdictional Permit ? Other:
Note: Information on required state permits can be obtained by contacting the Customer Service Center at
1-877-623-6748
III. PROJECT INFORMATION
1. STORMWATER TREATMENT METHODS (Describe briefly how stormwater will be treated):
Under the existing stormwater management plan approval for Phase 4 of the Briar Chapel development, 6 wet pond
BMP's serve as the primary water quality treatment devices. The majority of the single-family residential lots were
shown to be treated by a wet pond BMP. To allow more flexibility in the lot grading, this permit modification
proposes to install a bioretention area to provide water quality treatment for several lots that were previously permitted
to be treated by a wet pond (but will now be treated by the bioretention area).
Important Note: attach a detailed narrative (one to two pages) describing stormwater management for the
project.
2. RIVER BASIN/STREAM INFORMATION
a. Stormwater runoff from this project drains to which River Basin?: Cape Fear River Basin
b. Nearest named stream: Pokeberry Creek
c. Water quality classification of nearest named stream: WS-IV; NSW
1/2009 Version 1.1 Page 2 of 5
3. TOTAL PROJECT AREA: I Approx 174 (acres)
4. PROJECT BUILT UPON AREA: I Approx 35 %
5. DRAINAGE AREAS (How many drainage areas does the project have?): i bioretention area
Complete the following information for each drainage area. If there are more than two drainage areas in the
project, attach an additional sheet with the information for each area provided in the same format as below.
Basin Information Drainage Area 1 Drainage Area 2
Receiving Stream Name Pokeberry Creek
Receiving Stream Class WS-IV; NSW
Drainage Area 42,233 SF
Existing Impervious* Area N/A
Proposed Impervious*Area 15,700 SF
% Impervious* Area (total) 37.2%
Impervious* Surface Area Determination (Breakdown)
Impervious* Surface Area Drainage Area 1 Drainage Area 2
On-site Buildings 15,700 SF (RESID LOTS)
On-site Streets N/A
On-site Parking N/A
On-site Sidewalks N/A
Other on-site N/A
Off-site N/A
Total: 15,700 SF Total:
* Impervious area is defined as the built upon area including, but not limited to, buildings, roads, parking
areas, sidewalks, gravel areas, etc.
6. EXPLAIN HOW THE OFF-SITE IMPERVIOUS AREA WAS DERIVED:
N/A
IV. DEED RESTRICTIONS AND PROTECTIVE COVENANTS
Deed restrictions and protective covenants are required to be recorded for all subdivisions, outparcels and
future development draining to the proposed stormwater management devices prior to the sale of any lot. If
applicable, please complete and submit a copy of the deed restrictions and protective covenants along with
your application.
1/2009 Version 1.1 Page 3 of 5
V. SUPPLEMENT FORMS
1. The applicable stormwater management supplement form(s) listed below must be submitted for each
BMP specified for this project. The most current form(s) located on the 401/wetlands unit website at
http://h2o.enr.state.nc.us/su/bmp forms.htm must be used. Please include both the Design Summary and
the Required Items Checklist along with all required items and supporting design calculations.
(Check the supplement forms that will be required for your project):
?X Bioretention Supplement ? Level Spreader/Filter Strip/Restored Buffer
Supplement
? Dry Detention Supplement
? Grassed Swale Supplement ? Sand Filter Supplement
? Infiltration Basin Supplement ? Stormwater Wetland Supplement
? Infiltration Trench Supplement ? Wet Detention Supplement
VI. SUBMITTAL REQUIREMENTS
Only complete application packages will be accepted and reviewed by the Division of Water Quality (DWQ).
A complete package includes all of the items listed below. The complete application package should be
submitted to the DWQ Central Office.
1. Please indicate that you have provided the following required information by initialing in the space
provided next to each item.
Initials
• Original and two copies of the Express Review Stormwater Management Application
• Signed and Notarized Inspection and Maintenance Agreement
• Three copies of the applicable Supplement Form(s) for each BMP J
• Application processing fee (payable to DWQ)
• Detailed narrative description of stormwater treatment/management
• Three copies of plans and specifications, including: J
? Development/Project name
? Engineer and firm
? Legend
? North arrow
? Scale
? Revision number & date
? Mean high water line
? Dimensioned property/project boundary
? Location map with named streets or NCSR numbers
? Original contours, proposed contours, spot elevations, finished floor elevations
? Details of roads, drainage features, collection systems, and stormwater control measures
? Wetlands and streams delineated, or a note on plans that none exist
? Existing drainage (including off-site), drainage easements, pipe sizes, runoff calculations
? Drainage areas delineated
? Vegetated buffers (where required)
1/2009 Version 1.1 Page 4 of 5
VII. AGENT AUTHORIZATION
If you wish to designate authority to another individual or firm so that they may provide information on your
behalf, please complete this section.
1. DESIGNATED AGENT (individual or firm): EcoEngineering
2. MAILING ADDRESS:
PO Box 14005
RTP, NC 27709
Phone: [phone] Fax: [phone]
VIII. APPLICANT'S CERTIFICATION
1, (print or type name of person listed in General Information, item 2)
P'?Ut-?Fp? 17 , certify that the information included on this application form is, to
the best of my knowledge, correct and that the project will be constructed in conformance with the approved
plans, that the required deed restrictions and protective covenants (if applicable) will be recorded, and that the
proposed project complies with the requirements of 15A NCAC 2H .1000.
Signature: 14/ ?T-- _ Date: / Z -Zo . 7a 10
a35l _ V r4-4P • is etAfL Gj4pe%-, u..C
1/2009 Version l.1 Page 5 of 5
'S[
BRIAR CHAPEL - PHASE 4
Final Stormwater Management Facility Design - Bioretention Area
General Description
Located off of US Highway 15-501, north of Andrews Store Road and south of Mann's Chapel Road in
Chatham County, NC is the proposed development known as Briar Chapel. Phase 4 of the proposed
development is approximately 174-acres and will consist of the construction of single-family lots, a
clubhous memty center, along with the associated utility, parking, and roadway infrastructure.
1W -
The overall proposed Briar Chapel development is located within the Cape Fear River Basin, and
drains to a stream (Pokeberry Creek) classified as Water Supply IV (WS-IV), and Nutrient Sensitive
Waters (NSW). As a result of the proposed development exceeding the maximum allowable limit for
stream impacts, an individual permit issued by The United States Army Corps of Engineers (USACE)
was required (Clean Water Act Section 404 permit). Also, a Clean Water Act Section 401 Water
Quality Certification from NCDWQ was attached to the individual permit. Under the 401 Water
Quality Certification issued by NCDWQ, the proposed site will be required to comply with the
following stormwater management requirements:
1. A. final written stormwater management plan for each subwatershed (including signed and
notarized Operation and Maintenance agreements) shall be submitted to the 401 Oversight
and Express Permitting Unit. The stormwater management plan maybe submitted to DWQ
in phases for written approval as long as no impact to wetlands or streams occur in that
phase until written approval is received from DWQ.
2. The stormwater plans shall utilize constructed wetlands, bioretention areas, wet ponds
followed b_y Forested filter strips and similar best management practices designed to remove
nutrients. The stormwater management plan mast include plans, specifications, and
worksheets.for stormwater management facilities that are appropriate for the surface water
classification and designed to remove at least 85% TSS according to the most recent
version of the NCDENR Stormwater Best Management Practices Manual.
3. For low densitv areas of the project with low impervious surface area, engineered
stormwater management facilities are not expected. For these areas of lower impervious
area, similar best management practices that remove nutrients such as grassed swales and
vegetated riparian buffers should be sufficient rather than more intensive engineered
stormwater devices such as constructed wetlands.
In addition to the above DWQ stormwater requirements, the following stormwater quality and quantity
items are required per Section 8.3 ("Stormwater Controls") of the Chatham County Compact
Communities Ordinance:
1. Control and treat the first inch of runoff from the project site and from any offsite drainage
routed to an on-site control structure. Ensure that the draw down time for this treatment
volume is a minimum o/. forty eight (48) hours and a maximum of one hundred and twenty
(120) hours.
2. Maintain the discharge rate for the treatment volume at or below the pre-development
discharge rate for the 1-year. 24-hour storm.
To satisfy these stormwater requirements, Phase 4 of the Briar Chapel development is currently
permitted with DWQ to be treated via water quality ponds with preformed scour hole/level spreader
outlets that will provide sheet flow of the I" runoff volume into the existing stream buffers. The
existing stream buffers downstream of these facilities will be utilized as forested filter strips. Lots
#349-#353 were shown in the current DWQ permit to be treated by water quality pond #2. However,
due to site topography constraints, these lots (when developed) will be difficult to direct to water
quality pond #2. As a result, a bioretention area is proposed behind lot #353 that is designed to capture
and treat stormwater runoff from half of lots #349-350 and all of lots 9351-353.
Permit Number:
(to be provided by DWQ)
O??F W ATF9pG
ATA ti
WDENR
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
BIORETENTION CELL SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part III) must be printed, filled out and submitted along with all of the required information.
I. PROJECT INFORMATION
Project name Briar Chapel - Phase 4
Contact name Jeremy Finch, PE
Phone number 919-361-5000
Date January 5, 2011
Drainage area number To Bioretention Area
I. DESIGN INFORMATION
Site Characteristics
Drainage area 42,233 ft2
Impervious area 15,700 ft2
Percent impervious 37.2% %
Design rainfall depth 1.0 inch
Peak Flow Calculations
Is pre/post control of the 1-yr, 24-hr peak flow required?
1-yr, 24-hr runoff depth
1-yr, 24-hr intensity
Pre-development 1-yr, 24-hr peak flow
Post-development 1-yr, 24-hr peak flow
Pre/Post 1-yr, 24-hr peak control
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
Cell Dimensions
Ponding depth of water
Ponding depth of water
Surface area of the top of the bioretention cell
Length:
Width:
-or- Radius
Media and Soils Summary
Drawdown time, ponded volume
Drawdown time, to 24 inches below surface
Drawdown time, total:
In-situ soil
Soil permeability
Planting media soil:
Soil permeability
Soil composition
% Sand (by volume)
% Fines (by volume)
% Organic (by volume)
N - See Note (Y or N) 4 NOV
N/A in
N/A in/hr
N/A ft3/sec
N/A ft3/sec
#VALUE! ft3/sec
1,354.0 ft3
1,600.0 ft3 OK
N/A ft3
N/A ft3
N/A ft3
#VALUE!ft3
N/A ft3
9 inches OK
0.75 ft
1,857.0 ft2 OK
51 ft OK
45 ft OK
ft
4.5 hr OK
16.5 hr OK
21 hr
Not Known in/hr OK
2.00 in/hr OK
PKE A*T twafdw nr? Fk"00 61y
qo l tn?- a;g-T $? I S ?Rc50
Y COA-m wn cawr-i
#VALUE!
85-88% Sand should be -85-88%
8-12% Fines should be -8-12%
3-5% Organic should be -3-5%
Total: 0%
Phosphorus Index (P-Index) of media 30 (unitless) OK
Form SW401-Bioretention-Rev.8
June 25. 2010
Parts I and It. Design Summary, Page 1 of 2

Basin Elevations
Temporary pool elevation
Type of bioretention cell (answer "Y" to only one of the two
following questions):
Is this a grassed cell?
Is this a cell with trees/shrubs?
Planting elevation (top of the mulch or grass sod layer)
Depth of mulch
Bottom of the planting media soil
Planting media depth
Depth of washed sand below planting media soil
Are underdrains being installed?
How many clean out pipes are being installed?
What factor of safety is used for sizing the underdrains? (See
BMP Manual Section 12.3.6)
Additional distance between the bottom of the planting media and
the bottom of the cell to account for underdrains
Bottom of the cell required
SHWT elevation
Distance from bottom to SHWT
Internal Water Storage Zone (IWS)
Does the design include IWS
Elevation of the top of the upturned elbow
Separation of IWS and Surface
Planting Plan
Number of tree species
Number of shrub species
Number of herbaceous groundcover species
Additional Information
Does volume in excess of the design volume bypass the
bioretention cell?
Does volume in excess of the design volume flow evenly distributed
through a vegetated filter?
What is the length of the vegetated filter?
Does the design use a level spreader to evenly distribute flow?
Is the BMP located at least 30 feet from surface waters (50 feet if
SA waters)?
Is the BMP localed at least 100 feet from water supply wells?
Are the vegetated side slopes equal to or less than 3:1?
Is the BMP located in a proposed drainage easement with access
to a public Right of Way (ROW)?
Inlet velocity (from treatment system)
Is the area surrounding the cell likely to undergo development in
the future?
Are the slopes draining to the bioretention cell greater than 20%?
Is the drainage area permanently stabilized?
Pretreatment Used
(Indicate Type Used with an "X" in the shaded cell)
Gravel and grass
(flinches gravel followed by 3-5 ft of grass)
Grassed swale
Forebay
Other
Form SW401-Bioretention-Rev.8
June 25, 2010
Permit Number:
(to be provided by DWQ)
433.75 fmsl
Y (Y or N) OK
(Y or N)
433 fmsl
N/A inches Insufficient mulch depth, unless installing grassed cell.
431 fmsl
2ft
n111ft
Y (Y or N)
12 OK
10 OK
1ft
429.67 fmsl
427.63 fmsl
2.04 ft OK
N (Y or N)
fmsl
433 ft
Grassed Cell
Grassed Cell
Grassed Cell #VALUE!

Y (Y or N) OK
N (Y or N) Excess volume must pass through filter.
N/A ft
N (Y or N) Show how flow is evenly distributed.
Y (Y or N) OK
Y (Y or N) OK
Y (Y or N) OK
Y (Y or N) OK
9.19 ft/sec Insufficient inlet velocity unless energy dissipating devices are
being used.
N (Y or N) OK
N (Y or N) OK
Y (Y or N) OK
OK
Parts I and II. Design Summary, Page 2 of 2
Permit No:
(to be assigned by DWQ)
IIL 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.
"Sf 131 "ro 03 1. Plans (1" - 50' or larger) of the entire site showing:
Sw Z Ex?t)&r- Design at ultimate build-out,
?N (LE(?y2'? Off-site drainage (if applicable),
Delineated drainage basins (include Rational C coefficient per basin),
Cell dimensions,
Pretreatment system,
High flow bypass system,
Maintenance access,
Recorded drainage easement and public right of way (ROW),
Clean out pipe locations,
Overflow device, and
Boundaries of drainage easement.
7F BI TO 43 2. Plan details (1" = 30' or larger) for the bioretention cell showing:
Cell dimensions
Pretreatment system,
High flow bypass system,
Maintenance access,
Recorded drainage easement and public right of way (ROW),
Design at ultimate build-out,
Off-site drainage (if applicable),
Clean out pipe locations,
Overflow device, and
Boundaries of drainage easement.
Indicate the P-Index between 10 and 30
?0 Q3 3. Section view of the bioretention cell (1" = 20' or larger) showing:
Side slopes, 3:1 or lower
Underdrain system (if applicable), and
Bioretention cell layers [ground level and slope, pre-treatment, ponding depth, mulch depth, fill media
depth, washed sand, filter fabric (or choking stone if applicable), #57 stone, underdrains (if applicable),
SHWT level(s), and overflow structure]
3 F S rnf. w?° 4. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. The
fle" Pw5 results of the soils report must be verified in the field by DWQ, by completing & submitting the soils
POA090 investigation request form. County soil maps are not an acceptable source of soils information. All
f So16s elevations shall be in feet mean sea level (fmsl). Results of soils tests of both the planting soil and the in
PLOAT Nor situ soil must include:
Qwofko- -Soil permeability,
5Nt/ ?? Soil composition (% sand, % fines, % organic), and
rift*- ow&K P-index.
"
'
d 5. A detailed planting plan (1
= 20
or larger) prepared by a qualified individual showing:
A variety of suitable species,
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.
dr 6. A construction sequence that shows how the bioretention cell will be protected from sediment until the
entire drainage area is stabilized.
r7R? 7. The supporting calculations (including underdrain calculations, if applicable).
Sb`- 8. A copy of the signed and notarized inspection and maintenance (I&M) agreement.
sR 9. A copy of the deed restriction.
Form SW401-Bioretention-Rev.7 Part III, Page 1 of 1
t
Permit Number:
(to be provided by DYVQ)
Drainage Area Number:-__________
Bioretention 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 operation and maintenance procedures:
- Immediately after the bioretention cell is established, the plants will be watered
twice weekly if needed until the plants become established (commonly six
weeks).
- Snow, mulch or any other material will NEVER be piled on the surface of the
bioretention cell.
- Heavy equipment will NEVER be driven over the Bioretention cell.
- Special care will be taken to prevent sediment from entering the bioretention cell.
- Once a year, a soil test of the soil media will be conducted.
After the bioretention cell is established, I will inspect it 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 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 problems: How I will remediate the problem:
The entire BMP Trash/ debris is resent. Remove the trash/debris.
The perimeter of the Areas of bare soil and/or Regrade the soil if necessary to
bioretention cell 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.
The inlet device: pipe, The pipe is clogged (if Unclog the pipe. Dispose of the
stone verge or swale applicable). sediment off-site.
The pipe is cracked or Replace the pipe.
otherwise damaged (if
applicable).
Erosion is occurring in the Regrade the swale if necessary to
swale (if applicable). smooth it over and provide erosion
control devices such as reinforced
turf matting or riprap to avoid
future problems with erosion.
Stone verge is clogged or Remove sediment and clogged
covered in sediment (if stone and replace with clean stone.
applicable).
Form SW401-Bioretention O&M-Rev.3
Page 1 of 4
BMP element:
The pretreatment area
The bioretention cell:
vegetation
The bioretention cell:
soils and mulch
Potential problems:
Flow is bypassing
pretreatment area and/or
gullies have formed.
Sediment has accumulated to
a depth greater than three
inches.
Erosion has occurred.
Weeds are present.
Best professional practices
show that pruning is needed
to maintain optimal plant
health.
Plants are dead, diseased or
dying.
Tree stakes/wires are present
six months after planting.
Mulch is breaking down or
has floated away.
Soils and/or mulch are
clogged with sediment.
An annual soil test shows that
p1 l has dropped or heavy
metals have accumulated in
the soil media.
How I will remediate the problem:
Regrade if necessary to route all
flow to the pretreatment area.
Restabilize the area after grading.
Search for the source of the
sediment and remedy the problem if
possible. Remove the sediment and
restabilize the pretreatment area.
Provide additional erosion
protection such as reinforced turf
matting or riprap if needed to
prevent future erosion problems.
Remove the weeds, preferably by
hand.
Prune according to best professional
practices.
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 a soil test indicates
it is necessary.
Remove tree stake/wires (which
can kill the tree if not removed).
Spot mulch if there are only random
void areas. Replace whole mulch
layer if necessary. Remove the
remaining much and replace with
triple shredded hard wood mulch at
a maximum depth of three inches.
Determine the extent of the clogging
- remove and replace either just the
top layers or the entire media as
needed. Dispose of the spoil in an
appropriate off-site location. Use
triple shredded hard wood mulch at
a maximum depth of three inches.
Search for the source of the
sediment and remedy the problem if
possible.
Dolomitic lime shall be applied as
recommended per the soil test and
toxic soils shall be removed,
disposed of properly and replaced
with new planting media.
Form SW441-13ioreteittion 0&M-Rev.3 Page 2 of 4
BMP element: Potential problems-, How 1 will remediate the problem:
The underdrain system Clogging has occurred. Wash out the underdrain system.
(if applicable)
The drop inlet Clogging has occurred. Clean out the drop inlet. Dispose of
the sediment off-site.
The drop inlet is damaged Repair or replace the drop inlet.
The receiving water Erosion or other signs of Contact the NC Division of Water
damage have occurred at the Quality 401 Oversight Unit at 919-
outlet. 733-1786.
Dorm SW401-Bioretention O&M-Rev.3 Page 3 of 4
Permit Number:
(to be provided by DWQ)
I acknowledge and agree by my signature below that I am responsible for the
performance of the maintenance procedures listed above. I agree to notify DWQ of any
problems with the system or prior to any changes to the system or responsible party.
Project name:Briar Chapel - Phase 4
BMP drainage area number:Bioretention Area
Print name:
Title: AOxsisTR-t4? V%(- =- P¢ -SIDt T _.__
Address: 1 k.IV40 V444=-L.l G.t2e.? 1G u? ??L 2?Si4
Phone: [phone]
Signature: x,[,14, . V '7v? - -
Date: 1Z- so -201 b
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president.
I, GCS i f I'SDh , a Notary Public for the State of
VY Latb k yta_, County of 1. f Clc- len b , do hereby certify that
1.i9 i 1) c0.m mWMfOrd personally appeared before me this J-6
day of.., IDer lae , --2-61 b , and acknowledge the due execution of the
forgoing bioretention maintenance requirements. Witness my hand and official seal,
SEAL
My commission expires 311 12
Form SW401-Bioretention I&M-Rev. 2 Page 4 of 4
,JAN 1 9 2011
BOOK 15 0 4 PAGE 0 878
Prepared by / Upon recording,
please return to:
1o Anne P. Stubblefield
Hyatt & Stubblefield, P.C.
1200 Peachtree Center, South Tower
225 Peachtree Street, N.E.
Atlanta, GA 30303
STATE OF NORTH CAROLINA
COUNTY OF CHATHAM
FILED
CHATHAM COUNTY NC
TREVA B. SEAGROVES
REGISTER OF DEEDS
FILED Mar 16, 2010
AT . 04:02:59 pm
BOOK 01504
START PAGE 0878
END PAGE 0883
INSTRUMENT # 02340
EXCISE TAX (None)
NOTE TO CLERK: Please Cross-Reference to:
Declaration at Book 1372
Page 884
Community Covenant at Book 1372
Page 996
SUPPLEMENTAL DECLARATION
OF COVENANTS, CONDITIONS AND RESTRICTIONS AND
SUPPLEMENT TO THE COMMUNITY COVENANT
FOR
BRIAR CHAPEL
(PHASE 4, SEC Ioh 4)
This Supplemental Declaration of Covenants, Conditions and Restrictions and
Supplement to the Community Covenant for Briar Chapel ("Supplement") is made by NNP-
Briar Chapel, LLC, a North Carolina limited liability company (the "Declarant").
Background Statement
The Declarant is the developer of the planned community located in Chatham County,
North Carolina known as Briar Chapel. The Declarant executed and filed that- that certain
Declaration of Covenants, Conditions, and Restrictions for Briar Chapel recorded November 16,
2007 in Deed Book 1370, Page 1020, et seq., and re-recorded November 28, 2007 in Deed Book
1372, Page 884, et seq., in the Office of the Register of Deeds of Chatham County, North
Carolina (as it may be amended and supplemented, the "Declaration") and that certain
Community Covenant for Briar Chapel recorded on November 28, 2007 in Deed Book 1372,
BOOK 1504PAG£0879
Page 996, et .req., in the Office of the Register of Deeds of Chatham County, North Carolina (as
it may be amended and supplemented, the "Covenant"). The Declaration has been amended by
that instrument recorded on June 12, 2009 in Book 1465, Page 482, et seq., in the Office of the
Register of Deeds of Chatham County, North Carolina ("First Amendment") and that
instrument recorded on June 19, 2009 in Book 1466, Page 675, et seq., 'in the Office of the
Register of Deeds of Chatham County, North Carolina ("Second Amendment")..
Pursuant to Sections 9.1 and 9.3 of the Declaration, the Declarant reserved the right to
expand the Briar Chapel community by recording one or more Supplemental Declarations
submitting to the terms of the Declaration all or any portion of the property described on Exhibit
"B" of the Declaration ("Expansion Property") and/or to impose on such property additional
covenants and easements, with the consent of the owner of such property (if not the Declarant).
Pursuant to the Section 4.1 of the Community Covenant, the Declarant may, with the
consent of the owner thereof, submit all or any portion of the Expansion Property described on
Exhibit "B" of the Community Covenant to the terms of the Community Covenant and/or impose
additional covenants and easements on such property.
The property described on Exhibit "A" to this Supplement (the "Additional Property")
is a portion of the Expansion Property described on Exhibit "B" to the Declaration and Exhibit
"B" to the Community Covenant.
As the owner of the Additional Property, the Declarant desires to submit such the
Additional Property to the terms of the Declaration, the Community. Covenant, and this
Supplement.
NOW, THEREFORE, the Declarant hereby submits the real property described on
Exhibit "A" of this Supplement to the provisions of the Declaration, the Community Covenant,
and this Supplement, which shall hereafter encumber the title to such property and shall be
binding upon all persons having any right, title, or any interest in such property, their respective
heirs, legal representatives, successors, successors-in-title, and assigns. The provisions of this
Supplement shall also be binding upon Briar Chapel Community Association, Inc., a North
Carolina nonprofit corporation (the "Association") and Briar Chapel Community Council, Inc., a
North Carolina nonprofit corporation (the "Council"), in accordance with the terms of the
Declaration and the Community Covenant.
ARTICLE I
Definitions
The definitions set forth in Article II of the Declaration are incorporated by reference
in this Supplement.
BOOK 15 0 4 PAGE0880
ARTICLE II
Desianation of Service Areas
Pursuant to Section 7.3 of the Declaration, the Additional Property has been assigned
to the Service Area(s), if any, designated on Exhibit "A" to this Supplement.
ARTICLE III
Additional Covenants, Restrictions and Easements
The additional covenants, restrictions and easements, if any, set forth in Exhibit "B"
of this Supplement shall apply to the Additional Property and shall be binding upon the owners
and occupants of Units within the Additional Property, their guests and invitees, in addition to
the terms of the Declaration.
ARTICLE IV
Amendment
4.1 By the Declarant.
Until termination of the Class "B" Control Period, the Declarant may unilaterally amend
this Supplement for any purpose. Thereafter, until termination of the Development and Sale
Period, the Declarant may unilaterally amend this Supplement to reflect any revisions or
amendments to any plats referenced on Exhibit "A," and, provided the amendment has no
material adverse effect upon any right of any Owner without such Owner`s consent in writing.-
for any other purpose.
Notwithstanding this reserved right, a revision or amendment to a plat shall not require an
amendment to this Supplement so long as no property is added or excluded from the plat by the
revision or amendment thereto. The Declarant reserves the right to record revised, amended, or
additional plats that only affect internal boundaries between lots, combine lots, or subdivide lots
shown on the original plat and, so long as they do not alter the overall property submitted to the
Declaration by this Supplement, such revised, amended or additional plats shall not necessitate
an amendment to this Supplement.
4.2. Owners.
Except as otherwise specifically provided in this Article IV, this Supplement may be
amended only by the affirmative vote or written consent, or any combination thereof, of Owners
of at least 67% of the Units within the Additional Property and the written consent of the
Association, acting through its board of directors. In addition, so long as the Declarant owns any
Unit within the Additional Property, the consent of the Declarant shall be required to amend this
Supplement.
4.3. Validity and Effective Date.
No amendment may remove, revoke, or modify any right or privilege of the Declarant or
without the written consent of the Declarant (or the assignee of such right or privilege).

eoox 15 0 4 PAGE 0 8 81
If an Owner consents to any amendment to this Supplement, it will be conclusively
presumed that such Owner has the authority to consent, and no contrary provision in any
Mortgage or contract between the Owner and a third party will affect the validity of such
amendment.
Any amendment shall become effective upon recording, unless a later effective date is
specified in the amendment. No action to challenge the validity of an amendment may be
brought more than two years after its recordation. In no event shall a change of conditions or
circumstances operate to amend any provisions of this Supplement.
In witness of the foregoing, the Declarant has executed this Supplement on the L" day
of M,'Ch ,2010.
DECLARANT: NIVP-BRIAR CHAPEL, LLC, a Delaware limited
liability company
STATE OF NORTH CAROLINA
COUNTY OF
1, G. L.4t„ P:WIVA IJ,, , a Notary Public in and for ?? k =? ?? County, North
Carolina, certify that Keith Hurand personally came before me this day and acknowledged that
he is Assistant Vice President of NNP-BRIAR CHAPEL, LLC, a Delaware limited liability
company, and that by authority duly given and as a fact of said limited liability company, he
executed the foregoing instrument on behalf of said limited liability company.
Witness my hand and official stamp or seal, this : t day of _ -4r k , 20?.
By: -r
?name: 16eith
Its:
Notary Public
My Commission Expires:
11;//14
[NOTARY SEAL]
O -
itkOTAqI,
;30+01: cadcx:. iupp Ded - P9 +. Sect i .OUS IJ. lix-
4
AIJ3Li0 C

BOOK 1 5) 0 4 PAGE 0 8 8 2
EXHIBIT "A"
Addition I Projactly_
ALL THOSE TRACTS OR PARCELS OF LAID lying and being in Chatham
County, North Carolina, and being more particularly described as on that certain Subdivision,
Easement Dedication and Right-of-Way Dedication Plat of Briar Chapel Phase 4, Section 4
recorded on ZO-LG'in Plat Book Pages ? -(?j as Instrument No.
in the office of the Register of Deeds of Chatham County, North Carolina, as such
plat may be revised from time to time.
BOOK 1504PAGE0883
EXHIBIT "B"
ditional Covenants, Restrictions, and Easements
1. Maximum Permitted Building Area. Pursuant to Section 16.8 of the Declaration, as
amended by the First Amendment, Exhibit "F" of the Declaration shall be supplemented to
include the following Maximum Permitted Building, Area for Units within the Additional
Property:
Maximum Permitted Buildina Area
Consoctfon `•
rawino Lot i
o. i Lord Plat
SUMP 92!
{ Record Plat I
Lot No. Lot Tvne

I maximum
Imnerv/ous
/bear a Wa Quelity
Poond No
112 See Ex. A I 317 80' Lot 4,300 1
113 318 80' Lot 4,300 1
114 319 80' Lot 4,300 1
115 " 1 320 80' Lot 4,300
116 321 80' Lot 4,300 1
117 322 ; 80' Lot 4,300 1
118 " i 323 80' Lot 4.300
1
119 i 324 i 80' Lot 4,300 1
120 325 60' Lot 3.700 { 1
121 326 60' Lot 3,700 1
122 I 327 60' Lot 3,700
1
123 f i 328 60' Lot 3,700 1
124 329 60' Lot i 3,700 1
125 " 330 60' Lot 3,700 1
132 331 60' Lot 3,700 1
133 332 I 60' Lot 3,700 1
134 333 60' Lot 3,700 1
135 " 334 ; 60' Lot 3,700 1
136 335 60' Lot 3,700 1
137 1 336 60' Lot 11 3,700 NIA
138 351 70' Lot 4,000 2
139 352 70' Lot 4,000 2
140 353 70' Let 4,000 2
141 { 337 50' Lot 3,400 WA
142 338 50' Lot 3.400 2
143 i 339 50' Lot 3,400 2
144 340 80' Lot 4,300 2
145 341 80' Lot 4,300 2
146 342 80' Lot 4,300 2
147 ; 343 80' Lot 4,300 2
148 344 80' Lot 4,300 2
149 345 80' Lot 1 4,300 2
150 346 80' Lot 4,300 2
151 347 60' Lot + 3,700 2
152 348 60' Lot 3,700 2
153 349 60' Lot 3,700 2
154 350 60' Lot 3,700 2
r?
EcoEngineering
A division of The John R. McAdams Company, Inc.
o "@gv D
AN 1 9 2011
BRIAR CHAPEL - PHASE 4
CHATHAM COUNTY, NORTH CAROLINA
Bioretention Area Final Design Calculations
NEW-09002
•
January 2011
Jeremy V. Finch, PE
Project Manager
Research Triangle Park, NC
Post Office Box 14005
Research Triangle Park,
North Carolina 27709
29 G ^geridian Parkway
North Carolina 27713
5646
919-287-4262
919-361-2269 Fax
www,ecoengr.com i Design Services Focused On Client Success
• BRIAR CHAPEL - PHASE 4
Final Stormwater Management Facility Design - Bioretention Area
General Description
Located off of US Highway 15-501, north of Andrews Store Road and south of Mann's Chapel Road in
Chatham County, NC is the proposed development known as Briar Chapel. Phase 4 of the proposed
development is approximately 174-acres and will consist of the construction of single-family lots, a
clubhouse/amenity center, along with the associated utility, parking, and roadway infrastructure.
The overall proposed Briar Chapel development ' is located within the Cape Fear River Basin, and
drains to a stream (Pokeberry Creek) classified as Water Supply IV (WS-IV), and Nutrient Sensitive
Waters (NSW). As a result of the proposed development exceeding the maximum allowable limit for
stream impacts, an individual permit issued by The United States Army Corps of Engineers (USAGE)
was required (Clean Water Act Section 404 permit). Also, a Clean Water Act Section 401 Water
Quality Certification from NCDWQ was attached to the individual permit. Under the 401 Water
Quality Certification issued by NCDWQ, the proposed site will be required to comply with the
following stormwater management requirements;
4.
1. A final written stormwater management plan for each subwatershed (including signed and
notarized Operation and Maintenance agreements) shall be submitted to the 401 Oversight
and Express Permitting Unit. The stormwater management plan may be submitted to DWQ
in phases for written approval as long as no impact to wetlands or streams occur in that
phase until written approval is reeeived.from DWQ.
• 2. The stormwater plans shall utilize constructed wetlands, Bioretention areas, wet ponds
followed by forested filter strips and similar best management practices designed to remove
nutrients. The stormwater management plan must include plans, specifications, and
worksheets for stormwater management.facilities that are appropriate.for the surface water
classification and designed to remove at least 85% TSS according to the most recent
version of the NCDENR Stormwater Best Management Practices Manual.
3. For low density areas of the project with low impervious surface area, engineered
stormwater management.facilities are not expected. For these areas of lower impervious
area, similar best management practices that remove nutrients such as grassed swales and
vegetated riparian. buffers should be sucient rather than more intensive engineered
stormwater devices such-as constructed wetlands.
In addition to the above DWQ stormwater requirements, the following stormwater quality and quantity
items are required per Section 8.3 ("Stormwater Controls") of the Chatham County Compact
Communities Ordinance:
1. Control and treat the first inch- of runoff from the project site and. from any offsite drainage
routed to an on-site control structure. Ensure that the draw down time.for this treatment
volume is a minimum of forty eight (48) hours and a maximum of one hundred and twenty
(120) hours.
2. Maintain the discharge rate for the treatment volume at or below the pre-development
discharge rate for the 1 -year, 24-hour storm.
• To satisfy these stormwater requirements, Phase 4 of the Briar Chapel development is currently
permitted with DWQ to be treated via water quality ponds with preformed scour hole/level spreader
outlets that will provide sheet flow of the 1" runoff volume into the existing stream buffers. The
existing stream buffers downstream of these facilities will be utilized as forested filter strips. Lots
• #349-#353 were shown in the current DWQ permit to be treated by water quality pond #2. However,
due to site topography constraints, these lots (when developed) will be difficult to direct to water
quality pond #2. As a result, a bioretention area is proposed behind lot #353 that is designed to capture
and treat stonmwater runoff from half of lots #349-350 and all of lots #351-353. This report contains
the final design calculations for the proposed bioretention area behind lot #353. Please refer to the
summary of results and discussion of results sections 'of this report for additional information.
Calculation Metliodolo
Rainfall data for the Chatham County, NC region is from NOAA Atlas 14, with a partial
duration series assumption. The rainfall depths were entered into a spreadsheet that calculated a
center-weighted storm based upon the NOAA Atlas 14 depths. The 1-year/24-hour rainfall
depth is 2.95 inches, the 2-Year/24-hour rainfall depth is 3.56 inches, the 10-Year/24-hour
rainfall depth is 5.15 inches, and the 100-year/24-hour rainfall depth is 7.61 inches. All of these
"computed" storms were modeled within the hydrologic model. Please reference the rainfall
data section within this report for additional information.
y Using maps contained within the Chatham County- Soil Survey, the watershed soils were
determined to be from hydrologic soil group (HSG) `B' soils. Since the method chosen to
compute the post-development peak flow rates and runoff volumes is dependent upon the soil
type, all hydrologic calculations are based upon the assumption of HSG `B' soils.
A composite SCS Curve Number was calculated for the post-development condition using SCS
curve numbers and land cover conditions. Land cover conditions for the post-development
condition were taken from the proposed development plan.
• The post-development time of concentration to the bioretention area was assumed to be 5
minutes in the post-development condition.
All on-site topo was taken from a flown aerial topographic survey by others provided to The
John R. McAdams Company, Inc. by McKim & Creed. The drainage map for the post-
development condition has been included in this report.
Pondpack Version 10.0, by Haestad Methods, was used to generate post-development peak
flow rates and generate the stage-discharge rating curve for the proposed bioretention area.
Final routing calculations for the bioretention area were also performed within Pondpack.
y The stage-storage rating curve and stage-storage function for the proposed bioretention area was
generated externally in a spreadsheet and then input into Pondpack.
A velocity dissipater is provided at the end of the principal spillway outlet for the bioretention
area to prevent erosion and scour in the downstream area. The dissipater is constructed using
nprap, underlain with a woven geotextile filter fabric. The filter fabric is used to minimize the
loss of soil particles beneath the riprap apron. The dissipater is sized for the 10-year storm event
using the NYDOT method. It is a permanent feature of the outlet.
i- Water quality sizing calculations for each facility were performed in accordance with the N.C.
Stormwater Best Management Practices manual (NCDENR July 2007). The bioretention
surface area was sized using the runoff volume computed using the Simple Method and a
maximum ponding depth of 9-inches.
0
• ? For 100-year storm routing calculations, a "worst case condition" was modeled in order to
ensure the proposed bioretention area would safely pass the 100-year storm event. The
assumptions used in this scenario are as follows:
The starting water surface elevation in the bioretention area, just prior to the 100-year
storm event, is at the top of the principal spillway structure. This scenario could occur as
a result of a clogged soil media or a rainfall event that lingers for several days. This
could also occur as a result of several rainfall events in a series, before the facility has
an opportunity to draw down the storage pool between the bioretention surface and the
riser crest elevation.
2. A minimum of 1.02-ft of freeboard between the peak elevation during the "worst case"
scenario and the top of the dam was achieved for the bioretention area.
Discussion of Results
As previously stated, this report contains the final design calculations for the proposed bioretention
area located behind lot #353 within Phase 4 of the Briar Chapel development. This facility is proposed
to capture stormwater runoff from lots #349-353 (originally permitted to drain to water quality pond
#2) and provide water quality treatment. Please refer to the Summary of Results tables for additional
information.
Conclusion
If the development on this tract is built as proposed within this report, then the requirements set forth in
the Water Quality Certification #3402 (WQC #3402) and Section 8.3 ("Stormwater Controls") of the Chatham
County Compact Communities Ordinance will be met with the proposed bioretention area. However,
modifications to the proposed development may require that this analysis be revised. Some
modifications that would require this analysis to be revised include:
1. The proposed site impervious surface exceeds the amount accounted for in this report.
2. The post-development watershed breaks change significantly from those used to prepare this
report.
The above modifications may result in the assumptions within this report becoming invalid. The
computations within this report will need to be revisited if any of the above conditions become
apparent as development of the proposed site moves forward.
0
•
BRIAR CHAPEL - PHASE 4
NEW-09002
SUMMARY OF RESULTS
Design Drainage Area =
Design Impervious Area =
0.97 acres
0.36 acres
Top of Dam = 435.00 ft
Surface Elevation = 433.00 ft
Required Surface Area = 1,805 sf
Provided Surface Area = 1,857 sf
Design Ponding Depth = 9 inches
Riser Size = 4x4 ft
Riser Crest = 433.75 ft
Barrel Diameter = 15 inches
# of Barrels = 1
Invert In = 429.60 feet
Invert Out = 428.00 feet
Length = 33 feet
Slope = 0.0485 ft/ft
•
Return
Period Inflow
[cfs] Outflow
[cfs] Peak WSEL
[ft] Freeboard
[ft]
1-Year 1.49 0.18 433.77 1.23
2-Year 2.21 0.59 433.80 1.20
10-Year 3.82 3.51 433.92 1.08
100-Year L 5.82 5.54 433.99 1.01
J. FINCH, PE
1/5/2011
•
•
•
USGS MAP
1
SOILS INFORMATION
2
PRECIPITATION DATA
3
HYDROLOGIC CALCULATIONS
4
FINAL BIORETENTION AREA DESIGN
CALCULATIONS
5

•
USGS MAP

C,
BRIAR CHAPEL - PHASE 4
NEW-09002
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Date: 12/9/2010
Scale: 1 inch equals 2000 feet
Copyright (C) 1998, Maptech, Inc.
I

SOILS INFORMATION
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NEW-09002
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BRIAR CHAPEL - PHASE 4 WATERSHED SOIL
NEW-09002 INFORMATION
TO BIORETENTION
• _> Watershed soils - To WQ Pond #1
Symbol Name Soil Classification
WeD Wedowee Sandy Loam B
WeE Wedowee Sandy Loam B
References:
1) SCS TR-55. UNITED STATES DEPARTMENT OF AGRICULTURE. SOIL
CONSERVATION SERVICE. 1986.
HSG B = 100%
J. FINCH, PE
12/9/2010
_> Conclusion
Watershed soils are from 'HSG B' and 'HSG D'soils. The relative percentage of each HSG
was calculated. These percentages were then used in the computation of the composite curve numbers.
Cover Condition SCS CN - HSG B
Impervious 98
Open 61
Wooded 55

0
[jEcoEngineering
A division of The John R. McAdams Company, Inc.
•
MEMORANDUM
Date: December 21, 2010
To: Jeremy Finch, PE
From: George Buchholz, REM, PW
Re: Briar Chapel - Phase 4 Bio Retention Area
Seasonal High Water Table
New-09002
A field investigation was conducted on December 17, 2010 at the proposed
location of the biorentention area associated with the Briar Chapel Phase 4
development. A soil boring was established within the biorentention area to
determine the approximate seasonal high water table depth from the soil
surface. Below is a brief summary of the soil type(s) and the approximate
seasonal high water table depth.
Biorentention Area
. Soil Type(s):
Wedowee sandy loam, 10 to 15 percent slopes: gently sloping to steep, very
deep, well drained.
Wedowee sandy loam, 15 to 25 percent slopes: steep, very deep, well drained.
Soil Boring Results:
It is anticipated that the approximate seasonal high water table depth from the
soil surface for this biorentention area is 26 inches.
General Soil Boring Observations
In general, the profile of the soil borings graded from light yellowish brown
sandy loams near the surface to yellowish brown with light-gray mottles that
are sandy at lower elevations and grayish with prominent pale reddish brown
mottles which are sandy at very low elevations. Below is a photograph of a
sample boring.
Research Triangle Park, NC
Post Office Box 14005
Research Triangle Park,
North Carolina 27709
2 Meridian Parkway
North Carolina 27713
.,-5646
919-287-4262
919-361-2269 Fax
www.ecoengrcom Design Services Focused On Client Success
•
•
0
Soil boring profile located within biorentention area.
plus 3a mmm I"" unwm 9001
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PRECIPITATION DATA
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BRIAR CHAPEL - PHASE 4
NEW-09002
•
Precipitation Frequency Data Server

Page 1 of 2
POINT PRECIPITATION`
FREQUENCY ESTIMATES
FROM NOAA ATLAS 14 „North Carolina 35.827003 N 79.102889 W 456 feet
from "Precipitation-Frequency Atlas of the United States" NOAA Atlas 14, Volume 2, Version 3
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland, 2004
Extracted: Mon Dec 6 2010
confidence Limits Seasonality Related Info GIS data Maps D Return to State Map
Precipitation Frequency Estimates (inches)
ARI* 5 10 15 30 60 120 [91 10 20 30 60
3 hr 6 hr 24 hr 48 hr 4 day 7 day
(years) min
0.41 0.66 da d d d d
min min
0.83 1.13 1.41 1.68 1.79 2.15 2.54 2.95 3.44 3.85 4.43 5.04 6.75 8.37 10.67 12.79
0 0.49 0.78 0.98 1.36 1.70 2.03 2.16 2.59 3.06 3.56 4.15 4.62 5.29 5.99 7.96 9.85 12.50 14.91
F5 0.56 0.90 1.14 1.62 2.08 2.50 2.67 3.21 3.81 4.46 5.15 5.68 6.42 7.19 9.40 11.45 14.30 16.83
10 0.62 0.99 1.26 1.82 2.37 2.88 3.09 3.71 4.43 5.15 5.92 6.52 7.33 8.13 10.54 12.69 15.69 18.31
25 0.68 1.09 1.38 2.04 2.71 3.34 3.62 4.38 5.28 6.10 6.97 7.66 8.56 9.40 12.09 14.32 17.52 20.21
50 0.72 1.15 1.46 2.20 2.98 3.71 4.05 4.92 5.97 6.85 7.79 8.56 9.53 10.40 13.31 15.58 18.90 21.66
100 0.76 1.21 1.53 2.34 3.23 4.06 4.47 5.47 6.69 7.61 8.63 9.48 10.53 11.41 14.54 16.82 20.25 23.04
200 0.79 1.26 1.59 2.47 3.47 4.41 4.90 6.03 7.45 8.40 9.48 10.43 11.56 12.44 15.79 18.07 21.60 24.39
500 0.83 1.31
.63 7 4.87 5. 47 6.80 8.49 9.49 10.66 11.72 12.97 13.84 17.49 19.74 23.37 26.14
1.65 2 3.7
1000 0.86 1.35 1.69 2.74 4.00 5.23 5.95 7.43 9.38 10.34 11.59 12.75 14.08 14.94 18.82 21.02 24.72 27.45

* These precipitation frequency estimates are based on a partial duration series. ARI is the Average Recurrence Interval.
Please refer to NOAA Atlas 14 Document for more information. NOTE: Formatting forces estimates near zero to appear as zero.
C,

II * Upper bound of the 90% confidence interval I)
Precipitation Freauencv Estimates (inches)
200 0.87 1.38 1.73 2.70 3.79 4.84 5.36 6.56 8.05 9.02 10.19 11.20 12.36 13.30 16.80 19.16 22.76 25.67
500 0.91 1.43 1.80 2.87 4.12 5.34 5.99 7.40 9.18 10.20 11.48 12.63 13.90 14.82 18.65 20.98 24.69 27.57 _]F ARI** 10 30 60 120 12 24 48 10 20 30 45 60
(years) m??F15
min mm mm mm min F r hr hr hr hr day day day 11 day 11 day day day
11 0.45 0.72 0.91 1.24 1.55 1.85 1.96 2.35 2.77 3.15 3.69 4.12 4.72 5.36 7.14 8.85 11.22 13.40
0 0.54 0.86 1.08 1.49 1.86 2.23 2.37 2.84 3.34 3.81 4.44 4.94 5.63 6.37 8.42 10.39 13.13 15.63
0 0.62 0.99 1.25 1.77 2.27 2.75 2.94 3.51 4.16 4.76 5.51 6.08 6.84 7.64 9.94 12.08 15.01 17.64
10 0.68 1.08 1.37 1.99 2.59 3.16 3.39 4.06 4.84 5.50 6.34 6.97 7.80 8.64 11.15 13.39 16.48 19.20
25 0.74 1.19 1.50 2.22 2.96 3.66 3.96 4.77 5.73 6.52 7.46 8.20 9.12 10.01 12.80 15.12 18.39 21.21
50 0.79 1.26 1.59 2.40 3.25 4.06 4.43 5.36 6.47 7.33 8.34 9.17 10.17 11.08 14.11 16.46 19.86 22.74
F 1o_ I 0.83 1.32 1.67 2.56 3.52 4.45 4.89 5.95 7.24 8.16 9.26 10.17 11.25 12.18 15.44 17.80 21.32 24.23
1000 024 1.47 1.85 3.00 4.38 5.75 6.53 8.11 10.15 11.14 12.49 13.78 15.13 16.02 20.11 22.39 26.16 28.99
` The upper bound of the confidence interval at 90% confidence level is the value which 5% of the simulated quantile values for a given frequency are greater than.
`* These precipitation frequency estimates are based on a partial duration series. ARI is the Average Recurrence Interval.
Please refer to NOAA Atlas 14 Document for more information. NOTE: Formatting prevents estimates near zero to appear as zero.
II * Lower bound of the 90% confidence interval (I
Precipitation Freauencv Estimates (inches)
?u1 10 11 15 11 30u 120 uu 12
ears mm min mm mm min min hr hr hr
1 0.38 0.61 0.76 1.04 1.29 1.53 1.64 1.97 2.33
0.45 0.72 0.90 1.24 1.56 1.85 1.98 2.38 2.81
0.52 0.83 1.04 1.49 1.90 2.28 2.44 2.94 3.49
10 0.57 0.91 1.15 1.66 2.17 2.61 2.82 3.39 4.05
25 0.62 0.99 1.25 1.85 2.47 3.02 3.28 3.97 4.78
24 48 ?4 Fd 10 20 30 45 60
hr hr day day 11 day 11 day day 11 day
2.76 3.23 3.61 4.17 4.76 6.38 7.93 10.19 12.23
3.34 3.89 4.33 4.98 5.65 7.53 9.33 11.91 14.24
4.17 4.82 5.32 6.05 6.78 8.88 10.83 13.61 16.07
4.82 5.54 6.09 6.89 7.65 9.95 11.99 14.92 17.47
5.68 6.49 7.13 8.02 8.82 11.37 13.50][16 62 19.25
http:llhdsc.nws.noaa.gov/cgi-binlhdsclbuildout.perl?type=pf&units=us&series=pd&statena... 12/6/2010
•

Precipitation Frequency Data Server
Page 2 of 2
50 0.66 1.04 1.32 1.99 2.70 3.33 3.64 4.43 5.38 6.37 7.23 7.93 8.90 119 12.47 14.66 17.90 20.59
100 0.69 1.09 1.38 2.11 2.91 3.62 3.99 4.88 5.96 7.06 7.99 8.76 9.80 10.65 13.58 15.79 19.13 21.86
200 0.71 1.13 1.42 2.21 3.11 3.91 4.34 5.33 6.56 7.76 8.74 9.60 10.71 11.57 14.69 16.92 20.34 23.09
500 0.74 1.16 1.47 2.33 3.35 4.27 4.79 5.92 7.35 8.72 9.78 10.74 11.94 12.81 16.20 18.40 21.91 24.68
1000 0.75 1.19 1.49 2.41 3.52 4.55 5.15 6.39 7.99 9.46 10.59 11.62 12.90 13.76 17.36 19.53 23.09 25.86
The lower bound of the confidence interval at 90% confidence level is the value which 5% of the simulated quantile values for a given frequency are less than.
These precipitation frequency estimates are based on a partial duration maxima series. ARI is the Average Recurrence Interval.
Please refer to NOAA Atlas 14 Document for more information. NOTE: Formatting prevents estimates near zero to appear as zero.
Text version of tables
http://hdsc.nws.noaa.gov/cgi-binlhdsclbuildout.perl?type=pf&units=us&series=pd&statena... 12/6/2010
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HYDROLOGIC CALCULATIONS
•
0
BRIAR CHAPEL - PHASE 4
NEW-09002
BRIAR CHAPEL - PHASE 4 HYDROLOGIC CALCULATIONS
NEW-09002 Post-development - To Bioretention Area
•
Ll
0
Assume.
HSG Impervious Open Wooded
A 98 39 30
B 98 61 55
C 98 74 70
D 98 80 77
HSG'A' = 0.0%
HSG'B' = 100.0%
HSG'C' = 0.0%
HSG'D' = 0.0%
Cover Condition SCS CN Comments
Impervious 98
Open 61 Assume good condition
Wooded 55 Assume good condition
J. FINCH, PE
1/3/2011
A. Watershed Breakdown
Total 60-ft Single-Family Residential Lots = 1 Lot
Impervious Per 60-ft Single-Family Lot (Inc House, Patio, D/W, S/W) = 3,700 SF
Total Impervious Area From 60-ft Single-Family Lots = 3,700 SF
= 0.08 acres
Total 70-ft Single-Family Residential Lots = 3 Lot
Impervious Per 70-ft Single-Family Lot (Inc House, Patio, D/W, S/W) = 4,000 SF
Total Impervious Area From 70-ft Single-Family Lots = 12,000 SF
= 0.28 acres
Contributing Area SCS CN Area [acres] Comments
Onsite impervious 98 0.36 -
Onsite open 61 0.61 Assume good condition
Onsite wooded 55 0.00 Assume good condition
Onsite and 100 0.00 -
Offsite impervious 98 0.00 -
Offsite open 61 0.00 Assume good condition
Offsite wooded 55 0.00 Assume good condition
Offsite and 100 0.00 -
Total area =
Composite SCS CN =
% Impervious =
B. Time of Concentration Information
***Time of concentration was assumed tc
0.97 acres
0.0015 sq.mi.
75
37.1%
be 5 minutes
Time of Concentration = 5.00 minutes
SCS Lag Time = 3.00 minutes (SCS Lag = 0.6* Tc)
Time Increment = 0.87 minutes (= 0.29*SCS La
To Bioretention
11 i Qm. I PIi
, ¦ w
¦w
D
CL
C.
0

X
0
c
CD
0
0 0
Bioretention
Bioretention Out
Type.... Master Network Summary Page 2.01
Name.... Watershed
File.... X:\Projects\NEW\NEW-09002\Storm\Phase 4 - Lot #351-353\Bioretention Area Design\D
MASTER DESIGN STORM SUMMARY
Network Storm Collection: Briar Chapel - P
Total
Depth
Return Event in
------------
1-Yr ------
2.9500
2-Yr 3.5600
10-Yr 5.1500
100-Yr 5.1500
Rainfall
Type
----------------
Time-Depth Curve
Time-Depth Curve
Time-Depth Curve
Time-Depth Curve
RNF ID
Briar Chapel - 1
Briar Chapel - 2
Briar Chapel - 1
Briar Chapel - 1
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*Node=Outfall; +Node=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
0 Return HYG Vol
Node ID
-------------
---- Type
---- Event
------ cu.ft Trun
---------- --
BIORETENTION IN POND 1 3268
BIORETENTION IN POND 2 4734
BIORETENTION IN POND 10 9054
BIORETENTION IN POND 100 16518
BIORETENTION OUT POND 1 1668
BIORETENTION OUT POND 2 3133
BIORETENTION OUT POND 10 7454
BIORETENTION OUT POND 100 14918
*BIORETENTION OUT JCT 1 1668
*BIORETENTION OUT JCT 2 3133
*BIORETENTION OUT JCT 10 7454
*BIORETENTION OUT JCT 100 14918
is
Qpeak
min
722.00
722.00
721.00
721.00
756.00
732.00
723.00
722.00
756.00
732.00
723.00
722.00
Max
Qpeak Max WSEL Pend Storage
cfs ft cu.ft
-------- -------- ------------
1.49
2.21
3.82
5.82
.18 433.77 1640
.59 433.80 1727
3.51 433.92 2025
5.54 433.99 2182
.18
.59
3.51
5.54
SIN: Bentley Systems, Inc.
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Type.... Master Network Summary Page 2.02
Name.... Watershed
File.... X:\Projects\NEW\NEW-09002\Storm\Phase 4 - Lot #351-353\Bioretention Area Design\D
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*Node=Outfall; +Node=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Max
Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node ID
----------------- Type
---- Event
------ cu.ft Trun
---------- -- min
--------- cfs ft cu.ft
--

TO
BIORETENTION
AREA
1
3268
722.00 ------ -------- ------------
1.49
TO BIORETENTION AREA 2 4734 722.00 2.21
TO BIORETENTION AREA 10 9054 721.00 3.82
TO BIORETENTION AREA 100 16518 721.00 5.82
C7
0

SIN: Bentley Systems, Inc.
Bentley PondPack (10.00.027.00) 10:21 AM 1/5/2011
•
FINAL BIORETENTION AREA DESIGN
CALCULATIONS
0
Ll
BRIAR CHAPEL - PHASE 4
NEW-09002
BRIAR CHAPEL - PHASE 4 BIORETENTION AREA
NEW-09002
• Stage-Storage Function
Project Name: Briar Chapel - Phase 4
Designer: J. Finch, PE
Job Number: NEW-09002
Date: 1/5/2011
E
J. FINCH, PE
1/5/2011
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Volume
Contour Stage Area Area Volume Volume w/ S-S Fxn
(feet) (feet) (SF) (SF) (CF) (CF) (CF)
433.00 0.0 1,904
433.50 0.5 2,174 2039 1020 1020 0.50
434.00 1.0 2,452 2313 1157 2176 0.98
435.00 2.0 3,022 2737 2737 4913 2.02
Storage vs. Stage
6000
5000
y = 2217.2x11344
4000 R2 = 0.9996
LL
V
03000
S
N 2000
1000
0
0.0 0.5 1.0 Stage (feet) 1.5 2.0 2.5
Ks = 2217.2
b = 1.1344
•
BRIAR CHAPEL - PHASE 4 BIORETENTION AREA J. FINCH, PE
NEW-09002 1/5/2011
• _> Stage - Storage Function
Ks = 2217.2

•
b = 1.1344
Zo = 433.00
Elevation
[feet] Storage
[cq [acre-feet]
433.00 0 0.000
433.20 357 0.008
433.40 784 0.018
433.60 1242 0.029
433.75 1600 0.037
433.80 1721 0.040
434.00 2217 0.051
434.20 2727 0.063
434.40 3248 0.075
434.60 3779 0.087
434.80 4319 0.099
435.00 4867 0.112
Elevation
[feet] 100-Year
[cf] [acre-feet]
433.00 - -
433.20 - -
433.40 - -
433.60 - -
433.75 0 0.000
433.80 122 0.003
434.00 617 0.014
434.20 1127 0.026
434.40 1648 0.038
434.60 2179 0.050
434.80 2719 0.062
435.00 3268 0.075
0
Type.... Outlet Input Data
Name.... Bioretention
Page 2.01
• File.... X:\Projects\NEW\NEW-09002\Storm\Phase 4 - Lot #351-353\Bioretention Area Design\D
Title... Project Date: 12/6/2010
Project Engineer: J. Finch, PE
Project Title: Briar Chapel - Phase 4 Bioretention
Area
Project Comments :
REQUESTED POND WS ELEVATIONS:
Min. Elev.= 433.00 ft
Increment = .10 ft
Max. Elev.= 435.00 ft
OUTLET CONNECTIVITY
---> Forward Flow Only (UpStream to DnStream)
<--- Reverse Flow Only (DnStream to UpStream)
<---> Forward and Reverse Both Allowed
Structure No. Outfall E1, ft E2, ft
----------------- ---- ------- --------- ---------
Inlet Box RI ---> BA 433.750 435.000
Culvert-Circular BA ---> TW 429.600 435.000
TW SETUP, DS Channel
•
•
SIN: Bentley Systems, Inc.
Bentley PondPack (10.00.027.00) 1:34 PM 12/17/2010
Type.... Outlet Input Data
Name.... Bioretention
Page 2.02
• File.... X:\Projects\NEW\NEW-09002\Storm\Phase 4 - Lot #351-353\Bioretention Area Design\D
Title... Project Date: 12/6/2010
Project Engineer: J. Finch, PE
Project Title: Briar Chapel - Phase 4 Bioretention
Area
Project Comments:
OUTLET STRUCTURE INPUT DATA
Structure ID = RI
Structure Type = Inlet Box
-------------------
# of Openings = -----------------
1
Invert Elev. = 433.75 ft
Orifice Area = 16.0000 sq.ft
Orifice Coeff. _ .600
Weir Length = 16.00 ft
Weir Coeff. = 3.000
K, Reverse = 1.000
Mannings n = .0000
Kev,Charged Riser = .000
Weir Submergence = No
•
•
SIN: Bentley Systems, Inc.
Bentley PondPack (10.00.027.00) 1:34 PM 12/17/2010
Type.... Outlet Input Data
Name.... Bioretention
Page 2.03
0 File.... X:\Projects\NEW\NEW-09002\Storm\Phase 4 - Lot #351-353\Bioretention Area Design\D
Title... Project Date: 12/6/2010
Project Engineer: J. Finch, PE
Project Title: Briar Chapel - Phase 4 Bioretention
Area
Project Comments :
OUTLET STRUCTURE INPUT DATA

Structure ID = BA
Structure Type =
------------------- Culvert-Circular
-----------------
No. Barrels = 1
Barrel Diameter = 1.2500 ft
Upstream Invert = 429.60 ft
Dnstream Invert = 428.00 ft
Horiz. Length = 33.00 ft
Barrel Length = 33.04 ft
Barrel Slope = .04849 ft/ft
OUTLET CONTROL DATA ...
Mannings n = .0130
Ke = .5000 (forward entrance loss)
Kb = .023225 (per ft of full flow)
Kr = .5000 (reverse entrance loss)
HW Convergence = .001 +/- ft
INLET CONTROL DATA. ..
Equation form = 1
Inlet Control K = .0098
Inlet Control M = 2.0000
Inlet Control c = .03980
Inlet Control Y = .6700
T1 ratio (HW/D) = 1.136
T2 ratio (HW/D) = 1.283
Slope Factor = -.500
Use unsubmerged inlet control Form 1 equ. below T1 elev.
Use submerged inlet control Form 1 equ. above T2 elev.
In transition zone between unsubmerged and submerged inlet control,
interpolate between flows at T1 & T2...
At T1 Elev = 431.02 ft ---> Flow = 4.80 cfs
At T2 Elev = 431.20 ft ---> Flow = 5.49 cfs
•
SIN: Bentley Systems, Inc.
Bentley PondPack (10.00.027.00) 1:34 PM 12/17/2010
Type.... Outlet Input Data
Name.... Bioretention
Page 2.04
• File.... X:\Projects\NEW\NEW-09002\Storm\Phase 4 - Lot #351-353\Bioretention Area Design\D
Title... Project Date: 12/6/2010
Project Engineer: J. Finch, PE
Project Title: Briar Chapel - Phase 4 Bioretention
Area
Project Comments :
OUTLET STRUCTURE INPUT DATA
Structure ID = TW
Structure Type = TW SETUP, DS Channel
------------------------------------
FREE OUTFALL CONDITIONS SPECIFIED
CONVERGENCE TOLERANCES...
Maximum Iterations= 40
Min. TW tolerance = .01 ft
Max. TW tolerance = .01 ft
Min. HW tolerance = .01 ft
Max. HW tolerance = .01 ft
Min. Q tolerance = .00 cfs
Max. Q tolerance = .00 cfs
•
•
SIN: Bentley Systems, Inc.
Bentley PondPack (10.00.027.00) 1:34 PM 12/17/2010
Type.... Composite Rating Curve
Name.... Bioretention
Page 2.09
File.... X:\Projects\NEW\NEW-09002\Storm\Phase 4 - Lot #351-353\Bioretention Area Design\D
Title... Project Date: 12/6/2010
Project Engineer: J. Finch, PE
Project Title: Briar Chapel - Phase 4 Bioretention
Area
Project Comments:
***** COMPOSITE OUTFLOW SUMMARY ****
WS Elev, Total Q
Elev. Q
ft cfs
--------
433.00 -------
.00
433.10 .00
433.20 .00
433.30 .00
433.40 .00
433.50 .00
433.60 .00
433.70 .00
433.75 .00
433.80 .54
433.90 2.79
434.00 6.00
434.10 9.94
434.20 11.98
434.30 12.14
434.40 12.29
434.50 12.45
434.60 12.59
434.70 12.74
434.80 12.89
434.90 13.04
435.00 13.18
•
Notes
-------- Converge -------------------------
ft +/-ft
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Free Outfall
Contributing Structures
(no Q: RIBA)
(no Q: RI,BA)
(no Q: RI,BA)
(no Q: RI,BA)
(no Q: RI,BA)
(no Q: RIBA)
(no Q: RIBA)
(no Q: RIBA)
(no Q: RI,BA)
RIBA
RIBA
RIBA
RIBA
RI,BA
RIBA
RIBA
RI,BA
RIBA
RIBA
RIBA
RIBA
RI,BA
SIN: Bentley Systems, Inc.
Bentley PondPack (10.00.027.00) 1:34 PM 12/17/2010
Type.... Master Network Summary Page 2.01
Name.... Watershed
File.... X:\Projects\NEW\NEW-09002\Storm\Phase 4 - Lot #351-353\Bioretention Area Design\D
•
MASTER DESIGN STORM SUMMARY
Network Storm Collection: Briar Chapel - P
Total
Depth
Return Event in

1-Yr ----
2.9500
2-Yr 3.5600
10-Yr 5.1500
100-Yr 5.1500
Rainfall
-Type
---- ----------
Time-Depth Curve
Time-Depth Curve
Time-Depth Curve
Time-Depth Curve
RNF ID
Briar Chapel - 1
Briar Chapel - 2
Briar Chapel - 1
Briar Chapel - 1

MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*Node=Outfall; +Node=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Max
• Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node ID Type Event cu.ft Trun min
--------- cfs
-------- ft
-------- cu.ft
------------
--------------
BIORETENTION ---
IN ----
POND ------
1 ---------- --
3268 722.00 1.49
BIORETENTION IN POND 2 4734 722.00 2.21
BIORETENTION IN POND 10 9054 721.00 3.82
BIORETENTION IN POND 100 16518 721.00 5.82
BIORETENTION OUT POND 1 3268 724.00 1.28 33.83 207
BIORETENTION OUT POND 2 4733 723.00 2.01 433.87 290
BIORETENTION OUT POND 10 9054 723.00 3.60 433.92 431
BIORETENTION OUT POND 100 16518 722.00 5.57 433.99 581
*BIORETENTION OUT JCT 1 3268 724.00 1.28
*BIORETENTION OUT JCT 2 4733 723.00 2.01
*BIORETENTION OUT JCT 10 9054 723.00 3.60
*BIORETENTION OUT JCT 100 16518 722.00 5.57 t'4?-cftsl?
w5rt-
•
S/N: Bentley Systems, Inc.
Bentley PondPack (10.00.027.00) 10:22 AM 1/5/2011
Type.... Master Network Summary Page 2.02
Name.... Watershed
File.... X:\Projects\NEW\NEW-09002\Storm\Phase 4 - Lot #351-353\Bioretention Area Design\D
C7
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*Node=Outfall; +Node=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Max
Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node ID
----------------- Type
---- Event cu.ft Trun min
--------- cfs ft cu.ft
-------- -------- ------------
TO BIORETENTION AREA ------
1 ---------- --
3268 722.00 1.49
TO BIORETENTION AREA 2 4734 722.00 2.21
TO BIORETENTION AREA 10 9054 721.00 3.82
TO BIORETENTION AREA 100 16518 721.00 5.82
0 - - 'L -m

SIN: Bentley Systems, Inc.
Bentley PondPack (10.00.027.00) 10:22 AM 1/5/2011
BRIAR CHAPEL - PHASE 4 BIORETENTION AREA SIZING CALCULATIONS
NEW-09002
• Determination of Water Quality Volume (WV;,)
WQ v = (P) (R v)(A)/12
where,
WQv = water quality volume (in acre-ft)
Rv = 0.05+0.009(I) where I is percent impervious cover
A = area in acres
P = rainfall (in inches)
Input data:
Total area, A = 0.97 acres
Impervious area = 0.36 acres
Percent impervious cover, I = 37.2 %
Rainfall, P = 1.0 inches
Calculated values:
Rv= 0.38
WQv= 0.03 acre-ft
1,354 cf.
_> Bloretention Area Minimum Required Surface Area Calculation
WQ Volume = 1354 cf.
• Maximum Ponding Depth = 9 inches
Minimum SA Required = 1,805 square feet
=> Calculated Fonding Depth its Bioretention Area
Ks = 2217.2
b = 1.1344
V = 1,354
Surface Elevation = 433.00 feet

WQ Elevation = 433.65 feet
J. FINCH, PE
1/5/2011
0
BRIAR CHAPEL - PHASE 4 BIORETENTION AREA UNDERDRAIN SIZING
NEW-09002
0
Bio-Retention Surface Area 1857 sf @ EL = 433.00
Water Ponding Depth 9 in
Soil Layer Thickness 2.00 ft
Total Fill Layer Thickness 3.33 ft
Assume Soil Permeability of 2 in/hr
Assume n = 0.012 for PVC pipe
S = 0.5 %
Using Darcy's Law
qp= 12 in/hr ) [ 3.33 ft] _
-[ 2.00 ft
=
Q = (3.33 in/hr ) (1857 sf )
*Design System to Handle 10 Times Minimum Flow:
Design Q = 1.43 cfs
N*D= 16*(Q*n/S"0.5)^(3/8)
16 1.43 cfs 0.012 ^ 3/8
0.005 0.5
N*D= 9.4 inches
N= 3 D= 4 in
J. FINCH, PE
1/5/2011
3.33 in/hr per unit area
0.14 cfs
Use 3 - 4" PVC Pipes for drain system
Note: Calculation Methodology taken from NCSU "Workshop on Bio-Retention", Page 7, "Selecting"
Underdrain Pipes.
0 --
BRIAR CHAPEL - PHASE 4 BIORETENTION INLET J. FINCH, PE
NEW-09002 1/5/2011
•
Velocity Dissipator
NRCD Land Quality Section
Pipe Design
Entering the following values will provide you with the expected outlet velocity and depth of flow in a pipe,
assuming the Manning's roughness number is constant over the entire length of the pipe.
Flow Qlo (cfs) = 3.82
Slope S (%) = 1.90
Pipe Diameter Do (in) = 12
Manning's `n' = 0.009
Flow Depth (ft) = 0.52
Outlet Velocity (fps) = 9.189
NRCD Land Quality Section
NYDOT Dissipator Design Results
•
Pipe Diameter (ft) = 1.00
Outlet Velocity (fps) =.9.19
Apron Length (ft) = 6.00
d50 Stone Thickness
(inches) Class (inches)
3 A 9
6 B 22 <--
13 B or 1 22
23 2 27
Width = La + Do
Width=6+1
Width (ft) = 7
Use NCDOT Class `B' Rip Rap
d50 = 8"
6'L z 7'W z 22"Thick
0
BRIAR CHAPEL - PHASE 4 BIORETENTION OUTLET J. FINCH, PE
NEW-09002 1/3/2011
•
Velocity Dissipator
NRCD Land Quality Section
Pipe Design
Entering the following values will provide you with the expected outlet velocity and depth of flow in a pipe,
assuming the Manning's roughness number is constant over the entire length of the pipe.
Flow Qio (cfs) = 3.51
Slope S (%) = 4.85
Pipe Diameter Do (in) = 15
Manning's `n' = 0.013
Flow Depth (ft) = 0.42
Outlet Velocity (fps) = 9.601
NRCD Land Quality Section
NYDOT Dissipator Design Results
•
Pipe Diameter (ft) = 1.25
Outlet Velocity (fps) = 9.60
Apron Length (ft) = 7.50
d50 Stone Thickness
(inches) Class (inches)
3 A 9
6 B 22 E-
13 B or 1 22
23 2 27
Width = La + Do
Width = 7.5 + 1.25
Width (ft) = 8.75 Use 9-ft
Use NCDOT Class `B' Rip Rap
d50=8"
7.51L z 9'W z 22"Thick
0
F-
L
r
4
m
m
IL

•
OA
w`
W
E
E
r0
c/
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3

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0
C m C) C C 0
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