20072036 Ver 1_Stormwater Info_20080117

F
. o ~ ~ ~ 3~
„~ JORDAN LE TER OF TRANSMITTAL
JONES &
._. GOULDING t , ~ ~~ CJ
9101 Southern Pine Boulevard DATE: 1/15/2008
Suite 160 ~~^ PROJECT NO: 16022001
Charlotte, NC 28273 l..
Phone: [phone] ~ ~ ~ ~ ~ ~ ~ TTENTION: Water Quality Section
Fax: [phone]
TO: NCDENR RE:
Water Quality Section
610 East Center Ave.
Mooresville, NC 28115
PHONE [phone]
WE ARE SENDING YOU VIA UPS
Texland B ~ ended
Fueling Statio
;;
® Attached: ^ Under Separate Cover the Following Items:
® Drawings ^ Prints ^ Plans
^ Copy of Letter ®Submittals ®Reports
COPIES DATE NO. DESCRIPTION
2 1/11/08 1 Stormwater Mana ement Permit A lication
2 1/11/08 2 Bioretention Cell Su lement ' ' "~ '%
2 1/11/08 3 O&M A Bement
1 1/11/08 4 Processin fee of $505 ''~~l
1 1/11/08 5 Stormwater Mana ement Re ort ~' ' ~ ~ ~--`~"-~' t~ ~~ .4 ; ~~~'(
3 1/11/08 6 Site Plans and Details ;>a
THESE ARE TRANSMITTED AS CHECKED BELOW:
® For Approval
^ For Your Use/Files
^ As Requested
^ For Review and Comment
^ For Execution
^ No Exception Taken
^ Make Corrections Noted
^ Amend and Resubmit
^ Rejected-(See Remarks)
^ Other
^ Submit Copies for Distribution
^ Return Corrected Copies
^ Resubmit _ Copies for Approval
^ Return _ Approved Copies
REMARKS:
A soils report was not included. This was due to the fact that the only soil applicable to the performance of the
BMP was being removed and the fact that the water table in the area is low. If you do still require a soil report, I
would appreciate it if you could contact me immediately so I may go ahead and order the survey. Thank you.
~~
~'~`
r~~.
Copy:
Filename: Signed:
Alan .Moseley, P.E.
IF ENCLOSURES ARE NOT AS NOTED, KINDLY NOTIFY US AT ONCE
NC pE~+~
^ oQ Surface w~.¢;.
~~:

DW USE ONLY
Date Received Fee Paid Permit Number
O'1 - 2~ 3 to
State of North Carolina
Department of Environment and Natural Resources
Division of Water Quality
_ -E r a,
STORMWATER MANAGEMENT PERMIT APPLICATION FOR ~ ' ~ ~ ~ ~ ` ~~ z
This form maybe photocopied for use as an origiruil ~~~ ~--~
,~,~~ j. 's ZQ(iri
I. GENERAL INFORMATION
:r~, ;: '~ ~°r
~yrP.t?i ~ ,r s ~~ ~ ,t.{~,~..r ki
1. Applicants name (specify the name of the corporation, individual, etc. who owns the project)a~°~:~Ti_A~~'~~> `~'~~ ' ~"``~`"~
Quarles Petroleum
2. Print Owner/Signing Official's name and title (person legally responsible for facility and compliance):
Craig McBride, Corporate Engineer
3. Mailing Address for person listed in item 2 above:
1701 Fall Hill Avenue, Suite 300
City:Fredricksburg State: VA Zip:22401
Phone: (540 ) 361-4863 Fax: (540 ) 361-4674
Email:cmcbrideQquarlesinc.com
4. Project Name (subdivision, facility, or establishment name -should be consistent with project name on plans,
specifications, letters, operation and maintenance agreements, etc.):
Texland Blvd. Unattended Fueling Station
5. Location of Project (street address):
11219 Texland Blvd.
City:Charlotte County:Mecklenburg
6. Directions to project (from nearest major intersection):
Take Westinghouse Blvd. Exit off of I-77 and go east. Site is at corner of Texland and Westinghouse beside
lack In The Box
7. Latitude:35.1124 Longitude:80.9211 of project
8. Contact person who can answer questions about the project:
Name:Alan W. Moseley Telephone Number: (704 ) 527-4106 ext. 225
Email:amoseleyQjjg.com
II. PERMIT INFORMATION:
1. Specify whether project is (check one): ^New ^Renewal ®Modification
2. If this application is being submitted as the result of a renewal or modification to an existing permit, list the
existing permit numberDWO# 07-2036 and its issue date (if known)December 13,2007
3. Specify the type of project (check one):
^Low Density ^High Density ^Redevelop ^General Permit ^Universal SMP ®Other
4. Additional Project Requirements (check applicable blanks):
Form SWU-101 Version 8.07 Page 1 of 4

^CAMA Major ®Sedimentation/Erosion Control ®404/401 Permit ^NPDES Stormwater
Y Information on required state permits can be obtained by contacting the Customer Service Center at
1-877-623-6748.
III. PROJECT INFORMATION
1. In the space provided below, summarize how stormwater will be treated. Also attach a detailed narrative
(one to two pages) describing stormwater management for the project .
Biorentional cell is used to treat runoff from impervious areas.
2. Stormwater runoff from this project drains to the Catawba River basin.
3. Total Site Area: 1.618 acres 4. Total Wetlands Area: 0.164 acres
5. 100' Wide Strip of Wetland Area: acres (not applicable if no wetlands exist on site)
6. Total Project Area**:0.67 acres 7. Project Built Upon Area:41.4
8. How many drainage areas does the project have?1
9. 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 Sugar Creek
Stream Class & Index No. C, 11-137
Drainage Area (sf) 31799
Existing Impervious' Area (sf) 0
Proposed Impervious~Area (sf) 29185
Impervious' Area (total) 91.8
Impervious Surface Area Drainage Area 1 Drainage Area 2
On-site Buildings (sf) 60
On-site Streets (sf) 29125
On-site Parking (sf) 0
On-site Sidewalks (sf) 0
Other on-site (sf) 0
Off-site (sf) 0
Total (sf): 29125
'~ Impervious area is defined as the built upon area including, but not limited to, buildings, roads, parking areas,
sidewalks, gravel areas, etc.
**Total project area shall be calculated based on the current policy regarding inclusion of wetlands in the built upon area
percentage calculation.
10. How was the off-site impervious area listed above derived?N/A, offsite water bypasses BMP
IV. DEED RESTRICTIONS AND PROTECTIVE COVENANTS
One of the following deed restrictions and protective covenants are required to be recorded for all subdivisions,
outparcels and future development prior to the sale of any lot. If lot sizes vary significantly, a table listing each lot
number, size and the allowable built-upon area for each lot must be provided as an attachment.
Form SWU-101 Version 8.07 Page 2 of 4

Norm DRPC-1
Form DRPC-2
Form DRPC-3
Form DRPC-4
Form DRPC-5
Form DRPC-6
High Density Commercial Subdivisions
High Density Developments with Outparcels
High Density Residential Subdivisions
Low Density Commercial Subdivisions
Low Density Residential Subdivisions
Low Density Residential Subdivisions with Curb Outlets
By your signature below, you certify that the recorded deed restrictions and protective covenants for this
prolect shall include all the applicable items required in the above form, that the covenants will be binding on
all parties and persons claiming under them, that they will run with the land, that the required covenants
cannot be changed or deleted without concurrence from the State, and that they will be recorded prior to the
sale of any lot.
V. SUPPLEMENT FORMS
T'he applicable state stormwater management permit supplement form(s) listed below must be submitted for each
BMP specified for this project. Contact the Stormwater and General Permits Unit at [phone] for the status
and availability of these forms.
Form SW401-Low Density Low Density Supplement
Form SW401-Curb Outlet System Curb Outlet System Supplement
Form SW401-Off-Site System Off-Site System Supplement
Form SW401-Wet Detention Basin Wet Detention Basm Supplement
Form SW401-Infiltration Basin Infiltration Basin Supplement
Form SW401-Infiltration Trench Underground Infiltration Trench Supplement
Form SW401-Bioretention Cell Bioretention Cell Supplement
Form SW401-Level Spreader Level Spreader/Filter Strip/Restored Riparian
Form SW401-Wetland Constructed Wetland Supplement
Form SW401-Grassed Swale Grassed Swale Supplement
Form SW401-Sand Filter Sand Filter Supplement
Buffer Supplement
Form SWU-101 Version 8.07 Page 3 of 4

`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 appropriate DWQ Office. (Appropriate office may be found by locating project on the
interactive online map at http:/'h2o.enr.state.nc.us/su/ntsi maps.htm)
Please indicate that you have provided the following required information by initialing in the space provided
next to each item.
Initials
• Original and one copy of the stormwater Management Permit Application Form ~ti--~
• Original and one copy of the Deed Restrictions & Protective Covenants Form N/p
• Original of the applicable Supplement Form(s) and O&M agreement(s) for each BMP ~~-~--
• Permit application processing fee of $505 ($4,000 for Express) payable to NCDENR ~~~
• Calculations & detailed narrative description of stormwater treatment/management ~~
• Copy of any applicable soil report N/,~
• Three copies of plans and specifications (sealed, signed & dated), including: ~~
-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 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)
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. / ~~~
Designated agent (individual or firm): 1, rr`%h ~/~~~~'S ~ `l~'G~~Q/~cl
Mailing Address: ~~~~ .S~ c' fL/F`f"~7 ~i ~JCI ~~~V`~ ~ ~~~ ,~/~ l G~
City: l ~~d~C/- ~ ~i~ State: /V~/G1 Zip: ~r~> ,~ 7
Phone: (~~ 7~ 1 /~~7' ~7L'~C~~, Fax: ( 7~'T" 1 ~~'` SZ7- ~f ~ ~ c~
Email: ~?~~Ii? ~S!~~~ . Cors'1
VIII. APPLICANT'S CERTIFICATION
I, (print or type name of person listed in General Information, item 2) Cr'9 ~~~ ~~~+ ~f
certify that the information included on this permit application form is, 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 will be recorded, and that the proposed project complies with the requirements of 15A
NCAC 2H .1000.
Signature:,
Date: ! - ~~ - ~~
Form SWU-101 Version 8.07 Page 4 of 4

Permit Number:
(to be provided by DWQ)
o~oF wnr~9QG
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`- ~' -~
NCDENR
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 Quarles Q-Card 816
Contact name Alan W. Moseley, P.E.
Phone number 704-527-4106
Date January 2, 2008
Drainage area number 1
II. DESIGN INFORMATION
Site Characteristics
Drainage area 31,799 ftZ
Impervious area 29,185 ftZ
Percent impervious 91.8%
Design rainfall depth 12.0 inch
Peak Flow Calculations
Is prelpost control of the 1-yr, 24-hr peak flow required? N (Y or N)
1-yr, 24-hr runoff depth in
1-yr, 24-hr intensity in/hr
Pre-development 1-yr, 24-hr peak flow ft3/sec
Post-development 1-yr, 24-hr peak flow ft3/sec
Pre/Post 1-yr, 24-hr peak control ft3/sec
Storage Volume: Non•SR Waters
Design volume 2,731.0 ft3
Storage Volume: SR Waters
Pre-development 1-yr, 24-hr runoff ft3
Post-development 1-yr, 24-hr runoff ft3
Minimum volume required 0 ft3
Volume provided ft3
Cell Dimensions
Ponding depth of water 12 inches OK
Ponding depth of water 1.00 ft
Surface area of the top of the bioretention cell 2,784.1 ft2 OK
Length: 78 ft OK
Width: 38 ft OK
-or- Radius ft
Soils Report Summary
Drawdown time, ponded volume 8 hr OK
Drawdown time, to 24 inches below surface 6.4 hr OK
Drawdown time, total: 14.4 hr
In-situ soil:
Soil permeability 1.00 in/hr OK
Planting media soil:
Soil permeability 1.00 in/hr OK
Soil composition
Sand (by weight) 85% OK
Fines (by weight) 12% OK
Organic (by weight) 3% OK
Form SW401-Bioretention-Rev.2
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r a ;nrTif~'t 11i,r;.r;
Parts I and II. Design Summary, Page 1 of 2

i
flKosphorus Index (P-Index)
Basin Elevations
Temporary pool elevation
Planting elevation (top of the mulch)
Bottom of the cell
Planting depth
Depth of mulch
SHWT elevation
Are underdrains being installed?
Total: 100%
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
Distance from bottom to SHWT
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 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 recorded drainage easement with a
recorded access easement 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
(8'inches gravel followed by 3-5 ft of grass)
Grassed swale
Forebay
30 (unitless) OK
624 fmsl
622.5 fmsl OK
620.5 fmsl
2ft
2 inches OK
615.2 fmsl OK
Y (Y or N)
3 OK
10 OK
1ft
619.5 fmsl
4.3 ft OK
Y (Y or N) OK
N (Y or N)
Y (Y or N) OK
Y (Y or N) OK
Permit Number:
(to be provided by DWQJ
V J.J Il
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
0.72 ft/sec OK
N (Y or N) OK
N (Y or N) OK
Y (Y or N) OK
X
OK
Form SW401-Bioretention-Rev.2 Parts I and II. Design Summary, Page 2 of 2

Permit Number: O 1 ^ ~ 3 ~
(to be provided by DWQ)
Drainage Area Number:
Bioretention Inspection 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 inspection 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 inspection 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 roblems: How I will remediate the roblem:
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 a lication.
The inlet device: pipe, The pipe is clogged (if Unclog the pipe. Dispose of the
stone verge or Swale a licable . sediment off-site.
The pipe is cracked or Replace the pipe.
otherwise damaged (if
a licable .
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 roblems with erosion.
Stone verge is clogged or Remove sediment and clogged
covered in sediment (if stone and replace with clean stone.
a licable .
--a -.
f". 1 c.. G._. - ~
~Z4?
1,~ ~i ~_ ~! l U ~ ~3
Form SW401-Bioretention I&M-Rev.2 ,.~~ ;,p,.,, ,,,°~~~ `_ i;~R",Ay~.'47~~ "`' Page 1 of 4

BMP element: Potential roblems: How I will remediate the roblem:
The pretreatment area Flow is bypassing Regrade if necessary to route all
pretreatment area and/or flow to the pretreatment area.
flies have formed. Restabilize the area after radin .
Sediment has accumulated to Search for the source of the
a depth greater than three sediment and remedy the problem if
inches. possible. Remove the sediment and
restabilize the retreatment area.
Erosion has occurred. Provide additional erosion
protection such as reinforced turf
matting or riprap if needed to
revent future erosion roblems.
Weeds are present. Remove the weeds, preferably by
hand.
The bioretention cell: Best professional practices Prune according to best professional
vegetation show that pruning is needed practices.
to maintain optimal plant
health.
Plants are dead, diseased or Determine the source of the
dying. problem: soils, hydrology, disease,
etc. Remedy the problem and
replace plants. Provide aone-time
fertilizer application to establish the
ground cover if a soil test indicates
it is necessa
Tree stakes/wires are present Remove tree stake/wires (which
six months after lantin can kill the tree if not removed .
The bioretention cell: Mulch is breaking down or Spot mulch if there are only random
soils and mulch has floated away. void areas. Replace whole mulch
layer if necessary. Remove the
remaining much and replace with
triple shredded hard wood mulch at
a maximum de th of three inches.
Soils and/or mulch are Determine the extent of the clogging
clogged with sediment. -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
ossible.
An annual soil test shows that Dolomitic lime shall be applied as
pH has dropped or heavy recommended per the soil test and
metals have accumulated in toxic soils shall be removed,
the soil media. disposed of properly and replaced
with new lantin media.
Form SW401-Bioretention I&M-Rev.2 Page 2 Of 4

BMP element: Potential roblems: How I will remediate the roblem:
The underdrain system Clogging has occurred. Wash out the underdrain system.
(if a licable
The drop inlet Clogging has occurred. Clean out the drop inlet. Dispose of
the sediment off-site.
The dro inlet is dama ed Re air or re lace the dro 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.
Forni SW401-Bioretention I&M-Rev.2 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: Texland Blvd., Unattended Fuel Station
BMP drainage area number:
Print name: Craig McBride
Title: ~~t+r-~o!'y fc°_ ~~'-9i h ~E.~" ~ ~cit'r/~S ~t?~h ~~.~~~ . ~`1 ~,
Address: 1701 Fall Hill Ave. Suite 300
Phone: [phone]
Date: ~ ~~ ~ ~ _©~
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president.
I, ~ ,, -~.. , a Notary Public for the State of
~y
> ,-~aiu~of ~ r ~~,~,~~ ~, s~~~~ , do hereby certify that
,'C` G,~ v ~ ~ _ ~ ~ c~ ~ personally appeared before me this L 1~
day of , ~~, and acknowledge the due execution of the
forgoing bioretention aintenance requirements. Witness my hand and official seal,
SEAL
My commission expires
Form SW401-Bioretention I&M-Rev. 2
Page 4 of 4

o~-afl3~
STORMWATER MANAGEMENT PLAN
Quarles QCard 816
Unmanned Fuel Station
Charlotte, North Carolina
January 11, 2008
~.~` P~H Cqq •~
p •A•......~~~
/boy
Jordan, Jones & Goulding
9101 Southern Pine Blvd., Suite 160
Charlotte, North Carolina 28277
[phone]
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TABLE OF CONTENTS
PAGE
Narrative ..........................................................................................................................................1
Supporting Calculations ...................................................................................................................2

NARRATIVE
PROJECT DESCRIPTION
The purpose of this project is to construct an unmanned fueling station on a currently vacant lot
in Charlotte, NC. Approximately 1.8 acres will be disturbed during the construction process. Of
that area, approximately 1.6 acres is on the developed property and 0.17 acres is in a road Right-
of-Way.
SITE DESCRIPTION
The site is approximately 1.6 acres and is located off of Texland Blvd. at the corner of Texland
Blvd. and Westinghouse Blvd. in Charlotte, NC. The lot adjoins a restaurant to the southeast and
a vacant lot to the southwest. The site will be accessed from Texland Blvd. to the northwest.
Westinghouse Blvd. borders the site to the Northeast. The 6.63 acre drainage basin to the site
includes the neighboring parcels and a portion of Texland Blvd. Historical land use in the area
was wooded. The developed restaurant site includes a detention pond which returns the post-
development flows from that site to predevelopment levels.
ADJACENT PROPERTY
Land use in the immediate vicinity is commercial with the neighboring lot to the southwest being
vacant.
SOILS
The soil throughout the project area and associated drainage area is entirely Iredell fine sandy
loam, at 1-8 percent slopes (IrB) as identified on the latest USDA soils data. This soil type is
classified as Hydrology Group D utilizing Table 16 of the Mecklenburg County Soil Survey. A
soils survey was not conducted on the site. This is due to the fact that the bioretention area to be
installed will require a select fill material. Surrounding soil will not affect the bioretention area
as its porosity is less than that of the select fill and the water table in the area is significantly
below the pond bottom.

SUPPORTING CALCULATIONS
One bioretention pond will be utilized at the site to reduce total suspended solids (TSS) for the
site's impervious runoff to 85%. Design calculations for the bioretention area are on the
following pages.

Raingarden Sizing
1. Runoff Volume Calculations
(NCDENR Stormwater BMP Manual, 3.3.1., "Simple Method" - Schueler, 1987)
Calculate Runoff coefficient R„
Formula:
R~=0.05+0.9(IA)
Where:
IA =Impervious fraction (Impervious portion of drainage area/drainage area)
Drainage Area = 0.73 acres
Impervious Area = 0.67 acres
IA = 1.09
R~ = 1.03
Calculate volume of runoff
Formula:
V=3630*Rp*R~*A
Where:
V =Volume of runoff to be controlled (ft3)
Rp =Design storm depth (in)
A =Watershed area (ac)
Rp = 1 inch
A = 0.73 acres
V = 2730.98 ft3
2. Entrance Weir Length
(grater and King, 1976)
Minimum weir length perpendicular to flow calculated with a 1" depth of water
Formula:
Q = CL(H)l.s
Where:
Q =Peak storm for 1" - 6 hour storm (ft3/s) from hydrology software
C =Broad crested weir coefficient (assume 2.5 for 1"depth)
L =Length of weir perpendicular to flow (ft)
H =Head above weir crest (ft) (use 1" de th
Q = 1.07 (ft3/s)
C = 2.50
H = 1.00 inch
L = 17.79 ft minimum width
Velocity of stormwater:
Formula:
V= Q/A
Q = 1.07 (ft3/s)
A = 1.48 ftZ
V = 0.72 (ft/s)

3. Determine Size of Bioretention Pond
According to Section 12.3.3. of the NCDENR Stormwater BMP Manual, the cell must hold the first inch of
runoff from the entire area. The surface area required is equal to the required treatment volume divided
by the ponding depth.
d = 12 inches
A = 2730.98 ft2
4. Size Underdrain System
(NCDENR Stormwater BMP Manual, 5.7)
Determine flow rate throuah soil media
Darcv's Equation: Q = 2.32e-5 * k * A * (H / L)
Where:
Q = Flow (Rate of Draw) through Bioretention Soil (ft3/s)
k = Hydraulic Conductivity of soil (in./hr.)
A = Surface Area of Bio-Retention Area (ftz)
H = Height of Water above Drainage Pipe (Underdrain)
L = Thickness of Soil Bed
k = 1.0 in./hr.
H = 3.0 ft
L = 2.0 ft
Q = 0.0950 cfs
Determine pipe diameter to handle flow with a safety factor of 10:
(Bioretention Design Worksheet, Bill Hunt, NCSU)
Formula: Where:
D = 16 * [(Q * n) / So.s~~s~s> D =Diameter of single pipe (in.)
Q =Design flow (ft3/s)
n =roughness factor
S =slope
Safety Factor = 10
n = 0.011
S = 0.50%
D = 7.81 inches
See Table 5-1 of NCDENR Stormwater BMP Manual to determine size and number of pipes
For 7.81 inches use 2-6" pipes

5. Time to draw water down to 2 feet below surface:
(Bioretention Design Worksheet, Bill Hunt, NCSU)
Time to Drawdown water from Inundation to Saturation at Surface:
Volume of water above surface equals surface area times depth (ft3)
V~ = 2730.98 ft3
Time to remove V1 at flowrate Q hr
T~ = 8.0 hr
Time to draw down to 2.0 feet below surface:
Assume 40% Porosity
Volume=Areax2'x0.40
VZ = 2184.78 ft3
Time to remove VZ at flowrate Q (hr)
TZ = 6.4
Total time to draw to 2.0 feet below surface:
TT = 14.4 hr