20080828 Ver 1_More Info Received_20081119

Environmental Consultants, PA
Road • Raleigh, North Carolina 27614 • Phone: [phone] • Fax: [phone]
www.SandEC.com
Division of Water Quality
Attn: Ian McMillan/Annette Lucas
2321 Crabtree Boulevard
Suite 250
Raleigh, NC 27604
November 19, 2008
S&EC Project # 10459.W3
DWQProject # 08-0828
Action ID #2008-01615
NOV 2008
DENk - i#AJ `5 C)u)ALr Y
VjE?IANDS AND STORMV?'ATEK BRANCH
Re: Reply to the Division of Water Quality's 11/05/08 request for additional information
White Oak Development
Wake County, North Carolina
Dear Mr. McMillan and Ms. Lucas:
This letter is in response to your letter dated November 5, 2008 which requested
additional information for White Oak Development. The following restates your
questions/comments and is then followed by our response.
Additional Information Requested on November 5 2008
The Stormwater Management Plan that was approved by the Town of Apex on September
24, 2008 fails to meet the requirements of its local Phase II Program because no
stormwater treatment has been provided for the parking lot adjacent to the stream.
Because of this, the DWQ cannot accept the locally approved stormwater management
program as meeting the requirements of the 401 Certification Program. Please submit a
revised Stormwater management plan to the DWQ for review and approval that includes
the following items:
1. A stormwater management plan that removes a minimum of 85 percent
TSS and 30 percent TN from the Stormwater generated by the entire
proIect (including all parking areas For each proposed BMP, please
provide a completed BMP Supplement Form, with all the required
items. The BMP Supplement Forms are available at the following
website: http://h2o.enr.state.nc.uslsulbmp_forms.htm.
2. The Required Items Checklist portion of the Sand Filter Supplement
Form, with all required items attached In this information, please
Charlotte Office: Greensboro Office:
248 LePhillip Court 3817-E Lawndale Drive
Concord, NC 28025 Greensboro, NC 27455
Phone: [phone] Phone: [phone]
Fax: [phone] Fax: [phone]
provide boring data to show the level of the seasonal high water table
(SHWT) within the proposed footprint of the sand filter. The BMP
Manual requires that there be at least a two foot separation between
the invert of the sand filter and the SHWT. Since the Sand Filter has
been sited adjacent to a wetland, it seems likely that the SHWT is too
high to provide the needed separation. If the SHWT is too high to
tallow for a sand filter, then please either relocate the sand filter to
higher ground if possible or provide a more appropriate BMP for an
area with a high groundwater table.
Please see the attached supplemental information packet supplied by Jones & Cnossen
Engineering. This packet includes updated operation and maintenance agreements,
updated stormwater device supplement forms, revised stormwater calculations and a
geotechnical report.
Please feel free to call me if you require any further explanation.
Sincerely,
Nicole J. T omson
Regulatory Specialist
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Pre-Development Runoff Calculations
/. Calculate pre-development 'C-value'
Existing 51te 15 entirely wooded with natural slopes 1e55 than 7%. A C-value of 0.3 15 appropriate.
2. Calculate pre-development l -year runoff
Qpre = CIA
Qpre = (0.3)(3.0)(5.13)
Qpre = 4.6 cf5
3. Calculate pre-development 2-year runoff
Qpre = CIA
Qpre = (0.3)(5.8)(5.13)
Qpre = 8.9 cf5
4. Calculate pre-development / 0-year runoff
Qpre = CIA
Qpre = (0.3)(7.2)(5.13)
Qpre = I I . I cf5
Post-Development Runoff Calculations
l . Calculate post-development 'C-value'
Description Area (ac) C-value
Building and Parking Areas I .67 0.90
Thoroughfare Buffer 0.84 0.30
Stream Buffer 1.23 0.30
Landscape Areas 1.39 0.45
TOTAL DRAINAGE AREA 5.13 acres
Composite 'C-value' = 0.54
2. Calculate post-development l -year runoff without stormwater devices
Q;,, = CIA
Qpost = (0.54)(3.0)(5.13)
Q,151 = 8.3 cf5
3. Calculate post-development 2-year runoff without stormwater devices
Qpost = CIA
Qp05t = (0.54)(5.8)(5.13)
Qpost = 16. I cf5
4. Calculate post-development / 0-year runoff without stormwater devices
Qpost = CIA
Qpost = (0.54)(7.2)(5.13)
Qpost = 19.9 cf5
Page 3
5. Calculate post-development /-year runoff with stormwater devices
Description a Icf5
Pipe Storage Outflow 1 . 1
Parking Lot Direct Runoff 1.0 (0.7 ac * 3.0 * 0.5)
Site Direct Runoff 2.3 (2.23 ac * 3.0 * 0.35)
TOTAL 4.4 cf5
The calculated post-development runoff for the I -year storm (4.4 cf5) 15 1e55 than the calculated pre-
development runoff for the I -year storm (4.6 cf5).
6. Calculate post-development 2-year runoff with stormwater devices
OeSCnption
Pipe Storage Outflow
Parking Lot Direct Runoff
51te Direct Runoff
TOTAL
Q U5
1 .1
2.0 (0.7 ac * 5.8 * 0.5)
4.5 (2.23 ac * 5.8 * 0.35)
7.6 cf5
The calculated post-development runoff for the 2-year storm (7.6 cf5) 15 le55 than the calculated pre-
development runoff for the 2-year storm (8.9 cf5).
7. Calculate post-development 1 0-year runoff with stormwater devices
Description Q (cf5)
Pipe Storage Outflow 1.2
Parking Lot Direct Runoff 2.5 (0.7 ac * 7.2 * 0.5)
Site Direct Runoff 5.6 (2.23 ac * 7.2 * 0.35)
TOTAL 9.3 cf5
The calculated post-development runoff for the I 0-year storm (9.3 cf5) 15 1e55 than the calculated pre-
development runoff for the I 0-year storm ( I I . I cf5).
Page 3
Jones & Cnossen
Adc®?
ENGINEERING, PLLC
Civil Engineering I Construction Management I Land Planning
Cyndi Karoly
DWQ 401 Permitting Unit
I G50 Mail service Center
Raleigh, NC 27699-1 G50
RE: White Oak Development
DWQ Project # 08-0828
Dear Ms. Karoly,
221 N. SALEM ST, SUITE 200
PO BOX 1062
APEX, NC 27502
Office: 919-387-1174
Fax: [phone]
www.jonescnossen.com
November 12, 2008
We received your review letter dated November 5 and understand your concern with seasonal high
water table for this project. Based upon your concerns and our new bioretention areas, I personally
went to the site and hand augered holes at the locations of the three new bioretention areas and
the sand filter area. I augered holes two feet deep below existing ground and then returned to the
site later that day to monitor the holes for groundwater height.
The auger holes at bioretention areas 2 and 3 were completely dry which was no surprise based
upon the dry, coarse sand material that came out of the holes. The auger hole at bioretention area
l showed a moist silty sand soil type and no groundwater appeared in the hole. The auger hole at
the sand filter was a moist clayey silt sample when drilled and did accumulate approximately six
inches of water. The ground elevation at the auger hole was approximately 4 17.5 based upon
survey information and that would give us a groundwater elevation of 4 1 G.O. We made slight
modifications to the elevations at the sand filter to achieve the two feet of separation.
As construction manager on this site I can state that the area behind the proposed parking lot and
outside the Town of Apex buffer near the bioretention areas was over excavated approximately six to
eight feet. We used the excavated material on site for structural fill and then filled the hole with
topsoil from the site which has a high content of sand and organic material. This topsoil bed should
make an excellent base for the bioretention areas and the associated landscaping.
I hope that this information will satisfy the concern over soils and groundwater heights on this
project. Please feel free to call me if you have any questions.
S9MOnC5, 5P.E.
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Cc: Nicole Thomson, 5$EC
06102 DWQ groundwater letter.doc
Permit Number:
(to be provided by DWQ)
AAA
NCDENR
Hof warF9Q
O C
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 111) must be printed, filled out and submitted along with all of the required information.
1, PROJECT' INFORMATION
_
Project name
White Oak Development
Contact name Mr. Alonzo Wilson
Phone number 919-362-6768
Date November 11, 2008
Drainage area number Bioretention Area 1
--
II,, DESIGN INFORMATION J
Site Characteristics
Drainage area 5,940 ft2
Impervious area 4,774 ft2
Percent impervious 80.4% %
Design rainfall depth 1.0 inch
Peak Flow Calculations
Is pre/post control of the 1-yr, 24-hr peak flow required? N (Y or N)
1-yr, 24-hr runoff depth 0.42 in
1-yr, 24-hr intensity 5.13 in/hr
Pre-development 1-yr, 24-hr peak flow 4.600 ft3/sec
Post-development 1-yr, 24-hr peak flow 4.400 ft3/sec
Pre/Post 1-yr, 24-hr peak control -0.200 ft3lsec
Storage Volume: Non-SA Waters
Minimum volume required 329.0 ft3
Volume provided 340.0 ft3 OK
Storage Volume: SA Waters
1.5" runoff volume ft3
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 340.0 ft2 OK
Length: 34 ft OK
Width: loft OK
-or- Radius ft
Media and Soils Summary
Drawdown time, ponded volume 6 hr OK
Drawdown time, to 24 inches below surface 12 hr OK
Drawdown time, total: 18 hr
In-situ soil:
Soil permeability 2.00 in/hr OK
Planting media soil:
Soil permeability 2.00 in/hr OK
Soil composition
% Sand (by weight) 85% OK
% Fines (by weight) 10% OK
% Organic (by weight) 5% OK
Total: 100%
Phosphorus Index (P-Index) of media 10 (unitless) OK
Form SW401-Bioretention-Rev.5 Parts I and II. Design Summary, Page 1 of 2
Permit Number:
(to be provided by DWQ)
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?
1.00 fmsl OK
y (Y or N) OK
n (Y or N)
0 fmsl
3 inches OK
-3 fmsl
3ft
0 inches
N (Y or N)
How many clean out pipes are being installed? N
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 0 ft
the bottom of the cell to account for underdrains
Bottom of the cell required -3 fmsl
SHWT elevation -5 fmsl
Distance from bottom to SHWT 2 ft
Planting Plan
Number of tree species 0
Number of shrub species 0
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? _
OK
OK
OK
Y (Y or N) OK
Y (Y or N) OK
What is the length of the vegetated filter? Du 11
Does the design use a level spreader to evenly distribute flow? Y (Y or N) Submit a level spreader supplement.
Is the BMP located at least 30 feet from surface waters (50 feet if Y (Y or N) OK
SA waters)?
Is the BMP localed at least 100 feet from water supply wells? Y (Y or N) OK
Are the vegetated side slopes equal to or less than 3:1? Y (Y or N) OK
Is the BMP located in a proposed drainage easement with access
f W ROW 1) Y (Y or N) OK
to a public Right o ay ( ). _
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
0.56 ft/sec OK
N (Y or N) OK
N (Y or N) OK
Y (Y or N) OK
X
OK
Form SW401-Bioretention-Rev.5 Parts I and II. Design Summary, Page 2 of 2
Permit Number:
(to be provided by DWQ)
?CF W A TF9
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 111) must be printed, filled out and submitted along with all of the required information.
I. PROJECT INFORMATION
Project name White Oak Development
Contact name Mr. Alonzo Wilson
Phone number 919-362-6768
Date November 11, 2008
Drainage area number Bioretention Area 2
Ill. DESIGN INFORMATION
Site Characteristics
Drainage area 11,580 ft2
Impervious area 9,420 ft2
Percent impervious 81.3% %
Design rainfall depth 1.0 inch
Peak Flow Calculations
Is pre/post control of the 1-yr, 24-hr peak flow required? N (Y or N)
1-yr, 24-hr runoff depth 0.42 in
1-yr, 24-hr intensity 5.13 in/hr
Pre-development 1-yr, 24-hr peak flow 4.600 ft3/sec
Post-development 1-yr, 24-hr peak flow 4.400 ft3/sec
Pre/Post 1-yr, 24-hr peak control -0.200 ft3/sec
Storage Volume: Non-SA Waters
Minimum volume required 772.0 ft3
Volume provided 780.0 ft3 OK
Storage Volume: SA Waters
1.5" runoff volume ft3
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 820.0 ft2 OK
Length: 82 ft OK
Width: loft OK
-or- Radius ft
Media and Soils Summary
Drawdown time, ponded volume 12 hr OK
Drawdown time, to 24 inches below surface 24 hr OK
Drawdown time, total: 36 hr
In-situ soil:
Soil permeability 2.00 in/hr OK
Planting media soil:
Soil permeability 2.00 in/hr OK
Soil composition
% Sand (by weight) 85% OK
% Fines (by weight) 10% OK
% Organic (by weight) 5% OK
Total: 100%
Phosphorus Index (P-Index) of media 10 (unitless) OK
Form SW401-Bioretention-Rev.5 Parts I and II. Design Summary, Page 1 of 2
Permit Number:
(to be provided by DWQ)
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?
1.00 fmsl OK
Y (Y or N) OK
(Y or N)
0 fmsl
0 inches Insufficient mulch depth, unless installing grassed cell.
-3 fmsl
3ft
0 inches
N (Y or N)
ft
N OK
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
fmsl
Bottom of the cell required
0 3 5 fmsl
SHWT elevation
Distance from bottom to SHWT 2 ft OK
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
0
0
3 OK
Y (Y or N) OK
Y (Y or N) OK
ou It
Y (Y or N) Submit a level spreader supplement.
Y (Y or N) OK
Y (Y or N) OK
Y (Y or N) OK
Y (Y or N) OK
1
08 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
X
OK
Form SW401-Bioretention-Rev.5 Parts I and II. Design Summary, Page 2 of 2
Permit Number:
(to be provided by DWQ)
o??¢ W ATF9?G
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.
L PROJECT INFORMATION
Project name White Oak Development
Contact name Mr. Alonzo Wilson
Phone number 919-362-6768
Date November 11, 2008
Drainage area number Bioretention Area 3
Il. DESIGN INFORMATION
Site Characteristics
Drainage area 9,021 ft2
Impervious area 6,760 ft2
Percent impervious 74.9% %
Design rainfall depth 1.0 inch
Peak Flow Calculations
Is pre/post control of the 1-yr, 24-hr peak flow required? N (Y or N)
1-yr, 24-hr runoff depth 0.42 in
1-yr, 24-hr intensity 5.13 in/hr
Pre-development 1-yr, 24-hr peak flow 4.600 ft3/sec
Post-development 1-yr, 24-hr peak flow 4.400 ft3/sec
Pre/Post 1-yr, 24-hr peak control -0.200 ft3/sec
Storage Volume: Non-SA Waters
Minimum volume required 553.0 ft3
Volume provided 560.0 ft3 OK
Storage Volume: SA Waters
1.5' runoff volume ft3
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 560.0 ft2 OK
Length: 56 ft OK
Width: loft OK
-or- Radius ft
Media and Soils Summary
Drawdown time, ponded volume 6 hr OK
Drawdown time, to 24 inches below surface 12 hr OK
Drawdown time, total: 18 hr
In-situ soil:
Soil permeability 2.00 in/hr OK
Planting media soil:
Soil permeability 2.00 in/hr OK
Soil composition
% Sand (by weight) 85% OK
% Fines (by weight) 10% OK
% Organic (by weight) 5% OK
Total: 100%
Phosphorus Index (P-Index) of media 10 (unitless) OK
Form SW401-Bioretention-Rev.5 Parts I and II. Design Summary, Page 1 of 2
Permit Number:
(to be provided by DWQ)
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
1.00 fmsl OK
y (Y or N) OK
n (Y or N)
0 fmsl
3 inches OK
-3 fmsl
3ft
0 inches
Are underdrains being installed? N (Y or N)
How many clean out pipes are being installed? N OK
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 0 ft
the bottom of the cell to account for underdrains
Bottom of the cell required -3 fmsl
SHWT elevation -5 fmsl
Distance from bottom to SHWT 2 ft OK
Planting Plan
Number of tree species 3
Number of shrub species 3
Number of herbaceous groundcover species 3 OK
Additional Information
e esign vo ume ypass e
I o
Does volume n excess Y (Y or N) OK
bioretention cell?
Does volume in excess of the design volume flow evenly distributed Y (Y or N) OK
through a vegetated filter?
What is the length of the vegetated filter? 50 ft
Does the design use a level spreader to evenly distribute flow? Y (Y or N) Submit a level spreader supplement.
Is the BMP located at least 30 feet from surface waters (50 feet if Y (Y or N) OK
SA waters)?
Is the BMP localed at least 100 feet from water supply wells? Y (Y or N) OK
Are the vegetated side slopes equal to or less than 3:1? Y (Y or N) OK
Is the BMP located in a proposed drainage easement with access Y (Y or N) OK
to a public Right of Way (ROW)?
Inlet velocity (from treatment system) 0.84 ft/sec OK
Is the area surrounding the cell likely to undergo development in N (Y or N) OK
the future?
Are the slopes draining to the bioretention cell greater than 20%? N (Y or N) OK

Is the drainage area permanently stabilized?
Y
(Y or N) th d I b th
f
OK
Pretreatment Used
(Indicate Type Used with an "X" in the shaded cell)
Gravel and grass
X
(81inches gravel followed by 3-5 ft of grass)
Grassed swale OK
Forebay
Other
Form SW401-Bioretention-Rev.5 Parts I and II. Design Summary, Page 2 of 2
Permit No:
(to be assigned by DWQ)
III. REQUIRED ITEMS CHECKLIST
Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to
indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a
requirement has not been met, attach justification.
Pagel Plan
Initials Sheet No.
1. Plans (1" - 50' or larger) of the entire site showing:
Design at ultimate build-out,
Off-site drainage (if applicable),
Delineated drainage basins (include Rational C coefficient per basin),
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.
G ?3 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
c- 13 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]
4. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. The
results of the soils report must be verified in the field by DWQ, by completing & submitting the soils
investigation request form. County soil maps are not an acceptable source of soils information. All
elevations shall be in feet mean sea level (fmsl). Results of soils tests of both the planting soil and the in
situ soil must include:
Soil permeability,
Soil composition (% sand, % fines, % organic), and

1 7? P-index.
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.
? 6. An assurance that the installed system will meet design specifications upon initial operation once the
project is complete and the entire drainage area is stabilized.
l 7. A construction sequence that shows how the bioretention cell will be protected from sediment until the
entire drainage area is stabilized.
T 8. The supporting calculations (including underdrain calculations, if applicable).
9. A copy of the signed and notarized inspection and maintenance (I&M) agreement.
_ 10. A copy of the deed restriction.
Form SW401-Bioretention-Rev.5 Part III, Page 1 of 1
Bioretention Area Calculations Project # 06102
Drainage Area 1:
Drainage Area = 0.13 acres
Q (flow) = 0.84 cfs
la (Impervious Area) = 0.72 %
Calculate Rv number:
Rv = 0.05 + 0.9 la
Rv = 0.698 unitless
Calculating Required Volume of Bioretention Area:
V (volume) = 3630 * Rd*Rv*A
Rd = design depth of rainfall =1.0 in
A = Watershed area = 0.13 Acres
V = 329 cubic feet
Calculating Required Surface Area of Bioretention Area:
Surface Area = Volume/ Depth
Depth = 12 inches
Surface Area = 329 sq ft
Choose Appropriate Dimensions:
Since the miminimum side length is 10 feet, we have decided on dimensions of 34'x10'. This would make
are proposed surface area 340 sq ft and the volume 340 cubic feet and it satisfies the requirements.
Drainage Area 2:
Drainage Area = 0.27 acres
Q (flow) = 1.08 cfs
la (Impervious Area) = 0.82 %
Calculate Rv number:
Rv = 0.05 + 0.9 la
Rv = 0.788 unitless
Calculating Required Volume of Bioretention Area:
V (volume) = 3630 * Rd*Rv*A
Rd = design depth of rainfall = 1.0 in
A = Watershed area = 0.27 Acres
V = 772 cubic feet
Page 1 of 2
Bioretention Area Calculations Project # 06102
Calculating Required Surface Area of Bioretention Area:
Surface Area = Volume/ Depth
Depth = 12 inches
Surface Area = 772 sq ft
Choose Appropriate Dimensions:
Since the miminimum side length is 10 feet, we have decided on dimensions of 78'x10'. This would make
are proposed surface area 780 sq ft and the volume 780 cubic feet and it satisfies the requirements.
Drainage Area 3:
Drainage Area = 0.21 acres
Q (flow) = 0.84 cfs
la (Impervious Area) = 0.75 %
Calculate Rv number:
Rv = 0.05 + 0.9 la
Rv = 0.725 unitless
Calculating Required Volume of Bioretention Area:
V (volume) = 3630 * Rd*Rv*A
Rd = design depth of rainfall = 1.0 in
A = Watershed area = 0.27 Acres
V = 553 cubic feet
Calculating Required Surface Area of Bioretention Area:
Surface Area = Volume/ Depth
Depth = 12 inches
Surface Area = 553 sq ft
Choose Appropriate Dimensions:
Since the miminimum side length is 10 feet, we have decided on dimensions of 56'x10'. This would make
are proposed surface area 560 sq ft and the volume 560 cubic feet and it satisfies the requirements.
Page 2 of 2
nn
O
CAS°Y
BIORETENTION AREA OPERATION & 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
or the public, and the pollutant removal efficiency of the BMP.
PROJECT:
White Oak Development
RESPONSIBLE PARTY: White Oak Foundation PHONE # [phone]
CONTACT.
Alonzo Wilson
ADDRESS: 1621 White Oak Church Rd.
Apex, NC 27523
NUMBER OF BIORETENTION AREAS: 3
Bioretention is the use of plants and soils for removal of pollutants from stormwater runoff via
adsorption, filtration, sedimentation, volatilization, ion exchange, and biological decomposition.
The bioretention system is defined as the bioretention cell, outlet structure, pretreatment
including forebays, grassed swales, and the vegetated filter if one is provided.
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). The watering should take place on designated days according to the
odd/even watering schedule cited in the Town of Apex Code of Ordinances.
• 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.
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. 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 Problems Problem Remediation
The entire BMP Trash/debris is present. Remove the trash/debris.
Regrade the soil if necessary to
The perimeter of the Areas of bare soil and/or remove the gully and plant a ground
cover. Water until it is established,
bioretention cell erosive gullies have formed. provide lime and a one-time
fertilizer application.
The pipe is clogged (if Unclog the pipe. Dispose of the
applicable). sediment off-site.
The pipe is cracked or
otherwise damaged (if Replace the pipe.
applicable).
Regrade the swale if necessary to
The inlet device: pipe, Erosion is occurring in the smooth it over and provide erosion
stone verge, or swale swale (if applicable). 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).
Flow is bypassing Regrade if necessary to route all
pretreatment area and/or flow to the pretreatment area. Re-
gullies have formed. stabilize the area after grading.
Search for the source of the
Sediment has accumulated to sediment and remedy the problem if
The pretreatment area a depth greater than 3 inches. possible. Remove the sediment and
restabilize the pretreatment area.
Provide additional erosion
Erosion has occurred. protection such as reinforced turf
matting or riprap if needed to
prevent future erosion problems.
Weeds are present. Remove the weeds, preferably by
hand.
Best professional practices
The bioretention cell: show that pruning is needed Prune according to best
vegetation to maintain optimal plant professional practices.
health.
BMP Element Potential Problems Problem Remediation
Determine the source of the
problem: soils, hydrology, disease,
Plants are dead, diseased, or etc. Remedy the problem and
dying. replace plants. Provide a one-time
fertilizer application to establish
ground cover.
Tree stakes/wires are present Remove tree stake/wires (which can
six months after planting. kill tree if not removed).
Spot mulch if there are only random
void areas. Replace whole mulch
Mulch is breaking down or layer if necessary. Remove the
has floated away. remaining mulch and replace with
triple shredded hard wood mulch at
a maximum depth of 3 inches.
Determine the extent of the
clogging. Remove/replace top
layers or entire media as needed.
The bioretention cell: soils Dispose of the spoil in an
and mulch Soils and/or mulch are appropriate off-site location. Use
clogged with sediment. triple shredded hard wood mulch at
a maximum depth of 3 inches.
Search for the source of the
sediment and remedy the problem if
possible.
An annual soil test shows Dolomitic lime shall be applied as
that 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 planting media.
The underdrain system Clogging has occurred. Wash out the underdrain system.
Clogging has occurred.
ggmg Clean out the drop inlet. Dispose of
the sediment off-site.
The drop inlet
The drop inlet is damaged. Repair or replace the drop inlet.
Erosion or other signs of Contact the Town of Apex Public
The outlet device damage have occurred in the Works & Utilities Department at
outlet. 249-3427.
I acknowledge and agree by my signature below that I am financially responsible for the
performance of the maintenance procedures listed above. I will perform the maintenance as
outlined, as part of the regulations set forth in Section 6.1.12 of the Town of Apex Unified
Development Ordinance.
I understand that this Agreement shall endure to the benefit of my successors in title,
whomsoever they may be in the future. I agree to notify the Town of Apex of any problems with
the BMP or prior to any changes to the BMP or responsible party.
Note: The legally responsible party should not be an HOA unless more than 50% of the lots have
been sold and a resident of the subdivision has been named the president.
Print name: C's
nA- Title: ? U IT = : y DA`rlbt
Address: 1b21 Wd 11' C7d 0 i7 ?±??X? 1JG /523
Phone: !I -
Signature:.---Gs
Date:
I, s ? h n, F_d j)cL(&3 , a Notary Public for the State of ? h ('(?, int^... ,
County of u h(lam , do hereby certify that A t}n7 n W i tSo y'1 personally
appeared before me this J_ day of 1?aembe r , 20 and acknowledge the
due execution of the foregoing bioretention area maintenance requirements. Witness my hand
and official seal, jE F F
oTA
N
SEAL ?'•..ov \G : •G
My commission expires q - g -o g
4

' Y15%
NCDENR
5,703.00 ft2
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
LEVEL SPREADER, FILTER STRIP AND RESTORED RIPARIAN BUFFER SUPPLEMENT
This form must be completely filled out, printed and submitted.
DO NOT FORGET TO ATTACH THE REQUIRED ITEMS CHECKLIST AND ALL REQUIRED ITEMS (NEXT WORKSHEET)I
L PROJECT INFORMATION
Project name White Oak Development
Contact name Stuart Jones
Phone number 919-387-1174
Date July 18, 2008
Drainage area number Level Spreader 1
[11, DESIGN INFORMATION
For Level Spreaders Receiving Flow From a BMP
Type of BMP
Drawdown flow from the BMP cfs
For Level Spreaders Receiving Flow from the Drainage Area
Drainage area
Impervious surface area
Percent impervious
Rational C coefficient
Peak flow from the 1 in/hr storm
Time of concentration
Rainfall intensity, 10-yr storm
Peak flow from the 10-yr storm
Where Does the Level Spreader Discharge ?
To a grassed bioretention cell?
To a mulched bioretention cell?
To a wetland?
To a filter strip or riparian buffer?
Other (specify)
Filter Strip or Riparian Buffer Characterization (if applicable)
Width of grass
Width of dense ground cover
Width of wooded vegetation
Total width
Elevation at downslope base of level lip
Elevation at top of bank of the receiving water
Slope (from level lip to to top of bank)
Are any draws present?
Level Spreader Design
Forebay surface area
Feet of level lip needed per cfs
Answer "Y" to one of the following:
Length based on the 1 in/hr storm?
Length based on the 10-yr storm?
Length based on the BMP discharge rate?
Design flow
Is a bypass device provided?
4,000.00 ftz
70.14 %
0.59
0.08 cfs
5.00 min
7.2 in/hr
0.56 cfs
N (Y or N)
N (Y or N)
N (Y or N)
Y (Y or N)

Please complete filter strip characterizafion below.
60.00 ft
40.00 ft
ft
100.00 ft
420.00 fmsl
414.30 fmsl
5.70 %
N (Y or N)
sq ft
13 ft/cfs
N (Y or N)
Y (Y or N)
N (Y or N)
cfs
N (Y or N)
OK
OK
A bypass device is not needed.
Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.5 Parts I. and H. Design Summary, page 1 of 2
Length of the level lip
Are level spreaders in series?
Bypass Channel Design (if applicable)
Does the bypass discharge through a wetland?
Does the channel enter the stream at an angle?
Dimensions of the channel (see diagram below):
M
B
W
y
Peak velocity in the channel during the 10-yr storm
Channel lining material
13.00 ft Level spreader length OK.
N (Y or N)
(Y or N) Do not complete this section of the worksheet.
(Y or N) Do not complete this section of the worksheet.
Do not complete this section of the worksheet.
ft Do not complete this section of the worksheet.
ft Do not complete this section of the worksheet.
ft Do not complete this section of the worksheet.
ft Do not complete this section of the worksheet,
efs Do not complete this section of the worksheet
Do not complete this section of the worksheet
I
I ? ------------ Y --------------
M
M
i B i
Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.5 Parts I. and II. Design Summary, page 2 of 2
NCDENR
r
R i c
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
LEVEL SPREADER, FILTER STRIP AND RESTORED RIPARIAN BUFFER SUPPLEMENT
This form must be completely filled out, printed and submitted.
DO NOT FORGET TO ATTACH THE REQUIRED ITEMS CHECKLIST AND ALL REQUIRED ITEMS (NEXT WORKSHEET)I
L PROJECT INFORMATION _
Project name White Oak Development
Contact name Stuart Jones
Phone number 919-387-1174
Date July 18, 2008
Drainage area number Level Spreader 2
Il. DESIGN' INFORMATION
For Level Spreaders Receiving Flow From a BMP
Type of BMP
Drawdown flow from the BMP cfs
For Level Spreaders Receiving Flow from the Drainage Area
Drainage area 11,620.00 ftZ
Impervious surface area 8,300.00 ftZ
Percent impervious 71.43 %
Rational C coefficient 0.56
Peak flow from the 1 in/hr storm 0.15 cfs
Time of concentration 5.00 min
Rainfall intensity, 10-yr storm 7.2 in/hr
Peak flow from the 10-yr storm 1.08 cfs
Where Does the Level Spreader Discharge ?
To a grassed bioretention cell? N (Y or N)
To a mulched bioretention cell? N (Y or N)
To a wetland? N (Y or N)
To a filter strip or riparian buffer? Y (Y or N) Please complete filter strip characterization below.
Other (specify)
Filter Strip or Riparian Buffer Characterization (if applicable)
Width of grass 50.00 ft
Width of dense ground cover 50.00 ft
Width of wooded vegetation ft
Total width 100.00 ft
Elevation at downslope base of level lip 422.00 fmsl
Elevation at top of bank of the receiving water 415.20 fmsl
Slope (from level lip to to top of bank) 6.80 %
Are any draws present? N (Y or N) Olt
Level Spreader Design
Forebay surface area sq ft
Feet of level lip needed per cfs 13 ft/cfs
Answer "Y" to one of the following:
Length based on the 1 in/hr storm? N (Y or N)
Length based on the 10-yr storm? Y ' (Y or N)
Length based on the BMP discharge rate? N (Y or N)
Design flow cfs
Is a bypass device provided? N (Y or N) A bypass device is not needed.
Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.5 Parts 1. and H. Design Summary, page 1 of 2
Length of the level lip
Are level spreaders in series?
Bypass Channel Design (if applicable)
Does the bypass discharge through a wetland?
Does the channel enter the stream at an angle?
Dimensions of the channel (see diagram below):
M
B
W
y
Peak velocity in the channel during the 10-yr storm
Channel lining material
14.00 ft Level spreader length OK.
N (Y or N)
(Y or N) Do not complete this section of the worksheet.
(Y or N) Do not complete this section of the worksheet.
Do not complete this section of the worksheet.
ft Do not complete this section of the worksheet.
ft Do not complete this section of the worksheet.
ft Do not complete this section of the worksheet.
ft Do not complete this section of the worksheet.
cfs Do not complete this section of the worksheet.
Do not complete this section of the worksheet.
• `x
?
A
t i Y --------------
-------------
-------------
M M
i B i
Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.5 Parts I. and II. Design Summary, page 2 of 2
NCDENR
,,/ lp ..'J Aytti??
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
LEVEL SPREADER, FILTER STRIP AND RESTORED RIPARIAN BUFFER SUPPLEMENT
This form must be completely filled out, printed and submitted.
DO NOT FORGET TO ATTACH THE REQUIRED ITEMS CHECKLIST AND ALL REQUIRED ITEMS (NEXT WORKSHEET)i
L' PROJECT INFORMATION
Project name White Oak Development
Contact name Stuart Jones
Phone number 919-387-1174
Date July 18, 2008
Drainage area number Level Spreader 3
111, DESIGN INFORMATION
For Level Spreaders Receiving Flow From a BMP
Type of BMP
Drawdown flow from the BMP cfs
For Level Spreaders Receiving Flow from the Drainage Area
Drainage area
Impervious surface area
Percent impervious
Rational C coefficient
Peak flow from the 1 in/hr storm
Time of concentration
Rainfall intensity, 10-yr storm
Peak flow from the 10-yr storm
Where Does the Level Spreader Discharge?
To a grassed bioretention cell?
To a mulched bioretention cell?
To a wetland?
To a filter strip or riparian buffer?
Other (specify)
Filter Strip or Riparian Buffer Characterization (if applicable)
9,034.00 ftZ
6,567.00 ftZ
72.69 %
0.56
0.12 cfs
5.00 min
7.2 in/hr
0.84 cfs
N (Y or N)
N (Y or N)
N (Y or N)
Y (Y or N) Please complete filter strip characterization below,
Width of grass 45.00 ft
Width of dense ground cover 67.50 ft
Width of wooded vegetation ft
Total width 112.50 ft
Elevation at downslope base of level lip 423.00 fmsl
Elevation at top of bank of the receiving water 416.00 fmsl
Slope (from level lip to to top of bank) 6.22 %
Are any draws present? N (Y or N) OK
Level Spreader Design
Forebay surface area sq ft
Feet of level lip needed per cfs 13 fucfs
Answer "Y" to one of the following:
Length based on the 1 in/hr storm? N (Y or N)
Length based on the 10-yr storm? Y (Y or N)
Length based on the BMP discharge rate? N (Y or N)
Design flow cfs
Is a bypass device provided? N (Y or N) h bypass device is not needed.
Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.5 Parts I. and It. Design Summary, page 1 of 2
Length of the level lip
Are level spreaders in series?
Bypass Channel Design (if applicable)
Does the bypass discharge through a wetland?
Does the channel enter the stream at an angle?
Dimensions of the channel (see diagram below):
M
B
W
y
Peak velocity in the channel during the 10-yr storm
Channel lining material

M
13.00 ft Level spreader length GK.
N (Y or N)
(Y or N) Do not complete this section of the worksheet.
(Y or N) Do not complete this section of the worksheet.
Do not complete this section of the worksheet.
ft Do not complete this section of the worksheet.
ft Do not complete this section of the worksheet.
ft Do not complete this section of the worksheet,
ft Do not complete this section of the worksheet.
cfs Do not complete this section of the worksheet
Do not complete this section of the worksheet

y
M 1
i B i

Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.5 Parts I. and II. Design Summary, page 2 of 2
Ill. 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.
?M C-2 1. Plans (1" - 50' or larger) of the entire site showing:
- Design at ultimate build-out,
- Off-site drainage (if applicable),
- Delineated drainage basins (include Rational C coefficient per basin),
- Forebay (if applicable),
- High flow bypass system,
- Maintenance access,
- Proposed drainage easement and public right of way (ROW), and
- Boundaries of drainage easement.
_C-13 2. Plan details (1" = 30' or larger) for the level spreader showing:
- Forebay (if applicable),
- High flow bypass system,
- One foot topo lines between the level lip and top of stream bank,
- Proposed drainage easement, and
- Design at ultimate build-out.
1 C-13 3. Section view of the level spreader (1" = 20' or larger) showing:
Underdrain system (if applicable),
- Level lip,
- Upslope channel, and
- Downslope filter fabric.
4. A date-stamped photograph of the filter strip that clearly shows the type of vegetation that is present.
5. A construction sequence that shows how the level spreader will be protected from sediment until the entire
drainage area is stabilized.
-3 AT G-?3 6. The supporting calculations..
_5A:3 / 7. A copy of the signed and notarized operation and maintenance (0&M) agreement.
11 LA 8. A copy of the deed restrictions (if required).
Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.5 Part III, page 1 of 1
PP£k
oC??oz
FILTER STRIP, RESTORED RIPARIAN BUFFER, AND LEVEL
SPREADER OPERATION & 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
or the public, and the pollutant removal efficiency of the BMPP.
PROJECT: \K (Tr-- C,AAy- L.f3`PN? I i
RESPONSIBLE PARTY: *arrm c>m Pin 12A-flq ., 14--. PHONE #?(nZ-6'766
CONTACT: ALot.(70yy f L 1?
ADDRESS: I&-'71 Wd rl n l 0t7

NUMBER OF FILTER STRIPS:
NUMBER OF RESTORED RIPARIAN BUFFERS:
NUMBER OF LEVEL SPREADERS: 1j
A filter strip is a section of land capable of sustaining sheet flow and is either forested or
vegetated with turf grasses or other plants. Restored riparian buffers are natural or constructed
low-maintenance ecosystems adjacent to surface water bodies with trees, grasses, shrubs, and
herbaceous plants. Level spreaders do not remove pollutants by themselves, but they are crucial
in assuring the effectiveness of certain BMPs and in protecting the function of riparian buffers.
A level spreader consists of a concrete linear structure constructed at virtually zero percent
grade. One of the main purposes of a level spreader is to disperse concentrated stormwater flows
over a wide enough area to prevent erosion of the BMP or filter strip where it outlets.
Important inspection and maintenance procedures:
• Immediately after the filter strip is established, any newly planted vegetation will
be watered twice weekly if needed until the plants become established (commonly
six weeks). The watering should take place on designated days according to the
odd/even watering schedule cited in the Town of Apex Code of Ordinances.
• Once a year, the filter strip will be reseeded to maintain a dense growth of
vegetation.
• Stable groundcover will be maintained in the drainage area to reduce the sediment
load to the vegetation.
• Two to three times a year, grass filter strips will be mowed and the clippings
harvested to promote the growth of thick vegetation with optimum pollutant
removal efficiency. Turf grass should not be cut shorter than 3 to 5 inches and
may be allowed to grow as tall as 12 inches depending on aesthetic requirements.
• Once a year, the soil will be aerated and lime will be added if necessary.
• Remove any weeds or shrubs growing on level spreader or in swale.
• Inspect the level lip for settling, erosion, or concentrated flow.
After the filter strip is established, I will inspect it and the level spreader (if applicable) quarterly
and within 24 hours after every storm event greater than 1.0 inches. Records of inspection and
maintenance will be kept in a known, set location and will be available upon request.
2
Inspection activities shall be performed as follows. Any problems that are found shall be
repaired immediately.
BMP Element - Potential Problems. Problem Remediation
The entire filter strip Trash/debris is present. Remove the trash/debris.
system
The flow splitter device is Unclog the conveyance and dispose
h
i
d
i
if clogged. of any sediment off-site.
tter
ev
ce (
T
e flow spl
applicable) The flow splitter device is Make any necessary repairs or
damaged. replace if damage is too large for
repair.
The swale is clogged with Remove the sediment and dispose
sediment. of it off-site.
The level lip is cracked,
settled, undercut, eroded or Repair or replace lip.
otherwise damaged.
Regrade the soil to create a berm
The Swale and the level lip There is erosion around the that is higher than the level lip.
end of the level spreader that Plant a ground cover and water
shows stormwater has until it is established. Provide lime
bypassed it. and a one-time fertilizer
application.
Trees or shrubs have begun
to grow on the swale or just Remove them.
downslope of the level lip.
Areas of bare soil and/or Regrade the soil if necessary to

erosive gullies have formed. remove the gully, and then
reestablish proper erosion control.
The bypass channel
Turf reinforcement is Study the site to see if a larger
damaged or riprap is rolling bypass channel is needed (enlarge if
downhill. necessary). After this, reestablish
the erosion control material.
The filter strip Grass is too short or too Maintain grass at a height of
long. approximately three to six inches.
Regrade the soil if necessary to
Areas of bare soil and/or remove the gully, and then plant a
erosive gullies have formed. Found cover and water until it is
established. Provide lime and a
one-time fertilizer application.
Remove the sediment and
Sediment is building up on restabilize the soil with vegetation
the filter strip. if necessary. Provide lime and a
one-time fertilizer application.
Plants are desiccated. Provide additional irrigation and
fertilizer as needed.
BMP Element Potential Problems Problem Remediation
Determine the source of the
or
diseased
Plants are dead problem: soils, hydrology, disease,
,
,
dying. etc. Remedy the problem and
replace plants. Provide a one-time
fertilizer application.
Nuisance vegetation is Remove vegetation by hand if
choking out desirable possible. If pesticide is used, do not
allow it to get into the receiving
species. water.
Erosion or other signs of Contact the Town of Apex Public
The outlet device damage have occurred in the Works & Utilities Department at
outlet. 249-3427.
I acknowledge and agree by my signature below that I am financially responsible for the
performance of the maintenance procedures listed above. I will perform the maintenance as
outlined, as part of the regulations set forth in Section 6.1.12 of the Town of Apex Unified
Development Ordinance.
I understand that this Agreement shall endure to the benefit of my successors in title,
whomsoever they may be in the future. I agree to notify the Town of Apex of any problems with
the BMP or prior to any changes to the BMP or responsible party.
Note: The legally responsible party should not be an HOA unless more than 50% of the lots have
been sold and a resident of the subdivision has been named the president.
Print name: AI'0dzC> W IL?D?
Title: 1?6A9.2
Address: ko Z I \IV rrj--- oAk- ?P•
Phone:
Signature: S.tJ C
Date: q
I, khan i ? F i; P-W?? a Notary Public for the State of ? ? t?? Jrb I l nG ;
County of do hereby certify that aAonzo i I i bn r1 personally
appeared before me this J (f day of .2006 _ and acknowledge the
due execution of the foregoing filter strip, restored riparian buffer (if applicable) and level
spreader (if applicable) maintenance
SEAL
Witness my hand and official seal,
Q WE F,c?j
'co f. aO T.1 : =yam
aUIVT`(,
My commission expires (I ' q - 01

5

Permit Number:
(to be provided by DWQ)
O?O? W ATF?QG
A=&'(VA
NCDENR STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
SAND FILTER SUPPLEMENT
This form must be filled out on line, printed and submitted with all of the required information.
Make sure to also fill out and submit the Required Items Checklist (Section III) and the I&M Agreement (Section IV)
I. PROJECT INFORMATION
Project name WHITE OAK DEVELOPMENT
Contact name STUART JONES
Phone number 919-387-1174
Date September 8, 2008
Drainage area number 1
IL DESIGN INFORMATION
Site Characteristics
Drainage area (AD)
Impervious area
% Impervious (IA)
Design rainfall depth (RD)
Peak Flow Calculations
1-yr, 24-hr runoff depth
1-yr, 24-hr intensity
Pre-development 1-yr, 24-hr runoff
Post-development 1-yr, 24-hr runoff
Pre/Post 1-yr, 24-hr peak control
95,832.00 ft2 OK
35,170.00 ft 2
36.7%%
1.00 in
0.42 in
5.13 in/hr
4.60 ft3/sec
4.40 ft3/sec
-0.20 ft 3lsec
Storage Volume
Design volume (WQV)
Adjusted water quality volume (WQVAdi)
Volume contained in the sedimentation basin and on top of the sand filter
Maximum head on the sedimentation basin and sand filter (hM.FiRer)
Average head on the sedimentation basin and sand filter (hA)
Runoff Coefficient (Rv)
Type of Sand Filter
Open sand filter?
If this is an open sand filter: The clearance between the bottom of the sand
filter and the SHWT (dSHWT)
Closed/pre-cast sand filter?
If this is a closed sand filter: The clearance between the bottom of the sand
filter and the SHWT (dSHWT)
If this is a closed, underground closed sand filter: The clearance between
the surface of the sand filter and the bottom of the roof of the underground
structure (dspace)
3,037.00 ft3
2,277.75 ft 3 OK
2,340.00
3.60 ft OK
1.75 ft Ensure that the average is half of the max.
0.38 (unitless)
Y Yor N
2.00 ft
N Yor IN
ft
ft
Form SW401-Sand Filter-Rev.3 Parts I and II. Project Design Summary, Page 1 of 3
I t
Sedimentation Basin
Surface area of sedimentation basin (As) 200.00 ftZ
Sand Filter
Surface area of sand filter (AF) 450.00 ft Z
Depth of the sand media filter bed (dF) 1.50 ft
Coefficient of permeability for the sand filter (k) 3.50 (ft/day)
Time to drain the sand filter (t) 39.80 hours
Time to drain the sand filter (t) 1.66 days
Additional Information
Permit Number:
(to be provided by DWQ)
OK. Meets minimum, but may need to be increased to
contain the required volume if error under Storage
Volume section.
OK. Meets minimum, but may need to be increased to
contain the required volume if error under Storage
Volume section.
OK. Submit drainage calculations.
Does volume in excess of the design volume bypass the sand filter? Y Y or N OK
Is an off-line flow-splitting device used? Y Y or N OK
Does volume in excess of the design volume flow evenly distributed through a Y Y or N OK
vegetated filter?
What is the length of the vegetated filter? 185.00 ft
Does the design use a level spreader to evenly distribute flow? N Y or N Show how flow is evenly distributed.
Is the BMP located at least 30ft from surface waters (50ft if SA waters)? Y Y or N OK
Is the BMP located at least 100ft from water supply wells? Y Y or N OK
Are the vegetated side slopes equal to or less than 3:1 Y Y or N OK
Is the BMP located in a recorded drainage easement with a recorded access Y Y or N OK
easement to a public Right of Way (ROW)?
What is the width of the sedimentation chamber/forebay (Wsed)? 10.00 ft OK
What is the depth of sand over the outlet pipe? 1.16 ft OK
Figure 1: Open Sand Filter
iecti€tretttaticm Sa€ecl Fitter
C hatitbe€° Chamber
1 nr Fcwebat')
Flow Weir (uttet Pipe
i ,. 2t r , . i : iHI?J1
in-S tt€ Suit E Sea :?ttalttc Hiatt Water Taltie
.................................
?Ksm
Form SW401-Sand Filter-Rev.3 Parts I and II. Project Design Summary, Page 2 of 3
Permit No.
(to be provided by DWQ)
Ill. REQUIRED ITEMS CHECKLIST
Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal
package will result in a request for additional information. This will delay final review and approval of the project. Initial
in the space provided to indicate the following design requirements have been met. If the applicant has designated an agent, the
agent may initial below. If a requirement has not been met, attach justification.
Initials Pagel Plan
Sheet No.
1. Plans (1" - 50' or larger) of the entire site with labeled drainage area boundaries
- System dimensions (length, width, and depth) for both the sedimentation chamber and the filter
chamber
- Maintenance access,
- Flow splitting device,
- Proposed drainage easement and public right of way (ROW),
- Design at ultimate build-out,
- Off-site drainage (if applicable), and
- Boundaries of drainage easement.
?T G-111? 2. Plan details (1" = 50' or larger) for the sand filter showing:
- System dimensions (length, width, and depth) for both the sedimentation chamber and the filter
chamber
- Maintenance access,
- Flow splitting device,
- Proposed drainage easement and public right of way (ROW),
- Design at ultimate build-out,
- Off-site drainage (if applicable), and
- Boundaries of drainage easement.
i;Li 3. Section view of the sand filter (1" = 20' or larger) showing:
- Depth(s) of the sedimentation chamber and sand filter chamber,
- Depth of sand filter media
- Connection between the sedimentation chamber and the sand filter chamber,
- SHWT level(s)
- Outlet pipe, and
- Clearance from the surface of the sand filter to the bottom of the roof of the underground structure (if
applicable)
-AT 4. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. The
results of the soils report must be verified in the field by DWQ, by completing & submitting the soils
investigation request form. County soil maps are not an acceptable source of soils information.
_ 5. Supporting calculations (including drainage calculations)
6. Signed and notarized operation and maintenance (0&M) agreement
7. A copy of the deed restrictions (if required).
Form SW401-Sand Filter-Rev.3 Part III, Page 1 of 1
06012 Underdrain Calculations:
1. Determine flow rate through soil media and apply a safety factor of 10.
The infiltration value of the sand will be 6 in/hr. Therefore, when it is times by
the surface area of 450 sq ft and using appropriate conversion factors, the flow is equal to
0.063 cfs. The safety Q value then, Q equals 0.63 cfs.
Qa = Intensity * Area
Qa = (6 in/hr) * (1 ft/12 in) * (1 hr / 3,600 sec) * (450 sq ft) = 0.063 cfs.
Q = Qa *10 = (0.063 cfs) = 0.63 cfs
2. Use the following equation to find the diameter for a single pipe:
D= ((16* Q*n)/S1.5) i1
Where D = Diameter of single pipe, n = roughness factor (recommended to be
0.011), s = internal slope (recommended to be 0.5%). Units: Q (cfs), D (in).
D= ((16* 0.63*0.011)/0.0051.5)3/1= 1.18 inches
3. Now that D has been calculated for a single pipe, the Table 5-1 below converts "D" (in
inches) to a number of 4 or 6 inch underdrains at 0.5% slope to be used in the system.
Table 5-1
ttiintaer of Pines Required in the Underdrain
If D is less than # of 4" pipes If D' is less than # of 6" i es
5.13 2 7.84 2
5.95 3 9.11 3
6.66 4 10.13 4
7.22
7.75 6
8.20 7
The number of 4" pipes used will be 2.
PP E.Y
vn
O?Ty.CF?O2
SAND FILTER OPERATION & 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
or the public, and the pollutant removal efficiency of the BMP.
PROJECT: \N /A Crl?. 6>Aj- /VT
RESPONSIBLE PARTY: \144m o" Pbo?12Amr,*- . Ir-?-XHONE # 3(a2.-&7Z8
CONTACT: Lvi 1, 7_tt? \ V 1 y,-yr4
ADDRESS: I X21 ?? 1"f? dA ?pn!; td F-p
nl4- 2.-A:5913
NUMBER OF SAND FILTERS: 4
A sand filter is a device that allows stormwater to percolate down through a sand media where
pollutants are filtered out. The sand filter system is defined as the filter bed, outlet structure,
pretreatment including forebays, grassed swales, and the vegetated filter if one is provided.
Important inspection and maintenance procedures:
• The drainage area will be carefully managed to reduce the sediment load to the
sand filter.
• Once a year, sand media will be skimmed.
• The sand filter media will be replaced whenever it fails to function properly after
vacuuming.
After the sand filter is established, I will inspect it quarterly and within 24 hours after every
storm event greater than 1.0 inches. 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 Problems Problem Remediation
The entire BMP Trash/debris is present. Remove the trash/debris.
The adjacent pavement (if Sediment is present on the Sweep or vacuum the sediment as
applicable) pavement surface. soon as possible.
Regrade the soil if necessary to
Areas of bare soil and/or remove the gully and plant a ground
erosive gullies have formed. cover. Water until it is established,
The perimeter of the sand provide lime and a one-time
filter fertilizer application.
Vegetation is too short or too Maintain vegetation at a height of
long. approximately six inches.
The structure is clogged. Unclog the conveyance and dispose
of any sediment off-site.
The flow diversion
structure
Make any necessary repairs or
The structure is damaged. replace if damage is too large for
repair.
Search for the source of the
Sediment has accumulated to sediment and remedy the problem if
a depth greater than six possible. Remove the sediment and
inches dispose of it in a location where it
. will not cause impacts to streams or
the BMP.
The pretreatment area Provide additional erosion
Erosion has occurred protection such as reinforced turf
. matting or riprap if needed to
prevent future erosion problems.
Remove the weeds, preferably by
Weeds are present. hand. If pesticide is used, wipe it
on the plants rather than spraying.
Check to see if the collector system
The filter bed and Water is ponding on the is clogged and flush if necessary. If
water still ponds, remove the top
underdrain collection surface for more than 24 few inches of filter bed media and
system hours after a storm. replace. If water still ponds, then
consult an expert.
The outflow spillway and
Clogging has occurred.
Cloggi Clean out the outlet device.
pipe Dispose of the sediment off-site.
The outlet device is Repair or replace the outlet device.
damaged.
BMP Element Potential Problems Problem Remediation
Erosion or other signs of Contact the Town of Apex Public
damage have occurred in the Works & Utilities Department at
outlet. 249-3427.
L r
I acknowledge and agree by my signature below that I am financially responsible for the
performance of the maintenance procedures listed above. I will perform the maintenance as
outlined, as part of the regulations set forth in Section 6.1.12 of the Town of Apex Unified
Development Ordinance.
I understand that this Agreement shall endure to the benefit of my successors in title,
whomsoever they may be in the future. I agree to notify the Town of Apex of any problems with
the BMP or prior to any changes to the BMP or responsible party.
Note: The legally responsible party should not be an HOA unless more than 50% of the lots have
been sold and a resident of the subdivision has been named the president.
Print name: ALo1dZ0
t!V JI?Sc?I?[
Title: Address: I?2I VJ?I'T OAIL G?12.

Phone:
k
Signature: JU
Date: I I &f& E.
a Notary Public for the State of Ma"
County of do hereby certify that Mona) U 1 i l -1v1 personally
appeared before me this _ day of 20 Q? and acknowledge the
due execution of the foregoing sand filter maintenance requirements. Witness my hand
and official seal,
'fo%E F
ti tt t,60 TA
??. ;tea
cn
i 4
SEAL
(I G
'f' ''• •....... ...
My commission expires I-q-4q

4
OG102
WHITE OAK DEVELOPMENT
LOT I
5TORMWATER CALCULATIONS
APEX, NORTH CAROLINA
155UED: 1/7/2005
REVISED: 2/ 1 5/2008
PREPARED BY:
JONES t, CN055EN ENGINEERING, PLLC
P.O. BOX I OG2
APEX, NC 27502
919-387-1 174 (PHONE)
919-387-3375 (FAX)
,,.011It1110111
CA.
'aF?'61NEFQ:
/?3 40010•
r rr
Culvert Crossing - Marco Drive
Drainage Area = 399.5 acres
Tc = 33 minimum (L = 6500', H= 80')
C = 0.50 (composite)
C Factor
85 Acres of Commercial Property @ 0.70 = 59.5
20 Acres of Schoole @ 0.60 = 12.0
1 15 Acres of Medium Density Residential @ 0.50 = 57.5
179.5 Acres of Low Density Residential @ 0.40 = 71.8
200.8
Composite C = 200.8 / 399.5 = 0.50
1 so = 4.8 in/hr
I ioo = 5.3 m/hr
Q50 = 399.5 x 0.50 x 4.8 = 958.8 cfs
Q i oo = 399.5 x .50 x 5.3 = 1058.7 cfs
From HY-8 Calculation
50 year storm WSEL = 423.33
1 00 year storm WSEL = 423.48
Page 5
06102 1/4/ZUU

White Oak Lot 1 -10-Year Storm
8

Peak Flow = 6.3 YI Outlet Size = 12"
ime to ea = Inlet Pipe Size 24"

.0
Time (min) Inflow (cfs) Storage (cf) Stage (ft) Outflow (cfs)
0 0.0 0 0 0
0
0.5 0.2 0 0.00 0
5
1 0.6 5 0.02 0.6
1
1.5 1.3 5 0.03 0.6
21
2 2.2 26 0.13 1.4
25
2.5 3.2 52 0.26 1.9
37
3 4.1 89 0.45 2.5
48
3.5 5.0 136 0.69 3.1
56
4 5.7 192 0.97 3.7
59
4.5 6.2 252 1.27 4.2
59
5 6.3 310 1.57 4.7
48
5.5 6.2 359 1.81 5.0
34
6 5.7 393 1.98 5.3
12
6.5 5.4 405 2.04 5.4
0
7 4.7 405 2.04 5.4
-21
7.5 4.0 384 1.94 5.2
-35
8 3.5 349 1.76 5.0
-45
8.5 3.0 303 1.53 4.6
-48
9 2.6 255 1.29 4.3
-48
9.5 2.3 207 1.05 3.8
-47
10 2.0 160 0.81 3.4
-42
10.5 1.7 118 0.59 2.9
-36
11 1.5 82 0.42 2.4
-27
11.5 1.3 55 0.28 2.0
-21
12 1.1 34 0.17 1.5
-12
12.5 0.9 21 0.11 1.2
-9
13 0.8 13 0.06 1.0
06102 1/4/200

i e a o 1- - ear orm
CB-#-1-9

ea ow = I u e ize =
ime to ea = Inlet Pipe Size 24"

.0
Time min nflow c s orage c age Outflow c s
0

0.00 0

1 0.6 4 0.7

0.

2- 2.4
2 0.22
1
2.5 3.4 8 0.

5
3
4.4
.
0.62
4
3.5 5.4 8 0.95 3.6

4 80 1. 3
54
4.5 6. 3 1.73 4.9
5
8 28
41
5.5 6.7 32 .8
2
1 3
2
4 .1
-$
-
-
7 5.0 4
2.56
To

4.4
-1
8 3. 4 5.3
-4
8.5 3.3 1.68 4.
-8
9 .9 9
-4
6 3.8

10 2.1 6 0.71 3.2
-32
10.5 1. 6 0.48 2.6
-3
11 1.6 4 .3
-14
1 1.4 28 0.21 1.7
-1
1 1. 18 .13 1.4
-4
12.5 1.0 4 .10 1.
-5
TT .9 9 6
DBTG2-- 1/4/20U

ite Oa of - - ear Storm
CB

-
-
ea ow =

ime o eak =
Time- 1 --
ufFef Size
YFO
I nlet ipe ize =

4

.0
ime min n ow c s orage c age t u ow c s
0

4
4

-f 3-
1
1
2

1
4-0 1 .1

.5
7
.8 0 0.
4
14 1 .0
4

5.5 6. 2 2. 4
8
g .6

8-
-11
O 1 4
-Z
42 1.8
-33
.4 0
-41
g. X63
-3
12
-3
9.5
p
1
-29
1. .6

1. 1
-1
1 .2
-7
9 1 1.
-7
'I 0.
-2
12.5 1 0. 8 1?
-5
13- 1 0.8 6 O.S
06102 1/4/ZOUU

ar m
i e ak of - Z-
21

Peak ow = ut et ize =
Time o ea = In et ipe ize =

0.00
Time min n low c s) orage c S age ( u ow c s
0 0
0
0.5 0.1
4
0.5 4 0.01 0.1
T2
1.5 1. 1 0.
28
2 1. 4 9 0.3
4
2a5- .6
9
0.19
0.
6
4 155 0.5

0
03
34 0.75 0.8
11
5.1 459 1.00 0.9
1
5 5.2 4 1.2 1.1
Z
5.5 1 0 4 1.2
1
6 4. 8 1.80 1.
03
4
3
2 1.4

7.5 3.3 1 1.
56
9 11 1.
41
1 2.60 1.5
30
22 1.
2
9.5 1.9 1 2.71 I.b
1
10 1.6 1 3 l.b
2
1 .4 1254 1.5
-4
1 2 0 .72 1.5
-9
11. 1241
-15

2
0.9 -fZ26 1.5
-1
. 08 2.63 1.5
-2
13 0.7 186 2.58 1.
06102 1/ /200

White Oa o 1- 10-Year Storm
CB # 1

Peak ow = 6.5 u e ize = 61,
Time to ea = Inlet ipe Size 42"

0.
ime in n ow c s Storage c tage t Outflow c s
0 0.0 0 0
0
u.5 0.2 0 00.00
5
0.6 5 0.01
.1
16
1.5 1. 0 0.04 0.2
3
-
2 2.3 5-5 .1 0.3

3..3 1 4 0.25 0.5
8
4.2 9 0.43 0.6

-
- 108
3
3 5.1 306 00.67 .8
131
4 5.9 4437 0.95
4
--
4.5 6.4 585 1.27 1.1
5
5 1.
159
5.5 6.4 0
52
0 1.4
1
6.5 5.5 1
121
T309 2.85
9
1406 6 1.6

8 81 3.23 1.
57-
1 15
42
9
2.7
1 8
30
9. 1 1 1
1
2.0
62
??-

10. 1. 3
d
3 .8
-6
1.3 2 3.55 1.
-14
1 1. 161
-1
1. 1 9 .4
-23
15 .4
06102 1/4/2009

I?Nhi a Oa of - r orm
CB-#Z

ea ow = 2.6 u et ize =
Time to Pea = n e ipe i e=

ime min n low c s orage c age (ft) u ow c s
0

- 2
1 0.2
2
1
6
0.5 4
1
Z
Z1
4
-
3 1.7 71-
.6
39
2.1 1
4
4 15

4. 2.

6
1.35
5
5.5 2.5 322 1.63
8

7 1.89
4
41
8
1.9
45
1,

1
502
1
1. 14

1 2.

1

518 2.62

11 1.
-1
11 5 .0
-1
1 0.

4 g
-1
4 .31
-1
13 0. 4
? r
UIJ102 1/4/200

WW e a of 1 - -ear orm
# 22

ea ow = .2 ut a ize =
Time to ea = n e ipe ize =

Time mm Inflow c s orage c age t u ow c s
0 0

0.5 0.1 0
2
1 2

1.5 0.7 9 0.05 0.1
1
2 1.1 25 1
2
2.5 1.6 52- -Z726- 0.3
3
2.1 90 0.45 .4
49
3.5 3
9
2.9 1
67
4.5 T.I- 266- 1.34 .8

3 1.70 0.8

1 4
6
47 2.
56
6.5 2.7 3
50
2.4 80

2. 1? .12 .1
27
8 1.8 64
1
1. 62
4
1.2
10
1. 6 .4
- 4
9.5
7 1.2

6

10.5
-10
1
-13
4 3. 1.
-1
1 3. 1.
-1
1 0. 13 .1 1.1
-2
1 .0 .1