20041808 Ver 3_More Info Received_20090909

TALUPT& MIGHT
September 8, 2009
Mr. Joseph Gyamfi
NCDENR DWQ
2321 Crabtree Blvd.
Suite 250
Raleigh, NC 27604
Dear Mr. Gyamfi,
SEP - 9 2009
MIMI ANDS WA MRUWAtiWNCH
Re: Revised Calculations and Plans
Stanly County Airport 401 Water
Quality Certification and Storm
Water Management Plan Submittal
Stanly County Airport Terminal
Stanly County Airport
New London, North Carolina
TBI Project No.: 3803-0803
DWQ Exp # 04-18080
Please find enclosed two (2) copies of the requested revised calculations and plan sheets per the
DWQ letter dated September 2, 2009 for the above referenced project.
If you have any questions regarding this matter, please feel free to contact me.
Sincerely,
Chad Vernon
Enclosure
cc: David Griffin, Stanly County Airport
Ronald A. Geiger, HDR
ENGINEERING & PLANNING CONSULLANIS
4944 PARKWAY PLAZA BOULEVARD SUITE 350 CHARLOLTE. NORTH CAROLINA 28217 704.426.6070 FAX [phone]
CHARLOTTE. NORTH CAROLINA , WILMINGTON, NORTH CAROLINA • RICHMOND. VIRGINIA , COLUMBIA. SOUTH CAROLINA
Albemarle-Stanly County Airport HDR Engineering, Inc
Terminal Project September 4,2009
Bioretention Calculations for Drainage Area A
Drawdown Calculations
Total volume to be treated 17,874 cft
Permeability of Soil (PoS) 1.5 in/hr
Surface Area of Soil (SA) 17,908 cft
Draw down time for ponded area
V to be treated
PoS * SA of Soil
17874 _ 8.0 hrs
0.125 17908
Drawdown Time to 24 in below surface
1 ft of Ponding Depth into soil is 8.0 hrs
2 ft of soil is 16.0 hrs
Total Drawdown time 24.0 hrs
Underdrain Sizing
Q in Volume 17,874 cft
Time 24.0 hr
Factor of V = 1.03 cfs
Safety (5) T
Using Orifice Equation
CD 0.4
D 6 in
Area 0.20 sqft
Havg 1.5 ft
g 32.17 ft/s^2
Q out = Cd * A * SQRT (2gH) = 1.54 cfs
Using BMP manual the minimum diameter required is:
D = 16*(Q*n /( S A 0.5)) ^3/8
n 0.011
S 0.005
D 8.06 in
Using a 6 in underdrain exceeds the flow into the underdrains by 0.51 cfs
NCDENR recommends two 6 in underdrains, the plan includes 4 underd rains spaced 50 feet apart.
Therefore, no backwater will occur.
Albemarle-Stanly County Airport
Terminal Project
Bioretention Swale Calculations for Albemarle-Stanly County Airport
HDR Engineering, Inc
September 4,2009
Drainage Drainage Pervious Impervious Impervious
Section Area (sgft) Area (ac) Area (sqft) Area (sqft) Area (ac)
A 360,094 8.27 141,774 218,320 5.01
Ponding Depth 1 ft
Basin Dimension Summary
Section Width (ft) Length (ft)
A 74 242
Drainage Area A
Impervious portion of Drainage Area 5.01 = 0.61
Total Drainage Area 8.27
Rv= 0.05+0.91A = 0.60
Volume 3630*Rp*R„*A = 17,874 cft
Width = 74 ft
Length = 242 ft
Surface Area of Bioretention Cell = 17,908 sqft
Albemarle-Stanly County Airport
Terminal Project
HDR Engineering, Inc
September 4,2009
Velocity Calculations for Albemarle-Stanly County Airports Biosretention Entrance
Bioretention Design section Vertical Z therefore no slope
A Rectangular shape
L delta h i
ft ft ft/ft
770 16.00 0.021 Qd es;9n = 36.74 cfs
Manning's Equation
Q v B Y z A n P R
Cfs fps ft ft sq ft Grass ft
32.57 1.0 242 0.133 0 32.3 0.035 484.27 0.07
36.74 1.1 242 0.143 0 34.7 0.035 484.27 0.07
60.48 1.3 242 0.193 0 46.8 0.035 484.27 0.10
88.73 1.5 242 0.243 0 58.9 0.035 484.27 0.12
121.15 1.7 242 0.293 0 71.0 0.035 484.27 0.15
Bioretention Entrance Flows
teepest ?

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a
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Min. Sidq
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iQ N ; Ft ed, AC; Area, sgft. Area, AA-- Slope t1cfe " iP 10 yv C?a 1 f!s
A 595 579 770 360,094 8.3 218,320 5.0 5 :1 0.021 Fescue 36.74 1.1
I = 7.33 in/hr

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Albemarle-Stanly County Airport
Terminal Project
Bioretention A
4.57 inches
0.19 in/hr
5.80 min
770 ft
16.00 ft
Precipitation Frequencv Estimates (inches)

ARI*
(years)
5 min
10 min
15 min
30 min
60 min
120 min
3 hr
6 hr
12 hr
24 hr
48 hr
4 day
7 day
10 day
20 da
30 day
45 day
60 day
1 0.41 0.65 0.81 1.11 1.38 1.61 1.72 2.08 2.48 3.02 3.54 3.97 4.55 5.2 7.01 8.6 10.88 13.04
2 0.48 0.76 0.96 1.33 1.67 1.94 2.07 2.51 3 3.64 4.26 4.76 5.42 6.19 8.27 10.12 12.75 15.21
5 0.56 0.89 1.13 1.6 2.05 2.41 2.59 3.14 3.76 4.57 5.31 5.88 6.61 7.45 9.76 11.77 14.58 17.19
10 0.61 0.98 1.24 1.79 2.33 2.76 2.98 3.62 4.37 5.3 6.14 6.76 7.55 8.43 10.94 13.05 15.98 18.72
25 0.67 1.07 1.36 2.01 2.67 3.2 3.5 4.27 5.19 6.29 7.25 7.96 8.84 9.75 12.53 14.72 17.81 20.68
50 0.71 1.14 1.44 2.17 2.93 3.54 3.9 4.78 5.85 7.09 8.14 8.92 9.87 10.8 13.77 16.01 19.2 22.18
100 0.75 1.19 1.5 2.3 3.17 3.87 4.3 5.29 6.53 7.9 9.05 9.9 10.93 11.85 15.03 17.3 20.56 23.61
200 0.78 1.24 1.56 2.43 3.41 4.18 4.71 5.82 7.24 8.74 9.99 10.92 12.02 12.93 16.3 18.58 21.89 25
500 0.81 1.29 1.62 2.58 3.69 4.59 5.25 6.54 8.22 9.89 11.28 12.32 13.51 14.39 18.04 20.3 23.64 26.83
1000 0.84 1.32 1.65 2.68 3.91 4.9 5.67 7.09 9 10.81 12.3 13.43 14.7 15.54 19.4 21.62 24.96 28.2
.IN .,....y ...c ,,,-y., -... IN.
Read Chart:
Intensity, Peak 10-yr, 24-hr
d(in)/24hr
Time of Conc.: Tc=
=(L3/H).385/128
Hydraulic Length, L
Change in Elev., H
Intensity, Peak 10-yr
d(in)/t,(min)*60(min/hr)
Depth at Tc & 10-yr: d=
Intensity, Peak 1-yr
d(in)/t,(min)*60(min/hr)
Depth at T. & 1-yr: d=
Intensity, Peak 1-yr, 24-hr
d(in)/24hr
Depth at 24hr& 1-yr: d=
5.80 in/hr
0.56 in
0.45 in/hr
in
HDR Engineering, Inc
September 4,2009
Albemarle, North Carolina
Precipitation Data Chart From: http://hdsc.nws.noaa.gov/hdsc/pfds/
(Calculate this value from the hydraulic length and the change in elevation along the hydraulic length)
Furthest distance water flows to BMP
Over hydraulic length
0.13 in/hr Use time of concentration to determine the "1-yr" storm, but not the "1-yr, 24-hr" storm. Note that the "1-yr, 24-hr"
3.02 in value discussed here is the regulated storm.
Form SW401-Bioretention-Rev.8
July 30, 2009
Permit No:
(to be assigned by DWQ)
Red triangles at the upper right hand corner indicate design comments
Please complete the yellow shaded items.
004 warEy°
? y
A7?
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 Ill) must be printed, filled out and submitted along with all of the required information.
L PROJECT INFORMATION
Project name Albemarle-Stanly County Airport New Terminal Building
Contact name Ron Geiger
Phone number 704-338-6825
Date July 16, 2009
Drainage area number A
II. DESIGN INFORMATION
Site Characteristics
Drainage area 292,455.10 ft2
Impervious area 195,078.00 ft2
Percent impervious 66.7% %
Design rainfall depth 1.0 inch
Peak Flow Calculations
Is pre/post control of the 1-yr, 24-hr peak flow required? (Y or N)
1-yr, 24-hr runoff depth 3.02 in
1-yr, 24-hr intensity 0.13 in/hr
Pre-development 1-yr, 24-hr peak flow 0.52 ft3/sec Q = CIA = 0.6*0.13*292455/43560
Post-development 1-yr, 24-hr peak flow 0.56 ft3/sec Q = CIA = 0.64*0.13*292,455/43560
Pre/Post 1-yr, 24-hr peak control 0.03 ft3/sec
Storage Volume: Non-SA Waters
Minimum volume required 17,874.39 ft3
Volume provided 17,908.0 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
Pending depth of water 12 inches OK
Pending depth of water 1.00 ft
Surface area of the top of the bioretention cell 17908.00 ft2 OK
Length: 242.00 ft OK
Width: 74.00 ft OK
-or- Radius ft
Media and Soils Summary
Drawdown time, ponded volume 7.98 hr OK
Drawdown time, to 24 inches below surface 15.97 hr OK
Drawdown time, total: 23.95 hr
In-situ soil,
Soil permeability 0.01 in/hr Insufficient. Increase infiltration rate.
Planting media soil:
Soil permeability 1.50 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 20 (unitless) OK
Form SW401-Bioretention-Rev.8
July 30, 2009

Basin Elevations
Temporary pool elevation
Type of bioretention cell (answer "Y" to only one of the two
following questions):
Is this a grassed cell?
Is this a cell with trees/shrubs?
Planting elevation (top of the mulch or grass sod layer)
Depth of mulch
Bottom of the planting media soil
Planting media depth
Depth of washed sand below planting media soil
Are underdrains being installed?
How many clean out pipes are being installed?
What factor of safety is used for sizing the underdrains? (See
BMP Manual Section 12.3.6)
Additional distance between the bottom of the planting media and
the bottom of the cell to account for underdrains
Bottom of the cell required
SHWT elevation
Distance from bottom to SHWT
•
Internal Water Storage Zone (IWS)
Does the design include IWS
Elevation of the top of the upturned elbow
Separation of IWS and Surface
Planting Plan
Number of tree species
Number of shrub species
Number of herbaceous groundcover species
575.00 fmsl
y (Y or N) OK
n (Y or N)
574 fmsl
2 inches OK
571.8 fmsl
2.2 ft
0.3 ft
y (Y or N)
18 OK
4 OK
1ft
570.5 fmsl
565 fmsl
5.5 ft OK
Y (Y or N)
570.7 fmsl
3.3 ft OK
0
0
1 Recommend more species.
Additional Information
Does volume in excess of the design volume bypass the
bioretention cell? y (Y or N) OK
Does volume in excess of the design volume flow evenly

distributed through a vegetated filter? y (Y or N) OK
What is the length of the vegetated filter? 30 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
SA waters)? y (Y or N) OK
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

to a public Right of Way (ROW)? y (Y or N) OK
Inlet velocity (from treatment system) 0.9 ft/sec OK
Is the area surrounding the cell likely to undergo development in
the future? n (Y or N) OK
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) OK
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) x
Grassed swale n OK
Forebay n
Other
Permit No:
(to be assigned by DWQ)
Form SW401-Bioretention-Rev.8
July 30, 2009
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T NO ES. Q z
1. CONTRACTOR SHALL INSTALL FESCUE SOD IN THE DENUDED AREAS OF THE BIORETENTION SWALE W
AND FILTER STRIP. ONLY AONE-TIME FERTILIZER APPLICATION WILL BE ALLOWED FOR INITIAL J
ESTABLISHMENT.
L
2. BMP'S ARE LOCATED ON A PUBLIC AIRPORT AND CAN BE ACCESS FOR MAINTENANCE AS 50 25 0 5o ioo X50
NEEDED. E:NUINE:l;K1NU & Y N1NG (INSULT
3. ALL THE PROPERTY SHOWN TO THE WEST OF AIRPORT ROAD IS OWNED BY STANLY COUNTY. 4944 PARKWAY PLAZA BOULEVARD SUITE 350 SHT.
SCALE IN FEET 4. THE PHOSPHORUS INDEX OF THE SELECTED SOIL MIX SHALL BE LESS THAN 20. CHARLOTTE, NORTH CAROUNA 28217
HDR Engineering, inc. PHONE: [phone] FAX: [phone]
5. THE "FUTURE IMPERVIOUS" SHALL BE MAINTAINED AS SHEET FLOW INTO THE ADJACENT GRASS 1"=50' of the Carolinas NORTH CAROLINA LICENSE NO. C•1163
SWALES AND AT NO POINT SHALL CONCENTRATED FLOW BE DIRECTLY DISCHARGED INTO THE www.talbertandbright.com OF
SWALES/DITCHES. 128 S Tryon Street, Suite 1400 1 Charlotte, NC 28202

W
Q °
- TI 3 T L
SURFACE L W
BIO SWALE ID ELEVATION (FEET) (FEET) E1 574.00 242 74
Z
O
4" UNDERDRAIN, , W
LENGTH=O.SW 5 A
(TYP.)
L
a

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NO NOTE 1 ° M W
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LONGITUDINAL CC CONNECT UNDERDRAIN m z o
UNDERDRAIN TO LIMITS OF MEDIA A~ TO INLET OR DAYLIGHT ° W z m m °w
AS SHOWN ON PLANS W ~ ~ ° ~ z w cn
LIMITS OF GRASS ESTABLISHED CLEAN-OUT RISER ~ ~ ~ ~ U
BY PERMANENT SODDING TYP. ~ o o a W W w ~ ~ ~ = Q
( ) ° d. a ° U °
NOT TO SCALE
NOTE:
1. UNDERDRAIN PIPE OUTSIDE OF MEDIA, AND
CLEAN-OUT RISERS TO BE SOLID 6" PIPE.
LONGITUDINAL PIPES SHALL BE 6" PERFORATED
AND LATERAL PIPES SHALL BE 4" PERFORATED. li
ALL PERFORATED PIPES SHALL HAVE A MIMIMUM
OF 4" N0. 57 STONE AROUND ALL SIDES.
2. ALL PIPING WITHIN THE UNDERDRAIN SYSTEM
SHALL HAVE A MINIMUM SLOPE OF 0.5 PERCENT
AND SHALL BE CONSTRUCTED OF SCHEDULE 40
(PERFORATED AND NON PERFORATED) PVC PIPE.
W
3 4" CLEAN OUT 3
-'1 RISER W CAP 1r {T'
,s, _ BIORETENTION SURF, EARTHEN BERM ~ JTION SURFACE BIO-SWALE
~ ~ ~ - - ~ ~ ELEVATION 574.00 )N 574.00 OVERFLOW
GRASS L'
IN-SITU SOIL ~ ESTABLISHED IN-SITU SOIL 4" 2 4" CLEAN OUT RISER W/CAP ~
BY SODDING
1 ~ r~ ~ ~ ,r`
,kt ~ - ~ ~ ~ , , ,ri., ~ .fi a, ..w~: f ' ' ''l~.. : r E r' f ! J f ~ r ,t'.r tf~ r,_ r.r j~/"{' l r ~ " i iii'' r i,~f/ r~l,% /,~'1 ~r~ tr°.
2'
r--- ~ - TO UNDERDRAIN _ ~ COLLECTOR ' ~9
e - _
FILTER FABRIC AMOCO PROPER F ( 4 WASHED SAND
4551, MIRAFI 160N, OR APPROVED
EQUAL) 8" N0. 57 STONE (TYP.) FILTER FABRIC 6" LONGITUDIP LONGITUDINAL 2' FILL/SOIL MEDIA
6" LONGITUDINAL UNDERDRAIN (AMOCO PROPER UNDERDRAIN, IDERDRAIN, GRADE 4" WASHED SAND 85% SAND,
4" UNDERDRAIN, 2' FILL SOIL MEDIA 4551, MIRAFI 160N, TO DAYLIGHT DAYLIGHT AS 8" NO. 57 STONE 10~ FINES, TOWN ON PLANS 5% ORGANIC
PERFORATED PIPE 85% SAND OR APPROVED SHOWN ON PL GRASS ESTABLISHED
6" LONGITUDINAL UNDERDRAIN 10% FINES EQUAL) 5% ORGANIC BY SODDING
I S
NOT TO SCALE NOT TO SCALE o
~ J
' ~
N®TES: a
1. PERFORATED UNDERDRAIN PIPE SHALL BE WRAPPED WITH FILTER can
FABRIC. 2. ALL WORK REQUIRED TO CONSTRUCT THE B(ORETENTION SWALE F-
SHALL BE IN ACCORDANCE WITH THE REQUIREMENTS IDENTIFIED ON
THE PLANS AND SHALL BE PAID FOR AT THE CONTRACT UNIT I-
PRICE FOR THE °BIORETENTION SWALE" ITEM OF WORK. 3, DO NOT INSTALL BID-RETENTION FILTER MEDIA LAYERS AND H
UNDERDRAIN SYSTEM UN11L AREAS DRAINING TO BID-RETENTION Z W
SWALE ARE STABILIZED.
° M
0
0
w
a
z w
J_
W
EN01NEEFUNG PLANNING CONSULTANTS
4944 PARKWAY PLAZA BOULEVARD, SUITE 350 S HT.
CHARLOM NORTH CAROLINA 28217
HDR Engineering, Inc. PHONE 70"2&6070 FAX: [phone]
of the Carolinas NORTH CAROLINA LICENSE NO. C•1163
www.talbertandbright.com O F
128 S Tryon Street, Suite 1400 1 Charlotte, NC 28202