20130427 Ver 1_Stormwater Info_20130529

Stormwater
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Raleigh,
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Soil & Environmental Consultants, PA
11010 Raven Ridge Road - Ralcigb, North Carolina 27614 9 Phone: [phone] - Fax: (919) U&9467
www.SandEC.com

Tableof Contents ................................................................................................................. i
Listof Figures ....................................................................................................................... ii
Listof Appendices ................................................................................................................ ii
Project Location, Background && Description ...................................................................... I
Stor[OVwaterManage00ent Plan .......................................................................................... i
Nitrogen Export Calculations .............................................................................................. 2
Limitations........................................................................................................................... 3
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List of Appendices

III 117TWITT MOO
Stormwater Management Plan
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The locations depicted for the rain barrels are approximate and may require
modification based on the constructed location of downspouts from the roof gutter
system. Similarly the exact location and configuration of the bioretention area may
moded at the time of construction however the design surface area, poncling dept
and bioretention media depth will be adhered to. I
Nitrogen Export Calculations
Nutrient otYset in the form
• Total Nitrogen (TN) buy down is required by the Division
of Water Quality (DWQ) as part of the project's permitting requirements. We estimat
Nitrogen Export rates associated with the existing site conditions and proposed site
conditions using methods outlined in the Neuse River Basin: Model Stormwater
Program for Nitrogen Control guidelines. I
roll &MV49JU9 301M.M.1 - •• - a •

ent at
estimate the offset paym,,� 0.25 acres x 4.63 lbs./ac./yr. (8-23 - 3.60) x $20.29/lb.
I Ct prior
times 30 years • $704.57. We understand this fee will�be confirmed , • D WQ prior
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11010 Rom Ridge Rd.- RaWgh, NC 27614
(919) WSM - (919) 646"7
Web Pap, www.SwidEC..com

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I 2029.P I fiepre 2 - NRC5
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Soil & Environmental Consultants, PA
11010 Rmn Mdp Rd • RRIMOK NC 27614
(919) P&M • (M) 846-9467
Web Par: www.SwKtEC.corn

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!Client: H.J. MORK15
iCON5TRUCTION, INC.

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Supporting Nitrogen • • CalcuWions

1,1103 Dreamy Way
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Step I Determine area for each type of land use and enter in in Column (2).
Step 2 Total the areas for each type of land use and enter at the bottom of Column (2).
Step 3 Multiply the areas in Column (2) • the TN export coefficients in Column (3) and enter in Column (4).
Step 4 Total the TN exports for each type of land use and enter at the bottom of Column (4).
Step 5 Determine the export coefficient by dividing the total TN export from uses at the
bottom • Column (4) • the total area at the bottom • Column (2).
PROPOSED CONDITIONS
Nitrogen Export Rate Calculations: I Based on Proposed Site Uses I
(1)
(2)
(3)
(3)
(4)
Type of
Area
TN Export
TN Export
Land Cover
(acres)
Coeff.
(acres)
from Use
Coeff.
(lbs./ac./y-r.)
Qbs./ y r.
Peranently Protected Undisturbed
0.00
0.60
C bs./ yr.
0.00
Open Space (forest, unmown meadow)
(Dist and Limited Site Buffers as Perm. Protect. Undisturbed Open Space)
Permanently Protected Managed
0.25
1.20
0.30
Open Space (grass, landscaping, etc.)
(Assume No
Perm. Protect. Undisturbed Open
Space)
Impervious Surfaces (roads, parking,
0.00
21.20
0.00
lots, driveways, roofs, paved storage
Open Space (grass, landscaping, etc.)
(Assume All Non-imperv. Areas to be Managed Open Space)
Impervious Surfaces (roads, parking,
areas, etc.)
21.20
TOTAL
L. .....
0.25
0.30
Total Nitrogen Export Coefficient = L
. . .. .......
1. 0 lbs./ac./yr.
PROPOSED CONDITIONS
Nitrogen Export Rate Calculations: I Based on Proposed Site Uses I
(1)
(2)
(3)
(4)
Type of
Area
TN Export
TN Export
Land Cover
(acres)
Coeff.
from Use
(lbs./ac./Ar.)
_
C bs./ yr.
Peranently Protected Undisturbed
0.00
1 0.60
1
0.00
Open Space (forest, unmown meadow)
(Assume No
Perm. Protect. Undisturbed Open
Space)
Permanently Protected Managed
0.16
1.20 1
0.19
Open Space (grass, landscaping, etc.)
(Assume All Non-imperv. Areas to be Managed Open Space)
Impervious Surfaces (roads, parking,
0.09
21.20
1.86
lots, driveways, roofs, paved storage
areas, etc.)
TOTAL
0.25
2.06
Total Nitrogen Export Coefficient
3 lbs./ac./yr.
to remove enough Nitrogen to bring the TN export rate below 3.6 lbs./ac./yr.
Nitrogen Export Rate Evaluation:
If the computed TN export rate for the post-development site is greater than 6.0 lbs./ac./yr. then the Owner must use on-site BMP's to bring
the development's export down to 6.0 lbs./ac./yr. Then the Owner may utilize one of the following options;
1.) Supplemental BMP's to reduce the TN export rate down to 3.6 lbs./ac./yr.
2.) Pay a one-time offset payment of $330/lb. to bring the rate down to 3.6 lbs./ac./yr.
3.) Do a combination of BMP's and offset payment to bring the rate down to 3.6 lbs./ac./yr.
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