20120813 Ver 2_WFS BMP Design_20190206

Duck Waterfront Shoppes
Proposed Parking Addition
Stormwater Management Calculations
Design Storm Rainfall Depth (R p)
Drainage Basin Area Data
Additional Drainage Area
Off -Site Drainage Area
TotalDrainageArea (A)
Soils Report Data
Stormwater Wetland
Calculations
1.5 in.
11,815 sf. 0.271 ac.
0 sf. 0.00 ac.
11,815 sf. 0.271 ac.
Soil Type Sandy Hydric Soils -
Infiltration Rate* (IR) 0.5 in/hr +
Seasonal High Water Table Elev. 1.0 ft. rust
Soils Data Based On Site Evaluation Performed by Protocal Sampling Services
Subarea
Description
Area
(FT`)
Factor
©
Adj. Impervious
I Area (FT')
Adj. Impervious
Area Ac.
Additional As haltParkin &Concrete
1 8,277
1.00
1177
0.19
Open Space
3,538
0.00
0
0.09
Total Addition Built -Upon Area
1 8,277
0.19
Runoff Volume Calculation
Impervious Fraction (IA)
0.701
70%
Runoff Coefficient (R v) = .05+ .9(IA)
0.680
Additional Volume of Runoff to be controlled (V) = 3630*Ro *R v *A
1,005
ft s
Wetland BMP - Treatment Volume Calculations
Existing Permanent Pool Elevation (PPE) (Also Shallow Water/Deep Pool Top)
1.00
ft. MI
Existing Temporary Pool Elevation (TPE) (Also Shallow Land Top)
1.50
ft. msl
Existing Depth of Temporary Pool (D yi"„ �,)
0.5
ft.
Additional Surface Area at Permanent Pool
1,962
ft Z
Additional SurfaceArea of Temporary Pool
2,061
ft z
Additional Temporary Pool Volume Provided
1,006
fts
Storage Provided > Storage Required
YES
2/6/2019
NOTE:
These calculations are preliminary and are subject to change based on final design. The calculations intend to support the
general volumetric and surface area of an existing stormwater wetland BMP being proposed for expansion in accordance
with current NCDEQ stormwater regulations. The proposed BMP expansion will serve a proposed parking area addition
as illustrated on an exhibit prepared by Bissell Professional Group and titled "DUCK WATERFRONT SHOPPES
PARKING & STORMWATER BMP EXPANSION," dated 05/20/2016. Said exhibit and these calculations are only
to be utilized to support a request being made for related wetland impacts. ,
R D
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. S
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