HomeMy WebLinkAboutSW6210505_Supplement 1_20210524Permit No.
(to be provided by DWQ)
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STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN 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.
Project name
FTCC EmergenncyServices Campus
Contact person
Richard Lee
Phone number
(910)-237-5758
Date
5/12/2021
Drainage area number
1
II. DESIGN INFORMATION
Site Characteristics
Drainage area
93,304 ftz
Impervious area, post -development
74,636 ftz
% impervious
79.99 %
Design rainfall depth
in
Storage Volume: Non -SA Waters
Minimum volume required
4,919 ft3
Volume provided
5,027 ft3
OK, volume provided is equal to or in excess of volume required.
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
ft3
Volume provided ft3
Peak Flow Calculations
Is the pre/post control of the lyr 24hr storm peak flow required?
Y (Y or N)
1-yr, 24-hr rainfall depth
1.0 in
Rational C, pre -development
0.40 (unitless)
Rational C, post -development
0.72 (unitless)
Rainfall intensity: 1-yr, 24-hr storm
1.36 in/hr OK
Pre -development 1-yr, 24-hr peak flow
6.05 ft3/sec
Post -development 1-yr, 24-hr peak flow
3.26 ft3/sec
Pre/Post 1-yr, 24-hr peak flow control
-2.79 ft3/sec
Elevations
Temporary pool elevation
87.38 fmsl
Permanent pool elevation
85.50 fmsl
SHWT elevation (approx. at the perm. pool elevation)
fmsl
Top of 1 Oft vegetated shelf elevation
86.50 fmsl
Bottom of 1 Oft vegetated shelf elevation
85.50 fmsl
Sediment cleanout, top elevation (bottom of pond)
79.00 fmsl
Sediment cleanout, bottom elevation
78.00 fmsl
Sediment storage provided
1.00 ft
Is there additional volume stored above the state -required temp. pool?
N (Y or N)
Elevation of the top of the additional volume
fmsl
Form SW401-Wet Detention Basin-Rev.9-4/18/12 Parts I. & II. Design Summary, Page 1 of 2
Permit No.
(to be provided by DWQ)
Surface Areas
Area, temporary pool
Area REQUIRED, permanent pool
SA/DA ratio
Area PROVIDED, permanent pool, Aps n_pW
Area, bottom of 1 Oft vegetated shelf, Aba shelf
Area, sediment cleanout, top elevation (bottom of pond), Abot_pood
Volumes
Volume, temporary pool
Volume, permanent pool, Vpertn_pool
Volume, forebay (sum of forebays if more than one forebay)
Forebay % of permanent pool volume
SA/DA Table Data
Design TSS removal
Coastal SA/DA Table Used?
Mountain/Piedmont SA/DA Table Used?
SA/DA ratio
Average depth (used in SA/DA table):
Calculation option 1 used? (See Figure 10-2b)
Volume, permanent pool, Vpertn_pool
Area provided, permanent pool, Aperml,00l
Average depth calculated
Average depth used in SA/DA, d_ (Round to nearest 0.5ft)
Calculation option 2 used? (See Figure 10-2b)
Area provided, permanent pool, Aperml,00l
Area, bottom of 1 Oft vegetated shelf, Aba shelf
Area, sediment cleanout, top elevation (bottom of pond), Abot_pond
"Depth" (distance b/w bottom of 1 Oft shelf and top of sediment)
Average depth calculated
Average depth used in SA/DA, de,,, (Round to down to nearest 0.5ft)
Drawdown Calculations
Drawdown through orifice?
Diameter of orifice (if circular)
Area of orifice (if -non -circular)
Coefficient of discharge (Co)
Driving head (Ho)
Drawdown through weir?
Weir type
Coefficient of discharge (C.)
Length of weir (L)
Driving head (H)
Pre -development 1-yr, 24-hr peak flow
Post -development 1-yr, 24-hr peak flow
Storage volume discharge rate (through discharge orifice or weir)
Storage volume drawdown time
Additional Information
Vegetated side slopes
Vegetated shelf slope
Vegetated shelf width
Length of flowpath to width ratio
Length to width ratio
Trash rack for overflow & orifice?
Freeboard provided
Vegetated filter provided?
Recorded drainage easement provided?
Capures all runoff at ultimate build -out?
Drain mechanism for maintenance or emergencies is:
6,631 ft'
2,743 ft'
2.94 (unitless)
2,887 ft` OK
2,887 ft'
424 ft,
5,027 ft' OK
8,981 ft'
1,796 ft'
20.0% % OK
90 %
N (Y or N)
N (Y or N)
2.94 (unitless)
N (Y or N)
8,981 ft'
2,887 ft'
ft Need 3 ft min.
ft
Y (Y or N)
2,887 ft'
2,887 ft'
424 ft'
6.50 ft
4.26 ft OK
4.5 ft OK
Y (Y or N) Do not enter data for both an orifice and a weir.
4.00 in
In
z
0.60 (unitless)
1.88 ft
Y (Y or N) Do not enter data for both an orifice and a weir.
RISER (unitless)
3.33 (unitless)
12.56 ft
0.53 ft
6.05 ft3/sec
3.26 ft3/sec
0.02 ft3/sec
3.30 days OK, draws down in 2-5 days.
10 :1
OK
10 :1
OK
10.0 ft
OK
3 :1
OK
4.0 :1
OK
N (Y or N)
Trash rack or similar device recommended.
0.6 ft
Insufficient freeboard, minimum of 1-ft required
Y (Y or N)
OK
Y (Y or N)
OK
Y (Y or N)
OK
Form SW401-Wet Detention Basin-Rev.9-4/18/12 Parts I. & II. Design Summary, Page 2 of 2