SW6120801_401 Certification Application_20120822

Permit No
AUG 2 2
A2012
AIPA NR-._TEi QJ
NCDENR
Sit/ t z Q�v 1
(to be provided by DWQ)
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 111) must be printed, filled out and submitted along with aft of the required information.
I. PROJECT INFORMATION
Project name Lot 1A Averitl Properties
Contact person Rob Balland, P.E.
Phone number 910-791-6707
Date 8f312012
Drainage area number 1
Q�oF w a r�qQ�
7 .y
P <
11. DESIGN INFORMATION
Site Characteristics
Drainage area
195.584 qz
Impervious area, post -development
109.250 q2
% impervious
55.86 %
Design rainfall depth
1.0 in
Storage Volume: Non -SA Waters
Minimum volume required 9,013 q3
Volume provided
9,691 q3
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
q3
Minimum volume required
ft3
Volume provided ft3
Peak Flow Calculations
Is the prelpost control of the 1 yr 24hr storm peak flow required?
N (Y or N)
1-yr, 24-hr rainfall depth
nla in
Rational C, pre -development
nfa (unitless)
Rational C, post -development
Na. (unitless)
Rainfall intensity: 1-yr, 24-hr storm
Na. iNhr #VALUE!
Pre -development 1-yr, 24-hr peak flow
Na ft3lsec
Post -development 1-yr, 24-hrpea k flow
Na g3lsec
Pre/Post 1-yr, 24-hr peak flow control
#VALUEI ft3lsec
Elevations
Temporary pool elevation
191.44 fmsl
Permanent pool elevation
190.50 fmsl
SHINT elevation (approx. at the perm. pool elevation)
189.00 fmsl
Top of 1 Oft vegetated shelf elevation
191.00 fmsl
Bottom of 1 Oft vegetated shelf elevation
190.00 fmsl
Sediment cleanout, top elevation (bottom of pond)
187.00 fmsl
Sediment cleanout, bottom elevation
186.00 fmsl
Sediment storage provided
1.00 ft
Is there additional volume stored above the state -required temp, pool?
Y (Y or N)
Elevation of the top of the additional volume
191.4 fmsl OK
Form SW441-Wet Detention Sasm-RA.94113/12 Parts I. & II. Design Summary, Page 1 of 2

Permit
(to be provided by DWQ)
Surface Areas
Area, temporary pool
Area REQUIRED, permanent pool
SAIDA ratio
Area PROVIDED, permanent pool, Ater,,,,.
Area, bottom of 1 Oft vegetated shelf, Aw
Area, sediment cleanout, top elevation (bottom of pond), A.y,,
Volumes
Volume, temporary pool
Volume, permanent pool, Vp—_Poc�
Volume, forebay (sum of forebays if more than one forebay)
Forebay % of permanent pool volume
SA1DA Table Data
Design TSS removal
Coastal SAlDA Table Used?
Mounta WPledmo;it SA/DA Table Used?
SA/DA ratio
Average depth (used in SAIDA table):
Calculation option 1 used? (See Figure 10-2b)
Volume, permanent pool, Vperm_pW
Area provided, permanent pool, AMMJ, d
Average depth calculated
Average depth used in SAIDA, d, (Round to nearest 0.5h)
Calculation option 2 used? (See Figure 10-2b)
Area provided, permanent pool, A, ,,,,-PW
Area, bottom of 1 Off vegetated shelf, At, ho
fk :tt,386 ftZ .
6,748 ft'
d.� Z3:-451(unidess) '
C8;493]ft` OK
' 4T579� ft`
r 2,1061it'
9.6911 ft3 OK
17,1041M'
3,339] h'
19.5% % OK
90 %
( N J(YorN)
F Y I(YorN)
3.45 (unitless)
N�1(Y or N)
17,104 ft'
8,493 ft`
ift
_ - 7-ft
( Y •'I(YorN)
8,493 fC
4,679 e
Area, sediment cleanout, top elevation (bottom of pond), Abdpand
2,106 ftz
"Depth" (distance b/w bottom of 10ft shelf and top of sediment)
3.00 ft
Average depth calculated ('
3.00111.
Average depth used in SAIDA, dv. (Round to down to nearest 0.5ft)
3.0jh
Drawdown Calculations
Drawdown through orifice? (.YY
(Y or N)
Diameter of orifice (if circular) (,. _ .
, 1.251
in
Area of orifice (if -non -circular) [' `
I in'
Coefficient of discharge (Co) , .. ,::
:; .0.64
(unitless)
Driving head (He) (
0.62
It
Drawdown through weir? 17 „'
oN ;
(Y or N)
Weir type
:
1(unitless)
Coefficient of discharge (C.) r ,I:,
„,., , .-
(unitless)
Length of weir (L) I ,._ ._,,
ft
Driving head (H) I .
It
Pre -development 1-yr, 24-hr peak flow f .:; .'..:'
0.051190/sec
Post -development 1-yr, 24-hr peak flow M .° `�,
,4A81ft'isec
Storage volume discharge rate (through discharge orifice or weir) °'' :
6.03
ft3lsec .
Storage volume drawdown time
i
3.24
days
Additional Information
Vegetated side slopes
3�:1
Vegetated shelf slope
( 10I :1
Vegetated shelf width
(' J'"' 10.01ft
Length of fiowpath to width ratio
(:: 31:1
Length to width ratio
I 3.01:1
Trash rack for overflow & orifice?
( Y I (Y or N)
Freeboard provided
( 2.5 ft
Vegetated filter provided?
f N I(Y or N)
Recorded drainage easement provided?
I Y - I(Y or N)
Capures all runoff at ultimate build -out?
l Y I (Y or N)
Drain mechanism for maintenance or emergencies is:
[Pump out
Need 3 ft min.
OK
OK
OK, draws down in 2-5 days. .
OK
OK
OK
OK
OK
OK
OK
OK
OK
OK
t
Form SW401-Wet Detention Basin-Rev.9.411B1Q Parts I, & II, Design Summary. Page 2 of 2