SW6090701_401 Certification Application_20090708

Permit No.
(to be provided by DWp)
*AA%
NCDENR
Contact person
Phone number
Date
Drainage area number
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
WET DETENTION BASIN SUPPLEMENT
This lorm 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.
ISI•.if14-_ 17-111
07,06.09
Combined Drainage Areas to Wet Pond
II. DESIGN INFORMATION
Site Characteristics
Drainage area _ 1,559,013 rye
Impervious area, post -development 493,099 fe -
%impervio is 31.63 % -
Design rainfall depth 1.0 in
Storage Volume: Non -SA Waters
Minimum volume required -
Volume provided
Storage Volume: SA Waters
1.5'runofl volume
Pre -development 1-yr. 24-hr runoff
Post -development 1-yr, 24-hr runoff
Minimum volume required
Volume provided
Peak Flow Calculations
Is the prelpost control of the lyr 24hr stone peak flow required?
1-yr, 24-hr rainfall depth
Rational C, pre -development
Rational C, post -development
Rainfall intensity: 1-yr, 24-hr stone
Pre -development 1-yr, 24-hr peak flow
Post -development 1-yr, 24-hr peak flow
PrelPost 1-yr, 24-hr peak flow control
Elevations
Temporary pool elevation
Permanent pool elevation
SHINT elevation (approx. at the perm. pool elevation)
Top of 1011 vegetated shelf elevation
Bottom of 10111 vegetated shelf elevation
Sediment cleanout, top elevation (bottom of pond)
Sediment Geanout, bottom elevation
Sediment storage provided
Is there additional volume stored above the state -required temp. pool?
Elevation of the top of the additional volume
Of W^A TFq
_-- \O~
f
43,480 fls OK -
117,0371t3
OK volume provided is equal to or in excess of volume required.
fe
ft'
fts
Oft
ft'
Y (Y or N)
3.0 in
0.60 (uni0ess)
0.70 (unilless)
0.13 inlhr OK -
8.68 ft'/sec -
2.66 fP/sec
-6.02 ft"Isec
.158.27 find
157.00 final
fmsl
157.50 dmsl
156.50 final
154.00 fmsl
153.00 himl
1.00 ft
(Y or N)
fmsl
Data not needed for calculation option #1, but OK 0 provided.
Data not needed for calculation option #1, but OK if provided.
Forth SW401-Wer Detention BasinRev.&WQW - Pars I. a II. Design Summary, Pape 1 of 2

Permit No.
(to be provided by DWQ)
II. DESIGN INFORMATION
Surface Areas
Area, temporary pool
45,012 flr
Area REQUIRED, permanent pod
29.309 ft
SAIDA ratio
1.88 (unifless)
Area PROVIDED, permanent pod, Ap
38,437 ft' OK
_p,
Area, bottom of 1011 vegetated shelf, Ab,(_y,w
37,259 ft
Area, sediment deanoul, top elevation (bottom of pond), Abd
31,520 ft'
Volumes
Volume, temporary pool
117,037 ft3 OK
Volume, permanent pool, Vo _caw
135,263 ff3
Volume, forebay (sum of forebays if more than one forebay)
33,999 ffa
Foebay % of permanent pool volume
25.1 % % Insufficient forebay volume.
SAIDA Table Data
Design TSS removal
Coastal SAIDA Table Used?
Mountair/Piedmonl SAIDA Table Used?
SAIDA ratio
Average depth (used in SAIDA table):
Calculation option 1 used? (See Figure 10-2b)
Volume, permanent pool, Vr,,,,_m,
Area provided, permanent pod, A,_ma
Average depth calculated
Average depth used in SAIDA, d„, (Round to nearest 0.511)
Calculation option 2 used? (See Figum 10-21b)
Area provided, permanent pod, A,, a_sa,
Area, bottom of 10ft vegetated shelf, Abau a,
Area, sediment deanoul, top elevation (bottom of pond), Ae,.,
'Depth' (distance b/w bottom of 100 shelf and top of sediment)
Average depth calculated
Average depth used in SAIDA, d., (Round to nearest 0.5ft)
Drawdown Calculations
Drawdown through orifice?
Diameter of office (If circular)
Area of orifice (if-roncircular)
Coefficient of discharge (Ce)
Driving head (Hj
Drawdown through weir?
Weirtype
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 draw town time
90 %
N (Y or N)
Y (Y or N)
1.88 (unifless)
Y (Y or N)
135,263 ft'
OK
38,437 ft
OK
3.51 It
OK
3.5 It
OK
N (Y or N)
It,
It'
M
Y (Y or N)
SAD7G�
In2
0.60 (unifless)
0.42 ft
N (Y or N)
(unifless)
(unitess)
it
ft
8.68 fP/sec OK
2.66 83/sec OK
0.25 ftl/sec
2.00 days OK, draws down in 2-5 days.
OK drawdown time is correct.
Additional Information
Vegetated side slopes
3 :1
OK
Vegetated shelf slope
10 :1
OK
Vegetated shelf width
10.0 it
OK
Length of Ifowpath to width ratio
3 :1
OK
Length to width ratio
1.7 A
OK
Trash rack for overflow 8 orifice?
Y (Y or N)
OK
Freeboard provided
1.0 it
OK
Vegetated filter provided?
N (Y or N)
OK
Recorded drainage easement provided?
Y (Y or N)
OK
Capures all runoff at dtimate build -out?
Y (Y or N)
OK
Drain mechanism for maintenance or emergencies
Pond must be pumped out
Far SW401-Wet Dearnon Sasin-Rev.6-220r09 Pans I. a It. Design Summary, Page 2 of 2