SW1080104_401 Certification Application_20080507

Permit No.
(to be provided by OWQ)
NCDENR p Y
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 all of the required information.
I:; PROJECT INFORMATION �Y = 4'' r `' { x� • ;'
Project name Mills River Elementary School
Contact person Brian Dey, PE
Phone number 704-841-2588
Date 2/11/2008
Drainage area number 1
11� DESIGN INFORMATION,-,,
Site Characteristics
Drainage area 501,088 tt2
impervious area 253,774 ft'
% impervious 50,64459736 %
Design rainfall depth in
Storage Volume: Nan -SR Waters
Minimum volume required
it,
Volume provided
ft3
Storage Volume: SR Waters
1-yr, 24-hr runoff depth
in
Pre -development 1-yr, 24-hr runoff
tts
Post -development 1-yr, 24-hr runoff
ft3
Minimum volume required
ft3
Volume provided
it,
Peak Flow Calculations
Is pre/post control of the 1-yr 24-hr peak flow required?
Y
(Y or N)
1-yr, 24-hr rainfall depth
3.3
in
Rational C, pre -development
0.4
(uniiless)
Rational C, past -development
0.6
(unitless)
Rainfall intensity: 1-yr, 24-hr storm
0.1
in/hr
Pre -development 1-yr, 24-hr peak f w
0.7 ___
ft3lsec
Post -development 1-yr, 24-hr peak flow
0.9
ff3lsec
Pre/Post 1-yr, 24-hr peak flow control
' 0.2
ft3/sec
Basin Elevations •
Basin bottom elevation
2092.00
f1
Sediment cleanout elevation
2093,00
ft
Bottom of shelf elevation
2101.50
it
Permanent pool elevation
2102.00
it
Top of shelf elevation
2102.50
ft
Temporary pool elevation
2103.87
it
Volume and Surface Area Calculations
SA/DA ratio
1.73
(uniiless)
Surface area at the bottom et she$
6845.00
fe
Volume at the bottom of shelf
22795.00
f13
Permanent pool, surface area required
- 8,712
ft,
Permanent pool, surface area provided
8,946
ft,
Permanent pool volume
26,727
ft3
Average depth for SA1DA tabtes
2.98759222
It
Surface area at the top of shelf
11248
fe
Volume at the top of shelf
31759
ft3
OK
Minimum of 3 ft required, Increase depth
Fore SW401-Wet Delertion Basin-Rev.3 Parts'l.'& II. Design Sdmmary, Page 1 pf 2

"i
Permit No.
(to be provided by DWQ)
II.,DESIGN INFORMATION• :.r:'v:,
Forebay volume
5,221
ft3
Forebay % of permanent pool volume
20
%
OK
Temporary pool, surface area provided
13,190
ft'
Drawdown Calculations
1
Treatment volume drawdown time
2.52
days
OK
Treatment volume discharge rate
0.10
ft31s
Pre -development 1-yr, 24-hr discharge
0.71
ft3/s
OK
Post -development 1-yr, 24-hr discharge
0.10
it31s
OK
Additional Information
Diameter of orifice
2,00
in
Design TSS removal-
85
%
Basin side slopes
3
:1
OK
Vegetated shelf slope
10
:1
OK
Vegetated shelf width
10
tt
OK
Length of flowpath to width ratio
3
:1
OK
Length to width ratio
1.5
:1
OK. `
Trash rack for overflow & orifice?
Y
(Y or N)
OK
_Freeboard provided
1
ft
OK
Vegetated filter provided?
Y
(Y or N)
OK
Recorded drainage easement provided?
Y
(Y or N)
OK
Capures all runoff at ultimate build -out?
Y
(Y or N)
OK
Drain mechanism for maintenance or emergencies
Form Sw401-Wet Detention Basin-Rev.3
Parts I. & II. Design Summary, Page 2 of 2

III ERERUIREDITEMSiCHECKLIST w��att" � �� ; �� e`,
Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to
indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a
requirement has not been met, attach justification.
Pagel Plan
Initials Sheet No.
• MY) 6 C4.0/Grading Plant. Plans (i" - 50' or larger) of the entire site showing:
C7.21Site Details
Design at ultimate bui[d-out,
Off -site drainage (if applicable),
Delineated drainage basins (include Rational C coefficient per basin),
- Forebay (if applicable),
High flow bypass system,
Maintenance access,
Recorded drainage easement and public right of way (ROW), and
Boundaries of drainage easement.
C4.0/Grading Plan
2. Plan details (1' = 30' or larger) for the level spreader showing:
C72/Site Details
Forebay (if applicable),
High flow bypass system,
One foot topo lines between the level lip and top of stream bank,
Recorded drainage easement, and
Design at ultimate, build -out.
M 06 C721Site Details
3. Section view of the level spreader (1" = 20' or larger) showing: - • ��`.+ � +�• '' : - • �. '
Underdrain system (if applicable),
Level lip,
Upslope channel, and _
-- • •
Downslope filter fabric.
NIA N/A
4. A date -stamped photograph of the filter strip that clearly shows the type of vegetation that'is present.
M 3 C'1.31Gengral
5. An assurance that the installed system will meet design specifications upon initial operation once tfie'.
Notes
project is complete and the entire drainage area is stabilized. -
f Al C7.3/General
6. A construction sequence that shows how the level spreader will be protected from sediment until the en6re�
Notes
drainage area is stabilized. y=
MV? Ifs Calcbook
7. The supporting calculations.
A) 06 Attached
8. A copy of the signed and notarized inspection and maintenance (11 10) agreement.
NIA NIA
9. A copy of the deed restriction,
Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.3 Part 111, page 1 of 1

NCDENR
y� r
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
LEVEL SPREADER, FILTER STRIP AND RESTORED RIPARIAN BUFFER 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 all of the required information.
11., PROJECT. INFORMATIONF,•J;,' q.i..,+, :'—
Project name Mills River Elementary School
Contact name Brian Dey, PE
Phone number 704-841-2331
Date February 11, 2008
Drainage area number 1
II: DESIGN, INFORMATION." 111
For Level Spreaders Receiving Flow From a BMP
Type of BMP Wet Detention Pond
Drawdown flow from the BM P 0.1 cfs
For Level Spreaders Receiving Flow from the Drainage Area
Drainage area
Impervious surface area
Percent impervious ---
Rational C coefficient
Peak flow from the 1 inlhr store
Time of concentration
Rainfall intensity, 10-yr storm
Peak flow from the 10-yr storm
Where Does the Levol Spreader Discharge?
To a bioretention cell?
To a wetland?
To a filter strip or riparian buffer?
Other (specify)
Filter Strip or Riparian Buffer Characterization (if applicable)
Width of grass
Width of dense ground cover
_ Width of wooded vecetatian
Total width
Slope (from level lip to to top of bank)
Are any draws present?
Level Spreader Design
Forebay surface area
Feet of level lip needed per cis
Answer "Y" to one of the following:
Length based on the 1 inlhr storm?
Length based on the 10-yr, 24-hr stony?
Length based on the SMP discharge rate?
Design flow
Is a bypass; device provided`)
Length of the level lip
Are level spreaders in series? -
Do not complete this section of the worksheet
fiz
fl2
Do not complete this section of the worksheet.
Do not complete this section of the worksheet.
cis
Do not complete this section of the worksheet.
min
_ inlhr
Do not complete this section of the worksheet.
cis
Do not complete this section of the worksheet.
N (Y or N)
N (Y or N)
Y (Y or N) Please complete filter strip characterization below.
13 ft ;
0 ft
0 it
13 it
2 %
N (Y or N) OK
500 sq it OK
13 fticfs
N (Y or N)
N (Y or N)
Y (Y or N)
0.1 cis
Y (Y or N) OK
13 ft #VALUE!
N (Y or N)
Form SW401-Level Spreader, Filter Srr,p, Restored Riparian Buffer•Rev,3 Parts I. and H. Design Summary, page 1 of 2 -

Bypass Channel Design (if applicable)
Does the bypass discharge through a wetland? (Y or N)
Does the channel enter the stream at an angle?
Dimensions of the channel (see diagram below):
M ft
IS It
W ft
y ft
Peak velocity in the channel during the 10-yr, 24-hr storm cfs
Channel lining material
• W •
---------------o
M,
i B i
9
Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.3
Parts I. and II. Design Summary, page 2 of 2