SW8120607_COMPLIANCE_20120719

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW ez��gz 7
DOC TYPE
El CURRENT PERMIT
❑ APPROVED PLANS
❑ HISTORICAL FILE
fD COMPLIANCE EVALUATION INSPECTION
DOC DATE
a2��D7/g
YYYYMMDD

WET DETENTION POND ANALYSIS -ALL RULES
FILE NAME 81WQ818tormwateriiPermits & Projects12012020607 HD%2012 07 excel WP 120607
PROJECT # SW8 1120607 REVIEWER IS Pusey
Initial Run Date 7I19112
PROJECT NAME Friendly Mart Hwy 258 Last modified 19-Jul-12
Receiving Stream JUT of New River
Drainage Basin White Oak
Class IC NSW I
Within 1/2 mile? �Y or N
Index No 119-0) 1
Site Area 241 acres ODrainage Are;
Is new DA being added? N Y or N New Added DA
Rules- "2008" or "Ph2" 2008 Total DA
IMPERVIOUS AREAS - BUA Runoff C
Buildings 1136000 square feet 1
Street square feet 098
Parking 4475700 square feet 095
Sidewalks 65500 square feet 0 95
Future 720600 square feet 0 95
Other square feet �?
BUA at Old IDS square feet ?7
TOTAL 63972 00 Iscivare feet
SURFACE AREA CALCULATION (Including old and new DA and BUA)
Overall % Impervious 89 87%
QAverage Design Depth 3 09 feet
TSS, 85 or 90 90 %
Old D:
ODra;nage Area
0
BUA
000
Post development Rv=
0 001
Old BUA Design Storm
Old BUA Design Volume
0
1 5" New BUA Design Storm Volume
1 yr 24 hour precipitation depth (inches) from NOAA chart
Predevelopment Rv value (0 05 if no existing BUA)
1 yr 24 hr Pre -development volume
1 yr 24 hr Post -development volume
2008 Design Volume 7642 cubic feet
Phase 2 Design Volume 7642 - 400
Required Volume
Top of Sediment
Bottom of Shelf
Permanent Pool
Top of Shelf
Temporary Pool
Volume met at elev
**Vol Prov at TPE
7642
cf
msl
msl
msl
msl
msl
msl
3900
4600
4650
4700
4740
4747
1cf
7877
"" only works if TPE ? top of shelf elevation
user input req
formula
Breakdown of BUA C old DS
Buildings/Lots
Street
Parking / SW
Other
SAIDA Ratio 10 68% - 10 1%
Req SA 1 7387 isf ' " Different due
Prov SA 7573 Isf interpolation en
OK
6397200
sf
0 859
unitless
inches
7642
37
0 05
Note do not include previously approved BUA as existir
1097
cubic feet
18850
cubic feet
Area sf
Inc volume
12200
000
Forebay
140800
497250
Area, sf
Inc volume
Acc volume
23000
000
000
428900
1581650
1581650
616500
261350
1843000
801100
354400
2197400
948800
349980
2547380
FOREBAY
Perm Pool Volume=
23403
Req Forebay Volume=
Provided Volume=
WNIA
Percent=
Max Pumo HP
ORIFICE CALCULATION
Average Head
Flow 02, cfs
Flow Q5, cfs
No of Orifices
Diameter, inches
❑rawdown =
1 yr 24 hr intensity, in/hr
Runoff Coefficient
1 yr 24 hr peak Q
Onfrce flow<ty24hr 7
feet
cfs
cfs
or weir H x W
days
NOAA chart a
unitless
cfs
02 Area z 250
05 Area z 100
Orifice Area = 177
Ava Flow Q= 0 031
in x
# of end contractions, N =_
discharge coefficient, C
Effective weir length, L
sq inches
sq inches
sq inches
cfs
in
1331
1000
028
0 044
0 018
1
150
28
750
089
1087
YES -OK

Crystal Coast Enaineenna. PA
205-3 Ward Road
Swansboro NC 28584
910-325-0006
Business License C•2553
PROJECT Friendly Mart
tc=5mcns
110= 75
PIPE
Ccum
INCR
AREA
INCR
Q10
A
090
034
230
B
090
012
081
C
090
019
128
D
090
Oil
074
E
090
0 17
115
F
090
012
081
G
090
015
101
H
090
000
000
1
065
010
049
J
065
010
049
K
065
020
098
a
TOTAL TOTAL
AREA Q10
" 11L1111,�r
r�
_ t
'•.,, K. Nam;.••
!l11//11 j1
OUTLET
DIAMETER LENGTH GRADE VELOCITY ZONE LENGTH WIDTH
12"
151
0 38%
15"
69
0 38%
18"
127
0 38%
12"
65
0 50%
12"
134
0 50%
15"
60
0 50%
24"
18
0 50%
60
18"
26
1 00%
70
15"
114
0 20%
30
15"
93
0 48%
40
15"
117
0 25%
30
TYPE
2 12
6 Cl"B"
2 9
5 CI"B"
1 8
4 CI"B"
1 8
4 CI"B"
1 8
4 CI"B"

S 1WQSISTORMWATERIFORMSICHECKLIST
STORMWATER SUBMITTAL REQUIREMENTS
WET DETENTION POND
Objective
✓A_ Collect all runoff from all BUA (proposed and/or existing and/or offsite) as the case may be, by
any means including piping or swales, and direct it to the pond
B Check the proposed pond design to make sure it meets or exceeds the minimum design
criteria for surface area, volume and drawdown
II Wbat makes up a complete wet detention pond application package?
✓/ Two sets of sealed, signed & dated layout & grading plans with appropriate details
,/ Completed & signed application (SWU-101) with supplement(s), SW-401-Wet Detention
Basin, SW-401-Level Spreader, and signed & notarized inspection and maintenance
agreements
Deed restriction document, if applicable (for subdivisions & projects with outparcels)
�Dp Sealed, signed & dated calculations
Estimated seasonal high water table elevation at all pond locations
For Phase II projects only - Chlorides test results if the project is within'/z mile of SA waters
and a wet pond is proposed Chlorides testing must be accomplished by averaging the
chloride concentration of five (5) water samples taken'/2 mile downstream from the project
site, that are taken on separate days, within one hour of high tide, and not within 48 hours
following a rain event The samples must be analyzed by a State certified laboratory
III BIMS entry (for DWQ use only)
Enter & track application acknowledged date, review date, add info requested/received dates, permit
issue dates, permit expiration date, and drainage area and streamlwaterbody info Best done after the
add info letter is written and before sending permit up for signature
IV Shell documents (for DWQ use only)
Permit shells sIwgslstormwateAshellslhighcompond
sIwgslstormwaterlshellslhighsubpond
s IwgslstormwaterlshelIs\HDhybrid
Calculations s Iwgslstormwaterlexcel spreads heetslpond or
s IwgslstormwateAexcel spreads heetslmultipie pond
V Review Procedure
A APPLICATION
An original signature is required Photocopied signatures cannot be accepted
A completed wet detention pond supplement and a signed, dated and notarized wet
detention pond Inspection and Maintenance Agreement with an original signature
The numbers on the supplement match up to the numbers used in the calculations and
/shown on the plan details
kBuilt -upon areas are reported in square feet in Section III 9
Receiving stream name and classification This is important because in the non -Phase II
counties, a wet pond cannot be used on a project that is within'/ mile of and draining to
/ SA waters For Phase 11, a wet pond is allowed within '/2 mile of SA waters
✓6 Section 1119 is filled in-cannot_be left blank One column must be filled in for each
proposed wet pond
✓ ( 7 j If the applicant is a corporation, partnership or LLC, look it up on the Secretary of State
Corporations Database Make sure corporation is spelled correctly (capitalization and
punctuation matter) and that the person signing the application is at least a vice-
president in the corporation, a General Partner in the partnership, a member in a
member -managed LLC, or the manager of a manager -managed LLC Need
documentation to support if the Articles of Incorporation do not list the members or
managers of the LLC If an agent signs, then a letter of authorization is needed from the
president, vice president, general partner, member or manager
�u- For subdivided projects, a signed and notarized deed restriction statement must be
-� provided
Page 4 of 12

Wet Detention Pond, cont
B CALCULATIONS
The orifice is sized based on drawing down the calculated minimum volume in 25
days The average head to use in the orifice equation is approximately onethird of
the distance between the permanent pool elevation (PPE) and the elevation of the
next available outlet above the permanent pool The elevation of the next available
outlet must be either the elevation where the minimum volume is provided, or it can
be higher The temporary pool elevation (TPE) b report on the supplement will be
the elevation of the next available outlet above the PPE The temporary pool volume
(TPV) to report on the supplement is the volume between the specified PPE and the
TPE
For Phase II protects that are within'/ mile of ard draining to SR waters, the
difference in runoff volume from the predevelopment and postclevelopment
/ conditions for the 1 year 24 hour storm must be controlled and treated
�?l Required volume calculation based on 1 5" storm for Phase I I projects (non -SR waters)
and 1" storm for all other classes of receiving stream
For Phase II projects, discharge the storage volume at a rate equal to or less than
the pre -development discharge rate for the 1 year 24 hour storm
For Phase II projects draining to SA waters, no discharge to surface waters may occur
from wet ponds The discharge leaving the orifice must be directed to a natural area
capable of providing effective infiltrated for the 1 year 24 hour storm prior to reaching
surface waters
The average pond depth can be determined by dividing the permanent pool volume by
the permanent pool surface area, or by using the approved formula in the BMP Manual
The result must be rounded to the nearest 0 5 foot, so that it is between 3 ft and 7 5 ft
Parts of the pond can be deeper than 7 5 ft , but in no case can any part of the pond be
less than 3 ft deep Note that the sediment storage is not considered part of the
permanent pool
,9� If the 85% TSS chart is used a 30' vegetated filter must be provided at the outlet of the
pond If the 90% TSS chart is used, no filter is required
V%8 Use the correct SAIDA TSS chart from the BMP Manual noting that there are different
/ charts for different areas of the State
✓9 Required surface area at permanent pool
Provided surface area at permanent pool (Based on pond dimensions)
1 Table of elevations, areas, incremental volumes and accumulated volumes for overall
pond and for forebay, to verify volumes provided
Forebay designed to hold 20% of the permanent pool volume (Range of 18%-22% OK )
Non -erosive flow for 10 yr storm in the vegetated filter, if using 85% TSS
The seasonal high watertable must be no lowerthan 6" belowthe proposed permanent
pool elevation to assure that the necessary temporary storage volume will be available
above the permanent pool Otherwise, the consultant must provide a detailed soils
analysis report which takes into account the soil type, transmissivity, groundwater
volume flowing into the pond and the orifice size to demonstrate that the required
storage volume will be available above the proposed permanent pool elevation
5 Rounding numbers off during the calculation process can result in deficiencies Do not
,.,,'round the numbers until you get to the final result
An additional one foot must be excavated below the bottom elevation of the pond The 1
foot sediment accumulation depth is not included in either the permanent pool volume
calculation or the average depth calculation
Page 5 of 12

Wet Detention Pond, cont
C. PLANS- Due to storage space constraints, plan sheets should be kept to a minimum and
must be folded to no more than 8 5" x 14" For small commercial single wet pond projects, the
plan set could consist of only 2 or 3 sheets, layout, grading and details For larger projects,
show as much information as possible on as few sheets as possible, without cluttering them
up
r/1 Development/Project Name
Engineer name and firm
Legend
North Arrow
Location Map with nearest intersection of two major roads shown Major road is any 1, 2,
6-15�or 3 digit NC, US or interstate highway
/ Scale- standard engineering scale, no off-the-wall stuff
.•i Date
Revision number and date, if applicable
Original contours, proposed contours, spot elevations, finished floor elevations, pipe
inverts, swale inverts, etc
Existing drainage (piping, swales, ditches, ponds, etc ), including off -site Include a map
delineating the offsite drainage areas
Property/Project boundary lines, bearing & distances
> ' Mean High Water Line or Normal High Water Line, if applicable
The permanent pool elevation must beat or above the SHWT If adjacent a wetland, the
permanent pool level must be set such that the wetland is not drained through the pond
Drainage easement widths, pipe sizes and swale inverts are provided
Wetlands delineated, or a note on the plans that none exist Get a copy of the wetlands
delineation map signed by the Corps of Engineers, or contact the appropriate field rep
for the Corps to see if they can email a statement regarding the status of the delineation
&Air Details for the roads, parking, cul-de-sacs, including sidewalk width, radii, dimensions &
slopes
,4T— Apartment / Condo development- Provide a typical building footprint with dimensions
rid note all concrete and wood deck areas
_,,and
drainage area for each wet pond is clearly delineated and numbered to match up to
he calculations and supplement Drainage area delineation is best done as a separate
plan sheet / /
A pond section detail to inc! de the forebay, a�.0 foot wide vege�ted shelf, pertin t
elevatio for the bottom,-ediment cleanout, permanent pool,"tempora pool,"and
SHWTf3 1 slopes above the permanent pool, 10 1�pes on the shelf and the weir
elevation between the main pond and the forebay
0' The 10' vegetated shelf extends 6" below and 6" above the permanent pool elevation
An outlet structure detail showing a trash rack with 56" square openings, the necessary
orifice invert elevation (i e , the permanent pool), orifice size and temporary pool
elevation
Dimensions for each line and arc formed by the permanent pool contour
:2 - Where the 85% TSS chart was used, a 30 ft filter strip is required to be shown on the
plans & detailed (elevations, inverts, slopes, and flow spreader mechanism) Please
note that the filter strip is not a ditch
4 A forebay is provided for each inlet and located so as to pre%ent short-circuiting
,,25— The pond must have a minimum 1 5 1 length to width ratio and a minimum 3 1 flow path
length Artificial "baffles" of timber, vinyl, or earth can be used to create a longer flow
path The top elevation of the baffle should be set at the temporary pool elevation or
higher
llz26 A Vegetation plan is specified for the pond, including slopes Wetlands species are
listed for planting on the 10 1 shelf Weeping Love Grass is not suitable as a permanent
, � vegetated cover for pond slopes
Vl/ All roof drainage must be directed to the pond Show the roof drain collection lines on
the plan This is necessary for projects where the buildings back up the propertylines
where roof drainage may leave the site prior to going through the pond
Page 6 of 12