SW6230807_Supplement-EZ Form_20240327

DRAINAGE AREAS
1 Is this a high density project? Yes
2 If so,number of drainage areas/SCMs 1
3 Does this project have low density areas? No
4 If so,number of low density drainage areas 0
Is all/part of this project subject to previous rule
5 versions? No
FORMS LOADED
DRAINAGE AREA INFORMATION Entire Site 1
4 Type of SCM Wet Pond
5 Total drainage area(sq ft) 419,623 416,247
6 Onsite drainage area(sq ft) 416,247 416,247
7 Offsite drainage area(sq ft) 4,500
8 Total BUA in project(sq ft) 278,342 278,342
New BUA on subdivided lots(subject to
9 permitting)(sq ft)
New BUA not on subdivided lots(subject to
10 permitting)(sf)
11 Offsite BUA(sq ft) 4,500 4,500
12 Breakdown of new BUA not on subdivided lots:
-Parking(sq ft) 221,231 221,231
-Sidewalk(sq ft) 6,841 6,841
-Roof(sq ft) 24,569 24,569
-Roadway(sq ft)
-Future(sq ft)
-Other,please specify in the comment box
below(sq ft) 20,801 20,801 _
New infiltrating permeable pavement on
13 subdivided lots(sq ft) _
New infiltrating permeable pavement not on
14 subdivided lots(sq ft)
Existing BUA that will remain(not subject to
15 permitting)(sq ft) 21,201 21,201
16 Existing BUA that is already permitted(sq ft)
17 Existing BUA that will be removed(sq ft) 206,610
18 Percent BUA 66% 67%
19 Design storm(inches) 1.0 in
20 Design volume of SCM(cu ft) 42530 cf
21 Calculation method for design volume Simple Method
ADDITIONAL INFORMATION
Please use this space to provide any additional information about the
22 drainage area(s):
This area refers to the existing access road to the south of the property that is
made up of gravel.It will remain as is and will not be disturbed during
construction.

WET POND
1'Drainage area number 1
2 Minimum required treatment volume(cu ft) 22525 cf
GENERAL MDC FROM 02H.1050
3 Is the SCM sized to treat the SW from all surfaces at build-out? Yes
4 Is the SCM located away from contaminated soils? Yes
5 What are the side slopes of the SCM(H:V)? 3:1
6 Does the SCM have retaining walls,gabion walls or other Yes
engineered side slopes?
7 Are the inlets,outlets,and receiving stream protected from erosion Yes
(10-year storm)?
8 Is there an overflow or bypass for inflow volume in excess of the Yes
design volume?
9 What is the method for dewatering the SCM for maintenance? Pump(preferred)
10 If applicable,will the SCM be cleaned out after construction? Yes
11 Does the maintenance access comply with General MDC(8)? Yes
12 Does the drainage easement comply with General MDC(9)? Yes
If the SCM is on a single family lot,does(will?)the plat comply with
13 General MDC(10)? N/A
14 Is there an O&M Agreement that complies with General MDC(11)? Yes
15 Is there an O&M Plan that complies with General MDC(12)? Yes
16 Does the SCM follow the device specific MDC? Yes
17 Was the SCM designed b an NC licensed professional? Yes
WET POND MDC FROM 02H.1053
18 Sizing method used HRT
19 Has a stage/storage table been provided in the calculations? Yes
20 Elevation of the excavated main pool depth(bottom of sediment 231.00
removal)(fmsl)
21 Elevation of the main pool bottom(top of sediment removal)(fmsl) 231.50
22 Elevation of the bottom of the vegetated shelf(fmsl) 238.00
23 Elevation of the permanent pool(fmsl) 239.00
24 Elevation of the top of the vegetated shelf(fmsl) 239.00
25 Elevation of the temporary pool(fmsl) 240.25
26 Surface area of the main permanent pool(square feet) 19015
27 Volume of the main permanent pool(cubic feet) 55338 cf
28 Average depth of the main pool(feet) 7.50 ft
29 Average depth equation used Equation 2
30 If using equation 3,main pool perimeter(feet)
31 If using equation 3,width of submerged veg.shelf(feet)
32 Volume of the forebay(cubic feet) a.3,829 b.5,225
33 Is this 15-20%of the volume in the main pool? Yes
34 Clean-out depth for forebay(inches) a.3.5ft b.6.5ft
35 Design volume of SCM(cu ft) 23922 cf
36 Is the outlet an orifice or a weir? Orifice
37 If orifice,orifice diameter(inches) 4 in
38 If weir,weir height(inches)
39 If weir,weir length(inches)
40 Drawdown time for the temporary pool(days) 2.4
41 Are the inlet(s)and outlet located in a manner that avoids short- Yes
circuiting?
42 Are berms or baffles provided to improve the flow path? Yes
43 Depth of forebay at entrance(inches) a.42 b.78
44 Depth of forebay at exit(inches) a&b 12
45 Does water flow out of the forebay in a non-erosive manner? Yes
46 Width of the vegetated shelf(feet) 6 ft
47 Slope of vegetated shelf(H:V) 6:1
48 Does the orifice drawdown from below the top surface of the No
permanent pool?
Does the pond minimize impacts to the receiving channel from the
49 1-yr,24-hr storm? Yes
50 Are fountains proposed?(If Y,please provide documentation that No
MDC(9)is met.)
51 Is a trash rack or other device provided to protect the outlet Yes
system?
52 Are the dam and embankment planted in non-clumping turf grass? Yes
53 Species of turf that will be used on the dam and embankment Bermunda
54 Has a planting plan been provided for the vegetated shelf? Yes
ADDITIONAL INFORMATION
55 Please use this space to provide any additional information about
the wet pond(s):
2