SW5240201_Supplement-EZ Form_20240627

SUPPLEMENT-EZ COVER PAGE
FORMS LOADED
PROJECT INFORMATION
1 Project Name _ Wrenn Farms
2 Project Area(ac) 30 -
3 Coastal Wetland Area(ac) _ 0
4 Surface Water Area(ac) 0.51
5 Is this project High or Low Density? _ Both High and Low Density
6 I Does this project use an off-site SCM? No
COMPLIANCE WITH 02H.1003(4)
7 Width of vegetated setbacks provided(feet) _ _ _ 50 -
8 Will the vegetated setback remain vegetated? Yes
9 If BUA is proposed in the setback,does it meet NCAC 02H.1003(4)(c-d)? N/A_ _ _ _
10 Is streambank stabilization proposed on this project? No
NUMBER AND TYPE OF SCMs:
11 Infiltration System -
12 Bioretention Cell
13 Wet Pond 1
14 Stormwater Wetland
15 Permeable Pavement
16 Sand Filter _
17 Rainwater Harvesting(RWH)
18 Green Roof _
19 Level Spreader-Filter Strip(LS-FS)
20 Disconnected Impervious Surface(DIS)
21 Treatment Swale —_
22 Dry Pond
23 StormFilter
24 Silva Cell
25 Bayfilter
26 Filterra
FORMS LOADED
DESIGNER CERTIFICATION
27 Name and Title: John R Wadsworth.PE-Project Engineer _
28 Organization: Timmons Group._ -
29 Street address: 5410 Trinity Road,Suite 102
30 City,State,Zip: Raleigh.NC 27607
31 Phone number(s): - 919-866-4516
32 Email: [e-mail]
Certification Statement:
I certify,under penalty of law that this Supplement-EZ form and all supporting information were prepared under my direction or supervision;that the
information provided in the form is,to the best of my knowledge and belief,true,accurate,and complete;and that the engineering plans,
specifications,operation and maintenance agreements and other supporting information are consistent with the information provided here.
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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? Yes
4 If so,number of low density drainage areas 2
Is all/part of this project subject to previous rule
5 versions? No
FORMS LOADED
DRAINAGE AREA INFORMATION Entire Site 1 LD 1 LD 2
4 Type of SCM Wet Pond
5 Total drainage area(sq ft) 3633008 1592117 28749 68825
6 Onsite drainage area(sq ft) 1562932 1562932 28749 68824
7 Offsite drainage area(sq ft) 2268604 29185 N/A N/A
8 Total BUA in project(sq ft) 523368 sf 492228 sf 8022 sf 23118 sf
New BUA on subdivided lots(subject to permitting)
9 (sq ft) 201247 sf 201247 sf N/A N/A
New BUA not on subdivided lots(subject to
10 permitting)(sf) 274784 sf 261359 sf 3297 sf 10128 sf
11 Offsite BUA(sq ft) 29185 sf 29185 sf N/A N/A
12 Breakdown of new BUA not on subdivided lots: N/A N/A
-Parking(sq ft) 8712 sf 8712 sf
-Sidewalk(sq ft) 37026 sf 37026 sf
-Roof(sq ft)
-Roadway(sq ft) 113177 sf 99752 sf 3297 sf 10128 sf
-Future(sq ft) 115869 sf 115869 sf
-Other,please specify in the comment box
below(sq ft) N/A N/A
New infiltrating permeable pavement on
13 subdivided lots(sq ft) N/A N/A N/A N/A
New infiltrating permeable pavement not on
14 subdivided lots(sq ft) N/A N/A N/A N/A
Existing BUA that will remain(not subject to
15 permitting)(sq ft) N/A N/A N/A N/A
16 Existing BUA that is already permitted(sq ft) 17715 sf N/A 4725 sf 12990 sf
17 Existing BUA that will be removed(sq ft) N/A N/A N/A N/A
18 Percent BUA 33% 31% 11% 15%
19 Design storm(inches) 1.0 in
20 Design volume of SCM(cu ft) 101791 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):
Drainage area 1 drains to the SCM.The offsite BUA form Wrenn Villas to the
west.This is area is mostly road and right of way that will drain into Wrenn
Farms and be captured and directed to the SCM.Drainage area LD1 and LD2
are low density and drain to POI 2 and POI 3 respectively.

WET POND
1 Drainage area number 1 I
2 Minimum required treatment volume(Cu ft) 43638 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 engineered No
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 by an NC licensed professional? Yes
WET POND MDC FROM 02H.1053
18 Sizing method used SA/DA
19 Has a stage/storage table been provided in the calculations? Yes
20 Elevation of the excavated main pool depth(bottom of sediment 401.00
removal)(fmsl)
21 Elevation of the main pool bottom(top of sediment removal)(fmsl) 402.00
22 Elevation of the bottom of the vegetated shelf(fmsl) 407.00
23 Elevation of the permanent pool(fmsl) _ 408.00
24 Elevation of the top of the vegetated shelf(fmsl) 407.00
25 Elevation of the temporary pool(fmsl) 408.69
26 Surface area of the main permanent pool(square feet) 18533
27 Volume of the main permanent pool(cubic feet) 79581 cf
28 Average depth of the main pool(feet) 4.00 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) 13988 cf
33 Is this 15-20%of the volume in the main pool? Yes
34 Clean-out depth for forebay(inches) 12 in
35 Design volume of SCM(cu ft) 101791 cf
36 Is the outlet an orifice or a weir? Orifice
37 If orifice,orifice diameter(inches) _ 3 in
38 If weir,weir height(inches)
39 If weir,weir length(inches)
40 Drawdown time for the temporary pool(days) 2.8
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? No
43 Depth of forebay at entrance(inches) 60 in _
44 Depth of forebay at exit(inches) 66 in _
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? _
49 Does the pond minimize impacts to the receiving channel from the 1- Yes
yr,24-hr storm?
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 system? Yes
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 Bermuda
54 Has a planting plan been provided for the vegetated shelf? Yes
ADDITIONAL INFORMATION lir
55 Please use this space to provide any additional information about the
wet pond(s):
Wet Pond 4 12:08 PM 6/26/2024

LOW DENSITY
DESIGN REQUIREMENTS FOR LOW DENSITY PROJECTS FROM 02H.1003
1 Is project below density thresholds set forth in the applicable stormwater rule? Yes
2 Does project maximize dispersed flow and minimize channelization of flow? Yes
3 Has the use of piping been minimized per.1003(2)(c)? Yes
4 Side slopes of the vegetated conveyances(H:V) 3:1
5 Maximum velocity in the vegetated conveyances during the 10-year storm? 7.99
6 Are curb outlet swales proposed? No
7 Maximum longitudinal slope of curb outlet swale(s)(%)
8 Bottom width of curb outlet swale(s)(feet)
9 Maximum side slope of curb outlet swale(s)(H:V)
10 Minimum length of curb outlet swale(s)(feet)
11 Are treatment swales used instead of curb outlet swales? No
12 Is stormwater released at the edge of the setback as dispersed flow? N/A
13 Have stormwater outlets been designed to prevent downslope erosion? Yes
14 Are variations to rule.1003 proposed? No
ADDITIONAL INFORMATION
15 Please use this space to provide any additional information about this low density project:
Stormwater runoff will be conveyed with the use of a roadside swale and RCP pipes.Runoff will outlet at non-erosive velocities.
Calculcations pipes are provided in the stormwater impact analysis.
Drainage Pervious
Swale Area BUA area C Q Slope Vanow V,ct„ei Flow depth
# (ac) (ac) (ac) (cfs) (%) (fps) (fps) (ft)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30