SW3240502_Supplement-EZ Form_20240606

SUPPLEMENT-EZ COVER PAGE
FORMS LOADED
PROJECT INFORMATION
1 Project Name — Sage at Marvin
2 Project Area(ac)
3 Coastal Wetland Area(ac)
4 Surface Water Area(ac)
5 Is this project High or Low Density? Low
6 Does this project use an off-site SCM?
COMPLIANCE WITH 02H.1003(4)
7 Width of vegetated setbacks provided(feet)
8 Will the vegetated setback remain vegetated?
9 If BUA is proposed in the setback,does it meet NCAC 02H.1003(4)(c-d)?
10 Is streambank stabilization proposed on this project?
NUMBER AND TYPE OF SCMs:
11 Infiltration System _ 2_
12 Bioretention Cell
13 Wet Pond
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 Storm Filter
24 Silva Cell
25 Bayfilter
26 Filterra
FORMS LOADED
DESIGNER CERTIFICATION
27 Name and Title: Jonathon Rhine,Project Manager
28 Organization: Langan NC, Inc.
29 Street address: 227 W.Trade Street,Suite 320
30 City,State,Zip: Charlotte,NC 28202
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31 Phone number(s): _ 980-270-3919
32 Email: [e-mail]
Ccrsificat un Stater i,nt
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.
Designer
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DRAINAGE AREAS
1 Is this a high density project? No
2 If so,number of drainage areas/SCMs 0
3 Does this project have low density areas? Yes
4 If so,number of low density drainage areas 3
Is all/part of this project subject to previous rule
5 versions? No
FORMS LOADED
DRAINAGE AREA INFORMATION Entire Site LD 1 LD 2 LD 3
4 Type of SCM N/A Infiltration Basin Infiltration Basin None
5 Total drainage area(sq ft) 2416273.2 676399.68 1298610.72 441262.8
6 Onsite drainage area(sq ft) 1937269.511 645750.2227 1291519.289 0
7 Offsite drainage area(sq ft) 479003.6888 30649.4573 7091.4315 441262.8
8 Total BUA in project(sq ft) 472148 sf 124999 sf 281799 sf 65351 sf
New BUA on subdivided lots(subject to
9 permitting)(sq ft) 283532 sf 81022 sf 202510 sf sf
New BUA not on subdivided lots(subject to
10 permitting)(sf) 85524 sf 13328 sf — 72197 of sf
11 Offsite BUA(sq ft) - 103092 sf — 30649 sf 7091 sf 65351 sf _
12 Breakdown of new BUA not on subdivided lots: See Below _ See Below See Below See Below
-Parking(sq ft) See Below See Below See Below See Below
-Sidewalk(sq ft) See Below See Below See Below See Below
-Roof(sq ft) See Below See Below See Below _ See Below
-Roadway(sq ft) See Below See Below See Below See Below
-Future(sq ft) See Below See Below See Below See Below
-Other,please specify in the comment box
below(sq ft) See Below See Below See Below See Below
New infiltrating permeable pavement on
13 subdivided lots(sq ft) sf sf sf sf
New infiltrating permeable pavement not on
14 subdivided lots(sq ft) sf sf sf sf
Existing BUA that will remain(not subject to
15 permitting)(sq ft) 120405 sf 9458 sf 45597 sf 65351 sf
16 Existing BUA that is already permitted(sq ft) sf sf sf sf
17 Existing BUA that will be removed(sq ft) 22733 sf 22733 sf sf sf
18 Percent BUA 15% 17% 18% 0%
19 Design storm(inches) 2.9 in 2.9 in
20 Design volume of SCM(cu ft) 15481 cf 51726 cf
21 Calculation method for design volume NRCS NRCS
ADDITIONAL INFORMATION
Please use this space to provide any additional information about the
22 drainage area(s):
Each proposed lot will have an average of 13,500 SF BUA,but the exact Lconfiguration will be determined when the individual lots are developed.

INFILTRATION SYSTEM
1 Drainage area number 1 2
2 Minimum required treatment volume(cu ft) 13199 cf I 49963 cf 1
Grigpm.MDC F$OIt102H.1050
3 Is the SCM sized to treat the SW from all surfaces at build-out? Yes Yes
4 Is the SCM located away from contaminated soils? Yes Yes
5 What are the side slopes of the SCM(H:V or enter"Vertical'for
trenches)? 3:1 3:1
6 Does the SCM have retaining walls,gabion walls or other
engineered side slopes? No No
7 Are the inlets,outlets,and receiving stream protected from erosion
(10-year storm)? Yes Yes
8 Is there an overflow or bypass for inflow volume in excess of the
design volume? Yes Yes
9 What is the method for dewatering the SCM for maintenance? Pump(preferred) Pump(preferred)
10 If applicable,will the SCM be cleaned out after construction? Yes Yes
11 Does the maintenance access comply with General MDC(8)? Yes Yes
12 Does the drainage easement comply with General MDC(9)? Yes Yes
If the SCM is on a single family lot,does(will?)the plat comply with
13 General MDC(10)? N/A N/A
14 Is there an O&M Agreement that complies with General MDC(11)? Yes Yes
15 Is there an O&M Plan that complies with General MDC(12)? Yes Yes
16 Does the SCM follow the device specific MDC? Yes Yes
17 Was the SCM designed by an NC licensed professional? Yes Yes
INFILTRATION SYSTEM MDC FROM 02H.1051
18 I Proposed slope of the subgrade surface(%) 0% 0%
19 Are terraces or baffles provided? No No
20 Type of pretreatment: Other Other
Solis Data
21 Was the soil investigated in the footprint and at the elevation of the
infiltration system? Yes Yes
22 SHWT elevation(fmsl) 570.00 573.00
23 Depth to SHWT per soils report(in) 76.80 200.04
24 Ground elevation at boring in soils report(fmsl) 576.40 589.67
25 Is a detailed hydrogeologic study attached if the separation is
between 1 and 2 feet? N/A N/A
26 Soil infiltration rate(in/hr) See Below See Below
27 Factor of safety(FS) (2 is recommended): See Below See Below
Elevations
29 Bottom elevation(final) 572 ft 576 ft
30 Storage elevation(fmsl) 576.9 ft 583.ft
31 Bypass elevation(fmsl) 578 ft 585 ft
For Basins Only
32 Bottom surface area(112) 1326 ft 4180 ft
33 Storage elevation surface area(ft2) 5212.ft 11049.ft
For Trenches Only
34 Length(ft)
35 Width(ft)
36 Perforated pipe diameter,if applicable(inches)
37 Number of laterals
38 Total length of perforated piping
1 39 Stone type,if applicable
40 Stone porosity(%)
41 Is stone free of fines?
42 Is the stone wrapped in geotextile fabric?
43 Has at least one inspection port been provided?
Volumes/Drawdown
_ 44 Design volume of SCM(cu ft) 21792 cf 76264 of
45 Time to draw down(hours) 56 hrs 33hrs
ADDITIONAL INFORMATION
46 Please use this space to provide any additional information about
the infiltration system(s):
The grassed conveyance swales are pretreatment for both basins.The in-situ soil
between the bottom of basin and SHWT shall be replaced with K-4 sand(5
inches/hour)for both basins.
Infiltration 3 9:21 AM 4/23/2024

LOW DENSITY
DESIGN REQUIRENIEJSN o 1.0W DENSITY PROJECTS FROM 02H 4003
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? 6.63
6 Are curb outlet swales proposed? No
7 Maximum longitudinal slope of curb outlet swale(s)(%) N/A
8 Bottom width of curb outlet swale(s)(feet) N/A
9 Maximum side slope of curb outlet swale(s)(H:V) N/A
10 Minimum length of curb outlet swale(s)(feet) N/A
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:
This project also adheres to 15A NCAC 2B.0600-.0609,Site Specific Water Quality Management Plan for the Goose Creek
Watershed.This project uses pipes to bypass off-site stormwater runoff,and minimizes the use of pipes for on-site stormwater
runoff.The stormwater runoff for the swales was calculated using the NRCS method,and the"C"value below is actually the
weighted CN.
Drainage Pervious
Swale Area BUA area Q Slope Flow depth
lac) (ac) (ac1 (cis) (%) (fps) (fps) (It)
1 15.63 3.35 12.29 72.00 65.07 2.24 6.63 _ 1.65
2 0.13 0.04 0.09 82.00 0.75 1.07 1.53 0.27
3 1.34 0.37 0.97 80.00 7.16 1.10 2.87 0.76
4 6.31 2.35 3.96 79.00 32.81 2.35 5.69 1.23
5 4.13 1.33 2,80 79.00 21.49 2.44 5.19 1.02
8 0.87 0.42 0.45 85.00 5.28 2.40 3.62 0.55
7 0.21 0.08 0.13 84.00 1.24 2.14 2.29 0.29
8 1.62 0.88 0.74 85.00 9.81 2.37 4.21 0.73
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