SW6231104_Design Calculations_20240610

SUPPLEMENT-EZ COVER PAGE
FORMS LOADED
PROJECT INFORMATION
1 Project Name Tractor Supply Store-West End
2 Project Area(ac) 6.12
3 Coastal Wetland Area(ac) 0
4 Surface Water Area(ac) 0
5 Is this project High or Low Density? High
6 Does this project use an off-site SCM? no
COMPLIANCE WITH 02H.1003(4)
7 Width of vegetated setbacks provided(feet) 30-ft
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 1
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 StormFilter
24 Silva Cell
25 Bayfilter
26 Filterra
FORMS LOADED
DESIGNER CERTIFICATION
27 Name and Title: J.Branch Smith,PE
28 Organization: Paramounte Engineering,Inc.
29 Street address: 122 Cinema Drive
30 City,State,Zip: Wilmington,NC 28409
31 Phone number(s): 910-791-6707
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.
Designer
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Seal Date

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 PROJECT AREA Infiltration Basin
5 Total drainage area (sq ft) 267458 221500
6 Onsite drainage area (sq ft) 267458 221500
7 Offsite drainage area (sq ft) 0 0
8 Total BUA in project(sq ft) 139300 sf 139300 sf
New BUA on subdivided lots (subject to permitting)
9 (sq ft) .0sf .0sf
New BUA not on subdivided lots (subject to
10 permitting) (sf) 139300 sf 139300 sf
11 Offsite BUA(sq ft) .0 sf .0 sf
12 Breakdown of new BUA not on subdivided lots:
- Parking (sq ft) 84100 sf 84100 sf
- Sidewalk (sq ft) 28000 sf 28000 sf
- Roof(sq ft) 22200 sf 22200 sf
- Roadway(sq ft)
- Future (sq ft) 5000 sf 5000 sf
-Other, please specify in the comment box below
(sq ft) .0 sf .0sf
New infiltrating permeable pavement on subdivided
13 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) - -
16 Existing BUA that is already permitted (sq ft) - -
17 Existing BUA that will be removed (sq ft) 2000 sf 2000 sf
18 Percent BUA 52.10% 62.90%
19 Design storm (inches) 1.50 in
20 Design volume of SCM (cu ft) 17056 cf
21 Calculation method for design volume Simple
ADDITIONAL INFORMATION
Please use this space to provide any additional information about the
22 drainage area(s):

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Project Name: West End TSC
Client: West End Development Group pA RA M O UNTF
Prepared By: JBS
N E E R 1 N G. 1 N G.
Date: 5/22/24
Infiltration Basin - DA 1
Soil Type = Sandy Soils
EL. At Test Location = 597.50 HA-01 and HA-02
Depth to SHWL = 20.0 ft See ECS Test Report 33:6510-R1
SHWL = 577.50
Min. Bottom EL. = 585.00 Exceeds 24" above SHWL
Infiltration Rate = 2.62 in/hr HA-01
Infiltration Rate = 4.12 in/hr HA-02
Infiltration Rate Used = 2.62 in/hr
Infiltration Rate = 1.31 in/hr FofS = 2
Drainage Area = 221500 sf DA 1
BUA Area to System = 139300 sf DA 1
% Impervious 62.9%
Runoff Coefficent (Rv) = 0.616 in/in
Required 1.5" Runoff Volume 17,056 cf (Min. 1.0" Storm Depth per 15A NCAC 02H .1021 Non-Coastal H(
Required 1.5" Runoff Elev. 588.30 Elev.
Provided Runoff Volume = 17,056 cf SEE HYDROCAD STAGE-STORAGE TABLE
Bottom Area of Basin 2,850 sf
SA = FS * DV*12
K*T
where: SA = required minimum surface area of infiltration system(ft2)
FS = factor of safety(minimum of 2 is recommended)
DV = design volume(ft3)
K = hydraulic conductivity of soil(in/hr)
T = maximum dewatering time(72 hours)
Min. Surface Area of Basin = 2,170 SF from Equation 2 MDC #5 (above)
Drawdown Time = 2.28 days T(days) = Vol/ (Ir x SA)
54.82 hrs
Elev Stage Storage Storage Drained Qdarcy Drawdown Time
ft ft cf cf cfs sec min hours days
588.3 3.30 17,056 0 0.57040 0.0 0 0 0
587.0 2.00 9,264 7,792 0.34569 22540.1 375.67 6.26 0.26
586.5 1.50 6,289 10,767 0.25927 41528.0 692.13 11.54 0.48
586.0 1.00 3,754 13,302 0.17285 76958.1 1282.64 21.38 0.89
585.5 0.50 1,657 15,399 0.08642 178180.5 2969.67 49.49 2.06
585.0 0.00 0 17,056 0.00000 #DIV/0! #DIV/0! #DIV/0! #DIV/0!
Stage-Area -Storage Table:
Elevation Surface Area Volume
ft sf cf
585 2,850 0
586 4,087 3,469
587 5,433 8,229
588 6,900 14,395
588.30 7,400 17,056
589 8,563 22,127
590 10,396 31,606
591 12,382 42,995
592 14,534 56,453
593 16,707 72,074
594 19,564 90,209
595 21,964 110,884