SW6201102_Calcs_20210202

Narrative
ProjectDescription
ThisprojectisfortheconstructionofanewminimartandgasstationlocatedonToraBoraBlvdinFt.
BraggMilitaryBase.CurrentlythesiteisvacantwithadecreasingslopeheadingSouthtoNorthand
partiallywooded.Therearenowetlandslocatedwithintheprojectlimits.Improvementsto
thesitewill
betheconstructionofanewbuilding,gaspumpsandparkingarea.Thesitewillhavetwoconnection
pointstoToraBoraBLVD.Thetotalprojectisapproximately3.01acreswith1.89acresbeingtreatedin
aNCDEQStormwaterBMP.
Stormwaterfromthesitewillbecollectedviacatchbasinsandtrenchgratesandconveyedtoasand
filterdesignedtohandletherainfallevent.ThesandfilterisdesignedperchapterC6ofNCDEQ
StormwaterDesignManual.Thefilterwillhaveaminimumofofsandfrombottomofbasinand
minimumofofsandabovethe3underdrainpipeswithinthefilter.Stormwaterfromthesitewill
draintoStewartsCreek(C,18312454)locatedintheCapeFearRiverBasin.

PROJECT DATA:
Existing Site Data:(within Project Limits)
Existing wetlands 0.0 sf (0.0 acres)
Existing uplands 130,930 sf (3.01 acres)
Total proposed project area130,930 sf (3.01 acres)

Proposed Site Data: (within Project Limits)
Proposed building 6,510 sf (0.15 acres)
Proposed roads59,847 sf (1.37acres)
Proposed sidewalk 6,105 sf (0.14 acres)
Proposed pump station 600 sf (0.01 acres)
Total proposed impervious area73,062 sf (1.68 acres)

Existing Site Data:(within Sand Filter Drainage Delineation)
Existing wetlands 0.0 sf (0.0 acres)
Existing uplands 82,340 sf (1.89 acres)
Total proposed project area82,340sf(1.89acres)
Proposed Site Data: (within Sand Filter Drainage Delineation)
Proposed building 6,510 sf (0.15 acres)
Proposed roads56,579 sf (1.30 acres)
Proposed sidewalk 5,593 sf (0.13acres)
Total proposed impervious area68,682 sf (1.58 acres)

Soil Types Within Project Limits:
Abbreviation Type and Description Hydrologic Group Area
FaB Faceville Loamy SandB 3.01 ac
(See attached soils map)

SANDFILTERYARBOROUGHCOMPLEX
1.0"VOLUMEDETERMINATION:
DETERMINEIMPERVIOUSPERCENTAGETOSANDFILTER
areatobasin=82,340sf
=1.89acres
ImperviouswithinDrainage
ImperviousforwholesiteevenifnotdrainingtoSandFilterAreatoSandfilter
buildings/driveways=6,510sf6,510sf
pavedarea=59,847sf56,579sf
pumpstation=600sfsf
sidewalk=6,105sf5,593sf
totalimp.surface=73,062sf68,682sf
percentimp.=88.7%83.4%
DETERMINERUNOFFCOEFFICIENT(Rv)
I=88.7percentimpervious
Rv=?(runoffcoefficient,inchesperinch)
Rv=0.05+0.009(I)
Rv=0.85in/in
DETERMINEVOLUME
designstorm=1inch
Rv=0.85in/in
drainagearea=1.89acres
volume=?
volume=(designstorm)(Rv)(drainagearea)
volume=0.13acreft
1.0"volume=5,832cfofrequiredstoragevolume
AdjustedWaterQualityVolume=4,374cfthatmustbecontainedbetweenthe
(ADJWQV)sedimentationchamberandthe
sandfilter(abovethesand)
MINIMUMSANDFILTERBASINSURFACEAREA
SA=ADJWQV/PondingDepth
PondingDepth=2 ft
SA=2,187sf
STAGESTORAGEFORSANDFILTER
STORAGETABLE:
SedimentChamberINCREMENTAL
ELEVATIONAREAVOLUMESTORAGE
(ft)(sf)(cf)(cf)
261486Sed.StorageNotusedincalcs
262975
2631,5701,2731,273
2642,2701,920 3,193
SandChamber
INCREMENTAL
ELEVATIONAREAVOLUMESTORAGE
(ft)(sf)(cf)(cf)
260456BottomofSandNotusedincalcs
261829Notusedincalcs
2621,252TopofSand
2631,7241,4881,488
2642,2441,984 3,472
TotalWaterQualityStorage=6,665cf
CALIBRE ENGINEERING
PO BOX 4041
WILMINGTON, NC 28406

SedimentChamber,SandChamberandforebayberm
INCREMENTAL
ELEVATIONAREAVOLUMESTORAGE
(ft)(sf)(cf)(cf)
2644,623
2656,0215,322 5,322
DETERMINEDRAWDOWN
Orificesize=6in
Orificecoefficient(C)=0.60
Averagehead(h)=(264262)/30.66ft
Orificecrosssectionalarea(A)=pixr^2=3.14x(r/12)^2=0.20sf
Accelerationduetogravity(g)=32.2ft/s^2
Q=CA(2gh)^1/2=0.6x0.20x(2x32.2x0.66)^1/2=0.78cfs
4,374/0.78=5,608seconds=1.56Hours
UNDERDRAINCALCULATION
mediaflowrate=2in/hr
linearinfiltrationrate=2in/hr
=0.000046ft/sec
bottomoffilterarea=456sf
3drate=0.021cfs
factorofsafety=10
0.21cfs
D=16{(Qxn)/S^0.5}^0.375
D=diameterofsinglepipe
n=0.011roughnessfactor
S=0.005slope
Q=0.21cfs
D=4.4352
fromNCDENRManualchapterA5ifD<9.11
Then36"underdrainpipesrequired.
CALIBRE ENGINEERING
PO BOX 4041
WILMINGTON, NC 28406

Hydrograph Summary Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020
Hyd.HydrographPeakTimeTime toHyd.InflowMaximumTotalHydrograph
No.typeflowintervalPeakvolumehyd(s)elevationstrge usedDescription
(origin)(cfs)(min)(min)(cuft)(ft)(cuft)
1SCS Runoff0.14527401,375------------------Pre-Dev
2SCS Runoff4.674272414,326------------------Post-Dev
3Reservoir2.408273014,3262262.731,978Routed
Sand_filter.gpwReturn Period: 1 YearTuesday, 01 / 26 / 2021

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020Tuesday, 01 / 26 / 2021
Hyd. No. 1
Pre-Dev
Hydrograph type= SCS RunoffPeak discharge= 0.145 cfs
Storm frequency= 1 yrsTime to peak= 12.33 hrs
Time interval= 2 minHyd. volume= 1,375 cuft
Drainage area= 1.890 acCurve number= 55
Basin Slope= 0.0 %Hydraulic length= 0 ft
Tc method= UserTime of conc. (Tc)= 5.00 min
Total precip.= 3.07 inDistribution= Type III
Storm duration= 24 hrsShape factor= 484
Pre-Dev
Q (cfs)Q (cfs)
Hyd. No. 1 -- 1 Year
0.500.50
0.450.45
0.400.40
0.350.35
0.300.30
0.250.25
0.200.20
0.150.15
0.100.10
0.050.05
0.000.00
02468101214161820222426
Time (hrs)
Hyd No. 1

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020Tuesday, 01 / 26 / 2021
Hyd. No. 2
Post-Dev
Hydrograph type= SCS RunoffPeak discharge= 4.674 cfs
Storm frequency= 1 yrsTime to peak= 12.07 hrs
Time interval= 2 minHyd. volume= 14,326 cuft
Drainage area= 1.890 acCurve number= 92
Basin Slope= 0.0 %Hydraulic length= 0 ft
Tc method= UserTime of conc. (Tc)= 5.00 min
Total precip.= 3.07 inDistribution= Type III
Storm duration= 24 hrsShape factor= 484
Post-Dev
Q (cfs)Q (cfs)
Hyd. No. 2 -- 1 Year
5.005.00
4.004.00
3.003.00
2.002.00
1.001.00
0.000.00
024681012141618202224
Time (hrs)
Hyd No. 2

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020Tuesday, 01 / 26 / 2021
Hyd. No. 3
Routed
Hydrograph type= ReservoirPeak discharge= 2.408 cfs
Storm frequency= 1 yrsTime to peak= 12.17 hrs
Time interval= 2 minHyd. volume= 14,326 cuft
Inflow hyd. No.= 2 - Post-DevMax. Elevation= 262.73 ft
Reservoir name= Sand FilterMax. Storage= 1,978 cuft
Storage Indication method used.
Routed
Q (cfs)Q (cfs)
Hyd. No. 3 -- 1 Year
5.005.00
4.004.00
3.003.00
2.002.00
1.001.00
0.000.00
02468101214161820222426
Time (hrs)
Hyd No. 3Hyd No. 2Total storage used = 1,978 cuft

Hydrograph Summary Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020
Hyd.HydrographPeakTimeTime toHyd.InflowMaximumTotalHydrograph
No.typeflowintervalPeakvolumehyd(s)elevationstrge usedDescription
(origin)(cfs)(min)(min)(cuft)(ft)(cuft)
1SCS Runoff4.274272413,660------------------Pre-Dev
2SCS Runoff12.01272438,944------------------Post-Dev
3Reservoir4.312273838,9432264.197,708Routed
Sand_filter.gpwReturn Period: 10 YearTuesday, 01 / 26 / 2021

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020Tuesday, 01 / 26 / 2021
Hyd. No. 1
Pre-Dev
Hydrograph type= SCS RunoffPeak discharge= 4.274 cfs
Storm frequency= 10 yrsTime to peak= 12.07 hrs
Time interval= 2 minHyd. volume= 13,660 cuft
Drainage area= 1.890 acCurve number= 55
Basin Slope= 0.0 %Hydraulic length= 0 ft
Tc method= UserTime of conc. (Tc)= 5.00 min
Total precip.= 7.00 inDistribution= Type III
Storm duration= 24 hrsShape factor= 484
Pre-Dev
Q (cfs)Q (cfs)
Hyd. No. 1 -- 10 Year
5.005.00
4.004.00
3.003.00
2.002.00
1.001.00
0.000.00
02468101214161820222426
Time (hrs)
Hyd No. 1

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020Tuesday, 01 / 26 / 2021
Hyd. No. 2
Post-Dev
Hydrograph type= SCS RunoffPeak discharge= 12.01 cfs
Storm frequency= 10 yrsTime to peak= 12.07 hrs
Time interval= 2 minHyd. volume= 38,944 cuft
Drainage area= 1.890 acCurve number= 92
Basin Slope= 0.0 %Hydraulic length= 0 ft
Tc method= UserTime of conc. (Tc)= 5.00 min
Total precip.= 7.00 inDistribution= Type III
Storm duration= 24 hrsShape factor= 484
Post-Dev
Q (cfs)Q (cfs)
Hyd. No. 2 -- 10 Year
14.0014.00
12.0012.00
10.0010.00
8.008.00
6.006.00
4.004.00
2.002.00
0.000.00
024681012141618202224
Time (hrs)
Hyd No. 2

Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020Tuesday, 01 / 26 / 2021
Hyd. No. 3
Routed
Hydrograph type= ReservoirPeak discharge= 4.312 cfs
Storm frequency= 10 yrsTime to peak= 12.30 hrs
Time interval= 2 minHyd. volume= 38,943 cuft
Inflow hyd. No.= 2 - Post-DevMax. Elevation= 264.19 ft
Reservoir name= Sand FilterMax. Storage= 7,708 cuft
Storage Indication method used.
Routed
Q (cfs)Q (cfs)
Hyd. No. 3 -- 10 Year
14.0014.00
12.0012.00
10.0010.00
8.008.00
6.006.00
4.004.00
2.002.00
0.000.00
02468101214161820222426
Time (hrs)
Hyd No. 3Hyd No. 2Total storage used = 7,708 cuft

Pond Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® 2019 by Autodesk, Inc. v2020Tuesday, 01 / 26 / 2021
Pond No. 1 - Sand Filter
Pond Data
Contours -User-defined contour areas. Conic method used for volume calculation. Begining Elevation = 262.00 ft
Stage / Storage Table
Stage (ft)Elevation (ft)Contour area (sqft)Incr. Storage (cuft)Total storage (cuft)
0.00262.002,22700
1.00263.003,2942,7432,743
2.00264.004,6233,9396,682
3.00265.006,0215,30611,988
Culvert / Orifice StructuresWeir Structures
\[A\]\[B\]\[C\]\[PrfRsr\]\[A\]\[B\]\[C\]\[D\]
Rise (in)= 12.006.000.000.00 Crest Len (ft)= 2.000.0010.000.00
= 12.006.000.000.00= 264.000.00264.500.00
Span (in)Crest El. (ft)
= 1300= 3.333.332.603.33
No. BarrelsWeir Coeff.
Invert El. (ft)= 260.00260.000.000.00 Weir Type= 1---Broad---
Length (ft)= 60.003.000.000.00 Multi-Stage= YesNoNoNo
= 0.200.000.00n/a
Slope (%)
= .013.013.013n/a
N-Value
Orifice Coeff.= 0.600.600.600.60 Exfil.(in/hr)= 0.000(by Contour)
= n/aYesNoNo= 0.00
Multi-StageTW Elev. (ft)
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
Stage / Discharge
Stage (ft)
Elev (ft)
3.00265.00
2.00264.00
1.00263.00
0.00262.00
0.002.004.006.008.0010.0012.0014.0016.00
Discharge (cfs)
Total Q

VELOCITY CONTROL FOR PIPE OUTFALL:
Sandfilter Outfall - 12" PIPE OUTFALL:
Qpeak = 4.48cfs from 12" pipe (see sheet C504)
Q = VAV = Q / A
=4.48/0.79
=5.7ft/sec
From chart 8.06b, Q =4.48cfs
d =12"
d50 =0.20ft or2.4", use 4"
La =9ft
3d =3.0ft
W = d + 0.4La =4.6ft dmax = 1.5 x d50 =6"
apron thickness = 1.5 x dmax =9"
apron dimensions: min. stone size =4inches
min. apron thickness =9inches
apron length =9ft
width of apron at pipe outlet =3ft
width of apron at end of apron =4.6ft
Outfall from CB1 - 18" PIPE OUTFALL:
Qpeak = 6.68cfs from 18" pipe (see sheet C120)
Q = VAV = Q / A
=6.68/1.77
=3.8ft/sec
From chart 8.06b, Q =6.68cfs
d =18"
d50 =0.20ft or2.4", use 4"
La =9ft
3d =4.5ft
W = d + 0.4La =5.1ft dmax = 1.5 x d50 =6"
apron thickness = 1.5 x dmax =9"
apron dimensions: min. stone size =4inches
min. apron thickness =9inches
apron length =9ft
width of apron at pipe outlet =5ft
width of apron at end of apron =5.1ft
CALIBRE
PO BOX 4041
WILMINGTON, NC 28406

Outfall from CB5 - 18" PIPE OUTFALL:
Qpeak = 2.55cfs from 18" pipe (see sheet C120)
Q = VAV = Q / A
=2.55/1.77
=1.4ft/sec
From chart 8.06b, Q =2.55cfs
d =18"
d50 =0.20ft or2.4", use 4"
La =9ft
3d =4.5ft
W = d + 0.4La =5.1ft dmax = 1.5 x d50 =6"
apron thickness = 1.5 x dmax =9"
apron dimensions: min. stone size =4inches
min. apron thickness =9inches
apron length =9ft
width of apron at pipe outlet =5ft
width of apron at end of apron =5.1ft
Outfall from CB8 - 18" PIPE OUTFALL:
Qpeak = 2.85cfs from 18" pipe (see sheet C120)
Q = VAV = Q / A
=2.85/1.77
=1.6ft/sec
From chart 8.06b, Q =2.85cfs
d =18"
d50 =0.20ft or2.4", use 4"
La =9ft
3d =4.5ft
W = d + 0.4La =5.1ft dmax = 1.5 x d50 =6"
apron thickness = 1.5 x dmax =9"
apron dimensions: min. stone size =4inches
min. apron thickness =9inches
apron length =9ft
width of apron at pipe outlet =5ft
width of apron at end of apron =5.1ft
CALIBRE
PO BOX 4041
WILMINGTON, NC 28406

Sed. Basin 2 - 4" PIPE OUTFALL:
Qpeak = 1.96cfs from 4" pipe (see sheet C-120)
Q = VAV = Q / A
=1.96/0.09
=22.5ft/sec
From chart 8.06b, Q =1.96cfs
d =4"
d50 =0.10ft or1.2", use 4"
La =4ft
3d =1.0ft
W = d + 0.4La =1.9333ft dmax = 1.5 x d50 =6"
apron thickness = 1.5 x dmax =9"
apron dimensions: min. stone size =4inches
min. apron thickness =9inches
apron length =4ft
width of apron at pipe outlet =1ft
width of apron at end of apron =1.93ft
CALIBRE
PO BOX 4041
WILMINGTON, NC 28406

610 Spring Branch Road
Dunn, NC 28334
Ph: [phone]
www.BuildingAndEarth.com

January 20, 2021

Marshall-Waters-Woody Associates, Inc.
1736 East Sunshine Street
Springfield, MO 65804

Attention: Mr. Mark Cummins, Project Architect

Subject: Report of SHWT at Additional Locations
Yarborough Express Mart
Tora Bora Boulevard, North Carolina
Proposal Number: RD180486

Ladies and Gentlemen:

Building & Earth Sciences, LLP is pleased to submit this report of Seasonal High-Water
Table (SHWT) for the above stated project site. The purpose of our work included
having a NC licensed Soil Scientist visit the project site and determine the depth to
observed SHWT and three locations determined by the design team of Marshall-Waters-
Woody Associates and Calibre.

Mr. Mike Eaker of Southeastern Soil and Environmental Associates, under contract with
Building & Earth Sciences, visited the site to determine the depth of SHWT. A copy of
ched to this cover letter.

We appreciate the opportunity to provide these services, and look forward to working
with you on this project. If you have any questions regarding this proposal, please
contact me at your convenience.

Respectfully Submitted,
BUILDING & EARTH SCIENCES, LLP

Kurt A. Miller, PE
Branch Manager

Attachment: SHWT Observations by Southeastern Soil and Environmental Associates
Birmingham, AL Auburn, AL Huntsville, AL Montgomery, AL Columbus, GA
Louisville, KY New Orleans, LA Raleigh, NC Springdale, AR Little Rock, AR Tulsa, OK