SW4210301_STORMWATER_CALCS_03042021_20210316

AEV PARKING EXPANSION
J EFFERSON, NC
H YDROLOGIC AND H YDRAULIC A NALYSIS R EPORT

Prepared By: Prepared For: Project Site:
BREC, P.A.
Kenneth Osborne 150 Northwest Drive
1520 Meadowview Drive
Jefferson, NC 28640
Wilkesboro, NC 28697
NCBELS Firm #C-3448
[phone]
[e-mail]

4 March 2021

Max Prestwood III, PE
Project Engineer
BREC, P.A. AEV PARKING EXPANSION 1

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1.0 General Information ........................................................................................ 4
2.0 Methodology ................................................................................................... 4
2.1 Curve Number Calculations 4
2.2 Time of Concentration Calculations 5
2.3 Rainfall Data 6
2.4 Pipe Design 7
2.4.1 Outlet Design 7
2.5 Hydrology Calculations 8
2.6 Modified Curve Number Calculations 9
2.7 Sand Filter Design 10
2.7.1 Chamber and Filter Sizing 10
2.7.2 Underdrain Sizing 10
2.7.3 Anti-floatation Calculations 11
3.0 Results .......................................................................................................... 12
Appendix ............................................................................................................. 13
Post-Construction First Flush .............................................................................. 14

BREC, P.A. AEV PARKING EXPANSION
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Figure 1 - System Storage of First Flush ............................................................ 12

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Table 1 - Pre-Construction Drainage Area ............................................................ 4
Table 2 - Post-Construction Drainage Areas ........................................................ 5
Table 3 - Pre-Construction ToC ............................................................................ 6
Table 4 - Post-Construction ToC........................................................................... 6
Table 5 - NOAA Rainfall Depths ........................................................................... 6
Table 6 - NOAA Rainfall Intensity ......................................................................... 6
Table 7 - Composite Rational Coefficients ............................................................ 7
Table 8 - Pipe Design Summary ........................................................................... 7
Table 9 - Riprap Outlet Stone Sizing ..................................................................... 8
Table 10 - Riprap Apron Dimensions .................................................................... 8
Table 11 - Modified SCS Curve Numbers ............................................................. 9
Table 12 - Sand Filter State-Storage .................................................................. 10
Table 13 - Pipe Design Table ............................................................................. 13
BREC, P.A. AEV PARKING EXPANSION
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This document contains hydrologic and hydraulic calculations demonstrating
compliance with post-construction state and local stormwater regulations for the
construction of a gravel parking area at the intersection of Northwest
Dr. and Gates Ln. in Jefferson, NC. Specifically, regulations for this area require
water quality treatment of the first flush storm.

The subject tract is composed of a vacant field with managed turf cover. A pond
and an unnamed tributary to Naked Creek are located on a portion of the Parcel.
Buffer is shown from this feature. The majority of site is composed of BrD soils
which are hydrologic soil group B. Remaining portion of the site is CfE and BuC
soils which are also in hydrologic soil group B. Post construction stormwater
requirements will be satisfied with an above ground sand filter which is approved
by NCDEQ as a primary stormwater control measure (SCM).
2ȁΏ Methodology

One pre-construction drainage area and eight post-construction drainage areas
covering the subject tract and adjacent off-site areas were identified. See plan
sheets for delineation. The pre-construction drainage area outlets at OUTFALL-1
located at an existing concrete drainage ditch at the southeast corner of the site.
Drainage area POST-CON:8 was not routed to the sand filter due to topographic
limitations. The remaining drainage areas covering all proposed impervious
surfaces except for a small section of sidewalk in POST-CON:8 are routed to the
sand filter for treatment prior to discharge at OUTFALL-1.

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Composite SCS curve numbers were calculated as weighted averages using
values of 69 for fair grass coverage (pre-construction) and 61 for good grass
coverage (post-construction, maintained), and 98 for impervious surfaces in HSG
B soils.

For pre-construction drainage areas, the composite curve number is calculated as:

Table 1 - Pre-Construction Drainage Area

Name
(acres) (acres)
(acres) (acres)
PRE-CON:1 3.86 0.15 3.71 0.00 70.1
BREC, P.A. AEV PARKING EXPANSION
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For post-construction drainage areas, the composite curve number is calculated
as:

Table 2 - Post-Construction Drainage Areas

Name
(acres) (acres)
(acres) (acres)
POST-CON:1+ 0.12 0.00 0.12 0.00 61.0
POST-CON:2+ 0.60 0.59 0.01 0.00 97.5
POST-CON:3+ 0.62 0.62 0.00 0.00 98.0
POST-CON:4+ 0.75 0.75 0.00 0.00 98.0
POST-CON:5+ 0.08 0.08 0.00 0.00 98.0
POST-CON:6+ 1.15 0.05 1.11 0.00 62.5
POST-CON:7+ 0.31 0.03 0.28 0.00 64.4
POST-CON:8 0.23 0.00 0.22 0.00 61.2

+ Routed through sand filter prior to discharge.

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Time of concentration values for vegetated drainage areas were evaluated using
the segmental, lag, and FAA equations with a design value selected from the range
produced by these equations.

BREC, P.A. AEV PARKING EXPANSION
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Table 3 - Pre-Construction ToC

Name

PRE-CON:1 577 0.079 4.3-20.6 10

Table 4 - Post-Construction ToC

Name

POST-CON:1 253.4 0.074 6.6-13.5 10
POST-CON:2 253.2 0.015 4.2-10.0 7
POST-CON:3 293.1 0.014 4.8-10.4 7
POST-CON:4 293.1 0.014 4.8-10.4 7
POST-CON:5 110.1 0.029 1.5-8.8 5
POST-CON:6 605.5 0.047 15.0-25.0 19
POST-CON:7 134.6 0.114 2.9-9.3 7
POST-CON:8 153.0 0.098 3.8-9.5 7

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Rainfall data was taken from NOAA Atlas 14, Volume 2, Version 3 for Jefferson,
NC. Rainfall depths for each design storm are summarized below.

Table 5 - NOAA Rainfall Depths
Storm

First Flush 1.00

Table 6 - NOAA Rainfall Intensity
Storm
10 Year, 5 Min 6.38
BREC, P.A. AEV PARKING EXPANSION
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10 Year, 10 Min 5.11

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A composite post-construction rational coefficient was also assigned to each post
construction drainage area as needed for pipe design. The composite rational
coefficients were calculated using individual coefficients of 0.85 for impervious
surfaces, 0.08 for grass surfaces in HSG B soils.

Table 7 - Composite Rational Coefficients

Name
POST-CON:1 0.19 0.12
POST-CON:2 0.84 2.95
POST-CON:3 0.85 3.09
POST-CON:4 0.85 3.76
POST-CON:5 0.86 0.43
POST-CON:6 0.16 0.73
POST-CON:7 0.25 0.46
POST-CON:8 0.19 0.26

equation iteratively for the normal depth.

Table 8 - Pipe Design Summary
NAME

PIPE-1
15 0.13 2.0
PIPE-2
18 3.08 4.1
PIPE-3
24 6.17 5.0
PIPE-4
24 9.94 7.4
PIPE-5
15 0.73 3.7
PIPE-6
24 11.10 7.7
PIPE-7
24 11.56 11.4

See Appendix for complete pipe design table.
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BREC, P.A. AEV PARKING EXPANSION
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Outlet design for PIPE-4 and PIPE-5 was taken from Chapter 10 of HEC-14.
Riprap was calculated as:

Where,

Substituting the corresponding pipe diameters and design discharges into the
equation above yields:

Table 9 - Riprap Outlet Stone Sizing

NAME

PIPE-6 ЋЍ ЊЊ͵ЊЉ ЊЊ͵АЉ ЊЍ

A minimum of was chosen for each pipe which corresponds to
NCDOT Class A stone. Given the design , the dimensions of the apron were
1
taken from Table 10.1 equations from HEC 14.

Table 10 - Riprap Apron Dimensions
NAME

PIPE-6 ЋЍ ЊЋ Ћ͵Џ Џ͵Љ ЊЍ

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1
http://www.fhwa.dot.gov/engineering/hydraulics/pubs/06086/hec14ch10.cfm
BREC, P.A. AEV PARKING EXPANSION
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The water quality volume required to be treated from the first flush was
calculated using the Schueler method outlined in the NCDEQ Stormwater Design
2
Manual. The Schueler method utilizes the following equations:

Where is the impervious fraction of the drainage area, is a runoff coefficient,
is the rainfall depth, is the drainage area, and is the runoff volume. The
following parameters are used for the drainage routed to the sand filter.

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To route the through the sand filter, it is necessary to calculate a modified
SCS curve number to avoid underrepresenting the first flush. The modified curve
number is calculated as follows:

The modified curve numbers were used to route the first flush using an SCS 6 hour
balanced storm distribution. The remaining design storms were routed with
standard curve numbers and an SCS type II 24 hour storm distribution.

Table 11 - Modified SCS Curve Numbers
Name

POST-CON:1 0.05 77.22
POST-CON:2 0.94 99.45
POST-CON:3 0.95 99.57
POST-CON:4 0.95 99.57
POST-CON:5 0.95 99.57
POST-CON:6 0.09 80.21
POST-CON:7 0.13 83.00
POST-CON:8 0.05 77.63

2
https://deq.nc.gov/sw-bmp-manual
BREC, P.A. AEV PARKING EXPANSION
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The combined area of the sediment chamber and sand chamber is determined
from the relationship of the max water depth observed during the water quality
event, , and the adjusted water quality volume. The design value for
was chosen as . When coupled with the adjusted water quality volume,
, the resulting stage storage for the sand filter is
summarized below.

Table 12 - Sand Filter State-Storage

0.0 2,989 1,922 0 0 0
1.0 2,990 2,516 1,110 1,110 2,219
2.0 2,991 3,182 2,534 2,534 5,068
3.0 2,992 3,920 4,310 4,310 8,619

At , .
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The sediment chamber and filter chamber are equally sized. The sediment
chamber has an additional depression to assist with maintenance and
primary sediment deposition; however, this added volume is not considered in
calculations to meet minimum design criteria requirements. Given the filter
chamber area, the sand media area, , was selected as . This value
maximizes the available filter chamber area and preserves an easily installable
geometric shape for the sand media while preventing the sand media from being
installed adjacent to the toe of slope grading. Discharge through the sand media

Where,

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BREC, P.A. AEV PARKING EXPANSION
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Drawdown time is calculated as:

Discharge rate is calculated as:

After applying a safety factor of 10,

The diameter of a single pipe is calculated as:

Where,

Per Table 1 of Section A-5 of the NCDEQ Stormwater Design Manual, use (2) 6
inch pipes.

2.7.3 Anti-¥«® ³ ³¨®­ # «¢´« ³¨®­²

The outlet structure is a precast concrete box with side and
bottom wall thicknesses. Including concrete and reinforcing steel, the structure
has an empty mass of .

Assuming the total height of the box is exposed to buoyant forces, the volume of
water displaced by the box is calculated from the outside dimensions.

BREC, P.A. AEV PARKING EXPANSION
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The buoyant force is defined from the hydraulic forces acting on the box.

No additional mass needed mass of structure is greater than the buoyant force.

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The first flush storm is routed through the sand filter and reaches a max
storage depth of which does not exceed the design . The
water quality volume is discharged over a period of

Figure 1 - System Storage of First Flush

BREC, P.A. AEV PARKING EXPANSION
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V DESIGN

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(CFS)
Q DESIGN

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(CFS)
Q MAX

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(FT/FT)

Pipe Design Table
LEN (FT)
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Table
HGL
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DOWN

INV
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DOWN

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AEV PARKING EXPANSION
HGL UP
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INV UP
ЋВВЌ͵ЉЉЋВВЊ͵ВЎЋВВЊ͵ЊВЋВВЉ͵ЎЌЋВВЍ͵ЉЉЋВБВ͵ЎЉЋВБА͵ЉЉ

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DIA (IN)

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NAME tLt9tLt9tLt9tLt9tLt9tLt9tLt9
Appendix BREC, P

Post-#®­²³±´¢³¨®­ &¨±²³ &«´²h

BREC, P.A. AEV PARKING EXPANSION 14

Project Description
File Name ......................................................................AEV_1IN_6HR_SAND_FILTER_RAISED_BASIN.SPF
Description .....................................................................
C:\\Users\\chase\\AppData\\Local\\Temp\\4900012020_C100_V2_1_22323_1c7d43c1.sv$
Project Options
Flow Units ......................................................................CFS
Elevation Type ...............................................................Elevation
Hydrology Method ..........................................................SCS TR-55
Time of Concentration (TOC) Method ...........................User-Defined
Link Routing Method ......................................................Hydrodynamic
Enable Overflow Ponding at Nodes ...............................YES
Skip Steady State Analysis Time Periods ......................YES
Analysis Options
Start Analysis On ...........................................................Feb 17, 202100:00:00
End Analysis On ............................................................Feb 19, 202111:00:00
Start Reporting On .........................................................Feb 17, 202100:00:00
Antecedent Dry Days .....................................................0days
Runoff (Dry Weather) Time Step ...................................0 01:00:00 days hh:mm:ss
Runoff (Wet Weather) Time Step ..................................0 00:05:00 days hh:mm:ss
Reporting Time Step ......................................................0 00:00:05 days hh:mm:ss
Routing Time Step .........................................................5seconds
Number of Elements
Qty
Rain Gages ....................................................................1
Subbasins.......................................................................8
Nodes.............................................................................4
Junctions ...............................................................2
Outfalls ..................................................................1
Flow Diversions .....................................................0
Inlets ......................................................................0
Storage Nodes ......................................................1
Links...............................................................................6
Channels ...............................................................0
Pipes .....................................................................2
Pumps ...................................................................0
Orifices ..................................................................2
Weirs .....................................................................1
Outlets ...................................................................1
Pollutants .......................................................................0
Land Uses ......................................................................0
Rainfall Details
SNRain GageDataData SourceRainfallRainStateCountyReturnRainfallRainfall
IDSourceIDTypeUnitsPeriodDepthDistribution
(years)(inches)
1JEFFERSONTime Series1IN-6HR-BALANCEDCumulativeinches0.00

Subbasin Summary
SNSubbasinAreaPeak RateWeightedTotalTotalTotalPeakTime of
IDFactorCurveRainfallRunoffRunoffRunoffConcentration
NumberVolume
(ac)(in)(in)(ac-in)(cfs)(days hh:mm:ss)
10.12484.0061.001.000.000.000.00 0 00:10:00
20.60484.0097.501.000.740.441.00 0 00:07:00
30.62484.0098.001.000.790.491.09 0 00:07:00
40.75484.0098.001.000.790.591.32 0 00:07:00
50.08484.0098.001.000.790.060.15 0 00:05:00
61.15484.0062.501.000.000.000.00 0 00:19:00
70.31484.0064.401.000.000.000.00 0 00:07:00
80.23484.0061.201.000.000.000.00 0 00:07:00

Node Summary
SNElementElementInvertGround/RimInitialSurchargePondedPeakMax HGLMaxMinTime ofTotal
IDTypeElevation(Max)WaterElevationAreaInflowElevationSurchargeFreeboardPeakFlooded
ElevationElevationAttainedDepthAttainedFloodingVolume
AttainedOccurrence
(ft)(ft)(ft)(ft)(ft²)(cfs)(ft)(ft)(ft)(days hh:mm)(ac-in)
1SCM-RISERJunction2987.002993.002987.002993.0010.000.082987.070.005.930 00:000.00
2SITE-OUTLET(VIRTUAL)Junction2985.292991.292985.292991.290.000.082985.350.005.940 00:000.00
3EXISTING_CHANNELOutfall2980.000.082980.06
4SAND-FILTERStorage Node2989.002995.002989.000.003.552990.900.00

Total Time
Flooded
(min)
0.00
0.00
0.00

Subbasin Hydrology
Subbasin : {Site 1}.POST-CON:1
Input Data
Area (ac) .....................................................0.12
Peak Rate Factor ........................................484.00
Weighted Curve Number ............................61.00
Rain Gage ID ...............................................JEFFERSON
Composite Curve Number
AreaSoilCurve
Soil/Surface Description(acres)GroupNumber
-0.12-61.00
Composite Area & Weighted CN0.1261.00
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.00
Peak Runoff (cfs) ........................................0.00
Weighted Curve Number ............................61.00
Time of Concentration (days hh:mm:ss) .....0 00:10:00

Subbasin : {Site 1}.POST-CON:1

Subbasin : {Site 1}.POST-CON:2
Input Data
Area (ac) .....................................................0.60
Peak Rate Factor ........................................484.00
Weighted Curve Number ............................97.50
Rain Gage ID ...............................................JEFFERSON
Composite Curve Number
AreaSoilCurve
Soil/Surface Description(acres)GroupNumber
-0.60-97.50
Composite Area & Weighted CN0.6097.50
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.74
Peak Runoff (cfs) ........................................1.00
Weighted Curve Number ............................97.50
Time of Concentration (days hh:mm:ss) .....0 00:07:00

Subbasin : {Site 1}.POST-CON:2

Subbasin : {Site 1}.POST-CON:3
Input Data
Area (ac) .....................................................0.62
Peak Rate Factor ........................................484.00
Weighted Curve Number ............................98.00
Rain Gage ID ...............................................JEFFERSON
Composite Curve Number
AreaSoilCurve
Soil/Surface Description(acres)GroupNumber
-0.62-98.00
Composite Area & Weighted CN0.6298.00
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.79
Peak Runoff (cfs) ........................................1.09
Weighted Curve Number ............................98.00
Time of Concentration (days hh:mm:ss) .....0 00:07:00

Subbasin : {Site 1}.POST-CON:3

Subbasin : {Site 1}.POST-CON:4
Input Data
Area (ac) .....................................................0.75
Peak Rate Factor ........................................484.00
Weighted Curve Number ............................98.00
Rain Gage ID ...............................................JEFFERSON
Composite Curve Number
AreaSoilCurve
Soil/Surface Description(acres)GroupNumber
-0.75-98.00
Composite Area & Weighted CN0.7598.00
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.79
Peak Runoff (cfs) ........................................1.32
Weighted Curve Number ............................98.00
Time of Concentration (days hh:mm:ss) .....0 00:07:00

Subbasin : {Site 1}.POST-CON:4

Subbasin : {Site 1}.POST-CON:5
Input Data
Area (ac) .....................................................0.08
Peak Rate Factor ........................................484.00
Weighted Curve Number ............................98.00
Rain Gage ID ...............................................JEFFERSON
Composite Curve Number
AreaSoilCurve
Soil/Surface Description(acres)GroupNumber
-0.08-98.00
Composite Area & Weighted CN0.0898.00
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.79
Peak Runoff (cfs) ........................................0.15
Weighted Curve Number ............................98.00
Time of Concentration (days hh:mm:ss) .....0 00:05:00

Subbasin : {Site 1}.POST-CON:5

Subbasin : {Site 1}.POST-CON:6
Input Data
Area (ac) .....................................................1.15
Peak Rate Factor ........................................484.00
Weighted Curve Number ............................62.50
Rain Gage ID ...............................................JEFFERSON
Composite Curve Number
AreaSoilCurve
Soil/Surface Description(acres)GroupNumber
-1.15-62.50
Composite Area & Weighted CN1.1562.50
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.00
Peak Runoff (cfs) ........................................0.00
Weighted Curve Number ............................62.50
Time of Concentration (days hh:mm:ss) .....0 00:19:00

Subbasin : {Site 1}.POST-CON:6

Subbasin : {Site 1}.POST-CON:7
Input Data
Area (ac) .....................................................0.31
Peak Rate Factor ........................................484.00
Weighted Curve Number ............................64.40
Rain Gage ID ...............................................JEFFERSON
Composite Curve Number
AreaSoilCurve
Soil/Surface Description(acres)GroupNumber
-0.31-64.40
Composite Area & Weighted CN0.3164.40
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.00
Peak Runoff (cfs) ........................................0.00
Weighted Curve Number ............................64.40
Time of Concentration (days hh:mm:ss) .....0 00:07:00

Subbasin : {Site 1}.POST-CON:7

Subbasin : {Site 1}.POST-CON:8
Input Data
Area (ac) .....................................................0.23
Peak Rate Factor ........................................484.00
Weighted Curve Number ............................61.20
Rain Gage ID ...............................................JEFFERSON
Composite Curve Number
AreaSoilCurve
Soil/Surface Description(acres)GroupNumber
-0.23-61.20
Composite Area & Weighted CN0.2361.20
Subbasin Runoff Results
Total Rainfall (in) .........................................1.00
Total Runoff (in) ..........................................0.00
Peak Runoff (cfs) ........................................0.00
Weighted Curve Number ............................61.20
Time of Concentration (days hh:mm:ss) .....0 00:07:00

Subbasin : {Site 1}.POST-CON:8

Junction Input
SNElementInvertGround/RimGround/RimInitialInitialSurchargeSurchargePondedMinimum
IDElevation(Max)(Max)WaterWaterElevationDepthAreaPipe
ElevationOffsetElevationDepthCover
(ft)(ft)(ft)(ft)(ft)(ft)(ft)(ft²)(in)
1SCM-RISER2987.002993.006.002987.000.002993.000.0010.000.00
2SITE-OUTLET(VIRTUAL)2985.292991.296.002985.290.002991.290.000.000.00

Junction Results
SNElementPeakPeakMax HGLMax HGLMaxMinAverage HGLAverage HGLTime ofTime ofTotalTotal Time
IDInflowLateralElevationDepthSurchargeFreeboardElevationDepthMax HGLPeakFloodedFlooded
InflowAttainedAttainedDepthAttainedAttainedAttainedOccurrenceFloodingVolume
AttainedOccurrence
(cfs)(cfs)(ft)(ft)(ft)(ft)(ft)(ft)(days hh:mm)(days hh:mm)(ac-in)(min)
1SCM-RISER0.080.002987.070.070.005.932987.030.030 05:420 00:000.000.00
2SITE-OUTLET(VIRTUAL)0.080.002985.350.060.005.942985.320.030 05:430 00:000.000.00

Pipe Input
SNElementLengthInletInletOutletOutletTotalAveragePipePipePipeManning'sEntranceExit/BendAdditional
IDInvertInvertInvertInvertDropSlopeShapeDiameter orWidthRoughnessLossesLossesLosses
ElevationOffsetElevationOffsetHeight
(ft)(ft)(ft)(ft)(ft)(ft)(%)(in)(in)
1SCM-BARREL59.012987.000.002985.290.001.712.9000CIRCULAR24.00024.0000.01200.50000.50000.0000
2SITE-OUTLET-LINK(VIRTUAL)100.002985.290.002980.000.005.295.2900CIRCULAR24.00024.0000.01500.50000.50000.0000

InitialFlapNo. of
FlowGateBarrels
(cfs)
0.00No1
0.00No1

Pipe Results
SNElementPeakTime ofDesign FlowPeak Flow/Peak FlowTravelPeak FlowPeak FlowTotal TimeFroudeReported
IDFlowPeak FlowCapacityDesign FlowVelocityTimeDepthDepth/SurchargedNumberCondition
OccurrenceRatioTotal Depth
Ratio
(cfs)(days hh:mm)(cfs)(ft/sec)(min)(ft)(min)
1SCM-BARREL0.080 05:4241.720.002.560.380.060.030.00Calculated
2SITE-OUTLET-LINK(VIRTUAL)0.080 05:4345.090.002.670.620.060.030.00Calculated

Storage Nodes
Storage Node : SAND-FILTER
Input Data
Invert Elevation (ft) ..................................................................................2989.00
Max (Rim) Elevation (ft) ..........................................................................2995.00
Max (Rim) Offset (ft) ...............................................................................6.00
Initial Water Elevation (ft) ........................................................................2989.00
Initial Water Depth (ft) .............................................................................0.00
Ponded Area (ft²) .....................................................................................0.00
Evaporation Loss .....................................................................................0.00
Storage Area Volume Curves
Storage Curve : BASIN
StageStorageStorage
AreaVolume
(ft)(ft²)(ft³)
019220.000
125162219.00
231825068.00
339208619.00
4473012944.00
5561218115.00

Storage Node : SAND-FILTER (continued)
Outflow Weirs
SNElementWeirFlapCrestCrestLengthWeir TotalDischarge
IDTypeGateElevationOffsetHeightCoefficient
(ft)(ft)(ft)(ft)
1EM-SPILLWAYTrapezoidalNo2993.504.5010.001.003.33
Outflow Orifices
SNElementOrificeOrificeFlapCircularRectangularRectangularOrificeOrifice
IDTypeShapeGateOrificeOrificeOrificeInvertCoefficient
DiameterHeightWidthElevation
(in)(in)(in)(ft)
1PRIMARY-OUTLETSideRectangularNo18.0014.002991.000.63
2SECONDARY-OUTLETBottomRectangularNo36.0036.002993.000.63
Output Summary Results
Peak Inflow (cfs) ......................................................................................3.55
Peak Lateral Inflow (cfs) ..........................................................................3.55
Peak Outflow (cfs) ...................................................................................0.08
Peak Exfiltration Flow Rate (cfm) ............................................................0.00
Max HGL Elevation Attained (ft) ..............................................................2990.90
Max HGL Depth Attained (ft) ...................................................................1.9
Average HGL Elevation Attained (ft) .......................................................2989.47
Average HGL Depth Attained (ft) ............................................................0.47
Time of Max HGL Occurrence (days hh:mm) .........................................0 05:42
Total Exfiltration Volume (1000-ft³) .........................................................0.000
Total Flooded Volume (ac-in) ..................................................................0
Total Time Flooded (min) ........................................................................0
Total Retention Time (sec) ......................................................................0.00