HomeMy WebLinkAboutWPO202100002 Calculations 2021-01-11HOLISTIC VIRGINIA
STORMWATER MANAGEMENT CALCULATIONS PACKET
Date of Calculations
JANUARY 8, 2021
PREPARED BY:
COLLINS FNGI11JFERING
200 GARRETT STREET, SUITE K
CHARLOTTESVILLE, VA 22902
434.293.3719 PH
434.293.2813 FX
www.collins-engineering.com
SCS TR-55 Calculations
Soils Mapping (Source: NRCS Web Soil Survey Online Database)
Soils Table (Source: NRCS Web Soil Survey Online Database)
Albemarle County, Virginia (VA003)
Map Unit
symbol
Map Unit Name
Percent of
AOI
12E
Catoctin silt
17.9%
loam, 25 to 45
percent slopes
71B
Rabun clay
40.1%
loam, 2 to 7
percent slopes
72C3
Rabun clay, 7 to
41.9%
15 percent
slopes, severely
eroded
Totals for Area of
100.00/0
Interest
The NRCS web soil survey defines this development's soils as predominantly having a hydrologic group type B.
Precipitation Data
(Source: NOAA's National Weather Service, Hydrometerorological Design Studies Center, Atlas 14
Point Precipitation Frequency Estimates)
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POINT PRECIPITATION FREQUENCY (PF) ESTIMATES
WITH 9iR5 CONFIDENCE INTERVALS AND SUPPLEMENTARY INFORMATION
NOAA Atlas 14, Volume 2, Version 3
PDS-based precipitation frequency estimates with 90% confidence Intervals (in Inches)"
A.W ¢aunerre
Mn M (vela)
Duration
1 2 6 f0 26
0000000000
50 100 200 500 t0a1
2anr
3.04 3.66 4.70 5.56 6.83
(2 ]3361) (331-013) Id 21-59) (dW-621) (60G]fii)
7.93 9.13 10.5 12.5 142
(698-881) (ZW1001) (906-1'I6) (18&138) (11916T
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U.S. Department of Agriculture
Natural Resources Conservation Service
TR 55 Worksheet 3: Time of Concentration (Tt) or Travel Time (T,)
Project: Holistic Virginia
Location: Avon Ct.
Check One: Present X Developed X
Check One: Tc X T,
Segment ID,
Sheet Flow: (Applicable to Tc only)
1 Surface description (Table 3-1)
2 Manning's roughness coeff., n (Table 3-1
3 Flow length, L (total L < 100) (ft)
4 Two-year 24-hour rainfall, Pz (in.)
5 Land slope, s (ft/ft)
6 Compute Tt = [0.007(n*L)0.8] / P2 .S s0.4
Shallow Concentrated Flow:
7 Surface description (paved or unpaved)
8 Flow Length, L (ft)
9 Watercourse slope, s (ft/ft)
10 Average velocity, V (Figure 3-1) (ft/s)
11 T,= L/ 3600*V
Channel Flow:
12 Cross sectional flow area, a (ft)
13 Wetted perimeter, P. (ft)
14 Hydraulic radius, r = a/Pw (ft)
15 Channel Slope, s (ft/ft)
16 Manning's Roughness Coeff, n
17 V= [ 1.49r2/3s0 S ] / n
18 Flow length, L (ft)
19 Tt= L/ 3600*V
20 Watershed or subarea Ttor T,
(Add Tt in steps 6, 11 and 19)
Note: The shoretest SCS Tc is 0.10 hrs.
Designed By: FGM, PE
Checked By: SRC, PE
Through subarea
FL-ENG-21A
06/04
Date: 1/8/2021
Date: 1/8/2021
n/a
DA A
DA B-1
DA B-2
DA A
DA B
(Pre-Dev.)
(Pre-Dev.)
(Pre-Dev.)
(Post-Dev.)
(Post-Dev.)
Short
Short
Short
Dense
Dense
Grass
Grass
Grass
Grass
Grass
0.15
0.15
0.15
0.24
0.24
100
100
100
40
65
3.68
3.68
3.68
3.68
3.68
0.07
0.06
0.10
0.05
0.12
0.09
0.10
0.08
0.07
0.08
Unpaved
Unpaved
Unpaved
70
310
200
0.16
0.08
0.09
6.5
4.6
4.8
0.00
0.02
0.01
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WATERSHED SUMMARY FOR SUBAREA A
Area,
1-year Flow,
2-year Flow,
10-year Flow,
CN ac.
cfs
cfs
cfs
DA A (Pre-Dev.)
89 0.68
2.08
2.71
4.63
DA A (Post-Dev.)
84 1.36
2.04
3.02
6.43
WATERSHED SUMMARY FOR SUBAREA B
Area,
1-year Flow,
2-year Flow,
10-year Flow,
CN ac.
cfs
cfs
cfs
DA B-1 (Pre-Dev.)
78 1.49
2.69
3.81
7.46
DA B-2 (Pre-Dev.)
77 3.50
6.00
8.57
17.01
77 4.99
8.69
12.38
24.46
DA B (Post-Dev.)
91 4.31
3.30
10.83
21.75
Overall Acreage Summary
Pre -Development
Post -Development
Area, ac.
Area, ac.
DA A
0.68
1.36
1.49
DA B
4.31
3.50
5.67 5.67
Channel and Flood Protection Computations
9 VAC 25-870-66 (Subarea A)
Section B: Channel Protection
"Concentrated stormwater flow shall be released into a stormwater conveyance system and shall
meet the criteria in subdivision 1, 2 or 3 of this subsection..."
Section B.1: Manmade stormwater conveyance systems
"When stormwater from a development is discharged to a manmade stormwater conveyance
system, following the land -disturbing activity, either..." a. or b. shall be met:
Section B.1.b.
"The peak discharge requirements for concentrated stormwater flow to natural stormwater
conveyance systems in subdivision 3 of this subsection shall be met."
Section B.3
"... the maximum peak flow rate from the one-year 24-hour storm following the land -disturbing
activity shall be calculated either.." a. or b."
Section B.3.a.
In accordance with the following methodology:
Q Allowed (Calcuated( 15 1.F• * (Q Pre -Developed * [RV Pre -Developed)) (RV Developed )
Q Allowed (Calcuated( <
Where: Q Pre -Developed =
CN Pre -Developed=
5 Pre -Developed —
RV Pre -Developed =
CN Post -Developed —
5 Post -Developed —
RV Post-Developed—
I.F. =
Q Developed
2.05 cfs
2.08 cfs
(From Worksheet 4 Watershed Summary)
89
(From Worksheet 4 Watershed Summary)
1.23
(From SCS TR-55 eq. 2-4)
1.94 in.
(From SCS TR-55 eq. 2-3)
84
(From Worksheet 4 Watershed Summary)
1.85
(From SCS TR-55 eq. 2-4)
1.58 in.
(From SCS TR-55 eq. 2-3)
0.80
(Factor of Safety)
2.04 cfs
Section B.4 Limits of Analysis
The analysis terminates at the detention faclity since "...subsection 3 of this subsection is utilized to
show compliance with the channel protection criteria..."
9 VAC 25-870-66 (Subarea A)
Section C: Flood Protection
"Concentrated stormwater flow shall be released into a stormwater conveyance system and shall
meet one of the following criteria as demonstrated by use of acceptable hydrologic and hydraulic
methodologies:"
Section C.2:
"Concentrated stormwater flow to stormwater conveyance systems that currently experience
localized flooding [i.e. the floodplain] during the 10-year 24-hour storm event: The point of
discharge.." needs to meet either a. or b.
Section C.2.a.:
The point of discharge (the SWM facility outfall), "Confines the postdevelopment peak flow rate
from the 10-year 24-hour storm event within the stormwater conveyance system [the SWM
facility] to avoid the localized flooding. Detention of stormwater or downstream improvements
may be incorporated into the approved land -disturbing activity to meet this criterion...."
10-Year, 24-Hour Design Storm Peak Back Water Surface Elevation = 663.97 ft
Dry Detention Basin 'A' Top of Dam = 666.00 ft
(No overtopping Occurs)
Section C.3 Limits of Analysis
....stormwater conveyance systems shall be analyzed for compliance with flood protection
criteria to a point where:" a, b or c are met.
Section C.3.c.:
"The stormwater conveyance system [the SWM Facility outfall] enters a mapped floodplain or
other flood -prone area, adopted by ordinance, of any locality."
9 VAC 25-870-66 (Subarea B)
Section B: Channel Protection
"Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet
the criteria in subdivision 1, 2 or 3 of this subsection..."
Section B.1: Manmade stormwater conveyance systems
"When stormwater from a development is discharged to a manmade stormwater conveyance system,
following the land -disturbing activity, either..." a. or b. shall be met:
Section B.1.b.
"The peak discharge requirements for concentrated stormwater flow to natural stormwater conveyance
systems in subdivision 3 of this subsection shall be met."
Section B.3
"... the maximum peak flow rate from the one-year 24-hour storm following the land -disturbing activity
shall be calculated either.." a. or b."
Section B.3.a.
In accordance with the following methodology:
Q Allowed !� LF• * (Q Pre -Developed * [RV Pre -Developed I ) / (RV Developed )
Q Allowed
Where: Q Pre -Developed =
CN Pre -Developed =
S Pre -Developed =
RV Pre -Developed=
CN Post -Developed=
S Post -Developed =
RV Post -Developed =
I.F. =
Q Developed
< 3.61 cfs
8.69 cfs
(From Worksheet 4 Watershed Summary)
77
(From Worksheet 4 Watershed Summary)
2.97
(From SCS TR-55 eq. 2-4)
1.10 in.
(From SCS TR-55 eq. 2-3)
91
(From Worksheet 4 Watershed Summary)
0.97
(From SCS TR-55 eq. 2-4)
2.13 in.
(From SCS TR-55 eq. 2-3)
0.80
(Factor of Safety)
3.30 cfs
Section B.4 Limits of Analysis
The analysis terminates at the detention faclity since "...subsection 3 of this subsection is utilized to
show compliance with the channel protection criteria..."
9 VAC 25-870-66 (Subarea B)
Section C: Flood Protection
"Concentrated stormwater flow shall be released into a stormwater conveyance system and shall
meet one of the following criteria as demonstrated by use of acceptable hydrologic and hydraulic
methodologies:"
Section C.2:
"Concentrated stormwater flow to stormwater conveyance systems that currently experience
localized flooding [i.e. the floodplain] during the 10-year 24-hour storm event: The point of
discharge.." needs to meet either a. or b.
Section C.2.a.:
The point of discharge (the SWM facility outfall), "Confines the postdevelopment peak flow rate
from the 10-year 24-hour storm event within the stormwater conveyance system [the SWM
facility] to avoid the localized flooding. Detention of stormwater or downstream improvements
may be incorporated into the approved land -disturbing activity to meet this criterion...."
10-Year, 24-Hour Design Storm Peak Back Water Surface Elevation = 374.66 ft
Underground Detention System 'B' Crown of Pipe = 374.88 ft
Underground Detention System Str. B2 Rim Elev. = 376.20 ft
(No overtopping Occurs)
Section C.3 Limits of Analysis
....stormwater conveyance systems shall be analyzed for compliance with flood protection
criteria to a point where:" a, b or c are met.
Section C.3.c.:
"The stormwater conveyance system [the SWM Facility outfall] enters a mapped floodplain or
other flood -prone area, adopted by ordinance, of any locality."
Pre -Development SCS TR-55 Hydrographs
Worksheet 5b (Modified for Clarity): Basic watershed Data
1-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below
Subarea Tc (hrs.) Tt (hr.) la / P Am;Q (mi2-in)
DA A (Pre-Dev.) 0.10 0.10 0.08 0.0021
Hydrograph Time 1-yr Discharges
(hrs.)
(cfs)
0.0
0.00
11.0
0.05
11.3
0.07
11.6
0.11
11.9
0.69
12.0
1.33
12.1
2.08
12.2
1.28
12.3
0.45
12.4
0.30
12.5
0.25
12.6
0.21
12.7
0.18
12.8
0.16
13.0
0.14
13.2
0.12
13.4
0.11
13.6
0.09
13.8
0.09
14.0
0.08
14.3
0.07
14.6
0.07
15.0
0.06
15.5
0.05
16.0
0.05
16.5
0.04
17.0
0.04
17.5
0.04
18.0
0.04
19.0
0.03
20.0
0.03
22.0
0.02
26.0
0.00
2.50
2.00
1.50
1.00
0.50
0.00
0.0
SCS TR-55 Pre -Development Unit
Hydrograph (DA A)
5.0 10.0 15.0 20.0 25.0 30.0
Worksheet 5b (Modified for Clarity): Basic watershed Data
2-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below
Subarea Tc (hrs.) Tt (hr.) la / P Am;Q (mi2-in)
DA A (Pre-Dev.) 0.10 0.10 0.07 0.0027
Hydrograph Time 2-yr Discharges
(hrs.)
(cfs)
0.0
0.00
11.0
0.06
11.3
0.09
11.6
0.14
11.9
0.90
12.0
1.74
12.1
2.71
12.2
1.67
12.3
0.58
12.4
0.39
12.5
0.33
12.6
0.28
12.7
0.23
12.8
0.20
13.0
0.18
13.2
0.15
13.4
0.14
13.6
0.12
13.8
0.11
14.0
0.10
14.3
0.09
14.6
0.09
15.0
0.08
15.5
0.07
16.0
0.06
16.5
0.06
17.0
0.05
17.5
0.05
18.0
0.05
19.0
0.04
20.0
0.03
22.0
0.03
26.0
0.00
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0
SCS TR-55 Pre -Development Unit
Hydrograph (DA A)
Worksheet 51b (Modified for Clarity): Basic watershed Data
10-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Belov
Subarea Tc (hrs.) Tt (hr.) la / P Am•Q (mil -in)
DA A (Pre-Dev.) 0.10 0.10 0.04 0.0046
Hydrograph Time 10-yr Discharges
(hrs.)
(cfs)
0.0
0.00
11.0
0.11
11.3
0.16
11.6
0.24
11.9
1.53
12.0
2.97
12.1
4.63
12.2
2.86
12.3
0.99
12.4
0.67
12.5
0.56
12.6
0.48
12.7
0.39
12.8
0.35
13.0
0.30
13.2
0.26
13.4
0.23
13.6
0.21
13.8
0.19
14.0
0.17
14.3
0.16
14.6
0.15
15.0
0.13
15.5
0.12
16.0
0.11
16.5
0.10
17.0
0.09
17.5
0.09
18.0
0.08
19.0
0.07
20.0
0.06
22.0
0.06
26.0
0.00
5.00 r
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0
SCS TR-55 Pre -Development Unit
Hydrograph (DA A)
Worksheet 5b (Modified for Clarity): Basic watershed Data
1-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below
Subarea Tc (hrs.) Tt (hr.) la / P Am;Q (mi2-in)
DA B-1 (Pre-Dev.) 0.12 0.12 0.19 0.0027
Hydrograph Time 1-yr Discharges
(hrs.)
(cfs)
0.0
0.00
11.0
0.06
11.3
0.09
11.6
0.14
11.9
0.89
12.0
1.72
12.1
2.69
12.2
1.66
12.3
0.58
12.4
0.39
12.5
0.33
12.6
0.28
12.7
0.23
12.8
0.20
13.0
0.18
13.2
0.15
13.4
0.14
13.6
0.12
13.8
0.11
14.0
0.10
14.3
0.09
14.6
0.09
15.0
0.08
15.5
0.07
16.0
0.06
16.5
0.06
17.0
0.05
17.5
0.05
18.0
0.05
19.0
0.04
20.0
0.03
22.0
0.03
26.0
0.00
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0.0
SCS TR-55 Pre -Development Unit
Hydrograph (DA B-1)
5.0 10.0 15.0 20.0 25.0 30.0
Worksheet 5b (Modified for Clarity): Basic watershed Data
2-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below
Subarea Tc (hrs.) Tt (hr.) la / P Am;Q (mi2-in)
DA B-1 (Pre-Dev.) 0.12 0.12 0.16 0.0038
Hydrograph Time 2-yr Discharges
(hrs.)
(cfs)
0.0
0.00
11.0
0.09
11.3
0.13
11.6
0.20
11.9
1.26
12.0
2.44
12.1
3.81
12.2
2.35
12.3
0.82
12.4
0.55
12.5
0.46
12.6
0.39
12.7
0.32
12.8
0.29
13.0
0.25
13.2
0.21
13.4
0.19
13.6
0.17
13.8
0.16
14.0
0.14
14.3
0.13
14.6
0.12
15.0
0.11
15.5
0.10
16.0
0.09
16.5
0.08
17.0
0.08
17.5
0.07
18.0
0.07
19.0
0.06
20.0
0.05
22.0
0.05
26.0
0.00
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0.
SCS TR-55 Pre -Development Unit
Hydrograph (DA B-1)
Worksheet 5b (Modified for Clarity): Basic watershed Data
10-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below
Subarea Tc (hrs.) Tt (hr.) la / P Am*Q (mi2-in)
DA B-1 (Pre-Dev.) 0.12 0.12 0.10 0.0074
Hydrograph Time 10-yr Discharges
(hrs.)
(cfs)
0.0
0.00
11.0
0.18
11.3
0.25
11.6
0.39
11.9
2.47
12.0
4.78
12.1
7.46
12.2
4.60
12.3
1.60
12.4
1.09
12.5
0.91
12.6
0.77
12.7
0.63
12.8
0.56
13.0
0.49
13.2
0.42
13.4
0.38
13.6
0.34
13.8
0.31
14.0
0.28
14.3
0.25
14.6
0.24
15.0
0.21
15.5
0.19
16.0
0.17
16.5
0.16
17.0
0.15
17.5
0.14
18.0
0.13
19.0
0.11
20.0
0.10
22.0
0.09
26.0
0.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
SCS TR-55 Pre -Development Unit
Hydrograph (DA B-1)
0.0 5.0 10.0 15.0 20.0 25.0
30.0
Worksheet 5b (Modified for Clarity): Basic watershed Data
1-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below
Subarea Tc (hrs.) Tt (hr.) la / P Am;Q (mi2-in)
DA B-2 (Pre-Dev.) 0.10 0.10 0.20 0.0059
Hydrograph Time 1-yr Discharges
(hrs.)
(cfs)
0.0
0.00
11.0
0.14
11.3
0.20
11.6
0.32
11.9
1.99
12.0
3.85
12.1
6.00
12.2
3.70
12.3
1.29
12.4
0.87
12.5
0.73
12.6
0.62
12.7
0.51
12.8
0.45
13.0
0.39
13.2
0.34
13.4
0.30
13.6
0.27
13.8
0.25
14.0
0.23
14.3
0.20
14.6
0.19
15.0
0.17
15.5
0.15
16.0
0.14
16.5
0.12
17.0
0.12
17.5
0.11
18.0
0.11
19.0
0.09
20.0
0.08
22.0
0.07
26.0
0.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
0.0
SCS TR-55 Pre -Development Unit
Hydrograph (DA B-2)
5.0 10.0 15.0 20.0 25.0 30.0
Worksheet 5b (Modified for Clarity): Basic watershed Data
2-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below
Subarea Tc (hrs.) Tt (hr.) la / P Am;Q (mi2-in)
DA B-2 (Pre-Dev.) 0.10 0.10 0.16 0.0085
Hydrograph Time 2-yr Discharges
(hrs.)
(cfs)
0.0
0.00
11.0
0.20
11.3
0.29
11.6
0.45
11.9
2.83
12.0
5.49
12.1
8.57
12.2
5.29
12.3
1.84
12.4
1.25
12.5
1.04
12.6
0.88
12.7
0.73
12.8
0.64
13.0
0.56
13.2
0.48
13.4
0.43
13.6
0.39
13.8
0.36
14.0
0.32
14.3
0.29
14.6
0.27
15.0
0.25
15.5
0.22
16.0
0.20
16.5
0.18
17.0
0.17
17.5
0.16
18.0
0.15
19.0
0.13
20.0
0.11
22.0
0.10
26.0
0.00
9.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
0
SCS TR-55 Pre -Development Unit
Hydrograph (DA B-2)
Worksheet 5b (Modified for Clarity): Basic watershed Data
10-yr. 24-hr. SCS TR-55 Method Unit Hydrograph for the la/P & Tc Listed Below
Subarea Tc (hrs.) Tt (hr.) la / P Am;Q (mi2-in)
DA B-2 (Pre-Dev.) 0.10 0.10 0.11 0.0168
Hydrograph Time 10-yr Discharges
(hrs.)
(cfs)
0.0
0.00
11.0
0.40
11.3
0.57
11.6
0.89
11.9
5.62
12.0
10.89
12.1
17.01
12.2
10.49
12.3
3.65
12.4
2.48
12.5
2.07
12.6
1.75
12.7
1.45
12.8
1.28
13.0
1.11
13.2
0.96
13.4
0.86
13.6
0.77
13.8
0.71
14.0
0.64
14.3
0.57
14.6
0.54
15.0
0.49
15.5
0.44
16.0
0.39
16.5
0.35
17.0
0.34
17.5
0.32
18.0
0.30
19.0
0.25
20.0
0.22
22.0
0.20
26.0
0.00
18.00
16.00
14.00
12.00
10.00
&00
6.00
4.00
2.00
0.00
SCS TR-55 Pre -Development Unit
Hydrograph (DA B-2)
0.0 5.0 10.0 15.0 20.0 25.0
30.0
Dry Detention Basin 'A' Routing Calculations
Holistic Virginia- Dry Basin A
BasinFlow printout
INPUT:
Basin: Holistic Virginia- Dry Basin A
6 Contour Areas
Elevation(ft)
Area(sf)
Computed Vol.(cy)
661.50
1.00
0.0
662.00
95.00
0.7
663.00
319.00
7.9
664.00
686.00
26.1
665.00
1268.00
61.7
666.00
1964.00
121.1
Start—Elevation(ft)
4 Outlet Structures
Outlet structure 0
Orifice
661.50 Vol.(cy) 0.00
name: Barrel
area (sf) 3.142
diameter or depth (in) 24.000
width for rect. (in) 0.000
coefficient 0.500
invert (ft) 660.500
multiple 1
discharge out of riser
Outlet structure 1
Orifice
name: Low -Flow Orifice
area (sf) 0.378
diameter or depth (in) 8.330
width for rect. (in) 0.000
coefficient 0.500
invert (ft) 661.500
multiple 1
discharge into riser
Page 1
Outlet structure 2
Weir
name: Riser
diameter (in)
side angle
coefficient
invert (ft)
multiple
discharge
transition at (ft)
orifice coef.
orifice area (sf)
Outlet structure 3
Weir
Holistic Virginia- Dry Basin A
48.000
0.000
3.300
663.750
1
into riser
1.215
0.500
12.566
name: Emergency Spillway
length (ft)
10.000
side angle
0.000
coefficient
3.300
invert (ft)
664.750
multiple
1
discharge
through dam
4 Inflow Hydrographs
Hydrograph 0
SCS
name: 1-yr
24-hr SCS TR-55 Method Design Storm
Area (acres)
1.360
CN
84.000
Type 2
rainfall, P (in)
3.040
time of conc. (hrs)
0.1000
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
2.674
peak time (hrs)
11.917
volume (cy)
283.055
Page 2
Holistic Virginia- Dry Basin A
Hydrograph 1
SCS
name: 2-yr
24-hr SCS TR-55 Method Design Storm
Area (acres)
1.360
CN
84.000
Type 2
rainfall, P (in)
3.680
time of conc. (hrs)
0.1000
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
3.609
peak time (hrs)
11.917
volume (cy)
382.101
Hydrograph 2
SCS
name: 10-yr
24-hr SCS TR-55 Method Design Storm
Area (acres)
1.360
CN
84.000
Type 2
rainfall, P (in)
5.560
time of conc. (hrs)
0.1000
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
6.534
peak time (hrs)
11.917
volume (cy)
691.795
Hydrograph 3
SCS
name: 100-yr
24-hr SCS TR-55 Method Design Storm
Area (acres)
1.360
CN
84.000
Type 2
rainfall, P (in)
9.130
time of conc. (hrs)
0.1000
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
12.399
peak time (hrs)
11.917
volume (cy)
1312.685
Page 3
Holistic Virginia- Dry Basin A
OUTPUT:
Routing Method: storage -indication
Hydrograph 0
Routing Summary of
inflow (cfs)
discharge (cfs)
water level (ft)
storage (cy)
Hydrograph 1
Routing Summary of
inflow (cfs)
discharge (cfs)
water level (ft)
storage (cy)
Hydrograph 2
Routing Summary of
inflow (cfs)
discharge (cfs)
water level (ft)
storage (cy)
Hydrograph 3
Routing Summary of
inflow (cfs)
discharge (cfs)
water level (ft)
storage (cy)
Peaks: 1-yr 24-hr SCS TR-55 Method Design Storm
2.661 at
11.92 (hrs)
2.041 at
12.00 (hrs)
663.655 at
12.00 (hrs)
18.250
Peaks: 2-yr 24-hr SCS TR-55 Method Design Storm
3.592 at
11.92 (hrs)
3.021 at
11.94 (hrs)
663.827 at
11.94 (hrs)
21.936
Peaks: 10-yr 24-hr SCS TR-55 Method Design Storm
6.504 at
11.92 (hrs)
6.433 at
11.92 (hrs)
663.968 at
11.92 (hrs)
25.292
Peaks: 100-yr 24-hr
12.341 at
12.334 at
664.138 at
29.789
Tue Dec 22 14:26:37 EST 2020
SCS TR-55 Method Design Storm
11.92 (hrs)
11.92 (hrs)
11.92 (hrs)
Page 4
Underground Detention System 'B' Routing Calculations
Holistic Virginia- UGD System B
BasinFlow printout
INPUT:
Basin: Holistic Virginia- Underground Detention System B
0 Contour Areas
Elevation(ft) Area(sf) Computed Vol.(cy)
1 Storage Pipes
Storage pipe 0
name: UGD System
diameter (in) 120.000
length (ft) 143.000
invert (ft) 364.500
angle 0.287
volume (cy) 415.970
Start—Elevation(ft)
5 Outlet Structures
Outlet structure 0
Orifice
364.50 Vol.(cy) 0.00
name: Low -Flow Barrel
area (sf)
1.767
diameter or depth (in)
18.000
width for rect. (in)
0.000
coefficient
0.500
invert (ft)
364.490
multiple
1
discharge out
of riser
Outlet structure 1
Orifice
name: Low -Flow Orifice
area (sf) 0.307
diameter or depth (in) 7.500
width for rect. (in) 0.000
coefficient 0.500
invert (ft) 364.500
multiple 1
discharge into riser
Page 1
Outlet structure 2
Orifice
Holistic Virginia- UGD System B
name: Overflow / Emergency Spillway in Weir Plate
area (sf)
3.306
diameter or depth (in)
24.620
width for rect. (in)
0.000
coefficient
0.500
invert (ft)
372.250
multiple
1
discharge into
riser
Outlet structure 3
Weir
name:
Access Riser
diameter (in)
48.000
side angle
0.000
coefficient
3.300
invert (ft)
376.800
multiple
1
discharge
into riser
transition at (ft)
1.215
orifice coef.
0.500
orifice area (sf)
12.566
Outlet structure 4
Orifice
name: High Flow Barrel
area (sf) 1.767
diameter or depth (in) 18.000
width for rect. (in) 0.000
coefficient 0.500
invert (ft) 372.250
multiple 1
discharge into riser
Page 2
Holistic Virginia- UGD System B
3 Inflow Hydrographs
Hydrograph 0
SCS
name: 1-yr
24-hr SCS Design Storm
Area (acres)
4.310
CN
91.000
Type 2
rainfall, P (in)
3.040
time of conc. (hrs)
0.1000
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
11.531
peak time (hrs)
11.917
volume (cy)
1220.821
Hydrograph 1
SCS
name: 2-yr
24-hr SCS Design Storm
Area (acres)
4.310
CN
91.000
Type 2
rainfall, P (in)
3.680
time of conc. (hrs)
0.1000
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
14.832
peak time (hrs)
11.917
volume (cy)
1570.241
Hydrograph 2
SCS
name: 10-yr
24-hr SCS Design Storm
Area (acres)
4.310
CN
91.000
Type 2
rainfall, P (in)
5.560
time of conc. (hrs)
0.1000
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
24.759
peak time (hrs)
11.917
volume (cy)
2621.260
Page 3
Holistic Virginia- UGD System B
OUTPUT:
Routing Method: storage -indication
Hydrograph 0
Routing Summary
of
Peaks: 1-yr 24-hr
SCS Design Storm
inflow
(cfs)
11.477
at
11.92
(hrs)
discharge
(cfs)
3.304
at
12.10
(hrs)
water level
(ft)
372.020
at
12.10
(hrs)
storage
(cy)
318.695
Hydrograph 1
Routing Summary
of
Peaks: 2-yr 24-hr
SCS Design Storm
inflow
(cfs)
14.762
at
11.92
(hrs)
discharge
(cfs)
10.833
at
12.02
(hrs)
water level
(ft)
373.036
at
12.02
(hrs)
storage
(cy)
363.956
Hydrograph 2
Routing Summary
of
Peaks: 10-yr 24-hr
SCS Design Storm
inflow
(cfs)
24.643
at
11.92
(hrs)
discharge
(cfs)
21.753
at
11.96
(hrs)
water level
(ft)
374.659
at
11.96
(hrs)
storage
(cy)
413.072
Wed Dec 23 13:34:24 EST 2020
Page 4
Riprap Lined Outlet Protection Calculations
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