HomeMy WebLinkAboutWPO202000038 Calculations 2020-12-06SLEEP NUMBER FINAL SITE PLAN
STORMWATER MANAGEMENT CALCULATIONS PACKET
Date of Calculations
J U LY 10, 2020
PREPARED BY:
COLLINS ENG11,1==RING
200 GARRETT STREET, SUITE K
CHARLOTTESVILLE, VA 22902
434.293.3719 PH
434.293.2813 FX
www.collins-engineering.com
Lic. No. 035791
12/07/20
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 Map Unit Name percent of
Symbol AOI
27B Elioak loam, 2 61.3%
to 7 percent
slopes
34C Glenelg loam, 38.5%
7to15
percent slopes
91 Urban land 0.2%
Totals for Area of 100.00/0
Interest
The NRCS web soil survey defines this development's soils as 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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100m
300ft
POINT PRECIPITATION FREQUENCY (PF) ESTIMATES
WITH 90% CONFIDENCE INTERVALS AND SUPPLEMENTARY INFORMATION
NOAA Atlas 14, Volume 2, Version 3
PDSbased precipitation frequency estimates with 90% confidence intervals (in inches'
Average rewaerke irbml (years(
Dualion
o00 ,9 0® 166 99 ® ,600
24-0r
(2713.39)
(3. 9-4-10)
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Natural Resources Conservation Service
TR 55 Worksheet 3: Time of Concentration (TJ or Travel Time (TJ
Project: Sleepy's Designed By: FGM, PE
Location: North of 1425 Seminole Trail Checked By: SRC, PE
Check One: Present X Developed X
Check One: Tc X Ti Through subarea
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 Ti = [0.007(n*L)0.e] / P20.5 S A
Shallow Concentrated Flow:
7 Surface description (paved or unpaved)
8 Flow Length, L (ft)
9 Watercourse slope, s (ft/ft)
30 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, Pw (ft)
14 Hydraulic radius, r = a/Pw (ft)
15 Channel Slope, s (ft/ft)
16 Manning's Roughness Coeff, n
17 V= [ 1.49r2/3s° s ] / n
18 Flow length, L (ft)
19 T,= L/ 3600*V
20 Watershed or subarea TcorTt
(Add Tt in steps 6, 11 and 19)
Note: The shoretest SCS Tc is 0.10 hrs.
FL-ENG-21A
06/04
Date: 7/10/2020
Date: 7/10/2020
n/a
DAA&B
DAA
DAB
(Pre-Dev.)
(Post-Dev.)
(Post-Dev.)
Woods- Light
Woods- Light
Underbrush
Underbrush
0.4
0.4
100
100
3.66
3.66
0.16
0.16
0.15
0.15
Unpaved
Unpaved
150
20
0.12
0.35
5.6
3.0
0.01
0.00
0.16 1 0.15 1 0.10
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Channel and Flood Protection Computations
9 VAC 25-870-66
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
< 0.04 cfs
Section B.4 Limits of Analysis
0.13 cfs
(From Worksheet 4 Watershed Summary)
57
(From Worksheet 4 Watershed Summary)
7.66
(From SCS TR-55 eq. 2-4)
0.24 in.
(From SCS TR-55 eq. 2-3)
69
(From Worksheet 4 Watershed Summary)
4.45
(From SCS TR-55 eq. 2-4)
0.69 in.
(From SCS TR-55 eq. 2-3)
0.90
(Factor of Safety)
0.04 cfs
The analysis terminates at Subareas A & B since subsection B.3.a is met.
9 VAC 25-870-66
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.b.:
The point of discharge (Detention Basin B's Outfall), "releases a postdevelopment peak flow
rate for the 10-year 24-hour storm event that is less than the predevelopment peak flow rate
from the 10-year 24-hour storm event. Downstream stormwater conveyance systems do not
require any additional analysis to show compliance with flood protection criteria if this
option is utilized."
10-Year, 24-Hour Pre -Development Subareas A & B Peak Flow 1.33 cfs
10-Year, 24-Hour Post -Development Subareas A & B Peak Flow 1.26 cfs
Section C.3 Limits of Analysis
The flood protection analysis terminates at Subareas A & B since subsection C.2.b is met.
Post -Development Underground Detention Basin 'A'
Routings & Outflow Hydrographs
The following routing calculations and outflow hydrographs reflect the post -development
attenuation in Subarea A from the proposed underground detention basin A.
BasinFlow printout
INPUT:
Basin: Sleepys- UGD A Routings
0 Contour Areas
Elevation(ft)
1 Storage Pipes
Storage pipe 0
name: UGD
diameter (in)
length (ft)
invert (ft)
angle
volume (cy)
Start—Elevation(ft)
5 Outlet Structures
Outlet structure 0
Orifice
Sleepys- UGD A Routings
Area(sf) Computed Vol.(cy)
36.000
117.500
469.250
0.000
30.761
469.25 Vol.(cy) 0.00
name: Barrel
area (sf) 0.196
diameter or depth (in) 6.000
width for rect. (in) 0.000
coefficient 0.500
invert (ft) 469.150
multiple 1
discharge out of riser
Outlet structure 1
Orifice
name: Low -Flow Orifice
area (sf) 0.022
diameter or depth (in) 2.000
width for rect. (in) 0.000
coefficient 0.500
invert (ft) 469.250
multiple 1
discharge into riser
Page 1
Sleepys- UGD A Routings
Outlet structure 2
Orifice
name: Emergency Overflow Orifice
area (sf) 0.530
diameter or depth (in) 9.860
width for rect. (in) 0.000
coefficient 0.500
invert (ft) 471.250
multiple 1
discharge into riser
Outlet structure 3
Weir
name: Str
2
diameter (in)
48.000
side angle
0.000
coefficient
3.300
invert (ft)
474.000
multiple
1
discharge
into riser
transition at (ft)
1.215
orifice coef.
0.500
orifice area (sf)
12.566
Outlet structure 4
Culvert
name:
multiple
discharge
D (in)
h (in)
Length (ft)
Slope
Manning's n
Inlet coeff. Ke
Equation constant set
Invert (ft)
Emergency Overflow /
1
through dam
15.000
0.000
49.000
0.036
0.010
0.500
3
471.500
Bypass Pipe
Page 2
Sleepys- UGD A Routings
4 Inflow Hydrographs
Hydrograph 0
SCS
name: 1-yr
24-hr SCS TR-55 Design Storm
Area (acres)
0.540
CN
66.000
Type 2
rainfall, P (in)
3.020
time of conc. (hrs)
0.1500
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
0.349
peak time (hrs)
11.930
volume (cy)
40.199
Hydrograph 1
SCS
name: 2-yr
24-hr SCS TR-55 Design Storm
Area (acres)
0.540
CN
66.000
Type 2
rainfall, P (in)
3.660
time of conc. (hrs)
0.1500
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
0.559
peak time (hrs)
11.930
volume (cy)
64.483
Hydrograph 2
SCS
name: 10-yr
24-hr SCS TR-55 Design Storm
Area (acres)
0.540
CN
66.000
Type 2
rainfall, P (in)
5.520
time of conc. (hrs)
0.1500
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
1.315
peak time (hrs)
11.930
volume (cy)
151.660
Page 3
Hydrograph 3
SCS
name:
Area (acres)
CN
Type
rainfall, P (in)
time of conc. (hrs)
time increment (hrs)
time limit (hrs)
fudge factor
routed
peak flow (cfs)
peak time (hrs)
volume (cy)
Sleepys- UGD A Routings
100-yr 24-hr SCS TR-55 Design Storm
0.540
66.000
2
9.060
0.1500
0.0200
30.000
1.00
true
3.076
11.930
354.849
OUTPUT:
Routing Method: storage -indication
Hydrograph 0
Routing Summary
of
Peaks: 1-yr 24-hr
SCS TR-55 Design Storm
inflow
(cfs)
0.348
at
11.94
(hrs)
discharge
(cfs)
0.092
at
12.10
(hrs)
water level
(ft)
470.450
at
12.16
(hrs)
storage
(cy)
11.460
Hydrograph 1
Routing Summary
of
Peaks: 2-yr 24-hr
SCS TR-55 Design Storm
inflow
(cfs)
0.558
at
11.94
(hrs)
discharge
(cfs)
0.117
at
12.14
(hrs)
water level
(ft)
471.134
at
12.20
(hrs)
storage
(cy)
20.308
Hydrograph 2
Routing Summary of Peaks: 10-yr 24-hr SCS TR-55 Design Storm
inflow
(cfs)
1.313
at
11.94
(hrs)
discharge
(cfs)
1.280
at
11.96
(hrs)
water level
(ft)
471.757
at
11.96
(hrs)
storage
(cy)
27.423
Hydrograph 3
Routing Summary
of
Peaks: 100-yr
24-hr
SCS TR-55 Design Storm
inflow
(cfs)
3.073
at
11.94
(hrs)
discharge
(cfs)
3.004
at
11.94
(hrs)
water level
(ft)
472.207
at
11.94
(hrs)
storage
(cy)
30.639
Thu ]ul 09 13:26:24 EDT 2020
Page 4
Post -Development DA A
Outflow Hydrograph
(From UGD A's Routings)
Time (hrs)
Outflow (cfs)
0.0
0.00
0.5
0.00
1.0
0.01
1.5
0.01
2.0
0.01
2.5
0.01
3.0
0.01
3.5
0.01
4.0
0.01
4.5
0.01
5.0
0.01
5.5
0.01
6.0
0.01
6.5
0.01
7.0
0.01
7.5
0.01
8.0
0.01
8.5
0.01
9.0
0.01
9.5
0.01
10.0
0.02
10.5
0.02
11.0
0.02
11.3
0.03
11.6
0.03
11.9
0.07
12.0
0.08
12.1
0.09
12.2
0.09
12.3
0.09
12.4
0.09
12.5
0.09
12.6
0.08
12.7
0.08
12.8
0.08
13.0
0.07
13.2
0.07
13.4
0.06
13.6
0.05
13.8
0.04
14.0
0.03
14.3
0.02
14.6
0.02
15.0
0.01
15.5
0.01
16.0
0.01
16.5
0.01
17.0
0.01
17.5
0.01
18.0
0.01
19.0
0.01
20.0
0.01
22.0
0.01
26.0
0.00
26.5
0.00
27.0
0.00
27.5
0.00
0.10
0.09
0.08
0.m
0.06
0.05
0.04
0.03
0.02
0.01
0.00
Outflow Hydrograph (1-yr Design Storm)
0.0 5.0 10.0 15.0 20.0 25.0
30.0
Post -Development DA A
Outflow Hydrograph
(From UGD A's Routings)
Time (hm)
Outflow (cfs)
0.0
0.00
0.5
0.01
1.0
0.01
1.5
0.01
2.0
0.01
2.5
0.01
3.0
0.01
3.5
0.01
4.0
0.01
4.5
0.01
5.0
0.01
5.5
0.01
6.0
0.01
6.5
0.01
7.0
0.01
7.5
0.01
8.0
0.01
8.5
0.02
9.0
0.02
9.5
0.02
10.0
0.02
10.5
0.03
11.0
0.03
11.3
0.04
11.6
0.04
11.9
0.09
12.0
0.11
12.1
0.12
12.2
0.12
12.3
0.12
12.4
0.12
12.5
0.11
12.6
0.11
12.7
0.11
12.8
0.11
13.0
0.10
13.2
0.10
13.4
0.09
13.6
0.08
13.8
0.08
14.0
0.07
14.3
0.06
14.6
0.05
15.0
0.03
15.5
0.02
16.0
0.02
16.5
0.02
17.0
0.01
17.5
0.01
18.0
0.01
19.0
0.01
20.0
0.01
22.0
0.01
26.0
0.00
26.5
0.00
27.0
0.00
27.5
0.00
O.t4
O.0
OJO
O oa
O oe
O o4
0.02
O.00
Outflow Hydrograph (2-yr Design Storm)
0.0 5.0 10.0 15.0 20.0 25.0 MA
Post -Development DA A
Outflow Hydrograph
(From UGD A's Routings)
Time (hrs)
Outflow (ds)
0.0
0.00
0.5
0.01
1.0
0.02
1.5
0.02
2.0
0.02
2.5
0.02
3.0
0.02
3.5
0.02
4.0
0.02
4.5
0.02
5.0
0.02
5.5
0.02
6.0
0.02
6.5
0.03
7.0
0.03
7.5
0.03
8.0
0.03
8.5
0.03
9.0
0.03
9.5
0.04
10.0
0.04
10.5
0.05
11.0
0.06
11.3
0.06
11.6
0.08
11.9
0.77
12.0
1.28
12.1
0.75
12.2
0.36
12.3
0.23
12.4
0.18
12.5
0.15
12.6
0.13
12.7
0.12
12.8
0.12
13.0
0.12
13.2
0.11
13.4
0.11
13.6
0.11
13.8
0.10
14.0
0.10
14.3
0.09
14.6
0.09
15.0
0.08
15.5
0.06
16.0
0.05
16.5
0.04
17.0
0.03
17.5
0.03
18.0
0.03
19.0
0.02
20.0
0.02
22.0
0.02
26.0
0.02
26.5
0.01
27.0
0.01
27.5
0.01
1.40
1.20
1.00
0.30
0 60
0 00
0.20
0.00
Outflow Hydrograph (10-yr Design Storm)
0.0 5.0 10.0 15.0 20.0 25.0 MA
Post -Development DA A
Outflow Hydrograph
(From UGD A's Routings)
Time (hrs)
Outflow (cfs)
0.0
0.00
0.5
0.03
1.0
0.03
1.5
0.03
2.0
0.03
2.5
0.04
3.0
0.04
3.5
0.04
4.0
0.04
4.5
0.04
5.0
0.04
5.5
0.04
6.0
0.04
6.5
0.05
7.0
0.05
7.5
0.05
8.0
0.05
8.5
0.06
9.0
0.06
9.5
0.07
10.0
0.08
10.5
0.09
11.0
0.10
11.3
0.11
11.6
0.33
11.9
3.00
12.0
2.76
12.1
1.66
12.2
0.75
12.3
0.48
12.4
0.39
12.5
0.32
12.6
0.26
12.7
0.23
12.8
0.21
13.0
0.18
13.2
0.16
13.4
0.14
13.6
0.13
13.8
0.12
14.0
0.12
14.3
0.12
14.6
0.12
15.0
0.11
15.5
0.11
16.0
0.10
16.5
0.09
17.0
0.09
17.5
0.08
18.0
0.07
19.0
0.06
20.0
0.04
22.0
0.04
26.0
0.02
26.5
0.02
27.0
0.02
27.5
0.02
3.50
3.00
2.50
2.00
1.50
1.00
030
o o0
Outflow Hydrograph (100-yr Design Storm)
0.0 5.0 10.0 15.0 20.0 25.0 MA
Proposed Riprap Lined Outlet Protection
Calculations Below Underground Detention System 'A'
S L-cr Vlq
7(�alaz
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6p2EriiC-'R -MAN d�,oESs�+ f�r•� Rr:cPrwE�t]n�a MY Nr+'�vM�.
x S S F zcaEn�T p
Pam_ Q6.Akc 3.\$-41 M-LN, DUCL'ki QFicRCC?:ieN pYN ^�ileNS AM1E A% FFCtLcv%'%
(IAW 00 'a V%A,: \S�
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-
`a�r
,. C�:.A.- OsszGNr OU�`��a QRoS2c�;cN 9rr+�ewilcw ppc4a +) Rar_ As T&LawS:
LA = \or
Ws `� tb° � Cn`�C 6 � EKG�CE05 PT1N ,
via q's5%6N A rc
W1OiH
+� 5TONC- nCcmt� Pf+cF 56v� = i-d,r peu JEsex ILATt INS-\, \'a" ys GP.,EA,NtA
cktp-)
'- 0.81 rcA vuoY c G, A L
1992 3.18
M
rl
��
Q
J_
2
3
W
W H
rLL-� W
J
i
dte
o^
a
c
.
0 0
0
•p
n
-
'�Oy
��
r—a—•i
C U
O.
C
F W
W f
py
M
CO 6
O
O ~
F
t
N
O W E
QQX
Source: USDA-SCS
jaa3 -02Fs deidia OSp
N
O
M
SS
MOM
M►,\
Plate 3.18-4
III - 165
1992
3.18
PIPE OUTLET CONDITIONS
A A
'IPE OUTLET TO FLAT
REA WITH NO DEFINED
HANNEL
L a
0 %
I —I d
7-
SECTION A —A FILTER CLOTH KEY IN 6'-9`; RECOMMENDED FOR ENTIRE PERIMETER
I
3d0 (MIN.)
IPE OUTLET TO WELL
-
EFINED CHANNEL
d
SECTION A —A I T
FILTER CLOTH KEY IN 6'-0'; RECOMMENDED FOR ENTIRE PERIMETER
NOTES: 1. APRON LINING MAY BE RIPRAP, GROUTED RIPRAP, GABION
BASKET, OR CONCRETE,
2. La IS THE LENGTH OF THE RIPRAP APRON AS CALCULATED
USING PLATES 3.18-3 AND 3.18-4.
S. d = 1.5 TIMES THE MAXIMUM STONE DIAMETER, BUT NOT _
LESS THAN 6 INCHES.
Source: Va. DSWC
Plate 3.18-1
III - 157
Post -Development Subarea B Inflow 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 B (Post-Dev.) 0.10 0.10 0.21 0.0004
Time hrs.
Inflow (cfs)
0.0
0.00
11.0
0.00
11.3
0.00
11.6
0.00
11.9
0.02
12.0
0.07
12.1
0.21
12.2
0.27
12.3
0.19
12.4
0.11
12.5
0.08
12.6
0.06
12.7
0.05
12.8
0.04
13.0
0.04
13.2
0.03
13.4
0.03
13.6
0.03
13.8
0.02
14.0
0.02
14.3
0.02
14.6
0.02
15.0
0.02
15.5
0.02
16.0
0.01
16.5
0.01
17.0
0.01
17.5
0.01
18.0
0.01
19.0
0.01
20.0
0.01
22.0
0.01
26.0
0.00
0.30
0.25
0.20
0.15
0.10
0.05
0.00
SCS TR-55 Post -Development Unit
Hydrograph (DA B Inflow)
0.0 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 (Post-Dev.) 0.10 0.10 0.17 0.0006
Time hrs.
Inflow (cfs)
0.0
0.00
11.0
0.00
11.3
0.00
11.6
0.00
11.9
0.02
12.0
0.10
12.1
0.31
12.2
0.39
12.3
0.28
12.4
0.15
12.5
0.11
12.6
0.09
12.7
0.07
12.8
0.06
13.0
0.05
13.2
0.05
13.4
0.04
13.6
0.04
13.8
0.03
14.0
0.03
14.3
0.03
14.6
0.03
15.0
0.02
15.5
0.02
16.0
0.02
16.5
0.02
17.0
0.02
17.5
0.02
18.0
0.02
19.0
0.01
20.0
0.01
22.0
0.01
26.0
0.00
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0.0
SCS TR-55 Post -Development Unit
Hydrograph (DA B Inflow)
5.0 10.0 15.0 20.0 25.0
30.0
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 (mil -in)
DA B (Post-Dev.) 0.10 0.10 0.11 0.0011
Time hrs.
Inflow (cfs)
0.0
0.00
11.0
0.00
11.3
0.00
11.6
0.00
11.9
0.04
12.0
0.20
12.1
0.61
12.2
0.78
12.3
0.56
12.4
0.31
12.5
0.22
12.6
0.18
12.7
0.15
12.8
0.12
13.0
0.10
13.2
0.09
13.4
0.08
13.6
0.08
13.8
0.07
14.0
0.06
14.3
0.05
14.6
0.05
15.0
0.05
15.5
0.04
16.0
0.04
16.5
0.04
17.0
0.03
17.5
0.03
18.0
0.03
19.0
0.03
20.0
0.02
22.0
0.02
26.0
0.00
0.90
080
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
a
SCS TR-55 Post -Development Unit
Hydrograph (DA B Inflow)
Worksheet 51b (Modified for Clarity): Basic watershed Data
100-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 (mi2-in)
DA B (Post-Dev.) 0.10 0.10 0.11 0.0019
Time (hrs.)
Inflow (cfs)
0.0
0.00
11.0
0.00
11.3
0.00
11.6
0.00
11.9
0.07
12.0
0.33
12.1
1.01
12.2
1.30
12.3
0.92
12.4
0.51
12.5
0.37
12.6
0.29
12.7
0.24
12.8
0.20
13.0
0.17
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
0.07
16.5
0.06
17.0
0.06
17.5
0.05
18.0
0.05
19.0
0.04
20.0
0.04
22.0
0.04
26.0
0.00
1.40
SCS TR-55 Post -Development Unit
Hydrograph (DA B Inflow)
Post -Development Synchronized
Subareas A & B Hydrographs
The following hydrographs represent the synchronization of Subarea A's outflow hydrographs (from
proposed underground detention basin A) and Subarea B's inflow hydrographs. The synchronized
storm events represent the inflow hydrographs into proposed detention basin B.
Synchronized (Inflow) Unit Hydrograph into Detention Basin'B'
(This inflow hydrograph takes into account the upland subarea A's attenutation in Underground Detention System A, and the upland
unrouted subarea B.)
1-yr. 24-hr. SCS TR-55 Method Synchronized Unit Hydrograph
Time hrs.
Inflow s
0.0
0.00
0.5
0.00
1.0
0.01
1.5
0.01
2.0
0.01
2.5
0.01
3.0
0.01
3.5
0.01
4.0
0.01
4.5
0.01
5.0
0.01
5.5
0.01
6.0
0.01
6.5
0.01
7.0
0.01
7.5
0.01
8.0
0.01
8.5
0.01
9.0
0.01
9.5
0.01
10.0
0.02
10.5
0.02
11.0
0.02
11.3
0.03
11.6
0.03
11.9
0.09
12.0
0.15
12.1
0.30
12.2
0.36
12.3
0.28
12.4
0.20
12.5
0.16
12.6
0.15
12.7
0.13
12.8
0.12
13.0
0.11
13.2
0.10
13.4
0.09
13.6
0.08
13.8
0.07
14.0
0.05
14.3
0.04
14.6
0.03
15.0
0.03
15.5
0.03
16.0
0.02
16.5
0.02
17.0
0.02
17.5
0.02
18.0
0.02
19.0
0.02
20.0
0.01
22.0
0.01
26.0
0.00
26.5
0.00
27.0
0.00
27.5
0.00
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
SCS TR-55 Inflow Unit Hydrograph into Detention Basin B
(Accounts for Subarea A Attenuation)
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Synchronized (Inflow) Unit Hydrograph into Detention Basin'B'
(This inflow hydrograph takes into account the upland subarea A's attenutation in Underground Detention System A, and the upland
unrouted subarea B.)
2-yr. 24-hr. SCS TR-55 Method Synchronized Unit Hydrograph
Time hrs.
Inflow s
0.0
0.00
0.5
0.01
1.0
0.01
1.5
0.01
2.0
0.01
2.5
0.01
3.0
0.01
3.5
0.01
4.0
0.01
4.5
0.01
5.0
0.01
5.5
0.01
6.0
0.01
6.5
0.01
7.0
0.01
7.5
0.01
8.0
0.01
8.5
0.02
9.0
0.02
9.5
0.02
10.0
0.02
10.5
0.03
11.0
0.03
11.3
0.04
11.6
0.04
11.9
0.11
12.0
0.21
12.1
0.42
12.2
0.51
12.3
0.40
12.4
0.27
12.5
0.22
12.6
0.20
12.7
0.18
12.8
0.17
13.0
0.15
13.2
0.14
13.4
0.13
13.6
0.12
13.8
0.11
14.0
0.10
14.3
0.09
14.6
0.08
15.0
0.06
15.5
0.04
16.0
0.04
16.5
0.03
17.0
0.03
17.5
0.03
18.0
0.03
19.0
0.02
20.0
0.02
22.0
0.02
26.0
0.00
26.5
0.00
27.0
0.00
27.5
0.00
0.60
0.50
0.40
0.30
0.20
0.10
0.00
SCS TR-55 Inflow Unit Hydrograph into Detention Basin B
(Accounts for Subarea A Attenuation)
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Synchronized (Inflow) Unit Hydrograph into Detention Basin'B'
(This inflow hydrograph takes into account the upland subarea A's attenutation in Underground Detention System A, and the upland
unrouted subarea B.)
10-yr. 24-hr. SCS TR-55 Method Synchronized Unit Hydrograph
Time hrs.
Inflow s
0.0
0.00
0.5
0.01
1.0
0.02
1.5
0.02
2.0
0.02
2.5
0.02
3.0
0.02
3.5
0.02
4.0
0.02
4.5
0.02
5.0
0.02
5.5
0.02
6.0
0.02
6.5
0.03
7.0
0.03
7.5
0.03
8.0
0.03
8.5
0.03
9.0
0.03
9.5
0.04
10.0
0.04
10.5
0.05
11.0
0.06
11.3
0.06
11.6
0.08
11.9
0.81
12.0
1.48
12.1
1.36
12.2
1.14
12.3
0.79
12.4
0.49
12.5
0.37
12.6
0.31
12.7
0.27
12.8
0.24
13.0
0.22
13.2
0.20
13.4
0.19
13.6
0.18
13.8
0.17
14.0
0.16
14.3
0.15
14.6
0.14
15.0
0.12
15.5
0.11
16.0
0.09
16.5
0.07
17.0
0.06
17.5
0.06
18.0
0.06
19.0
0.05
20.0
0.04
22.0
0.04
26.0
0.02
26.5
0.01
27.0
0.01
27.5
0.01
1.60
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00
SCS TR-55 Inflow Unit Hydrograph into Detention Basin B
(Accounts for Subarea A Attenuation)
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Synchronized (inflow) Unit Hydrograph into Detention Basin'B'
(This inflow hydrograph takes into account the upland subarea A's attenutation in Underground Detention System A, and the upland
unrouted subarea B.)
100-yr. 24-hr. SCS TR-55 Method Synchronized Unit Hydrograph
Time hrs.
Inflow s
0.0
0.00
0.5
0.03
1.0
0.03
1.5
0.03
2.0
0.03
2.5
0.04
3.0
0.04
3.5
0.04
4.0
0.04
4.5
0.04
5.0
0.04
5.5
0.04
6.0
0.04
6.5
0.05
7.0
0.05
7.5
0.05
8.0
0.05
8.5
0.06
9.0
0.06
9.5
0.07
10.0
0.08
10.5
0.09
11.0
0.10
11.3
0.11
11.6
0.33
11.9
3.08
12.0
3.09
12.1
2.67
12.2
2.05
12.3
1.40
12.4
0.90
12.5
0.69
12.6
0.56
12.7
0.47
12.8
0.41
13.0
0.36
13.2
0.31
13.4
0.28
13.6
0.25
13.8
0.24
14.0
0.22
14.3
0.21
14.6
0.20
15.0
0.19
15.5
0.18
16.0
0.16
16.5
0.15
17.0
0.14
17.5
0.13
18.0
0.12
19.0
0.10
20.0
0.08
22.0
0.07
26.0
0.02
26.5
0.02
27.0
0.02
27.5
0.02
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
SCS TR-55 Inflow Unit Hydrograph into Detention Basin B
(Accounts for Subarea A Attenuation)
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Post -Development Detention Basin 'B'
Routings & Final Subarea A & B Outflows
Sleepys- Detention Basin B Routings
BasinFlow printout
INPUT:
Basin: Sleepys- Detention Basin B Routings
5 Contour Areas
Elevation(ft)
Area(sf)
Computed Vol.(cy)
469.00
72.00
0.0
470.00
306.00
6.5
471.00
846.00
27.0
472.00
1493.00
69.8
472.65
1775.00
109.0
Start—Elevation(ft)
4 Outlet Structures
Outlet structure 0
Orifice
469.00 Vol.(cy) 0.00
name: Barrel
area (sf) 0.785
diameter or depth (in) 12.000
width for rect. (in) 0.000
coefficient 0.500
invert (ft) 466.190
multiple 1
discharge out of riser
Outlet structure 1
Orifice
name: Low -Flow Orifice
area (sf) 0.009
diameter or depth (in) 1.250
width for rect. (in) 0.000
coefficient 0.500
invert (ft) 469.000
multiple 1
discharge into riser
Page 1
Sleepys- Detention Basin B Routings
Outlet structure 2
Weir
name: Riser
diameter (in)
36.000
side angle
0.000
coefficient
3.300
invert (ft)
470.650
multiple
1
discharge
into riser
transition at (ft)
0.912
orifice coef.
0.500
orifice area (sf)
7.069
Outlet structure 3
Weir
name: Emergency Spillway
length (ft)
5.000
side angle
75.960
coefficient
3.000
invert (ft)
471.650
multiple
1
discharge
through
dam
Page 2
4 Inflow Hydrographs
Hydrograph 0
Curve
name:
time incr (minlhrs)
time limit (minlhrs)
file:
volume (cy)
routed
time in hours
Hydrograph 1
Curve
Sleepys- Detention Basin B Routings
1 year SCS 24-hr Design Storm
0.10
27.50
1yr 24hr SCS TR-55 Post-Dev DA A-B Inflow Hydrograph.txt
80.96
true
true
name: 2 year SCS 24-hr Design Storm
time incr (minlhrs) 0.10
time limit (minlhrs) 27.50
file: 2yr 24hr SCS TR-55 Post-Dev DA A-B Inflow Hydrograph.txt
volume (cy) 121.70
routed true
time in hours true
Hydrograph 2
Curve
name: 10 year SCS 24-hr Design Storm
time incr (minlhrs) 0.10
time limit (minlhrs) 27.50
file: 10yr 24hr SCS TR-55 Post-Dev DA A-B Inflow Hydrograph.txt
volume (cy) 270.81
routed true
time in hours true
Hydrograph 3
Curve
name: 100 year SCS 24-hr Design Storm
time incr (minlhrs) 0.10
time limit (minlhrs) 27.50
file: 100yr 24hr SCS TR-55 Post-Dev DA A-B Inflow Hydrograph.txt
volume (cy) 535.33
routed true
time in hours true
Page 3
Sleepys- Detention Basin B Routings
OUTPUT:
Routing Method: storage -indication
Hydrograph 0
Routing Summary
of
Peaks:
1 year
SCS
24-hr Design Storm
inflow
(cfs)
0.364
at
12.20
(hrs)
discharge
(cfs)
0.043
at
12.40
(hrs)
water level
(ft)
470.628
at
12.50
(hrs)
storage
(cy)
16.977
Hydrograph 1
Routing Summary
of
Peaks:
2 year
SCS
24-hr Design Storm
inflow
(cfs)
0.508
at
12.20
(hrs)
discharge
(cfs)
0.102
at
12.30
(hrs)
water level
(ft)
470.665
at
12.30
(hrs)
storage
(cy)
17.852
Hydrograph 2
Routing Summary
of
Peaks:
10 year
SCS
24-hr
Design Storm
inflow
(cfs)
1.482
at
12.00
(hrs)
discharge
(cfs)
1.255
at
12.00
(hrs)
water level
(ft)
470.765
at
12.00
(hrs)
storage
(cy)
20.303
Hydrograph 3
Routing Summary
of
Peaks:
100 year
SCS
24-hr
Design Storm
inflow
(cfs)
3.092
at
12.00
(hrs)
discharge
(cfs)
3.092
at
12.00
(hrs)
water level
(ft)
470.865
at
12.00
(hrs)
storage
(cy)
22.985
Thu Jul 09 13:33:50 EDT 2020
Page 4
Water Quality Calculations Using the DEQ
Virginia Runoff Reduction Method for New Developments
(COMPLIANCE IS MET THROUGH THE BEST MANAGEMENT PRACTICE OF PURCHASING NUTRIENT CREDITS. THE
VRRM BOUNDARY IS DEFINED BY THE PROPOSED ESC LIMITS OF DISTURBANCE.)
ml
u
W
Q
O
p
S
pp
O
pp
O
p
S
00
O
00
O
O
O
O
O
W
OC
Q
Q
0
O
0
O
0
O
0
O
O
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