HomeMy WebLinkAboutWPO201600082 Calculations 2017-04-27 •
5th STREET COMMERCIAL DEVELOPMENT STORMWATER
MANAGEMENT CALCULATIONS PACKET
Date of Calculations
DECEMBER 12, 2016
Revised on
FEBRUARY 9, 2017
Revised on
APRIL 27, 2017
{Final revisions are'limited to,the adequate:channel's RiprapCalculations)f
PREPARED BY:
3 ' COLLINS: E.:-'Wr CIN Eft. '
200 GARRETT STREET, SUITE K
CHARLOTTESVILLE,VA 22902
434.293.3719 PH
434.293.2813 FX
www.collins-engineering.com APPROVED
by the Albemarle County
Community D t
opment Department
Date cy / 7
File WP /L' 000 wD
,
SCS TR-55 Calculations
Soils Mapping (Source: NRCS Web Soil Survey Online Database)
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Soils Table (Source: NRCS Web Soil Survey Online Database)
Map Unit Legend
Map Map Unit Name Percent
Unit of AOI
Symbol
22C3 Culpeper o .
percent slopes,clayl severelyam7tlo 15 1.5%
eroded
39E Nagel loam, 25 to 45 percent 20.8%
slopes
47C Louisburg sandy loam, 7 to 8.1%
15 percent slopes
47D Louisburg sandy loam, 15 to 3.40/0
25 percent slopes
76 Riverview loam 53.0%
95 Vstehadkee silt loam 13.2%
Totals for Area of Interest 100.00/o
Note: The soils' properties for this development are predominantly composed of hydrologic types A& B.
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U.S.Department of Agriculture FL-ENG-21A
Natural Resources Conservation Service 06/04
TR 55 Worksheet 2:Runoff Curve Number and Runoff
Project: 5th Street Commercial Development Designed By:FGM,PE Date: 2/9/2017
Location: 5th Street Checked By:SRC,PE Date: 2/9/2017
Check One: Present X Developed X
1.Runoff curve Number(CN)
Soil name and Cover description CN(weighted)=
Drainage Area Area Product of CN Calculated'S'
hydrologic group (Cover type,treatment,and hydrologic condition;percent impervious; CN total product/
Description Value
(Appendix A) unconnected/connected impervious area ratio) (Acres) x Area total area
DAA Impervious Areas 98 0.36 34.9
B Woods In Good Condition 55 0.26 14.3 66.5 5.04
(Present)
Lawns in Good Condition 61 1.49 91.1
DA 8 Impervious Areas 98 0.00 0.0
B Woods In Good Condition 55 0.92 50.6 56.2 7.81
(Present)
Lawns in Good Condition 61 0.22 13.4
DA A&B Impervious Areas 98 2.41 235.9
(Developed) B Woods in Good Condition 55 0.05 2.8 88.3 1.32
Lawns in Good Condition 61 0.79 48.4
Impervious Areas 98 2.16 211.7
DAD B Woods In Good Condition(For Channel Adequacy Calm Only) 55 0.87 47.9 79.2 2.63
Lawns in Good Condition(For Channel Adequacy Calcs Only) 61 1.08 65.9
Impervious Areas 98 0.00 0.0
DA C B Woods In Good Condition(For Channel Adequacy Calcs Only) 55 0.05 2.8 57.7 7.34
Lawns in Good Condition(For Channel Adequacy Calcs Only) 61 0.04 2.4
2.Runoff
1-Year Storm 2-Year Storm 10-Year Storm Drainage Area Description
Frequency-years 1 2 10 n/a
Rainfall,P(24 hour)-inches 3.04 3.69 5.57 n/a
Runoff,Cl-Inches 0.58 0.93 2.17 DA A(Present)
Runoff,Q-inches 0.24 0.46 1.36 DA 8(Present)
Runoff,Q-inches 1.88 2.47 4.25 DA A&B(Developed)
Runoff,Q-Inches
Runoff,Q-inches 1.23 1.73 3.32 DA D
Runoff,Q-inches 0.28 0.52 1.47 DA C
U.S.Department of Agriculture FL-ENG-21A
Natural Resources Conservation Service 06/04
TR 55 Worksheet 3:Time of Concentration(Ta)or Travel Time(Tx)
Project: 5th Street Commercial Development Designed By: FGM,PE Date: 2/9/2017
Location: 5th Street Checked By: SRC,PE Date: 2/9/2017
Check One: Present X Developed X
Check One: T, X Tx Through subarea n/a
DAA DAB DAA&B
Segment ID: (Present) (Present) (Developed) DA D DA C
Sheet Flow:(Applicable to T,only)
1 Surface description(Table 3-1) Dense Grass Dense Grass Dense Grass
2 Manning's roughness coeff.,n(Table 3-1 0.24 0.24 0.24
3 Flow length,L(total L<100)(ft) 100 100 100
4 Two-year 24-hour rainfall,P2(in.) 3.7 3.7 3.7
5 Land slope,s(ft/ft) 0.14 0.21 0.05
6 Compute Tx=[0.007(n*L)°'s]/P2 s s0.4 0.10 0.09 0.15
Shallow Concentrated Flow:
7 Surface description(paved or unpaved) Unpaved Unpaved Unpaved
8 Flow Length,L(ft) 80 185 490
9 Watercourse slope,s(ft/ft) 0.013 0.005 0.061
10 Average velocity,V(Figure 3-1)(ft/s) 1.8 1.2 4.0
11 Tx=L/3600*V 0.01 0.04 0.03
Channel Flow:
12 Cross sectional flow area,a(ft2)
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=[1.49r213s's]/n
18 Flow length,L(ft)
19 Tx=L/3600*V
20 Watershed or subarea Tc or TL
(Add Tx in steps 6,11 and 19) 0.11 0.13 0.10 0.18 0.10
(Most Conservative SCS Tc=0.10 hrs.)
U.S.Department of Agriculture FL-ENG-21C
Natural Resources Conservation Service 06/04
TR 55 Worksheet 4:Graphical Peak Discharge Method
Project: 5th Street Commercial Development Designed By: FGM,PE Date: 2/9/2017
Location: 5th Street Checked By: SRC,PE Date: 2/9/2017
•
Check One: Present X Developed X
Drainage Area Drainage Area Drainage Area Drainage Area Drainage Area Drainage Area
1.Data Description Description Description Description Description Description
DAA DAB DAA&B
' (Present) (Present) (Developed) DA D DA C
Drainage Area(Am)in miles'= 0.0033 0.0018 0.0051 0.0064 0.0001
Runoff curve number CN= 66.5 56.2 88.3 79.2 57.7
Time of concentration(Tc)= 0.11 0.13 0.10 0.18 0.10
Rainfall distribution type= II II II II II
Pond and swamp areas spread 0 0 0 0 0
throughout the watershed= i
2.Frequency-years 1 2 10 1 2 10 1 2 10 , 1 2 10 1 2 10
3.Rainfall,P(24 hour)-inches 3.04 3.69 5.57 3.04 3.69 5.57 3.04 3.69 5.57 3.04 3.69 5.57 3.04 3.69 5.57
4.Initial Abstraction,la-inches 1.01 1.01 1.01 1.56 1.56 1.56 0.26 0.26 0.26 0.53 0.53 0.53 1.47 1.47 1.47
5.Compute la/P 0.33 0.27 0.18 0.51 0.42 0.28_ 0.09 0.07 0.05 0.17 0.14 0.09 0.48 0.40 0.26
6.Unit peak discharge,Qu-csm/in 875 925 950 475 675 875 1000 1000 1000 - 800. 825 850 500 750 900
7.Runoff,Q from Worksheet 2-inches 0.58 0.93 2.17 0.24 0.46 1.36 1.88 2.47 4.25 1.23 1.73 3.32 0.28 0.52 1.47
8.Pond and Swamp adjustment factor,Fp 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
9.Peak Discharge,Qp-cfs
where Qp=Qu Am Q Fp 1.69 2.84 6.79 0.20 0.55 2.12, 9.54 12.54 21.56 6.31 9.15 18.10 0.02 0.05 0.19
WATERSHED SUMMARY
Pre-Development Post-Development
2-year Flow, 10-year Flow,, 2-year Flow, 10-year
CN Area,ac. cfs cfs CN Area,ac. cfs Flow,cfs
DA'A' 66.5 2.11 2.84 6.79
DA'B' 56.2 1.14 0.55 2.12 88.3 3.25 12.54 21.56
DA'C' - - - - 57.7 0.09 0.05 0.19
DA'D' - - - - 79.2 4.11 9.15 18.10
Total= 21.75 39.84
Adequate Channel Analysis to Moores Creek
(The following 6 sheets are the only revisions made to the previously reviewed&accepted`
SWM calculations packet):
5th Street Adequate Channel Outfall- 2-year
Complex Channnel- Trapezoidal Riprap Lined Adequate Channel (2-yr)
Input:
Slope 0.010
Flow (given) 21.500
line x y n
0 0.000 2.000 0.050 (first n value not used)
1 6.000 0.000 0.050
2 7.000 0.000 0.050
3 13.000 2.000 0.050
Output:
Depth 1.491
(y) ( 1.491)
Channel bed segment output:
line Q V A P
1 7.86 2.36 3.33 4.71
2 5.78 3.88 1.49 1.00
3 7.86 2.36 3.33 4.71
Wed Apr 26 10:20:18 EDT 2017
Page 1
5th Street Adequate Channel Outfall- 10-year
Complex Channnel- Trapezoidal Riprap Lined Adequate Channel (10-yr)
Input:
Slope 0.010
Flow (given) 39.841
line x y n
0 0.000 2.000 0.050 (first n value not used)
1 6.000 0.000 0.050
2 7.000 0.000 0.050
3 13.000 2.000 0.050
Output:
Depth 1.923
(Y) ( 1.923)
Channel bed segment output:
line Q V A P
1 15.50 2.80 5.55 6.08
2 8.84 4.60 1.92 1.00
3 15.50 2.80 5.55 6.08
Wed Apr 26 10:19:55 EDT 2017
Page 1
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Source: VDOT Drainage Manual Plate 3.19-3
III - 180
Chapter 13—Shore Protection
Appendix 1 30-4 Nomographs for Design of
Rock Slope Shore Protection
(For Shoal Water)
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2.5
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Find AN=3.5T
1---1
Nomograph&For Design Of Rock Slope Shore Protection
(For Shoal Water)
Source: 0iturfeiglit7.01147 go
I of 1 VDOT Drainage Manual
Storm Sewer Computations
(The proposed plan simply redirects the existing storm sewer, however calculations have
been provided for informational purposes showing it can handle the future development.)
o. m c° +o m . mm
A x Starting Structure
0 2
0
N . m CO o Ending Structure
a
0
m
0 0 0
rte
o N o 0 m A,Drainage area
(acres)
0 0 0 0 0
0
c io 0 o a i+n
0 0 0 0
C,rational coeR.
0 0 0 0 0
G
o m m o m
O
CA increment
o
l J m O W al8
N W
CA sum accumulated
N pp�
Ol w A N + O
Tc,time of conc.(min)
F. n u v, ti
o 0 o rn m
I,rainfall Intesity
G
O r
o a m+ o o
0,Row incr.(cfs)
i0 to a
Rt,tots flour°
14. V V
V m WV 1p
T n
O
tT
Invert in(ft)
ro =
w w w . • ti
CD o
A b
O N + V O rNli .
Invert out(ft)
0
m v ro fO m L,throat length(ft) ''D
O O o O 0 0 o c c n,manning's coeff.
o u
0 0 0 o N 0
10 O O O
S,slope
0
v
0 0 0 0 > N
D,Diameter(in)
W co,as•�o m.
Q P c,
°" FUtk Flow Capacity;cfs)
V A A A A (p
+ F.3 W W A
V,Velocity(fps)
0 0 0
w W N + +
Flow Time(min)
Remarks
Hydraulic Grade Line Calculation
Design Year: 10 Project: 5th St. Job#: 132093 Prepared by: FGM,PE
INLET OUTLET WATER " Do Q. Sro Hi i JUNCTION LOSS I FINAL INLET WATER RIM
STATION SURFACE ELEV ZW Vo Ho Qw VW Q;•V, V/2g H, ANGLE Ho H, 1.3H, .5H, H SURFACE ELEV. ELEV
376.00 58.31 30 15.13 0.001 0.08 7.4 0.2
2 7.4 4.9 36.2 0.4 0.13 0 0 0.34 N/A N/A 0.42 376.42 390.33
379.02 97.66 30 7.37 0.000 0.03 - 4.9 0.1
4 6.9 4.8 33.4 0.4 0.13 180 0.25342 0.47 N/A 0.24 0.27 379.29 391.50
379.61 112.05 30 6.93 0.000 0.03 4.8 0.1
6 6.9 4.8 -33.2 0.4 0.13 150 0.25342 0.47 N/A 0.24 0.27 379.88 391.50
380.27 64.43 30 6.87 0.000 0.02 4.8 0.1
8 6.9 4.9 33.4 0.4 0.13 180 0.25668 0.48 N/A 0.24 0.26 380.53 389.95
380.53 90.96 24 6.87 0.001 0.08 4.9 0.1
10 5.0 11.9 59.6 2.2 0.78 95 1.55044 2.42 3.14 1.57 1.66 382.18 390.52
382.18 76.88 15 4.99 0.006 0.46 11.9 0.6
CULVERT 0.00 180 0 0.55 0.72 0.36 0.82 383.00 385.66
Hydraulic Grade Line Page 1
DEQ Virginia Runoff Reduction Method
Water Quality Calculations
(COMPLIANCE IS MET THROUGH THE BEST MANAGEMENT PRACTICE OF PROTECTING
FOREST& OPEN SPACES AND THROUGH THE PURCHASING OF NUTRIENT CREDITS)
•
DEQ Virginia Runoff Reo'ucttan Method New Development Compliance Spreadsheet-Vers)on 3.0 ,
f a,2011 BMP Standards and Specifications i0 2013 Draft BMP Standards and Specifications -
I Project Name: 5th Street Commercial Development.Full Bulidout CCEAR ALL= data fnputceus
I Date: 12/12/2016 -_. ._.,. constant values
BMP Design Specifications List:2011 Stds&Specs calculation cells
Site Information final results'
it
?Post-Development Project(Treatment Volume and Loads)
'Land Cover(acres)
A Soils B Soils C Solis D Soils Totals
'Forest/Open Space(acres)-undisturbed, *.
•protected forest/open space or reforested land 0.55 5.08 _ 5.63
"Managed Turf(acres)-disturbed,graded for
overds or other turf to be mowed/managed 2.32 - 2.32
!Impervious Cover(acres) 246 • - . 2.46
( "Forest/Open Space areas must tre protected In accordance with the Virginia Runoff Reduction Method I 10.41 •1
,Constants Runoff Coefficients(Rv)
Annual Rainfall(inches) 43 A Soils B Soils C Soils D Soils
fTarget Rainfall Event(Inches) 1.00 Forest/Open Space 0.02 0.03 - 0.04 0.05
Total Phosphorus(TP)EMC(mg/L) 0.26 Managed Turf 0.15 0.20 0.22' 0.25
Total Nitrogen(TN)EMC(mg/L) 1.86 Impervious Cover 0.95 0.95 0.95 0.95
Target TP Load(lb/acre/yr) '041
Pj(unitless correction factor) 0.90
i
al;� ••: .Post Development?Requirement for SiteArea `^' S_ r '
4"
TP Load Reduction Required(Ib/yr) 2.49
LAND COVER SUMMARY-POST DEVELOPMENT
Land Cover Summary Treatment Volume and Nutrient Loads
Forest/Open Spare Cover(acres) 5.63. Treatment Volume 0.2470
(acre-ft)
Weighted Rv(forest) 0.03 Treatment Volume(cubic feet) , . 10,701
%Forest 54% TP Load(Ib/yr) 6.76
Managed Turf Cover(acres) , 2.32` TN Load(Ib/yr) 4837
(Informational Purposes Only)
Weighted Rv(turf) 0,20
%Managed Turf 22%
Impervious Cover(acres) 2A6
Rv(impervious) • 0.95
%Impervious 24%
Site Area(acres) 10.41" •
Site Rv 0.26