HomeMy WebLinkAboutSDP200800148 Calculations 2007-11-20AMENDMENT TO
HYDROLOGIC /HYDRAULIC CALCULATIONS
FOR
Luxor Subdivision & Road Networks
November 20, 2007
LOCATION:
Tax Map 78 Parcels 12B
Albemarle County, Virginia
PREPARED BY:
Dominion Development Resources, LLC
172 S. Pantops Drive
Charlottesville, VA 22911
P: 434.979.8121
F: 434.979.1681
Run -off Summary
Point of Pre -Dev Pre -Dev Pre -Dev Post -Post -Dev Post -Dev
Analysis DA 2 -Year 10 -Year Dev Rtd. 2-Rtd. 10-
DA Year Year
Outfall 3 3 26.71 37.38 3 Post 9.49 16.87
Outfall 2 2 77.46 111.13 2 Post &61.11 65.70
SWM #3
Outfall 1 1 122.88 175.25 Fontana 107.94 142.72
Pond, 1,
SWM2
Luxor Subdivision
Index
Index: 2
Summary: 3
Stormwater Management Pond ##3
Pre - Development:
Flood Hydrographs: 4 -6
Post - Development:
Flood Hydrographs: _7_9
Outlet Structures:10 11
Reservoir:12
Routed Hydrographs:13 14
Westminster Canterbury Pond, SWM ##2
Pre - Development:
Flood Hydrographs:15 17
Post - Development:
Flood Hydrographs:18 22
Outlet Structures:23 25
Reservoir: _ _26 27
Routed Hydrographs: _28 29
Stormwater Management Pond ##1
Pre - Development:
Flood Hydrographs:30 34
Post - Development:
Flood Hydrographs:35 42
Outlet Structures:43 44
Reservoir: _45
Routed Hydrographs:46 47
Uncontained Hydrographs:48 50
Combined Hydrographs:51 52
NOTE: DA Maps are part of the Luxor Stormwater Management Plans.
Dominion Development Resources, LLC Page 2
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Luxor Subdivision
Summary
Stormwater Management Facility #3 will provide water quality and volume control
measures for portions of existing Westminster Canterbury and Ashcroft Subdivision
currently handled by Stormwater Management Facility #2 and future residential and
commercial areas. The BMP measures for this facility will consist of an aquatic
bench, forebays, and extended detention.
Stormwater Management Facility #2 was originally designed to provide water quality
and volume control measures for Westminster Canterbury and Fontana. Post -
construction, Facility #2 will provide water quality and volume control measures
for Luxor Phase 1 &2 and parts of the Fontana Subdivision in addition to receiving
the routed flow from Facility U. The existing emergency spillway for Facility #2
will be removed and a new emergency spillway shall be constructed that will allow
for overland relief in a catastrophic event without impacting the adjacent existing
and proposed residential areas. The BMP measures for this facility consist of
forebays and extended detention.
Stormwater Management Facility #1 will provide water quality and volume control
measures for the North Pantops Commercial area, the Fontana Subdivision, and Phases
2 & 3 of the Luxor Subdivision. The construction of Facility #1 and the road
network for Luxor Subdivison will consist of the removal of the existing Fontana
Pond currently serving portions of the Fontana Subdivison. The area currently
flowing to the Fontana Pond will be redirected to Facility #1. The BMP measures
for this facility will consist of forebays, an aquatic bench, and extended
detention.
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Luxor Subdivision
Stormwater Management Facility #3
Pre - Development Hydrograph Report
Name:
Type:
DA -3, 2yr
Modified Rational
HYDROGRAPH INFORMATION
Peak Flow (Qp)26.71 cfs)
Time to Peak (Tp)17.00 min)
Time of Base (Tb)42.50 min)
Volume 0.78 ac -ft)
Time Step 1.00 min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION
Flow Multiplier 1.00
Receding Limb Factor 1.50
WEIGHTED WATERSHED AREA
Description Area Runoff Coef
Westminster (Undeveloped)9.10 0.30
Ashcroft 3.30 0.40
Luxor Woods /Brush 14.30 0.30
Overall Approximation 26.70 0.31
TIME CONCENTRATION -- User Defined
Time of Concentration (Tc)17.00 min)
RAINFALL DESCRIPTION
Distribution Type Synthetic
Total Precipitation 0.90 in)
Return Period 2 (yr)
Storm Duration 0.28 hr)
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Luxor Subdivision
Stormwater Management Facility #3
Pre - Development Hydrograph Report
Name:
Type:
DA -3, l0yr
Modified Rational
HYDROGRAPH INFORMATION
Peak Flow (Qp)37.38 cfs)
Time to Peak (Tp)17.00 min)
Time of Base (Tb)42.50 min)
Volume 1.09 ac -ft)
Time Step 1.00 min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION
Flow Multiplier
Receding Limb Factor
WEIGHTED WATERSHED AREA
Description Area
Westminster (Undeveloped) 9.10
Ashcroft 3.30
Luxor Woods /Brush 14.30
Overall Approximation 26.70
1.00
1.50
Runoff Coef
0.30
0.40
0.30
0.31
TIME CONCENTRATION -- User Defined
Time of Concentration (Tc) = 17.00 (min)
RAINFALL DESCRIPTION
Distribution Type = Synthetic
Total Precipitation = 1.26 (in)
Return Period = User Defined (yr)
Storm Duration = 0.28 (hr)
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Luxor Subdivision
Stormwater Management Facility #3
Pre - Development Hydrograph Report
Name: DA -3, 100yr
Type: Modified Rational
HYDROGRAPH INFORMATION
Peak Flow (Qp)53.73 cfs)
Time to Peak (Tp)17.00 min)
Time of Base (Tb)42.50 min)
Volume 1.57 ac -ft)
Time Step 1.00 min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION
Flow Multiplier 1.00
Receding Limb Factor 1.50
WEIGHTED WATERSHED AREA
Description Area Runoff Coef
Westminster (Undeveloped)9.10 0.30
Ashcroft 3.30 0.40
Luxor Woods /Brush 14.30 0.30
Overall Approximation 26.70 0.31
TIME CONCENTRATION -- User Defined
Time of Concentration (Tc)17.00 min)
RAINFALL DESCRIPTION
Distribution Type = Synthetic
Total Precipitation = 1.81 (in)
Return Period = 100 (yr)
Storm Duration = 0.28 (hr)
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Luxor Subdivision
Stormwater Management Facility #3
Post - Development Hydrograph Report
Name: DA -3, Post 2yr
Type: Modified Rational
HYDROGRAPH INFORMATION
Peak Flow (Qp)71.47 cfs)
Time to Peak (Tp)15.00 min)
Time of Base (Tb)37.50 min)
Volume 1.85 ac -ft)
Time Step 1.00 min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION
Flow Multiplier 1.00
Receding Limb Factor 1.50
WEIGHTED WATERSHED AREA
Description Area Runoff Coef
Pavilions -II 22.30 0.54
Westminster 10.76 0.70
Ashcroft 3.30 0.40
Overall Approximation 36.36 0.57
TIME CONCENTRATION -- User Defined
Time of Concentration (Tc)15.00 min)
RAINFALL DESCRIPTION
Distribution Type Synthetic
Total Precipitation 0.85 in)
Return Period 2 (yr)
Storm Duration 0.25 hr)
E ,
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Luxor Subdivision
Stormwater Management Facility #3
Post - Development Hydrograph Report
Name:DA -3, Post 10yr
Description
Type:Modified Rational
Pavilions -II 22.30
HYDROGRAPH INFORMATION
10.76 0.70
Peak Flow (Qp)99.41 cfs)
Time to Peak (Tp)15.00 min)
Time of Base (Tb)37.50 min)
Volume 2.57 ac -ft)
Time Step 1.00 min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION
Flow Multiplier
Receding Limb Factor
1.00
1.50
WEIGHTED WATERSHED AREA
Description Area Runoff Coef
Pavilions -II 22.30 0.54
Westminster 10.76 0.70
Ashcroft 3.30 0.40
Overall Approximation 36.36 0.57
TIME CONCENTRATION -- User Defined
Time of Concentration (Tc)
RAINFALL DESCRIPTION
Distribution Type
Total Precipitation
Return Period
Storm Duration
15.00 (min)
Synthetic
1.18 (in)
User Defined (yr)
0.25 (hr)
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Luxor Subdivision
Stormwater Management Facility #3
Post - Development Hydrograph Report
Name:
Type:
DA -3, Post 100yr
Modified Rational
HYDROGRAPH INFORMATION
Peak Flow (Qp)142.43 (cfs)
Time to Peak (Tp)15.00 min)
Time of Base (Tb)37.50 min)
Volume 3.68 ac -ft)
Time Step 1.00 min)
Flow Multiplier 1.00
RATIONAL HYDROGRAPH INFORMATION
Flow Multiplier 1.00
Receding Limb Factor 1.50
WEIGHTED WATERSHED AREA
Description Area Runoff Coef
Pavilions-II 22.30 0.54
Westminster 10.76 0.70
Ashcroft 3.30 0.40
Overall Approximation 36.36 0.57
TIME CONCENTRATION -- User Defined
Time of Concentration (TO 15.00 min)
RAINFALL DESCRIPTION
Distribution Type = Synthetic
Total Precipitation = 1.69 (in)
Return Period = 100 (yr)
Storm Duration = 0.25 (hr)
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Luxor Subdivision
Stormwater Management Facility #3
Outlet Structure Report
Type Stand Pipe
Name SWM #3 Riser
RATING CURVE LIMIT
Minimum Elevation
Maximum Elevation
Elevation Increment
STAND PIPE INFORMATION
480.00 (ft)
496.00 (ft)
0.50 (ft)
ORIFICE INFORMATION
Diameter = 4.00 (ft)
Crest Length = 12.57 (ft)
Effective Crest Length = 10.07 (ft)
Orifice Coefficient = 0.60
Fractional Open Area = 0.83
OPTIONAL WEIR INFORMATION
Type Rectangular Weir Suppressed
WEIR INFORMATION
Crest Length = 2.50 (ft)
Crest Elevation = 492.00 (ft)
Weir Coefficient = 3.33
Exponential = 1.50
OPTIONAL ORIFICE INFORMATION
Type : Circular Orifice
OPTIONAL ORIFICE INFORMATION
Diameter = 1.00 (ft)
Invert Elevation = 490.00 (ft)
Orifice Coefficient = 0.60
Number of Openings = 2
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Luxor Subdivision
Stormwater Management Facility #3
Outlet Structure Report
CULVERT INFORMATION
Type Circular Concrete - Square Edge with Headwall
OUTLET STRUCTURE INFORMATION
Stage Weirs
Diameter 36.00 in)
Invert Elevation 480.00 ft)
Pipe Length 292.00 ft)
Slope 0.078
490.00
Manning's n Value 0.013
0.00
Orifice Coefficient 0.60
0.00
Tailwater Elevation 468.40 ft)
Number of Barrels I
103.95
STAND PIPE STAGE VS. DISCHARGE
Elevation Stage Weirs Orifices Stand Pipe Culvert Total
ft)ft)cfs)cfs)cfs)cfs)cfs)
490.00 10.00 0.00 0.00 0.00 100.88 0.00
490.50 10.50 0.00 1.89 0.00 103.95 1.89
491.00 11.00 0.00 5.35 0.00 106.92 5.35
491.50 11.50 0.00 7.56 0.00 109.82 7.56
492.00 12.00 1.18 9.26 0.00 112.64 9.26
492.50 12.50 6.27 10.69 0.00 115.40 13.64
493.00 13.00 14.44 11.95 0.00 118.08 20.28
493.50 13.50 24.71 13.09 0.00 120.71 28.39
494.00 14.00 36.71 14.14 11.85 123.28 49.54
494.50 14.50 50.21 15.12 33.52 125.80 81.55
495.00 15.00 65.06 16.04 55.73 128.28 115.02
495.50 15.50 81.15 16.91 70.99 130.70 130.70
496.00 16.00 98.39 17.73 79.37 133.08 133.08
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Luxor Subdivision
Stormwater Management Facility #3
Reservoir Report
Reservoir Number: 3
Name: SWM Facility #3
RATING CURVE LIMIT
Minimum Elevation = 480.00 (ft)
Maximum Elevation = 496.00 (ft)
Elevation Increment = 0.50 (ft)
STAGE STORAGE INFORMATION
Storage Method: User - Defined Storage
Input Method: Area
Number Elevation Area Ave Area Volume Cumulative Volume
ft)
ft)sq ft)sq ft)cu ft)cu ft)
1 489.99 0.00 0.00 0.00 0.00
2 490.00 27952.00 13976.00 139.76 139.76
3 492.00 33606.00 30779.00 61558.00 61697.76
4 494.00 40817.00 37211.50 74423.00 136120.76
5 496.00 45510.00 43163.50 86327.00 222447.76
DISCHARGE INFORMATION
Structure Number: 1
Type:
Name: SWM #3 Riser
RESERVOIR STAGE STORAGE /DISCHARGE
Elevation Stage Area Storage Discharge
ft)ft)sq ft)cu ft)cfs)
490.00 10.00 27952.00 6988.00 0.00
490.50 10.50 29365.50 21317.37 1.89
491.00 11.00 30779.00 36353.50 5.35
491.50 11.50 32192.50 52096.37 7.56
492.00 12.00 33606.00 68546.00 9.26
492.50 12.50 35408.75 85799.69 13.64
493.00 13.00 37211.50 103954.75 20.28
493.50 13.50 39014.25 123011.19 28.39
494.00 14.00 40817.00 142969.00 49.54
494.50 14.50 41990.25 163670.81 81.55
495.00 15.00 43163.50 184959.25 115.02
495.50 15.50 44336.75 206834.31 130.70
496.00 16.00 45510.00 229296.00 133.08
Maximum Storage
Maximum Discharge
229296.00 (cu ft)
133.08 (cfs)
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Luxor Subdivision
Stormwater Management Facility #3
Routed Hydrograph Report
Name:
Type:
HYDROGRAPH INFORMATION
Peak Flow (Qp)
Time to Peak (Tp)
Time of Base (Tb)
Volume
Time Step
Peak Elevation
SWM3, 2yr
Reservoir: Modified Puls
RESERVOIR STRUCTURE INFORMATION
Name
Storage Type
Maximum Storage
Maximum Discharge
INFLOW HYDROGRAPH INFORMATION
Name
Peak Flow (Qp)
Time to Peak (Tp)
Time of Base (Tb)
Volume
Flow Multiplier
Name:
Type:
HYDROGRAPH INFORMATION
Peak Flow (Qp)
Time to Peak (Tp)
Time of Base ('Ib)
Volume
Time Step
Peak Elevation
SWM3, l0yr
Reservoir: Modified Puls
RESERVOIR STRUCTURE INFORMATION
Name
Storage Type
Maximum Storage
Maximum Discharge
INFLOW HYDROGRAPH INFORMATION
Name
Peak Flow (Qp)
Time to Peak (Tp)
Time of Base (Tb)
Volume
Flow Multiplier
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434) 984 -1599
9.49 (cfs)
35.00 (min)
1440.00 (min)
1.69 (ac -ft)
1.00 (min)
492.03 (ft)
SWM Facility #3
User- Defined Area
229296.00 (cu ft)
133.08 (cfs)
DA -3, Post 2yr
71.47 (cfs)
15.00 (min)
37.50 (min)
1.85 (ac -ft)
1.00
16.87 (cfs)
34.00 (min)
1440.00 (min)
2.41 (ac -ft)
1.00 (min)
492.74 (ft)
SWM Facility #3
User- Defined Area
229296.00 (cu ft)
133.08 (cfs)
DA -3, Post 10yr
99.41 (cfs)
15.00 (min)
37.50 (min)
2.57 (ac -ft)
1.00
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Luxor Subdivision
Stormwater Management Facility #3
Routed Hydrograph Report
Name:
Type:
SWM3, 100yr
Reservoir: Modified Puts
HYDROGRAPH INFORMATION
Peak Flow (Qp)34.50 (cfs)
Time to Peak (Tp)32.00 (min)
Time of Base (Tb)1440.00 (min)
Volume 3.52 (ac -ft)
Time Step 1.00 (min)
Peak Elevation 493.64 (ft)
RESERVOIR STRUCTURE INFORMATION
Name SWM Facility #3
Storage Type User - Defined Area
Maximum Storage 229296.00 (cu ft)
Maximum Discharge 133.08 (cfs)
INFLOW HYDROGRAPH INFORMATION
Name DA -3, Post 100yr
Peak Flow (Qp)142.43 (cfs)
Time to Peak (Tp)15.00 (min)
Time of Base (Tb)37.50 (min)
Volume 3.68 (ac -ft)
Flow Multiplier 1.00
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