HomeMy WebLinkAboutWPO201400101 Calculations 2015-07-10 CASCADIA SUBDIVISION
HYDROLOGIC/HYDRAULIC CALCULATIONS FOR
CASCADIA SUBDIVISION - BLOCKS 1-3
EXISTING EXTENDED DETENTION FACILITY "POND 1"`
February 3, 2015
Revised: May 1, 2015
LOCATION:
Tax Map 62, Parcel 25
Tax Map 78, Parcels 59 & 59A
Tax Map 78E, Parcel H1
Rio District, Albemarle County, Virginia
DEVELOPER:
Cascadia Development, LLC. �• T �,�
170 South Pantops Drive / '.
Charlottesville, Virginia 22903 //
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v MIC '�' ERS •
PREPARED BY: • 4 .No.33028
Dominion Engineering & Design, LLC
172 South Pantops Drive 'P,wr /U l
Charlottesville, VA 22911 SSjD�T� G
P: 434.979.8121
F: 434.979.1681
INDEX
Summary: 2-3
Pond 1 Water Quality Volume Report 4
Hydrographs:
Pond 1 Pre-Development 4-8
Pond 1 Post-Development 9-12
Pond Report: 13-14
Routed Hydrographs: 15-17
Appendix:
Soils Report
APPROVED
*Drainage Area Maps are included on Storm Water Management Plan by the Albemarle County
Community Development Department
Date 7 /0/i5
File
CASCADIA SUBDIVISION
Run-Off Summary
Pond 1
Pond one is an existing extended detention stormwater management facility used to detain and treat
stormwater run-off from the existing Fontana Subdivision. A small portion of the pond will be filled in,
reducing its volume slightly.
The existing, completely wooded, drainage area as shown on the approved Stormwater Management
Report by McKee Carson is 37.61 acres with a runoff coefficient of 0.20 (Cn=60) and was used to determine
the maximum allowable flow from the facility. The calculations below, using the SCS/TR-55 method,
demonstrate that the existing facility will still provide adequate detention and water quality volume.
Please note the overall drainage area as well as the impervious cover within the drainage area has been
decreased as compared to the approved design for Pond 1 by McKee/Carson. Refer to the Stormwater
management plan for a drainage area map, and additional calculations.
Pre-Development Conditions:
2 Yr. Pre-Development Run-Off(Cn=60) = 9.83 cfs
10 Yr. Pre-Development Run-Off(Cn=60) =42.60 cfs
Post-Development Release Rate Summary:
Q2 Post-Development Routed = 0.777 cfs < 9.83 cfs
Q10 Post-Development Routed = 7.074 cfs <42.60 cfs
( Please Refer Calculations on following Pages )
7
CASCADIA SUBDIVISION
Weighted Cn Values Based on Soil Types (Refer to soils report in appendix):
Pavement, Building, Patios, Sidewalks: 98
Fair Pasture/Yards: 64
Wooded Area: 60
Cn Value Calculations:
Pond-1 Pre-Development DA (37.61 Acres):
Wooded Area (Cn=60)—37.61 Acres
Cn=60
Pond-1 Post Development DA (20.03 Acres):
Existing Houses (Cn=98)— 1.21 Acres
Existing Pavement/Drives (Cn=98)—2.54 Acres
Existing Yards(Cn=64)—5.29 Acres
Proposed Pavement/Walks (Cn=98)—0.26 Acre
Proposed Yard (Cn=64)—0.90 Acre
Wooded Area (Cn=60)—9.83 Acres
4.01 (98) +6.19(64)+ 9.83(60) = 69
20.03
3
f
CASCADIA SUBDIVISION
Name: POND-1 (Existing Extended Detention Facility)
WATER QUALITY VOLUME REPORT
Sage
Bewaeon Contour Incremental Total Toni
Area Storage Storage Discharge
(R) (ft) (sue) WO (cam) (cfs)
0.00 368.43 100 0.000 0.000 0.000
1.77 370.20 2.200 2.036 2,036 0292
3.57 372.00 3.894 5,485 7.520 0.428
5.57 374.00 16,582 20,476 27,996 0.541
7.57 376.00 21.428 38.010 66.006 8.394
9.57 378.00 30.680 52,108 118,114 44.06
11.57 380.00 52.424 83.104 201,218 47.06
Quality Volume Required =2X(WQ Volume)
(2)WQ Volume = 2 [ (1/2in) /12 X impervious area (Sq. Ft. ) ]
2 [ (1/2in) /12 X 174, 676 Sq. Ft. ] = 14,556 Cu. Ft.
Provided Water Quality Volume For Ext. Detention (374.03) = 27,996 cu. Ft.
4
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD®Civil 3D®2013 by Autodesk, Inc.v10 Tuesday,02/3/2015
Hyd. No. 1
Pond-1 Pre-Dev. DA
Hydrograph type = SCS Runoff Peak discharge = 9.828 cfs
Storm frequency = 2 yrs Time to peak = 730 min
Time interval = 2 min Hyd. volume = 56,168 cuft
Drainage area = 37.610 ac Curve number = 60
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 23.30 min
Total precip. = 3.19 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
Pond-1 Pre-Dev. DA
Q (cfs) Q (cfs)
Hyd. No. 1 --2 Year
10.00 jt 10.00
8.00 8.00
6.00 6.00
4.00 4.00
2.00
2.00
0.00 - 0.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Time(min)
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD®Civil 3D®2013 by Autodesk, Inc.v10 Tuesday,0213/2015
Hyd. No. 1
Pond-1 Pre-Dev. DA
Hydrograph type = SCS Runoff Peak discharge = 42.60 cfs
Storm frequency = 10 yrs Time to peak = 728 min
Time interval = 2 min Hyd. volume = 167,174 cuft
Drainage area = 37.610 ac Curve number = 60
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 23.30 min
Total precip. = 4.83 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
Pond-1 Pre-Dev. DA
Q (cfs) Hyd. No. 1 -- 10 Year Q (cfs)
50.00 - 50.00
40.00 40.00
30.00 - — 30.00
20.00 - - 20.00
10.00 10.00
0.00 - 0.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Hyd No. 1
Time(min)
TR55 Tc Worksheet
Hydraflow Hydrographs Extension for AutoCAD®Civil 3D®2013 by Autodesk, Inc.v10
Hyd. No. 1
Pond-1 Pre-Dev. DA
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 300.0 0.0 0.0
Two-year 24-hr precip. (in) = 3.19 0.00 0.00
Land slope (%) = 23.00 0.00 0.00
Travel Time (min) = 19.50 + 0.00 + 0.00 = 19.50
Shallow Concentrated Flow
Flow length (ft) = 1100.00 0.00 0.00
Watercourse slope (%) = 9.00 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =4.84 0.00 0.00
Travel Time (min) = 3.79 + 0.00 + 0.00 = 3.79
Channel Flow
X sectional flow area (sqft) = 0.00 0.00 0.00
Wetted perimeter(ft) = 0.00 0.00 0.00
Channel slope (%) = 0.00 0.00 0.00
Manning's n-value = 0.015 0.015 0.015
Velocity (ft/s) =0.00
0.00
0.00
Flow length (ft) ({0})0.0 0.0 0.0
Travel Time (min) = 0.00 + 0.00 + 0.00 = 0.00
Total Travel Time, Tc 23.30 min
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD®Civil 3D®2013 by Autodesk, Inc.v10 Friday,05/1 /2015
Hyd. No. 2
Pond-1 Post-Dev. DA
Hydrograph type = SCS Runoff Peak discharge = 14.46 cfs
Storm frequency = 2 yrs Time to peak = 12.13 hrs
Time interval = 2 min Hyd. volume = 57,279 cuft
Drainage area = 20.030 ac Curve number = 69* Y
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 21.10 min
Total precip. = 3.19 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
*Composite(Area/CN)=[(4.010 x 98)+(6.190 x 64)+(9.830 x 60)]/20.030
Pond-1 Post-Dev. DA
Q (cfs) Hyd. No. 2 --2 Year Q (cfs)
15.00 15.00
1
12.00 12.00
9.00 9.00
6.00 6.00
3.00 3.00
0.00 - 0.00
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Hyd No. 2 Time(hrs)
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD®Civil 3D®2013 by Autodesk, Inc.v10 Friday,05/1 /2015
Hyd. No. 2
Pond-1 Post-Dev. DA
Hydrograph type = SCS Runoff Peak discharge = 38.10 cfs
Storm frequency = 10 yrs Time to peak = 12.13 hrs
Time interval = 2 min Hyd. volume = 135,785 cuft
Drainage area = 20.030 ac Curve number = 69*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 21.10 min
Total precip. = 4.83 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
*Composite(Area/CN)=[(4.010 x 98)+(6.190 x 64)+(9.830 x 60)]/20.030
Pond-1 Post-Dev. DA
Q (cfs) Hyd. No. 2 -- 10 Year Q (cfs)
40.00 40.00
30.00 30.00
20.00 20.00
10.00 10.00
0.00 - - - 0.00
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Hyd No. 2 Time(hrs)
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD®Civil 3D®2013 by Autodesk, Inc.v10 Friday,05/1 /2015
Hyd. No. 2
Pond-1 Post-Dev. DA
Hydrograph type = SCS Runoff Peak discharge = 91.86 cfs
Storm frequency = 100 yrs Time to peak = 12.10 hrs
Time interval = 2 min Hyd. volume = 317,507 cuft
Drainage area = 20.030 ac Curve number = 69*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = TR55 Time of conc. (Tc) = 21.10 min
Total precip. = 7.93 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
*Composite(Area/CN)=[(4.010 x 98)+(6.190 x 64)+(9.830 x 60)]/20.030
Pond-1 Post-Dev. DA
Q (cfs) Q (cfs)
Hyd. No. 2 -- 100 Year
100.00 100.00
90.00
90.00
80.00 _ 80.00
70.00 70.00
60.00 60.00
50.00 50.00
40.00 40.00
30.00 _ 30.00
20.00 20.00
10.00
Low
10.00
0.00
0.00
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Time(hrs)
- Hyd No. 2
TR55 Tc Worksheet
Hydraflow Hydrographs Extension for AutoCAD®Civil 3D®2013 by Autodesk, Inc v10
Hyd. No. 2
Pond-1 Post-Dev. DA
Description A B C Totals
Sheet Flow
Manning's n-value = 0.400 0.011 0.011
Flow length (ft) = 300.0 0.0 0.0
Two-year 24-hr precip. (in) = 3.19 0.00 0.00
Land slope (%) = 23.00 0.00 0.00
Travel Time (min) = 19.50 + 0.00 + 0.00 = 19.50
Shallow Concentrated Flow
Flow length (ft) = 400.00 0.00 0.00
Watercourse slope (%) = 22.00 0.00 0.00
Surface description = Unpaved Paved Paved
Average velocity (ft/s) =7.57 0,00 0.00
Travel Time (min) = 0.88 + 0.00 + 0.00 = 0.88
Channel Flow
X sectional flow area (sqft) = 2.00 0.00 0.00
Wetted perimeter(ft) = 1.25 0.00 0.00
Channel slope (%) = 8.70 0.00 0.00
Manning's n-value = 0.035 0.015 0.015
Velocity (ft/s) =17.20
0.00
0.00
Flow length (ft) ({0})780.0 0.0 0.0
Travel Time (min) = 0.76 + 0.00 + 0.00 = 0.76
Total Travel Time, Tc 21.10 min
Pond Report
Hydraflow Hydrographs Extension for AutoCAD®Civil 3D®2013 by Autodesk, Inc.v10 Monday,02/2/2015
Pond No. 1 - Existing Pond-1
Pond Data
Contours-User-defined contour areas.Average end area method used for volume calculation.Begining Elevation=368.43 ft
Stage/Storage Table
Stage(ft) Elevation(ft) Contour area(sqft) Incr.Storage(cuft) Total storage(cuft)
0.00 368.43 100 0 0
1.77 370.20 2,200 2,036 2,036
3.57 372.00 3,894 5,485 7,520
5.57 374.00 16,582 20,476 27,996
7.57 376.00 21,428 38,010 66,006
9.57 378.00 30,680 52,108 118,114
11.57 380.00 52,424 83,104 201,218
Culvert/Orifice Structures Weir Structures
[A] [B] [C] [PrfRsr] [A] [B] [C] [D]
Rise(in) = 24.00 3.00 16.20 0.00 Crest Len(ft) = 15.71 45.00 0.00 0.00
Span(in) = 24.00 3.00 16.20 0.00 Crest El.(ft) = 376.43 377.00 0.00 0.00
No.Barrels = 1 1 1 0 Weir Coeff. = 3.33 3.33 3.33 3.33
Invert El.(ft) = 368.43 368.43 374.03 0.00 Weir Type = 1 Rect --- ---
Length(ft) = 54.70 0.00 0.00 0.00 Multi-Stage = Yes Yes No No
Slope(%) = 0.23 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff. = 0.60 0.60 0.60 0.60 Exfil.(in/hr) = 0.000(by Contour)
Multi-Stage = n/a Yes Yes No TW Elev.(ft) = 0.00
Note Culvert/Orifice outflows are analyzed under inlet(ic)and outlet(oc)control Weir risers checked for orifice conditions(ic)and submergence(s)
Stage/Storage/Discharge Table
Stage Storage Elevation Clv A Clv B Clv C PrfRsr Wr A Wr B Wr C Wr D Exfil User Total
ft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs
0.00 0 368.43 0.00 0.00 0.00 --- 0.00 0.00 --- --- --- --- 0.000
0.18 204 368.61 0.05 oc 0.05 is 0.00 --- 0.00 0.00 --- --- --- --- 0.051
0.35 407 368.78 0.12 oc 0.11 is 0.00 --- 0.00 0.00 --- --- --- --- 0.107
0.53 611 368.96 0.15 oc 0.14 is 0.00 --- 0.00 0.00 --- --- --- --- 0.143
0.71 814 369.14 0.18 oc 0.17 is 0.00 --- 0.00 0.00 --- --- --- --- 0.171
0.89 1,018 369.32 0.20 oc 0.20 is 0.00 --- 0.00 0.00 --- --- --- --- 0.196
1.06 1,221 369.49 0.23 oc 0.22 is 0.00 --- 0.00 0.00 --- --- --- --- 0.218
1.24 1,425 369.67 0.25 oc 0.24 is 0.00 --- 0.00 0.00 --- --- --- --- 0.239
1.42 1,628 369.85 0.28 oc 0.26 is 0.00 --- 0.00 0.00 --- --- -- --- 0.257
1.59 1,832 370.02 0.28 oc 0.28 is 0.00 --- 0.00 0.00 --- --- --- --- 0.276
1.77 2,036 370.20 0.30 oc 0.29 is 0.00 --- 0.00 0.00 --- --- --- --- 0.292
1.95 2,584 370.38 0.32 oc 0.31 is 0.00 --- 0.00 0.00 --- --- --- --- 0.308
2.13 3,132 370.56 0.35 oc 0.32 is 0.00 --- 0.00 0.00 --- --- --- --- 0.323
2.31 3,681 370.74 0.35 oc 0.34 is 0.00 --- 0.00 0.00 --- --- --- --- 0.338
2.49 4,229 370.92 0.37 oc 0.35 ic 0.00 --- 0.00 0.00 --- --- --- --- 0.352
2.67 4,778 371.10 0.37 oc 0.37 is 0.00 --- 0.00 0.00 --- --- --- --- 0.366
2.85 5,326 371.28 0.40 oc 0.38 is 0.00 --- 0.00 0.00 --- --- --- --- 0.379
3.03 5,875 371.46 0.40 oc 0.39 is 0.00 --- 0.00 0.00 --- --- --- --- 0.392
3.21 6,423 371.64 0.43 oc 0.40 is 0.00 --- 0.00 0.00 --- --- --- --- 0.404
3.39 6,972 371.82 0.43 oc 0.42 is 0.00 --- 0.00 0.00 --- --- --- --- 0.416
3.57 7,520 372.00 0.43 oc 0.43 is 0.00 --- 0.00 0.00 --- --- --- --- 0.428
3.77 9,568 372.20 0.46 oc 0.44 is 0.00 --- 0.00 0.00 --- --- --- --- 0.440
3.97 11,615 372.40 0.46 oc 0.45 is 0.00 --- 0.00 0.00 --- --- --- --- 0.452
4.17 13,663 372.60 0.49 oc 0.46 is 0.00 --- 0.00 0.00 --- --- --- --- 0.464
4.37 15,710 372.80 0.49 oc 0.48 is 0.00 --- 0.00 0.00 --- --- --- --- 0.476
4.57 17,758 373.00 0.49 oc 0.49 is 0.00 --- 0.00 0.00 --- --- --- --- 0.487
4.77 19,806 373.20 0.52 oc 0.50 is 0.00 --- 0.00 0.00 --- --- --- --- 0.498
4.97 21,853 373.40 0.52 oc 0.51 is 0.00 --- 0.00 0.00 --- --- --- --- 0.509
5.17 23,901 373.60 0.52 oc 0.52 is 0.00 --- 0.00 0.00 --- --- --- --- 0.520
5.37 25,948 373.80 0.56 oc 0.53 is 0.00 --- 0.00 0.00 --- --- --- --- 0.530
5.57 27,996 374.00 0.56 oc 0.54 is 0.00 --- 0.00 0.00 --- --- --- --- 0.541
5.77 31,797 374.20 0.70 oc 0.55 is 0.15 is --- 0.00 0.00 --- --- --- --- 0.702
5.97 35,598 374.40 1.25 oc 0.55 is 0.68 is --- 0.00 0.00 --- --- --- --- 1.230
Continues on next page...
Existing Pond-1
Stage/Storage/Discharge Table
Stage Storage Elevation Clv A Clv B Clv C PrfRsr Wr A Wr B Wr C Wr D Exfil User Total
ft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs
6.17 39,399 374.60 2.11 oc 0.55 is 1.51 is --- 0.00 0.00 --- --- --- --- 2.060
6.37 43,200 374.80 3.10 oc 0.55 is 2.52 is --- 0.00 0.00 --- --- --- --- 3.068
6.57 47,001 375.00 4.27 oc 0.54 is 3.70 is --- 0.00 0.00 --- --- --- --- 4.243
6.77 50,802 375.20 5.44 oc 0.54 is 4.87 is --- 0.00 0.00 --- --- --- --- 5.405
6.97 54,603 375.40 6.27 oc 0.53 is 5.75 is --- 0.00 0.00 --- --- --- --- 6.272
7.17 58,404 375.60 7.06 oc 0.54 is 6.52 is --- 0.00 0.00 --- --- --- --- 7.055
7.37 62,205 375.80 7.76 oc 0.54 is 7.21 is --- 0.00 0.00 --- --- --- --- 7.755
7.57 66,006 376.00 8.40 oc 0.55 is 7.84 is --- 0.00 0.00 --- --- --- --- 8.394
7.77 71,217 376.20 8.99 oc 0.56 is 8.43 is --- 0.00 0.00 --- --- --- --- 8.986
7.97 76,428 376.40 9.54 oc 0.57 is 8.97 is --- 0.00 0.00 --- --- --- --- 9.540
8.17 81,638 376.60 13.72 oc 0.56 is 9.49 is --- 3.67 0.00 --- --- --- --- 13.72
8.37 86,849 376.80 22.27 oc 0.52 is 9.97 is --- 11.78 0.00 --- --- --- --- 22.27
8.57 92,060 377.00 33.35 is 0.39 is 10.44 is --- 22.52 0.00 --- --- --- --- 33.35
8.77 97,271 377.20 41.56 is 0.11 is 3.24 is --- 24.79 s 13.41 --- --- --- --- 41.55
8.97 102,482 377.40 42.54 is 0.06 is 1.68 is --- 19.83 s 20.96 s --- --- --- --- 42.53
9.17 107,692 377.60 43.16 is 0.04 is 1.11 is --- 17.81 s 24.18 s --- --- --- --- 43.13
9.37 112,903 377.80 43.72 is 0.03 is 0.81 is --- 16.65 s 26.16 s --- --- --- --- 43.64
9.57 118,114 378.00 44.26 is 0.02 is 0.62 is --- 15.89 s 27.52 s --- --- --- --- 44.06
9.77 126,424 378.20 44.78 is 0.02 is 0.51 is --- 15.48 s 28.74 s --- --- --- --- 44.74
9.97 134,735 378.40 45.29 is 0.01 is 0.42 is --- 15.06 s 29.47 s --- --- --- --- 44.95
10.17 143,045 378.60 45.79 is 0.01 is 0.36 is --- 14.83 s 30.24 s --- --- --- --- 45.44
10.37 151,356 378.80 46.29 is 0.01 is 0.31 is --- 14.56 s 30.69 s --- --- --- --- 45.57
10.57 159,666 379.00 46.79 is 0.01 is 0.27 is --- 14.58 s 31.59 s --- --- --- --- 46.45
10.77 167,977 379.20 47.27 is 0.01 is 0.25 is --- 14.61 s 32.38 s --- --- --- --- 47.24
10.97 176,287 379.40 47.75 is 0.01 is 0.21 is --- 14.24 s 32.16 s --- --- --- --- 46.62
11.17 184,597 379.60 48.23 is 0.01 is 0.19 is --- 14.01 s 32.17 s --- --- --- --- 46.38
11.37 192,908 379.80 48.70 is 0.01 is 0.18 is --- 14.16 s 32.99 s --- --- --- --- 47.33
11.57 201,218 380.00 49.17 is 0.01 is 0.16 is --- 13.96 s 32.94 s --- --- --- --- 47.06
...End
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD®Civil 3D®2013 by Autodesk, Inc.v10 Friday,05/1 /2015
Hyd. No. 3
Pond-1 Routed
Hydrograph type = Reservoir Peak discharge = 0.777 cfs -
Storm frequency = 2 yrs Time to peak = 16.23 hrs
Time interval = 2 min Hyd. volume = 57,275 cuft
Inflow hyd. No. = 2 - Pond-1 Post-Dev. DA Max. Elevation = 374.23 ft
Reservoir name = Existing Pond-1 Max. Storage = 32,340 cuft
Storage Indication method used.
Pond-1 Routed
Q (cfs) Q (cfs)
Hyd. No. 3 --2 Year
15.00 15.00
12.00 12.00
9.00 9.00
6.00 6.00
3.00 3.00
0.00 0.00
0 4 8 12 16 20 24 28 32 36 40 44 48
Time(hrs)
- Hyd No. 3 - Hyd No. 2 I Total storage used = 32,340 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD®Civil 3D®2013 by Autodesk, Inc.v10 Friday,05/1 /2015
Hyd. No. 3
Pond-1 Routed
Hydrograph type = Reservoir Peak discharge = 7.074 cfs
Storm frequency = 10 yrs Time to peak = 12.63 hrs
Time interval = 2 min Hyd. volume = 135,781 cuft
Inflow hyd. No. = 2 - Pond-1 Post-Dev. DA Max. Elevation = 375.61 ft
Reservoir name = Existing Pond-1 Max. Storage = 58,510 cuft
Storage Indication method used.
Pond-1 Routed
Q (cfs) Hyd. No. 3-- 10 Year Q (cfs)
40.00 40.00
30.00 30.00
20.00 20.00
10.00 10.00
0.00 - - 0.00
0 4 8 12 16 20 24 28 32 36 40 44 48
Time(hrs)
Hyd No. 3 Hyd No. 2 ' ! Total storage used = 58,510 cuft
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD®Civil 3D®2013 by Autodesk, Inc.v10 Friday,05/1 /2015
Hyd. No. 3
Pond-1 Routed
Hydrograph type = Reservoir Peak discharge = 43.68 cfs
Storm frequency = 100 yrs Time to peak = 12.37 hrs
Time interval = 2 min Hyd. volume = 317,503 cuft
Inflow hyd. No. = 2 - Pond-1 Post-Dev. DA Max. Elevation = 377.82 ft
Reservoir name = Existing Pond-1 Max. Storage = 113,479 cuft
Storage Indication method used.
Pond-1 Routed
Q (cfs) Q (cfs)
Hyd. No. 3 -- 100 Year
100.00 I 100.00
90.00 - _ 90.00
80.00 80.00
70.00 70.00
60.00 60.00
50.00 50.00
40.00 - _ _ 40.00
II
30.00 II 30.00
20.00 20.00
10.00 i 10.00
0.00 - _ ��:—_._______._._
- 0.00
0 4 8 12 16 20 24 28 32 36 40
Time(hrs)
Hyd No. 3 Hyd No. 2 11 I I l 1 Total storage used = 113,479 cuft
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February 2, 2015
Preface
Soil surveys contain information that affects land use planning in survey areas.They
highlight soil limitations that affect various land uses and provide information about
the properties of the soils in the survey areas. Soil surveys are designed for many
different users, including farmers, ranchers, foresters, agronomists, urban planners,
community officials, engineers, developers, builders, and home buyers. Also,
conservationists, teachers, students, and specialists in recreation, waste disposal,
and pollution control can use the surveys to help them understand,protect,or enhance
the environment.
Various land use regulations of Federal, State, and local governments may impose
special restrictions on land use or land treatment. Soil surveys identify soil properties
that are used in making various land use or land treatment decisions.The information
is intended to help the land users identify and reduce the effects of soil limitations on
various land uses.The landowner or user is responsible for identifying and complying
with existing laws and regulations.
Although soil survey information can be used for general farm, local, and wider area
planning,onsite investigation is needed to supplement this information in some cases.
Examples include soil quality assessments(http://www.nres.usda.gov/wps/portal/
nres/main/soils/health/)and certain conservation and engineering applications. For
more detailed information, contact your local USDA Service Center(http://
offices.sc.egov.usda.gov/locator/app?agency=nres) or your NRCS State Soil
Scientist(http://www,nres.usda.gov/wps/portal/nres/detail/soils/contactus/7
cid=nres142p2_053951).
Great differences in soil properties can occur within short distances. Some soils are
seasonally wet or subject to flooding. Some are too unstable to be used as a
foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic
tank absorption fields.A high water table makes a soil poorly suited to basements or
underground installations.
The National Cooperative Soil Survey is a joint effort of the United States Department
of Agriculture and other Federal agencies, State agencies including the Agricultural
Experiment Stations, and local agencies. The Natural Resources Conservation
Service (NRCS) has leadership for the Federal part of the National Cooperative Soil
Survey.
Information about soils is updated periodically. Updated information is available
through the NRCS Web Soil Survey, the site for official soil survey information.
The U.S. Department of Agriculture(USDA)prohibits discrimination in all its programs
and activities on the basis of race, color, national origin, age, disability, and where
applicable, sex, marital status, familial status, parental status, religion, sexual
orientation,genetic information, political beliefs, reprisal,or because all or a part of an
individual's income is derived from any public assistance program. (Not all prohibited
bases apply to all programs.) Persons with disabilities who require alternative means
2
for communication of program information(Braille, large print, audiotape, etc.)should
contact USDA's TARGET Center at(202) 720-2600 (voice and TDD). To file a
complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400
Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272
(voice) or(202) 720-6382 (TDD). USDA is an equal opportunity provider and
employer.
3
Contents
Preface 2
How Soil Surveys Are Made 5
Soil Map 7
Soil Map 8
Legend 9
Map Unit Legend 10
Map Unit Descriptions 10
Albemarle County, Virginia 12
12C—Catoctin silt loam, 7 to 15 percent slopes 12
12E—Catoctin silt loam, 25 to 45 percent slopes 13
23B—Davidson clay loam, 2 to 7 percent slopes 14
71 B—Rabun clay loam, 2 to 7 percent slopes 15
71C—Rabun clay loam, 7 to 15 percent slopes 16
71D—Rabun clay loam, 15 to 25 percent slopes 17
72B3—Rabun clay, 2 to 7 percent slopes, severely eroded 18
72C3—Rabun clay, 7 to 15 percent slopes, severely eroded 19
72E3—Rabun clay, 25 to 45 percent slopes, severely eroded 20
79B—Starr silt loam, 2 to 7 percent slopes 21
References 22
4
How Soil Surveys Are Made
Soil surveys are made to provide information about the soils and miscellaneous areas
in a specific area.They include a description of the soils and miscellaneous areas and
their location on the landscape and tables that show soil properties and limitations
affecting various uses. Soil scientists observed the steepness, length, and shape of
the slopes; the general pattern of drainage; the kinds of crops and native plants; and
the kinds of bedrock.They observed and described many soil profiles.A soil profile is
the sequence of natural layers, or horizons, in a soil. The profile extends from the
surface down into the unconsolidated material in which the soil formed or from the
surface down to bedrock. The unconsolidated material is devoid of roots and other
living organisms and has not been changed by other biological activity.
Currently,soils are mapped according to the boundaries of major land resource areas
(MLRAs). MLRAs are geographically associated land resource units that share
common characteristics related to physiography, geology, climate, water resources,
soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically
consist of parts of one or more MLRA.
The soils and miscellaneous areas in a survey area occur in an orderly pattern that is
related to the geology, landforms, relief, climate, and natural vegetation of the area.
Each kind of soil and miscellaneous area is associated with a particular kind of
landform or with a segment of the landform. By observing the soils and miscellaneous
areas in the survey area and relating their position to specific segments of the
landform,a soil scientist develops a concept,or model,of how they were formed.Thus,
during mapping, this model enables the soil scientist to predict with a considerable
degree of accuracy the kind of soil or miscellaneous area at a specific location on the
landscape.
Commonly, individual soils on the landscape merge into one another as their
characteristics gradually change. To construct an accurate soil map, however, soil
scientists must determine the boundaries between the soils. They can observe only
a limited number of soil profiles. Nevertheless,these observations, supplemented by
an understanding of the soil-vegetation-landscape relationship, are sufficient to verify
predictions of the kinds of soil in an area and to determine the boundaries.
Soil scientists recorded the characteristics of the soil profiles that they studied. They
noted soil color, texture, size and shape of soil aggregates, kind and amount of rock
fragments, distribution of plant roots, reaction, and other features that enable them to
identify soils. After describing the soils in the survey area and determining their
properties, the soil scientists assigned the soils to taxonomic classes (units).
Taxonomic classes are concepts. Each taxonomic class has a set of soil
characteristics with precisely defined limits. The classes are used as a basis for
comparison to classify soils systematically. Soil taxonomy, the system of taxonomic
classification used in the United States, is based mainly on the kind and character of
soil properties and the arrangement of horizons within the profile.After the soil
scientists classified and named the soils in the survey area, they compared the
5
Custom Soil Resource Report
individual soils with similar soils in the same taxonomic class in other areas so that
they could confirm data and assemble additional data based on experience and
research.
The objective of soil mapping is not to delineate pure map unit components; the
objective is to separate the landscape into landforms or landform segments that have
similar use and management requirements. Each map unit is defined by a unique
combination of soil components and/or miscellaneous areas in predictable
proportions. Some components may be highly contrasting to the other components of
the map unit. The presence of minor components in a map unit in no way diminishes
the usefulness or accuracy of the data. The delineation of such landforms and
landform segments on the map provides sufficient information for the development of
resource plans. If intensive use of small areas is planned, onsite investigation is
needed to define and locate the soils and miscellaneous areas.
Soil scientists make many field observations in the process of producing a soil map.
The frequency of observation is dependent upon several factors, including scale of
mapping, intensity of mapping, design of map units, complexity of the landscape, and
experience of the soil scientist. Observations are made to test and refine the soil-
landscape model and predictions and to verify the classification of the soils at specific
locations. Once the soil-landscape model is refined, a significantly smaller number of
measurements of individual soil properties are made and recorded. These
measurements may include field measurements, such as those for color, depth to
bedrock, and texture, and laboratory measurements, such as those for content of
sand, silt, clay, salt, and other components. Properties of each soil typically vary from
one point to another across the landscape.
Observations for map unit components are aggregated to develop ranges of
characteristics for the components. The aggregated values are presented. Direct
measurements do not exist for every property presented for every map unit
component. Values for some properties are estimated from combinations of other
properties.
While a soil survey is in progress, samples of some of the soils in the area generally
are collected for laboratory analyses and for engineering tests. Soil scientists interpret
the data from these analyses and tests as well as the field-observed characteristics
and the soil properties to determine the expected behavior of the soils under different
uses. Interpretations for all of the soils are field tested through observation of the soils
in different uses and under different levels of management. Some interpretations are
modified to fit local conditions, and some new interpretations are developed to meet
local needs. Data are assembled from other sources, such as research information,
production records, and field experience of specialists. For example, data on crop
yields under defined levels of management are assembled from farm records and from
field or plot experiments on the same kinds of soil.
Predictions about soil behavior are based not only on soil properties but also on such
variables as climate and biological activity. Soil conditions are predictable over long
periods of time, but they are not predictable from year to year. For example, soil
scientists can predict with a fairly high degree of accuracy that a given soil will have
a high water table within certain depths in most years, but they cannot predict that a
high water table will always be at a specific level in the soil on a specific date.
After soil scientists located and identified the significant natural bodies of soil in the
survey area, they drew the boundaries of these bodies on aerial photographs and
identified each as a specific map unit.Aerial photographs show trees, buildings,fields,
roads, and rivers, all of which help in locating boundaries accurately.
6
Soil Map
The soil map section includes the soil map for the defined area of interest, a list of soil
map units on the map and extent of each map unit, and cartographic symbols
displayed on the map. Also presented are various metadata about data used to
produce the map, and a description of each soil map unit.
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Custom Soil Resource Report
Map Unit Legend
Albemarle County,Virginia(VA003)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOl
12C Catoctin silt loam,7 to 15 percent 3.7 14.6%
slopes
12E Catoctin silt loam,25 to 45 0.8 3.1%
percent slopes
23B Davidson clay loam,2 to 7 1.5 6.0%
percent slopes
71B Rabun clay loam,2 to 7 percent 2.1 8.1%
slopes
71C Rabun clay loam,7 to 15 percent 3.5 13.7%
slopes
71D Rabun clay loam, 15 to 25 4.3 17.0%
percent slopes
72B3 Rabun clay,2 to 7 percent 0.4 1.6%
slopes,severely eroded
72C3 Rabun clay,7 to 15 percent 0.4 1.7%
slopes,severely eroded
72E3 Rabun clay,25 to 45 percent 2.4 9.4%
slopes,severely eroded
79B Starr silt loam,2 to 7 percent 6.3 24.7%
slopes
Totals for Area of Interest 25.4 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the soils
or miscellaneous areas in the survey area.The map unit descriptions, along with the
maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils.On the landscape,
however,the soils are natural phenomena,and they have the characteristic variability
of all natural phenomena. Thus, the range of some observed properties may extend
beyond the limits defined for a taxonomic class.Areas of soils of a single taxonomic
class rarely, if ever, can be mapped without including areas of other taxonomic
classes. Consequently,every map unit is made up of the soils or miscellaneous areas
for which it is named and some minor components that belong to taxonomic classes
other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
10
Custom Soil Resource Report
and behavioral characteristics divergent enough to affect use or to require different
management.These are called contrasting,or dissimilar,components.They generally
are in small areas and could not be mapped separately because of the scale used.
Some small areas of strongly contrasting soils or miscellaneous areas are identified
by a special symbol on the maps. If included in the database for a given area, the
contrasting minor components are identified in the map unit descriptions along with
some characteristics of each. A few areas of minor components may not have been
observed, and consequently they are not mentioned in the descriptions, especially
where the pattern was so complex that it was impractical to make enough observations
to identify all the soils and miscellaneous areas on the landscape.
The presence of minor components in a map unit in no way diminishes the usefulness
or accuracy of the data. The objective of mapping is not to delineate pure taxonomic
classes but rather to separate the landscape into landforms or landform segments that
have similar use and management requirements. The delineation of such segments
on the map provides sufficient information for the development of resource plans. If
intensive use of small areas is planned, however, onsite investigation is needed to
define and locate the soils and miscellaneous areas.
An identifying symbol precedes the map unit name in the map unit descriptions. Each
description includes general facts about the unit and gives important soil properties
and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major horizons
that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity,
degree of erosion, and other characteristics that affect their use. On the basis of such
differences, a soil series is divided into soil phases. Most of the areas shown on the
detailed soil maps are phases of soil series. The name of a soil phase commonly
indicates a feature that affects use or management. For example, Alpha silt loam, 0
to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.
These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps.The
pattern and proportion of the soils or miscellaneous areas are somewhat similar in all
areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps. Because of present or
anticipated uses of the map units in the survey area, it was not considered practical
or necessary to map the soils or miscellaneous areas separately. The pattern and
relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-
Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areas that
could be mapped individually but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion of
the soils or miscellaneous areas in a mapped area are not uniform. An area can be
made up of only one of the major soils or miscellaneous areas, or it can be made up
of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soil material
and support little or no vegetation. Rock outcrop is an example.
11
Custom Soil Resource Report
Albemarle County, Virginia
12C—Catoctin silt loam, 7 to 15 percent slopes
Map Unit Setting
National map unit symbol: kb7t
Mean annual precipitation: 25 to 65 inches
Mean annual air temperature: 54 to 59 degrees F
Frost-free period: 195 to 231 days
Farmland classification: Not prime farmland
Map Unit Composition
Catoctin and similar soils: 80 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Catoctin
Setting
Landform: Hillslopes
Landform position (two-dimensional): Summit
Landform position (three-dimensional): Interfluve
Down-slope shape: Convex
Across-slope shape: Convex
Parent material: Residuum weathered from greenstone
Typical profile
H1 -0 to 5 inches: silt loam
H2-5 to 18 inches: very channery silt loam
H3- 18 to 28 inches: extremely channery silt loam
H4-28 to 79 inches: bedrock
Properties and qualities
Slope: 7 to 15 percent
Depth to restrictive feature: 20 to 40 inches to lithic bedrock
Natural drainage class: Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water(Ksat): Very low to high (0.00
to 5.95 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Low(about 3.4 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification(nonirrigated): 3e
Hydrologic Soil Group: B
12
Custom Soil Resource Report
12E—Catoctin silt loam, 25 to 45 percent slopes
Map Unit Setting
National map unit symbol: kb7w
Mean annual precipitation: 25 to 65 inches
Mean annual air temperature: 54 to 59 degrees F
Frost-free period: 195 to 231 days
Farmland classification: Not prime farmland
Map Unit Composition
Catoctin and similar soils: 75 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Catoctin
Setting
Landform: Hillslopes
Landform position (two-dimensional): Summit
Landform position (three-dimensional): Interfluve
Down-slope shape: Convex
Across-slope shape: Convex
Parent material: Residuum weathered from greenstone
Typical profile
H1 -0 to 5 inches: silt loam
H2-5 to 18 inches: very channery silt loam
H3- 18 to 28 inches: extremely channery silt loam
H4-28 to 79 inches: bedrock
Properties and qualities
Slope: 25 to 45 percent
Depth to restrictive feature: 20 to 40 inches to lithic bedrock
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water(Ksat): Very low to high (0.00
to 5.95 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Low(about 3.4 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification(nonirrigated): 7e
Hydrologic Soil Group: B
13
Custom Soil Resource Report
23B—Davidson clay loam, 2 to 7 percent slopes
Map Unit Setting
National map unit symbol: kb8p
Mean annual precipitation: 25 to 65 inches
Mean annual air temperature: 54 to 59 degrees F
Frost-free period: 195 to 231 days
Farmland classification: All areas are prime farmland
Map Unit Composition
Davidson and similar soils: 80 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Davidson
Setting
Landform: Hillslopes
Landform position (two-dimensional): Summit
Landform position (three-dimensional): Interfluve
Down-slope shape: Convex
Across-slope shape: Convex
Parent material: Residuum weathered from greenstone
Typical profile
H1 -0 to 4 inches: clay loam
H2-4 to 10 inches: clay loam
H3- 10 to 63 inches: clay
H4- 63 to 88 inches: clay loam
Properties and qualities
Slope: 2 to 7 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water(Ksat): Moderately high to high
(0.57 to 1.98 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Moderate (about 8.6 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: B
14
Custom Soil Resource Report
71B—Rabun clay loam, 2 to 7 percent slopes
Map Unit Setting
National map unit symbol: kbdp
Mean annual precipitation: 25 to 65 inches
Mean annual air temperature: 54 to 59 degrees F
Frost-free period: 195 to 231 days
Farmland classification: All areas are prime farmland
Map Unit Composition
Rabun and similar soils: 80 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Rabun
Setting
Landform: Interfluves
Landform position (two-dimensional): Summit
Landform position (three-dimensional): Interfuve
Down-slope shape: Convex
Across-slope shape: Convex
Parent material: Residuum weathered from greenstone
Typical profile
H1 -0 to 6 inches: clay loam
H2- 6 to 48 inches: clay
H3-48 to 79 inches: silty clay loam
Properties and qualities
Slope: 2 to 7 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water(Ksat): Moderately high to high
(0.57 to 1.98 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Moderate (about 8.7 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification (nonirrigated): 2e
Hydrologic Soil Group: B
15
Custom Soil Resource Report
71C—Rabun clay loam, 7 to 15 percent slopes
Map Unit Setting
National map unit symbol: kbdq
Mean annual precipitation: 25 to 65 inches
Mean annual air temperature: 54 to 59 degrees F
Frost-free period: 195 to 231 days
Farmland classification: Not prime farmland
Map Unit Composition
Rabun and similar soils: 80 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Rabun
Setting
Landform: Interfluves
Landform position (two-dimensional): Backslope
Landform position (three-dimensional): Interfluve
Down-slope shape: Convex
Across-s lope shape: Convex
Parent material: Residuum weathered from greenstone
Typical profile
H1 -0 to 6 inches: clay loam
H2- 6 to 48 inches: clay
H3-48 to 79 inches: silty clay loam
Properties and qualities
Slope: 7 to 15 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water(Ksat): Moderately high to high
(0.57 to 1.98 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Moderate (about 8.7 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification(nonirrigated): 6e
Hydrologic Soil Group: B
16
Custom Soil Resource Report
71D—Rabun clay loam, 15 to 25 percent slopes
Map Unit Setting
National map unit symbol: kbdr
Mean annual precipitation: 25 to 65 inches
Mean annual air temperature: 54 to 59 degrees F
Frost-free period: 195 to 231 days
Farmland classification: Not prime farmland
Map Unit Composition
Rabun and similar soils: 75 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Rabun
Setting
Landform: Interfluves
Landform position (two-dimensional): Backslope
Landform position (three-dimensional): Side slope
Down-slope shape: Linear
Across-slope shape: Convex
Parent material: Residuum weathered from greenstone
Typical profile
H1 -0 to 6 inches: clay loam
H2- 6 to 48 inches: clay
H3-48 to 79 inches: silty clay loam
Properties and qualities
Slope: 15 to 25 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: High
Capacity of the most limiting layer to transmit water(Ksat): Moderately high to high
(0.57 to 1.98 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Moderate (about 8.7 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: B
17
Custom Soil Resource Report
72B3—Rabun clay, 2 to 7 percent slopes, severely eroded
Map Unit Setting
National map unit symbol: kbdt
Mean annual precipitation: 25 to 65 inches
Mean annual air temperature: 54 to 59 degrees F
Frost-free period: 195 to 231 days
Farmland classification: Not prime farmland
Map Unit Composition
Rabun and similar soils: 80 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Rabun
Setting
Landform: Interfluves
Landform position (two-dimensional): Summit
Landform position (three-dimensional): Nose slope
Down-slope shape: Convex
Across-slope shape: Convex
Parent material: Residuum weathered from greenstone
Typical profile
H1 -0 to 4 inches: clay
H2-4 to 48 inches: clay
H3-48 to 79 inches: silty clay loam
Properties and qualities
Slope: 2 to 7 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water(Ksat): Moderately high to high
(0.57 to 1.98 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Moderate (about 8.7 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: B
18
Custom Soil Resource Report
72C3—Rabun clay, 7 to 15 percent slopes, severely eroded
Map Unit Setting
National map unit symbol: kbdv
Mean annual precipitation: 25 to 65 inches
Mean annual air temperature: 54 to 59 degrees F
Frost-free period: 195 to 231 days
Farmland classification: Not prime farmland
Map Unit Composition
Rabun and similar soils: 80 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Rabun
Setting
Landform: Interfluves
Landform position (two-dimensional): Shoulder
Landform position (three-dimensional): Side slope
Down-slope shape: Convex
Across-slope shape: Convex
Parent material: Residuum weathered from greenstone
Typical profile
H1 -0 to 4 inches: clay
H2-4 to 48 inches: clay
H3-48 to 79 inches: silty clay loam
Properties and qualities
Slope: 7 to 15 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water(Ksat): Moderately high to high
(0.57 to 1.98 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Moderate (about 8.7 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification (nonirrigated): 4e
Hydrologic Soil Group: B
19
Custom Soil Resource Report
72E3—Rabun clay, 25 to 45 percent slopes, severely eroded
Map Unit Setting
National map unit symbol: kbdx
Mean annual precipitation: 25 to 65 inches
Mean annual air temperature: 54 to 59 degrees F
Frost-free period: 195 to 231 days
Farmland classification: Not prime farmland
Map Unit Composition
Rabun and similar soils: 80 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Rabun
Setting
Landform: Interfluves
Landform position (two-dimensional): Backslope
Landform position (three-dimensional): Side slope
Down-slope shape: Linear
Across-slope shape: Convex
Parent material: Residuum weathered from greenstone
Typical profile
H1 -0 to 4 inches: clay
H2-4 to 48 inches: clay
H3-48 to 79 inches: silty clay loam
Properties and qualities
Slope: 25 to 45 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: High
Capacity of the most limiting layer to transmit water(Ksat): Moderately high to high
(0.57 to 1.98 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Moderate (about 8.7 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 7e
Hydrologic Soil Group: B
20
Custom Soil Resource Report
79B—Starr silt loam, 2 to 7 percent slopes
Map Unit Setting
National map unit symbol: kbf9
Mean annual precipitation: 25 to 65 inches
Mean annual air temperature: 54 to 59 degrees F
Frost-free period: 195 to 231 days
Farmland classification: All areas are prime farmland
Map Unit Composition
Starr and similar soils: 80 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Starr
Setting
Landform: Drainageways
Landform position (two-dimensional): Footslope
Landform position (three-dimensional): Head slope
Down-slope shape: Concave
Across-slope shape: Convex
Parent material: Colluvium derived from igneous rock
Typical profile
H1 -0 to 18 inches: silt loam
H2- 18 to 53 inches: silty clay loam
H3-53 to 79 inches: gravelly clay loam
Properties and qualities
Slope: 2 to 7 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water(Ksat): Moderately high to high
(0.57 to 1.98 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: Occasional
Frequency of ponding: None
Available water storage in profile: High (about 9.4 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification (nonirrigated): 2e
Hydrologic Soil Group: B
21
References
American Association of State Highway and Transportation Officials(AASHTO).2004.
Standard specifications for transportation materials and methods of sampling and
testing. 24th edition.
American Society for Testing and Materials(ASTM). 2005. Standard classification of
soils for engineering purposes.ASTM Standard D2487-00.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of
wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service
FWS/OBS-79/31.
Federal Register. July 13, 1994. Changes in hydric soils of the United States.
Federal Register. September 18, 2002. Hydric soils of the United States.
Hurt,G.W.,and L.M.Vasilas,editors.Version 6.0,2006.Field indicators of hydric soils
in the United States.
National Research Council. 1995. Wetlands: Characteristics and boundaries.
Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S.
Department of Agriculture Handbook 18. http://www.nres.usda.gov/wps/portal/nres/
detai l/national/soils/?cid=nres 142p2_054262
Soil Survey Staff. 1999.Soil taxonomy:A basic system of soil classification for making
and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service,
U.S. Department of Agriculture Handbook 436. http://www.nres.usda.gov/wps/portal/
nres/detail/national/soils/?cid=nres142p2_053577
Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of
Agriculture, Natural Resources Conservation Service. http://www.nrcs.usda.gov/wps/
portal/nres/detail/national/soils/?cid=nres142p2_053580
Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and
Delaware Department of Natural Resources and Environmental Control, Wetlands
Section.
United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of
Engineers wetlands delineation manual. Waterways Experiment Station Technical
Report Y-87-1.
United States Department of Agriculture, Natural Resources Conservation Service.
National forestry manual. http://www.nres.usda.gov/wps/portal/nres/detail/soils/
home/?cid=nres142p2_053374
United States Department of Agriculture, Natural Resources Conservation Service.
National range and pasture handbook. http://www.nres.usda.gov/wps/portal/nres/
detail/national/landuse/rangepasture/?cid=stelprdb1043084
22
Custom Soil Resource Report
United States Department of Agriculture, Natural Resources Conservation Service.
National soil survey handbook, title 430-VI. http://www.nres.usda.gov/wps/portal/
nres/detail/soils/scientists/?ci d=nres 142 p2_054242
United States Department of Agriculture, Natural Resources Conservation Service.
2006. Land resource regions and major land resource areas of the United States,the
Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.
http//www.nres.usda.gov/wps/portal/nres/detail/national/soils/?
cid=nres142p2_053624
United States Department of Agriculture, Soil Conservation Service. 1961. Land
capability classification. U.S. Department of Agriculture Handbook 210. http://
www.nres.usda.gov/Internet/FSE_DOCUMENTS/nres142p2_052290.pdf
23
3 .
CASCADIA SUBDIVISION
HYDROLOGIC/HYDRAULIC CALCULATIONS FOR
CASCADIA SUBDIVISION — BLOCKS 1-3
December 1, 2014
Revised: June 10, 2015
LOCATION:
Tax Map 62, Parcel 25
Tax Map 78, Parcels 59 & 59A
Tax Map 78E, Parcel H1
Rio District, Albemarle County, Virginia
DEVELOPER:
Cascadia Development, LLC. T
170 South Pantops Drive �`�
Charlottesville, Virginia 22903
i —i/,q►�4. -
� •
1T ��add` RS •
PREPARED BY: • Ac.No.33028
Dominion Engineering & Design, LLC ■ _ _
172 South Pantops Drive . �'�D�j )Q / .-
Charlottesville, VA 22911 h'
P: 434.979.8121SSIONALCC'
F: 434.979.1681
INDEX
Summary: 2-7
Unit Hydrographs 8-9
Pre-Development:
Hydrographs: DA-Pond 2 10-12
Post-Development - Pond-2:
Hydrographs: DA-Pond 2 13-17
Water Quality Volume Report: 18
SWM-2 & Outlet Structure: 19-24
Routed Hydrographs: 25-29
APPROVED
by the Albemarle County
Community D v opment Department
Date '7- /v t 5
File W f p od 4—m/
CASCADIA SUBDIVISION
*Drainage Area Maps are included on Storm Water Management Plan
Run-Off Summary
Pond 2
Proposed Pond 2 is an approved wet pond facility with an aquatic bench that will provide stormwater quality
and detention. Pond 2 was designed for full build out of future Town District phase with an estimated
300,000 sf, of impervious area. The proposed design for the Town District, blocks 1-3, has a total
impervious cover of 408,897 sf. The estimated overall drainage area for pond 2 has also increased slightly
from 45.54 acres to 46.90 acres. Please refer to the following calculations which will demonstrate that the
pond design as approved will accommodate the additional impervious cover and drainage area
Because it has been determined that there are inadequate channels downstream, the allowable release rate
is determined per Albemarle County Design Standards Manual, Section F, lowering the allowable release
rate to a fraction of the pre-forested conditions run-off determined by the calculation below:
Q(allowable) <= Qf(Vf/VPost), where Qf is flow from the site in a well forested condition (Cn=51), Vf is
volume from the site in a well forested condition, and VPost is volume from the site in post-development
conditions.
In addition to meeting the above release rate requirements, the following conditions will also be met:
1. Detain the WQV(1" Runoff) and release over 48 hours.
2 Detain the 1 year 24-hour storm and release over 24 hours.
2
CASCADIA SUBDIVISION
Pre-Development Conditions:
1.5 Yr. Pre-Development Run-Off(Cn=51) = DA-A= 3.16 cfs
1.5 Yr Pre-Development Run-Off Volume = 42,253 Sq. Ft.
2 Yr, Pre-Development Run-Off(Cn=51) = DA-A= 3.83 cfs
2 Yr. Pre-Development Run-Off Volume =47,045 Sq. Ft.
10 Yr. Pre-Development Run-Off(Cn=51) = DA-A= 27.83 cfs
10 Yr, Pre-Development Run-Off Volume = 172,498 Sq. Ft.
Post-Development Conditions:
1.5 Yr. Post-Development Run-Off Volume = DA-X = 249,163 Sq. Ft.
2 Yr. Post-Development Run-Off Volume = DA-X = 261,796 Sq. Ft.
10 Yr. Post-Development Run-Off Volume = DA-X = 518,800 Sq. Ft.
Allowable Release Rate:
Q1.5 (allowable) = 3 16(42,253/256,568) = 0.520 cfs
Q2 (allowable) = 3 83(47,045/269.636) = 0.668 cfs
Q10 (allowable) = 27.83(172,498 /534,481) = 8.982 cfs
Post-Development Release Rate Summary:
Q1.5 Post-Development Routed = 0.48 cfs < 0.520 cfs
Q2 Post-Development Routed = 0.52 cfs < 0.668 cfs
Q10 Post-Development Routed = 8.83 cfs < 8.982 cfs
3
CASCADIA SUBDIVISION
Detention of the WQV(1" Runoff) and release over 48 hours:
WQV= 35,861 cf.
Average Flow Rate to Achieve 48 Hour Draw Down:
Q = 35,861 cf. / 172,800 sec.
Q = 0.208 cfs
Orifice Size Needed:
A= Q /[64.32 X (h/2)]^1/2 * (0.6)
Average h = 1'; Q = 0.208 cfs
A= 0.0611 sf.
d = 2 (A/3.14)^1/2 = 0.279 ft. => 3.348 In.
Orifice provided = 3.0 in. < 3.348 in.
Detention of the 1 year 24-hour storm and release over 24 hours:
1 year 24-hour storm volume = 231,303.6 cf (see hydrograph below)
Average Flow Rate to Achieve 24 Hour Draw Down:
Q = 231,303.6 cf. /86,400 sec.
Q = 2.677 cfs
Routed Flow for 1-year 24-hour storm = 0.45 cfs maximum < 2.677 cfs.
SIbra
0111T wcoe,
( Please Refer Calculations on following Pages )
4
CASCADIA SUBDIVISION
Soils Analysis:
DA-X& DA-A Soil Map
Custom Soil Resource Report
Soil Map
b
n
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11.
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a
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8.
13 Map Scale.1 a 510 N pined an A sa;a°'z 11'■sheer
N Me ers
0 200 200 3CC
Fea:
C 250 KC 1.2CC 1.
5
CASCADIA SUBDIVISION
Map Unit Legend
Albemarle County,Virginia(VA003)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
12C Catoctin silt loam,7 to 15 percent slopes 0.9 2.0%
12E Catoctin silt loam,25 to 45 percent 6.2 13.1%
slopes
71B Rabun clay loam,2 to 7 percent slopes 6.5 13.8%
71C Rabun clay loam,7 to 15 percent slopes 9.7 20.6%
71D Rabun clay loam,15 to 25 percent slopes 8.5 18.0%
72B3 Rabun clay,2 to 7 percent slopes, 0.5 1.1%
severely eroded
72C3 Rabun clay,7 to 15 percent slopes, 5.0 10.5%
severely eroded
72D3 Rabun clay, 15 to 25 percent slopes, 3.4 7.3%
severely eroded
72E3 Rabun clay,25 to 45 percent slopes, 2.6 5.5%
severely eroded
79B Starr silt loam,2 to 7 percent slopes 3.8 8.1%
Totals for Area of Interest 47.0 100.0%
Hydrologic Group B Soils: 71B 13.8%
71C 20.6%
71D 18.0%
72B3 1.1%
72C3 10.5%
72D3 7.3%
72E3 5.5%
76.8%
Hydrologic Group C Soils: 12C 2.0%
12E 13.1%
79B 8.1%
23.2%
Weighted Cn Values:
Pavement, Buidling, Patios, Sidewalks: 98
Fair Pasture/Yards: 62
Wooded Area: 57
Gravel: 86
6
CASCADIA SUBDIVISION
Cn Value Calculations:
DA-Pond 2 Pre-Development For 1.5-Year, 2-Year& 10-Year Storm Calculations:
Cn=51 per Albemarle County Design Standards Manual, Section F
DA-Pond 2 Post-Development(46.90 Acres):
From Blocks 4-7;
Houses (Cn=98)—4.270 Acres
Lead Walks/Patios (Cn=98)—0.250 Acre
Roads (Cn=98)—3.400 Acre
Walks (Cn=98) - 0.550 Acre
Neighborhood Center/Amenities (Cn=98)—0.551 Acre
Driveways (Cn=98)— 1.350 Acre
Proposed Yard (Cn=62)—5.893 Acre
Wooded Area (Cn=57)—3.000 Acres
Parks/Utility Strips (Cn=62)— 1.800 Acres
Proposed Blocks 1-3
Buildings (Cn=98)-4.482
Roads/Parking (Cn=98) -2.990 Acres
Sidewalks (Cn=98) - 1.012 Acre
Driveways (Cn=98) - 1.093 Acres
Wooded Area (Cn=57)—2.377 Acres
Grass Areas (Cn=62)— 14.072 Acres
19.948 (98) +21.575(62)+ 5.377(57) = 77.10 => 77
4690
7
CASCADIA SUBDIVISION
Name: DA-Pond 2 - Pre-Forested Condition (Cn=51)
Type: SCS Curvilinear Unit Hydrograph
[UNIT HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 91.85 (cfs)
Time to Peak (Tp) = 23.02 (min)
Time of Base (Tb) = 115.10 (min)
Volume = 3.89 (ac-ft)
Shape Factor = 484 .00
Time Step = 2.00 (min)
Excess Rain = 1.00 (in)
Storm Duration = 4 .59 (min)
Lag Time = 20.72 (min)
[BASIN INFORMATION]
[WEIGHTED WATERSHED AREA]
Description Area CN
Overall Approximation 46. 60 51
[TIME CONCENTRATION -- TR-55]
SHEET FLOW
Manning's Roughness Coef. (n) = 0.40
2-yr 24-hr Rainfall (R) = 3.70 (in)
Flow Length (L) = 300.00 (ft)
Land Slope (S) = 0.15 (ft/ft)
Travel Time of Sheet Flow = 21.48 (min)
SHALLOW FLOW
K_Coefficient (K) = 0.35
Flow Length (L) = 835.00 (ft)
Watercourse Slope (S) = 0.22 (ft/ft)
Travel Time of Shallow Flow = 8.48 (min)
Velocity (V) = 1. 64 (ft/s)
CHANNEL FLOW
Hydraulic Radius (R) = 0.26 (ft)
Manning's Roughness Coef. (n) = 0.03
Flow Length (L) = 1570.00 (ft)
Channel Slope (S) = 0.08 (ft/ft)
Travel Time of Channel Flow = 4 .57 (min)
[TIME OF CONCENTRATION]
Time of Concentration (Tc) = 34 .53 (min)
8
t
CASCADIA SUBDIVISION
Name: Pond 2 - Post-Development
Type: SCS Curvilinear Unit Hydrograph
[UNIT HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 118.80 (cfs)
Time to Peak (Tp) = 17.91 (min)
Time of Base (Tb) = 89.56 (min)
Volume = 3. 92 (ac-ft)
Shape Factor = 484.00
Time Step = 2.00 (min)
Excess Rain = 1.00 (in)
Storm Duration = 3.57 (min)
Lag Time = 16.12 (min)
[BASIN INFORMATION]
)
[WEIGHTED WATERSHED AREA]
Description Area CN
Overall Approximation 46. 90 77
]
[TIME CONCENTRATION -- TR-55]
SHEET FLOW
Manning's Roughness Coef. (n) = 0.40
2-yr 24-hr Rainfall (R) = 3.70 (in)
Flow Length (L) = 300.00 (ft)
Land Slope (S) = 0.19 (ft/ft)
Travel Time of Sheet Flow = 19.54 (min)
SHALLOW FLOW
K_Coefficient (K) = 0.35
Flow Length (L) = 430.00 (ft)
Watercourse Slope (S) = 0.20 (ft/ft)
Travel Time of Shallow Flow = 4.58 (min)
Velocity (V) = 1.57 (ft/s)
CHANNEL FLOW
Hydraulic Radius (R) = 0.27 (ft)
Manning's Roughness Coef. (n) = 0.01
Flow Length (L) = 1765.00 (ft)
Channel Slope (S) = 0.05 (ft/ft)
Travel Time of Channel Flow = 2.75 (min)
[TIME OF CONCENTRATION]
Time of Concentration (Tc) = 26.87 (min)
9
CASCADIA SUBDIVISION
Name: DA-Pond 2 Pre-Forested 1.5-Year (Cn=51)
Type: Computed Flood
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 3.16 (cfs)
Time to Peak (Tp) = 746.00 (min)
Time of Base (Tb) = 1552.59 (min)
Volume = 0. 97 (ac-ft)
Time Step = 2.00 (min)
Flow Multiplier = 1.00
[UNIT HYDROGRAPH INFORMATION]
Number = 3
Type = SCS Curvilinear
Peak Flow (Qp) = 91.85 (cfs)
Time to Peak (Tp) = 23.02 (min)
Time of Base (Tb) = 115. 10 (min)
Volume = 3.89 (ac-ft)
Shape Factor = 484 .00
Time Step: = 2.00 (min)
Excess Rain = 1.00 (in)
Lag Time = 20.72 (min)
[BASIN INFORMATION]
[WEIGHTED WATERSHED AREA]
Description Area CN
Overall Approximation 46. 60 51
[TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc) = 34 .53 (min)
[RAINFALL DESCRIPTION]
Distribution Type = SCS II
Total Precipitation = 3. 60 (in)
Return Period = 1.5 (yr)
Storm Duration = 24.00 (hr)
10
]
' r CASCADIA SUBDIVISION
Name: DA-Pond 2 Pre-Forested 2-Year (Cn=51)
Type: Computed Flood
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 3.83 (cfs)
Time to Peak (Tp) = 746.00 (min)
Time of Base (Tb) = 1552.59 (min)
Volume = 1.08 (ac-ft)
Time Step = 2.00 (min)
Flow Multiplier = 1.00
(
[UNIT HYDROGRAPH INFORMATION]
1 Number = 3
Type = SCS Curvilinear
Peak Flow (Qp) = 91.85 (cfs)
Time to Peak (Tp) = 23.02 (min)
Time of Base (Tb) = 115.10 (min)
Volume = 3.89 (ac-ft)
Shape Factor = 484.00
Time Step: = 2.00 (min)
Excess Rain = 1.00 (in)
Lag Time = 20.72 (min)
[BASIN INFORMATION]
[WEIGHTED WATERSHED AREA]
Description Area CN
i
Overall Approximation 46. 60 51
[TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc) = 34.53 (min)
[RAINFALL DESCRIPTION]
Distribution Type = SCS II
Total Precipitation = 3.70 (in)
Return Period = 2 (yr)
Storm Duration = 24.00 (hr)
)
11
CASCADIA SUBDIVISION
Name: DA-Pond 2 Pre-Forested 10-Year (Cn=51)
Type: Computed Flood
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 27.83 (cfs)
Time to Peak (Tp) = 738.00 (min)
Time of Base (Tb) = 1552.59 (min)
Volume = 3.96 (ac-ft)
Time Step = 2.00 (min)
Flow Multiplier = 1.00
[UNIT HYDROGRAPH INFORMATION]
Number = 3
Type = SCS Curvilinear
Peak Flow (Qp) = 91.85 (cfs)
Time to Peak (Tp) = 23.02 (min)
Time of Base (Tb) = 115.10 (min)
Volume = 3.89 (ac-ft)
Shape Factor = 484.00
Time Step: = 2.00 (min)
Excess Rain = 1.00 (in)
Lag Time = 20.72 (min)
[BASIN INFORMATION]
[WEIGHTED WATERSHED AREA]
Description Area CN
Overall Approximation 46. 60 51
[TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc) = 34 .53 (min)
[RAINFALL DESCRIPTION]
Distribution Type = SCS II
Total Precipitation = 5.60 (in)
Return Period = 10 (yr)
Storm Duration = 24.00 (hr)
12
CASCADIA SUBDIVISION
Name: DA-Pond 2 Post-Development 1-Year
Type: Computed Flood
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 57.41 (cfs)
Time to Peak (Tp) = 730.00 (min)
Time of Base (Tb) = 1526.16 (min)
Volume = 5.31 (ac-ft)
Time Step = 2.00 (min)
Flow Multiplier = 1.00
[UNIT HYDROGRAPH INFORMATION]
Number = 1
Type = SCS Curvilinear
Peak Flow (Qp) = 118.80 (cfs)
Time to Peak (Tp) = 17. 91 (min)
Time of Base (Tb) = 89.56 (min)
Volume = 3.92 (ac-ft)
Shape Factor = 484.00
Time Step: = 2.00 (min)
Excess Rain = 1.00 (in)
Lag Time = 16.12 (min)
[BASIN INFORMATION]
[WEIGHTED WATERSHED AREA]
Description Area CN
Overall Approximation 46. 90 77
[TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc) = 26.87 (min)
[RAINFALL DESCRIPTION]
Distribution Type = SCS II
Total Precipitation = 3.40 (in)
Return Period = 1 (yr)
Storm Duration = 24.00 (hr)
13
K CASCADIA SUBDIVISION
Name: DA-Pond 2 Post-Development 1.5-Year
Type: Computed Flood
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 64.07 (cfs)
Time to Peak (Tp) = 730.00 (min)
Time of Base (Tb) = 1526.16 (min)
Volume = 5.89 (ac-ft)
Time Step = 2.00 (min)
Flow Multiplier = 1.00
[UNIT HYDROGRAPH INFORMATION]
Number = 1
Type = SCS Curvilinear
Peak Flow (Qp) = 118.80 (cfs)
Time to Peak (Tp) = 17. 91 (min)
Time of Base (Tb) = 89.56 (min)
Volume = 3.92 (ac-ft)
Shape Factor = 484.00
Time Step: = 2.00 (min)
Excess Rain = 1.00 (in)
Lag Time = 16.12 (min)
[BASIN INFORMATION]
[WEIGHTED WATERSHED AREA]
Description Area CN
Overall Approximation 46. 90 77
[TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc) = 26.87 (min)
[RAINFALL DESCRIPTION]
Distribution Type = SCS II
Total Precipitation = 3.60 (in)
Return Period = 1.5 (yr)
Storm Duration = 24.00 (hr)
14
r CASCADIA SUBDIVISION
Name: DA-Pond 2 Post-Development 2-Year
Type: Computed Flood
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 67.45 (cfs)
Time to Peak (Tp) = 730.00 (min)
Time of Base (Tb) = 1526.16 (min)
Volume = 6.19 (ac-ft)
Time Step = 2.00 (min)
Flow Multiplier = 1.00
[UNIT HYDROGRAPH INFORMATION]
Number = 1
Type = SCS Curvilinear
Peak Flow (Qp) = 118.80 (cfs)
Time to Peak (Tp) = 17.91 (min)
Time of Base (Tb) = 89.56 (min)
Volume = 3.92 (ac-ft)
Shape Factor = 484.00
Time Step: = 2.00 (min)
Excess Rain = 1.00 (in)
Lag Time = 16.12 (min)
[BASIN INFORMATION]
[WEIGHTED WATERSHED AREA]
Description Area CN
Overall Approximation 46. 90 77
[TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc) = 26.87 (min)
[RAINFALL DESCRIPTION]
1 Distribution Type SCS II
Total Precipitation = 3.70 (in)
Return Period 2 (yr)
< Storm Duration = 24.00 (hr)
1
x
I
k
:
15
1
CASCADIA SUBDIVISION
Name: DA-Pond 2 Post-Development 10-Year
Type: Computed Flood
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 136.37 (cfs)
Time to Peak (Tp) = 728.00 (min)
Time of Base (Tb) = 1526.16 (min)
Volume = 12.27 (ac-ft)
Time Step = 2.00 (min)
Flow Multiplier = 1.00
[UNIT HYDROGRAPH INFORMATION]
Number = 1
Type = SCS Curvilinear
Peak Flow (Qp) = 118.80 (cfs)
Time to Peak (Tp) = 17. 91 (min)
Time of Base (Tb) = 89.56 (min)
Volume = 3.92 (ac-ft)
Shape Factor = 484.00
Time Step: = 2.00 (min)
Excess Rain = 1.00 (in)
Lag Time = 16.12 (min)
[BASIN INFORMATION]
[WEIGHTED WATERSHED AREA]
Description Area CN
Overall Approximation 46. 90 77
[TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc) = 26.87 (min)
[RAINFALL DESCRIPTION]
Distribution Type = SCS II
Total Precipitation = 5.60 (in)
Return Period = 10 (yr)
Storm Duration = 24.00 (hr)
16
E CASCADIA SUBDIVISION
Name: DA-Pond 2 Post-Development 100-Year
Type: Computed Flood
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 272.55 (cfs)
Time to Peak (Tp) = 728.00 (min)
Time of Base (Tb) = 1526.16 (min)
Volume = 24 . 64 (ac-ft)
Time Step = 2.00 (min)
Flow Multiplier = 1.00
[UNIT HYDROGRAPH INFORMATION]
Number = 1
Type = SCS Curvilinear
Peak Flow (Qp) = 118.80 (cfs)
Time to Peak (Tp) = 17. 91 (min)
Time of Base (Tb) = 89.56 (min)
Volume = 3. 92 (ac-ft)
Shape Factor = 484.00
Time Step: = 2.00 (min)
Excess Rain = 1.00 (in)
Lag Time = 16.12 (min)
[BASIN INFORMATION]
[WEIGHTED WATERSHED AREA]
Description Area CN
Overall Approximation 46. 90 77
[TIME CONCENTRATION -- User Defined]
Time of Concentration (Tc) = 26.87 (min)
[RAINFALL DESCRIPTION]
Distribution Type = SCS II
Total Precipitation = 9.10 (in)
Return Period = 100 (yr)
Storm Duration = 24.00 (hr)
17
CASCADIA SUBDIVISION
RESERVOIR REPORT
Name: Pond 2 (Retention Basin w/Aquatic Bench) ( WATER QUALITY VOLUME REPORT )
Name: Pond 2 - Storage
[RATING CURVE LIMIT]
Minimum Elevation = 345.00 (ft)
Maximum Elevation = 358.00 (ft)
Elevation Increment = 0.20 (ft)
[STAGE STORAGE INFORMATION]
Storage Method: User-Defined Storage
Input Method: Area
Number Elevation Area Ave Area Volume Cumulative
Volume
(ft) (sq ft) (sq ft) (cu ft) (cu ft)
1 344 . 99 0.00 0.00 0.00 0.00
2 345.00 28234.00 14117.00 141.17 141.17
3 346.00 30604.00 29419.00 29419.00 29560.17
4 348.00 35380.00 32992.00 65984.00 95544.17
5 348.50 39242.00 37311.00 18655.50 114199. 67
6 350.00 50655.00 44948.50 67422.75 181622.42
7 352.00 56835.00 53745.00 107490.00 289112.42
8 354.00 60195.00 58515.00 117030.00 406142.42
9 356.00 64854 .00 62524.50 125049.00 531191.42
10 358.00 69602.00 67228.00 134456.00 665647.42
11 358.33 76850.00 73226.00 24164 .58 689812.00
Quality Volume Required = 4X(WQ Volume) For 65% Removal Efficiency
WQ Volume = (1/2in) /12 X impervious area (Sq. Ft. )
(4) (1/2in) /12 X 451, 761 Sq. Ft. + 408,897 Sq Ft. (Proposed Blocks 1-3)
= 143,443 Cu. Ft.
Provided Water Quality Volume (Elev.=351) = 181,622.42 cu. Ft.
Pool Depth Zones:
Depth Zone Elevation Surface Area Percentage of Wet Storage Area
0' - 1.5' 350.00 - 348.50 11,413 sf. 22.5%
1.5' - 2' 348.50 - 348.00 3,862 sf. 7.6%
2' - 6' 348.00 - 345.00 35,380 sf. 69.9%
(Please Refer to approved Stormwater Management plan for Cascadia Blocks 4-7
for additional pool depth zone calculations)
18
4 , . r CASCADIA SUBDIVISION
RESERVOIR REPORT
Reservoir Number: 2
Name: Pond 2
[RATING CURVE LIMIT]
Minimum Elevation = 344.50 (ft)
Maximum Elevation = 358.33 (ft)
Elevation Increment = 0.20 (ft)
[STAGE STORAGE INFORMATION]
Storage Method: User-Defined Storage
Input Method: Area
Number Elevation Area Ave Area Volume Cumulative
Volume
(ft) (sq ft) (sq ft) (cu ft) (cu ft)
1 349. 99 0.00 0.00 0.00 0.00
2 350.00 50655.00 25327.50 253.27 253.27
3 352.00 56835.00 53745.00 107490.00 107743.27
4 354.00 60195.00 58515.00 117030.00 224773.27
5 356.00 64854.00 62524.50 125049.00 349822.27
6 358.00 69602.00 67228.00 134456.00 484278.27
7 358.33 71427.00 70514.50 23269.78 507548.06
[RESERVOIR STAGE STORAGE/DISCHARGE]
Elevation Stage Area Storage Discharge
(ft) (ft) (sq ft) (cu ft) (cfs)
349. 90 5.40 0.00 0.00 0.00
350.10 5.60 50964.00 5096.40 0.02
350.30 5.80 51582.00 15351.00 0.10
350.50 6.00 52200.00 25729.20 0.14
350.70 6.20 52818.00 36231.00 0.18
350. 90 6.40 53436.00 46856.40 0.21
351.10 6. 60 54054.00 57605.40 0.23
351.30 6.80 54672.00 68478.00 0.26
351.50 7.00 55290.00 79474 .20 0.28
351.70 7.20 55908.00 90594.00 0.30
351. 90 7.40 56526.00 101837.40 0.31
352.10 7.60 57003.00 113190.30 0.33
352.30 7.80 57339.00 124624 .50 0.35
352.50 8.00 57675.00 136125.90 0.36
352.70 8.20 58011.00 147694.50 0.38
352.90 8.40 58347.00 159330.30 0.39
353.10 8.60 58683.00 171033.30 0.41
353.30 8.80 59019.00 182803.50 0.42
353.50 9.00 59355.00 194640.90 0.43
353.70 9.20 59691.00 206545.50 0.45
353.90 9.40 60027.00 218517.30 0.46
354.10 9.60 60427. 95 230562.79 0.47
354.30 9.80 60893.85 242694. 97 0.48
354.50 10.00 61359.75 254920.33 0.55
19
f , A CASCADIA SUBDIVISION
354.70 10.20 61825. 65 267238.87 0.96
354. 90 10.40 62291.55 279650.59 1.46
355.10 10.60 62757.45 292155.49 1.79
)
355.30 10.80 63223.35 304753.57 2.06
355.50 11.00 63689.25 317444.83 2.29
355.70 11.20 64155.15 330229.27 2.49
355.90 11.40 64621.05 343106.89 7.36
356.10 11. 60 65091.40 356078.14 16.09
356.30 11.80 65566.20 369143.90 32.33
356.50 12.00 66041.00 382304 .62 55.40
356.70 12.20 66515.80 395560.30 84.03
356.90 12.40 66990. 60 408910.94 117.83
357.10 12.60 67465.40 422356.54 142.00
357.30 12.80 67940.20 435897.10 167.11
357.50 13.00 68415.00 449532.62 195.83
357.70 13.20 68889.80 463263.10 228.22
357. 90 13.40 69364.60 477088.54 264.35
358.10 13. 60 70155.03 491040.50 304.30
358.30 13.80 71261.09 505182.12 348.14
Maximum Storage = 507322.44 (cu ft)
Maximum Discharge = 355.06 (cfs)
)
}
20
CASCADIA SUBDIVISION
OUTLET STRUCTURE REPORT
Structure Number : 1
Type : Stand Pipe
Name : STAND PIPE
[RATING CURVE LIMIT]
Minimum Elevation = 344.50 (ft)
Maximum Elevation = 358.33 (ft)
Elevation Increment = 0.20 (ft)
[STAND PIPE INFORMATION]
[ORIFICE INFORMATION]
Diameter = 5.00 (ft)
Crest Length = 15.71 (ft)
Effective Crest Length = 15.71 (ft)
Orifice Coefficient = 0.60
Fractional Open Area = 1.00
[ORIFICE EQUATION]
Q = Co*A( (2gh) /k) ^0.5
[DEFINITIONS]
Co = Orifice Coefficient
A = Wetted Area, (sq ft)
[WEIR INFORMATION]
Crest Elevation = 355.70 (ft)
Weir Coefficient = 3.33
Exponential = 1.50
[WEIR EQUATION]
Q = Cw * L * H^exp
1 [DEFINITIONS]
Cw = Weir Coefficient
H = Headwater depth above inlet control section invert ft
L = Crest lenght ft
1
[OPTIONAL ORIFICE INFORMATION]
Type : Circular Orifice
[OPTIONAL ORIFICE INFORMATION]
Diameter = 0.25 (ft)
Invert Elevation = 350.00 (ft)
Orifice Coefficient = 0. 60
Number of Openings = 1
[ORIFICE EQUATION]
Q = Co*A( (2gh) /k) ^0.5
]
21
CASCADIA SUBDIVISION
[DEFINITIONS]
, Co = Orifice Coefficient
A = Wetted Area, (cfs)
k = 1
Structure Number : 2
Type : Circular Orifice
[OPTIONAL ORIFICE INFORMATION]
Diameter = 0.50 (ft)
Invert Elevation = 354 . 40 (ft)
Orifice Coefficient = 0. 60
Number of Openings = 2
[ORIFICE EQUATION]
Q = Co*A( (2gh) /k) ^0.5
[DEFINITIONS]
Co = Orifice Coefficient
A = Wetted Area, (cfs)
k = 1
[CULVERT INFORMATION]
Type : Circular Concrete - Square Edge with Headwall
[OUTLET STRUCTURE INFORMATION]
Diameter = 30.00 (in)
Invert Elevation = 346.00 (ft)
Pipe Length = 75.00 (ft)
Slope = 0.02
Manning's n Value = 0.01
Orifice Coefficient = 0.60
Tailwater Elevation = 344.58 (ft)
Number of Barrels = 1
[UNSUBMERGED EQUATION]
H/Diam = Hc/Diam+K* (Q/ (A*Diam^0.5) ) ^M-0.5*S
Coefficient K = 0.01
Coefficient M = 2.00
Q Maximum = 27.16
[SUBMERGED EQUATION]
H/Diam = c* (Q/ (A*Diam^0.5) ) ^2+Y-0.5*S
Coefficient c = 0.04
Coefficient Y = 0. 67
Q Minimum = 31.05
[DEFINITIONS]
H = Headwater depth above inlet control section invert, (ft)
Diam = Interior height of culvert barrel, (ft)
He = Specific head at critical depth (dc+Vc^2/2g) , (ft)
Q = Discharge, (cfs)
A = Full cross sectional area of culvert barrel, (sq ft)
S = Culvert barrel slope, (ft/ft)
22
i . CASCADIA SUBDIVISION
[STAND PIPE STAGE VS. DISCHARGE]
Elevation Stage Weirs Orifices Stand Pipe Culvert Total
(ft) (ft) (cfs) (cfs) (cfs) (cfs) (cfs)
349.90 5.40 0.00 0.00 0.00 36.88 0.00
350. 10 5. 60 0.00 0.02 0.00 38.48 0.02
350.30 5.80 0.00 0. 10 0.00 40.03 0. 10
350.50 6.00 0.00 0.14 0.00 41.51 0.14
350.70 6.20 0.00 0. 18 0.00 42. 95 0. 18
350. 90 6.40 0.00 0.21 0.00 44.33 0.21
351.10 6. 60 0.00 0.23 0.00 45. 68 0.23
351.30 6.80 0.00 0.26 0.00 46. 98 0.26
351.50 7.00 0.00 0.28 0.00 48.26 0.28
351.70 7.20 0.00 0.30 0.00 49.50 0.30
351. 90 7.40 0.00 0.31 0.00 50.70 0.31
352.10 7. 60 0.00 0.33 0.00 51.88 0.33
352.30 7.80 0.00 0.35 0.00 53.04 0.35
352.50 8.00 0.00 0.36 0.00 54 .17 0.36
352.70 8.20 0.00 0.38 0.00 55.27 0.38
352. 90 8.40 0.00 0.39 0.00 56.36 0.39
353.10 8. 60 0.00 0.41 0.00 57.42 0.41
353.30 8.80 0.00 0.42 0.00 58.47 0.42
353.50 9.00 0.00 0.43 0.00 59.49 0.43
353.70 9.20 0.00 0.45 0.00 60.50 0.45
353.90 9.40 0.00 0.46 0.00 61.50 0. 46
354 .10 9.60 0.00 0.47 0.00 62.47 0.47
354 .30 9.80 0.00 0.48 0.00 63.43 0.48
354 .50 10.00 0.00 0.55 0.00 64 .38 0.55
354 .70 10.20 0.21 0. 96 0.00 65.31 0. 96
354 .90 10.40 1.09 1.46 0.00 66.24 1.46
355.10 10.60 2.35 1.79 0.00 67.14 1.79
355.30 10.80 3.90 2.06 0.00 68.04 2.06
355.50 11.00 5. 69 2.29 0.00 68. 92 2.29
355.70 11.20 7. 68 2.49 0.00 69.80 2.49
355. 90 11.40 9.87 2. 68 4. 68 70. 66 7.36
356. 10 11. 60 12.24 2.85 13.23 71.51 16.09
356.30 11.80 14 .76 3.01 24 .31 72.35 27.33
356.50 12.00 17.44 3. 17 37.43 73.18 40. 60
356.70 12.20 20.27 3.31 52.31 74 .01 55. 62
356. 90 12.40 23.23 3.45 68.76 74 .82 72.21
357.10 12. 60 26.33 3.58 86. 65 75.62 75. 62
357.30 12.80 29.55 3.71 101.22 76.42 76.42
357.50 13.00 32.89 3.83 114 .58 77.21 77.21
357.70 13.20 36.35 3. 95 127. 94 77. 99 77. 99
357. 90 13.40 39.93 4 .07 140.17 78.76 78.76
358.10 13. 60 41.75 4 .18 146.40 79.53 79.53
358.30 13.80 0.00 4 .29 152.38 80.28 80.28
358.33 13.83 0.00 4 .30 153.26 80.40 80.40
23
CASCADIA SUBDIVISION
OUTLET STRUCTURE REPORT
Type : Trapezoidal Weir
Name : Weir
[RATING CURVE LIMIT]
Minimum Elevation = 356.00 (ft)
Maximum Elevation = 358.33 (ft)
Elevation Increment = 0. 10 (ft)
[OUTLET STRUCTURE INFORMATION]
Crest Length = 16.00 (ft)
Angle of Walls = 157.0000
Crest Elevation = 356. 10 (ft)
Weir Coefficient = 3.33
Exponential = 1.50
[TRAPEZOIDAL EQUATION]
Q = Cw * ( L + 0.8H * tan ( ang/2.0 ) ) * H^exp
[DEFINITIONS]
Cw = Weir Coefficient
H = Headwater depth above inlet control section invert
L = Crest lenght
ang = Angle of the walls
[MAXIMUM DISCHARGE]
Q = 274 . 67 (cfs)
[WEIR STAGE VS. DISCHARGE]
Elevation (ft) Stage (ft) Discharge (cfs)
356.10 0.10 0.00
356.20 0.20 1.73
356.30 0.30 5.00
356.40 0.40 9.40
356.50 0.50 14.80
356.60 0.60 21.15
356.70 0.70 28.41
356.80 0.80 36.57
356.90 0.90 45.62
357.00 1.00 55.55
357.10 1. 10 66.37
357.20 1.20 78.09
357.30 1.30 90.69
357.40 1.40 104.20
357.50 1.50 118.62
357.60 1.60 133.96
357.70 1.70 150.23
357.80 1.80 167.44
357.90 1.90 185.59
358.00 2.00 204.69
358.10 2.10 224.77
358.20 2.20 245.82
358.30 2.30 267.86
358.33 2.33 274.67
24
• CASCADIA SUBDIVISION
Name: Routing - Pond 2 1-Year
Type: Reservoir: Modified Puls
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 0.45 (cfs)
Time to Peak (Tp) = 1464 .00 (min)
Time of Base (Tb) = 2880.00 (min)
Volume = 1.27 (ac-ft)
Time Step = 2.00 (min)
Peak Elevation = 353.80 (ft)
Detention Time = NA
[RESERVOIR STRUCTURE INFORMATION]
Number = 2
Name = Pond 2
Storage Type = User-Defined Area
Maximum Storage = 507322.44 (cu ft)
Maximum Discharge = 355.06 (cfs)
[INFLOW HYDROGRAPH INFORMATION]
Number = 21
Name = Pond 2 Post 1-Year
Peak Flow (Qp) = 57.41 (cfs)
Time to Peak (Tp) = 730.00 (min)
Time of Base (Tb) = 1526.16 (min)
Volume = 5.31 (ac-ft)
Flow Multiplier = 1.00
25
• t , CASCADIA SUBDIVISION
Name: Routing - Pond 2 1.5-Year
Type: Reservoir: Modified Puls
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 0.48 (cfs)
Time to Peak (Tp) = 1464 .00 (min)
Time of Base (Tb) = 2880.00 (min)
Volume = 1.34 (ac-ft)
Time Step = 2.00 (min)
Peak Elevation = 354.20 (ft)
Detention Time = NA
[RESERVOIR STRUCTURE INFORMATION]
Number = 2
Name = Pond 2
Storage Type = User-Defined Area
Maximum Storage = 507322.44 (cu ft)
Maximum Discharge = 355.06 (cfs)
[INFLOW HYDROGRAPH INFORMATION]
Number = 4
Name = Pond 2 Post 1.5-Year
Peak Flow (Qp) = 64 .07 (cfs)
Time to Peak (Tp) = 730.00 (min)
Time of Base (Tb) = 1526. 16 (min)
Volume = 5.89 (ac-ft)
Flow Multiplier = 1.00
26
1. CASCADIA SUBDIVISION
Name: Routing - Pond 2 2-Year
Type: Reservoir: Modified Puls
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 0.52 (cfs)
Time to Peak (Tp) = 1462.00 (min)
Time of Base (Tb) = 2880.00 (min)
Volume = 1.39 (ac-ft)
Time Step = 2.00 (min)
Peak Elevation = 354.40 (ft)
Detention Time = NA
[RESERVOIR STRUCTURE INFORMATION]
Number = 2
Name = Pond 2
Storage Type = User-Defined Area
Maximum Storage = 507322.44 (cu ft)
Maximum Discharge = 355.06 (cfs)
[INFLOW HYDROGRAPH INFORMATION]
Number = 5
Name = Pond 2 Post 2-Year
Peak Flow (Qp) = 67.45 (cfs)
Time to Peak (Tp) = 730.00 (min)
Time of Base (Tb) = 1526. 16 (min)
Volume = 6.19 (ac-ft)
Flow Multiplier = 1.00
27
I
3 w r I 1 CASCADIA SUBDIVISION
i
Name: Routing - Pond 2 10-Year
Type: Reservoir: Modified Puls
]
3
1 [HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 8.83 (cfs)
Time to Peak (Tp) 836.00 (min)
Time of Base (Tb) = 2880.00 (min)
Volume 6.79 (ac-ft)
Time Step = 2.00 (min)
Peak Elevation = 355.96 (ft)
Detention Time = NA
[RESERVOIR STRUCTURE INFORMATION]
Number = 2
Name = Pond 2
Storage Type = User-Defined Area
Maximum Storage = 507322.44 (cu ft)
Maximum Discharge = 355.06 (cfs)
[INFLOW HYDROGRAPH INFORMATION]
Number = 6
Name = Pond 2 Post 10-Year
Peak Flow (Qp) = 136.37 (cfs)
Time to Peak (Tp) 728.00 (min)
Time of Base (Tb) = 1526.16 (min)
Volume = 12.27 (ac-ft)
Flow Multiplier = 1.00
4
28
I
)
CASCADIA SUBDIVISION
Name: Routing - Pond 2 100-Year
Type: Reservoir: Modified Puls
[HYDROGRAPH INFORMATION]
Peak Flow (Qp) = 168.64 (cfs)
Time to Peak (Tp) = 742.00 (min)
Time of Base (Tb) = 2880.00 (min)
Volume = 19.15 (ac-ft)
Time Step = 2.00 (min)
Peak Elevation = 357.31 (ft)
Detention Time = NA
[RESERVOIR STRUCTURE INFORMATION]
Number = 2
Name = Pond 2
Storage Type = User-Defined Area
Maximum Storage = 507322.44 (cu ft)
Maximum Discharge = 355.06 (cfs)
[INFLOW HYDROGRAPH INFORMATION]
Number = 7
Name = Pond 2 Post 100-Year
Peak Flow (Qp) = 272.55 (cfs)
Time to Peak (Tp) = 728.00 (min)
Time of Base (Tb) = 1526.16 (min)
Volume = 24.64 (ac-ft)
Flow Multiplier = 1.00
1
4.
; ,"741%,1'
29