HomeMy WebLinkAboutWPO201700020 Calculations 2022-04-13FOOTHILL CROSSING II VSMP AMENDMENT #6
STORMWATER MANAGEMENT CALCULATIONS
PACKET
Date of Calculations
February 16, 2022
Revised on
April 12, 2022
Lic. No. 035791
L 4/12/22
COLLINS ENGINEERING
200 GARRETT STREET, SUITE K
CHARLOTTESVILLE, VA 22902
434.293.3719 PH
434.293.2813 FX
www.collins-engineering.com
SCS TR-55 Calculations
(Calculations were updated for proposed DA 2B West and DA 3C in the post -development
condition. The existing, approved DA 2B West pre -development condition is unchanged.)
U.S. Department of Agriculture
Natural Resources Conservation Service
FL-ENG-21A
06/04
TR SS Worksheet 2: Runoff Curve Number and Runoff
Project: Foothill Crossing II VSMP k6 Designed By: KKW, PE Date: 2/10/22
Location: Crozet, VA Checked By: SRC, PE Date: 2/10/22
Check One: Present X Developed X
1. Runoff curve Number (CN)
Drainage Area
Soil name and
Cover description
Area
Product CN
CN(weighted)=
Calculated 'S'
hydrologic group
(Cover type, treatment, and hydrologic condition; percent
CN
total product/
Description
(Acres)
Area
xArea
Value
(Appendix A)
impervious; unconnected/connected impervious area ratio)
total area
B
Impervious Areas
98
0.17
16.7
D.A 42B West
B
Woods in Good Condition
55
5.20
286.0
(Pre -Developed)
B
Lawns in Good Condition (75%+Groundcover)
61
10.46
638.1
As Approved
C
Impervious Areas
98
0.00
0.0
63
5.94
DA=20.92
C
Woods in Good Condition
70
1.14
79.8
C
Lawns in Good Condition (75%+Groundcover)
74
1 3.95
1 292.3
B/C
Impervious Areas
98
9.43
923.7
DA k211 West
B
Woods in Good Condition
55
0.00
0.0
(Developed)
B
Lawns in Good Condition (75%+Groundcover)
61
8.14
496.2
Proposed
80
2.49
DA=19.79 ac
C
Woods in Good Condition
70
0.00
0.0
C
Lawns in Good Condition (75%+ Groundwver)
74
2.23
165.0
B/C
Impervious Areas
98
0.76
74.5
DA 113C
B
Woods in Good Condition
55
0.00
0.0
(Developed)
B
lawns in Good Condition (75%+ Groundcover)
61
0.27
16.5
Proposed
86
L63
DA=123 ac
C
Woods in Good Condition
70
0.00
0.0
C
lawns in Good Condition (75%+ Groundwver)
74
0.20
14.8
2. Runoff
1-Year Storm
2-Year Storm
I 10-Year Storm
Drainage Area Description
Frequency -years
1
2
10
n/a
Rainfall, P (24 hour)- inches
3.5
3.7
5.6
n/a
Runoff, Q-inches
0.65
0.75
1.88
D.A 42B West (Present)
Runoff, Q-inches
1.64
1.80
3A3
D.A k2B West(Developed)
Runoff, Q-inches
2.10
2.27
4,03
D.A 113C(Developed)
U.S. Department of Agriculture
Natural Resources Conservation Service
TR 55 Worksheet 3: Time of Concentration (T.) or Travel Time (T,)
Project: Foothill Crossing II VSMP #6
Location: Crozet, VA
Check One: Present
Check One: T,
Sheet Flow: (Applicable to T, only)
X Developed X
X Tt
Designed By: KKW, PE
Checked By: SRC, PE
Through subarea
FL-ENG-21A
06/04
Date: 2/10/22
Date: 2/10/22
D.A k2B West D.A#2B West D.A 83C
(Pre -Developed) As (Developed) (Developed)
Segment ID: Approved DA=20.92 Proposed DA=19.79 ac I Proposed DA=1.23 ac
1 Surface description (Table 3-1)
2 Manning's roughness coeff., n (Table 3-1
3 Flow length, L (total L < 100) (ft)
4 Two-year 24-hour rainfall, Pz(in.)
5 Land slope, s (ft/ft)
6 Compute Tr = [0.007(n*L)"] / Pis s°o
Shallow Concentrated Flow:
7 Surface description (paved or unpaved)
8 Flow Length, L (ft)
9 Watercourse slope, s (ft/ft)
10 Average velocity, V (Figure 3-1) (ft/s)
11 Tr=L/3600*V
Channel Flow:
12 Cross sectional flow area, a (ft)
13 Wetted perimeter, Pk, (ft)
14 Hydraulic radius, r= a/Pw (ft)
15 Channel Slope, s (ft/ft)
16 Manning's Roughness Coeff, n
17 V= [ 1.49rII'sus ] / n
18 Flow length, L (ft)
19 Tt= L/3600*V
20 Watershed or subarea T, or T,
(Add Tt in steps 6, 11 and 19)
Dense Grass
Dense Grass
Dense Grass
0.24
0.24
0.24
100
100
135
3.7
4.0
3.7
0.02 0.06 0.08
0.22 0.14 0.16
Unpaved
Unpaved
755
200
0.066
0.065
4.2
4.1
0.05
0.01
0.00
`a
3
N
£ n
N/A c @J N/A
a �
E
N
m
0.00 0.03 0.00
0.27 10.18 1 0.16
U.S. Department of Agriculture
Natural Resources Conservation Service
TR 55 Worksheet 4: Graphical Peak Discharge Method
Project: Foothill Crossing II VSMP #6
Location: Crozet, VA
Check One: Present X Developed X
1. Data
Designed By: KKW, PE Date: 2/10/22
Checked By: SRC, PE Date: 2/10/22
Drainage Area I Drainage Area I Drainage Area
Description Description Description
D.A #26 West
(Pre -Developed) As
Approved DA=20.92
D.A #2B West
(Developed) Proposed
DA=19.79 ac
D.A #3C
(Developed) Proposed
DA=1.23 ac
Drainage Area(Am)in milesz=
0.0327
0.0309
0.0019
Runoff curve number CN=
63
80
86
Time of concentration (Tc)=
0.27
0.18
0.16
Rainfall distribution type=
II
II
II
Pond and swamp areas spread
throughout the watershed=
0
0
0
2. Frequency -years
1
2
10
1
2
10
1
2
30
3. Rainfall, P (24 hour)- inches
3.5
3.7
5.6
3.5
3.7
5.6
3.5
3.7
5.6
4. Initial Abstraction, la- inches
1.187
1.187
1.187
0.497
0.497
0.497
0.326
0.326
0.326
5. Compute la/P
0.34
0.32
0.21
0.14
0.13
0.09
0.09
0.09
0.06
6. Unit peak discharge, Qu- csm/in
560
595
655
-
-
-
1000
1000
1000
7. Runoff, Qfrom Worksheet 2- inches
0.65
0.75
1.88
1.64
1.80
3.43
2.10
2.27
4.03
8. Pond and Swamp adjustment factor, Fp
1
1
1
1
1
1
1
1
1
9. Peak Discharge, Qp- cfs
11.87
14.54
40.29
ROUTED
4.03
4.37
7.74
9 VAC 25-870-66 (26 West Pond)
Section B: Channel Protection
NEW CALCULATION WITH AMENDMENT#6
"Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet
the criteria in subdivision 1, 2 or 3 of this subsection..."
Section B.1: Manmade stormwater conveyance systems
"When stormwater from a development is discharged to a manmade stormwater conveyance system,
following the land -disturbing activity, either..." a. or b. shall be met:
Section B.1.b.
"The peak discharge requirements for concentrated stormwater flow to natural stormwater conveyance
systems in subdivision 3 of this subsection shall be met."
Section B.3
"... the maximum peak flow rate from the one-year 24-hour storm following the land -disturbing activity
shall be calculated either.." a. or b."
Section B.3.a.
In accordance with the following methodology:
Q Allowed !� I.F. * (Q Pre -Developed * RV Pre -Developed ) / RV Developed
Q Allowed
Where: Q Pre -Developed =
CN Pre -Developed =
S Pre -Developed =
RV Pre -Developed=
CN Post -Developed=
S Post -Developed =
RV Post -Developed =
I.F. _
Q Developed
< 3.75 cfs
Section B.4 Limits of Analysis
11.87 cfs
(From Worksheet 4 Watershed Summary)
63
(From Worksheet 4 Watershed Summary)
5.94
(From SCS TR-55 eq. 2-4)
0.65 in.
(From SCS TR-55 eq. 2-3)
80
(From Worksheet 4 Watershed Summary)
2.49
(From SCS TR-55 eq. 2-4)
1.64 in.
(From SCS TR-55 eq. 2-3)
0.80
(Factor of Safety)
0.65 cfs
The analysis terminates at the outfall since subsection B.3.a is met.
Routed Watershed Summary for DA 2B West - Level II Wet Pond
1 year
2 year
10 year
100-yr elev.
Approved Post -Development Routing (cfs)
0.702
0.825
45.85
650.929
' Proposed Post -Development Routing (cfs)
0.648
0.788
42.82
650.956
'With the midflow orifice and riser brought up 0.25' each, this amendment reduces the outflows from the approved
DA 2B West level II wet pond.
Summary of Amended Drainage Areas
Approved Pre -Development (ac)
Proposed Post -Development (ac)
DA it2B West
20.92
DA#2B West
19.79
DA q3C
1.23
Total: 20.92
Total:
21.02
Summary of Watersheds
2-Year Storm
Approved Pre -Development (cfs)
Proposed Post -Development (cfs)
DA #IA
8.49
DA #1A
0.98
DA #2B East
6.97
DA#2B East
1.89
DA#2B West
14.54
DA#2B West
0.79
DA #3C
4.37
Total: 30.00
Total: 8.03
10-Year Storm
Approved Pre -Development (cfs)
Proposed Post -Development (cfs)
DA #IA
25.44
DA #1A
7.58
DA #213 East
27.79
DA#2B East
16.5
DA #2B West
40.29
DA ri213 West
42.82
DA#3C
7.74
Total: 93.52
Total: 74.64
Post -Development Coverage Summary (Water Quantity)
DA #213 West - (Glenbrook Phase III Pond) Coverage Summary
Analyzed with this Amendment (Increase in drainage area, increase in impervious area)
Proposed #213 West Drainage Area
19.79
ac
Hpprae
).47
ac
Road
151082
sf
Sidewalks
35502
sf
Homes
121104
sf
Driveways
51498
sf
Access Path
2485
sf
Future Development Allowance
48882
sf
Proposed DA #213 West Impervious Area
410553
sf
266263
sf
DA #3C - (Released) Drainage Summary - Approved with VSMP Amendment #5
Analyzed with this Amendment (Reduction in drainage area, increase in impervious area)
Proposed #3C Drainage Area
1.23
ac
Road
11379
sf
Sidewalks
3300
sf
Homes
13300
sf
Driveways
5014
sf
Proposed DA #3C Impervious Area
32993
sf
22696
sf
Post -Development Project Coverage Summary (Water Quality)
Project Area
21.97
ac
Road
131765
sf
Sidewalks
33862
sf
Homes
140642
sf
Driveways
49776
sf
Access Path
7728
sf
Future Development Allowance
48882
sf
Project Total Impervious Area
412655
sf
Post -Development Routing Calculations
(The approved SWM Facility 2B West pond has been evaluated for this plan's proposed DA
2B West drainage area, which includes the future phase IV. The riser top and midflow
orifice are raised each 0.25' to provide routed flows which are less than the pond's
approved outflows. These calculations, and the SWM Facility 2B West's energy balance
calculation, show water quantity compliance is met for the Glenbrook Subdivision.)
BasinFlow printout
INPUT:
Basin: Foothills Crossing II - Wet Pond Level II '2B' Design AMENDMENT #6
11 Contour Areas
Elevation(ft)
Area(sf)
Computed Vol.(cy)
638.00
1154.00
0.0
639.00
1957.00
57.0
640.00
3080.00
149.5
642.00
6230.00
487.5
643.00
8779.00
764.1
644.00
16427.00
1223.5
644.40
16518.00
1467.6
646.00
19193.00
2524.7
648.00
22740.00
4075.9
650.00
26510.00
5898.2
652.00
30508.00
8008.2
Start-Elevation(ft)
5 Outlet Structures
Outlet structure 0
Orifice
name:
area (sf)
diameter or depth (in)
width for rect. (in)
coefficient
invert (ft)
multiple
discharge
Outlet structure 1
Orifice
644.00 Vol.(cy)
Low -Flow Orifice
0.049
3.000
0.000
0.600
644.000
1
into riser
name: Mid -Flow Orifice
area (sf) 0.087
diameter or depth (in) 4.000
width for rect. (in) 0.000
coefficient 0.600
invert (ft) 648.250
multiple 1
discharge into riser
Outlet structure 2
Weir
name: Emergency Spillway
length (ft) 35.000
side angle 78.460
1223.53
coefficient 3.300
invert (ft) 650.250
multiple 1
discharge through dam
Outlet structure 3
Culvert
name: Barrel
multiple 1
discharge out of riser
D (in) 30.000
h (in) 0.000
Length (ft) 99.000
Slope 0.008
Manning's n 0.013
Inlet coeff. Ke 0.500
Equation constant set 3
Invert (ft) 643.070
Outlet structure 4
Weir
name:
Riser
diameter (in)
60.000
side angle
0.000
coefficient
3.300
invert (ft)
649.250
multiple
1
discharge
into riser
4 Inflow Hydrographs
Hydrograph 0
SCS
name: 1-Year 24-Hour SCS Method Storm
Area (acres)
19.790
CN
80.000
Type 2
rainfall, P (in)
3.500
time of conc. (hrs)
0.1800
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
36.127
peak time (hrs)
11.970
volume (cy)
4349.709
Hydrograph 1
SCS
name: 2-Year 24-Hour SCS Method Storm
Area (acres) 19.790
CN
80.000
Type 2
rainfall, P (in)
3.700
time of conc. (hrs)
0.1800
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
39.662
peak time (hrs)
11.970
volume (cy)
4775.344
Hydrograph 2
SCS
name:
10-Year 24-Hour SCS Method Storm
Area (acres)
19.790
CN
80.000
Type
2
rainfall, P (in)
5.600
time of conc. (hrs)
0.1800
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
75.558
peak time (hrs)
11.970
volume (cy)
9097.163
Hydrograph 3
SCS
name:
100-Year 24-Hour SCS Method Storm
Area (acres)
19.790
CN
80.000
Type
2
rainfall, P (in)
9.100
time of conc. (hrs)
0.1800
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
147.105
peak time (hrs)
11.970
volume (cy)
17711.423
OUTPUT:
Routing Method: storage -indication
Hydrograph 0
Routing Summary of Peaks: 1-Year 24-Hour SCS Method Storm
inflow
(cfs)
36.127
at
11.96
(hrs)
discharge
(cfs)
0.648
at
17.12
(hrs)
water level
(ft)
648.546
at
17.40
(hrs)
storage
(cy)
4546.189
Hydrograph 1
Routing Summary
of
Peaks: 2-Year
24-Hour
SCS
Method Storm
inflow
(cfs)
39.662
at
11.96
(hrs)
discharge
(cfs)
0.788
at
16.02
(hrs)
water level
(ft)
648.845
at
16.42
(hrs)
storage
(cy)
4811.760
Hydrograph 2
Routing Summary
of
Peaks: 10-Year
24-Hour SCS Method Storm
inflow
(cfs)
75.557
at
11.96
(hrs)
discharge
(cfs)
42.821
at
12.10
(hrs)
water level
(ft)
650.115
at
12.10
(hrs)
storage
(cy)
6011.486
Hydrograph 3
Routing Summary
of
Peaks: 100-Year
24-Hour SCS Method Storm
inflow
(cfs)
147.104
at
11.96
(hrs)
discharge
(cfs)
136.562
at
12.02
(hrs)
water level
(ft)
650.956
at
12.02
(hrs)
storage
(cy)
6870.003
Mon Feb 14 10:09:16 EST 2022
BasinFlow printout
INPUT:
Basin: Foothills Crossing II - Wet Pond Level II '2B' Design ORIGINAL APPROVED
11 Contour Areas
Elevation(ft)
Area(sf)
Computed Vol.(cy)
638.00
1154.00
0.0
639.00
1957.00
57.0
640.00
3080.00
149.5
642.00
6230.00
487.5
643.00
8779.00
764.1
644.00
16427.00
1223.5
644.40
16518.00
1467.6
646.00
19193.00
2524.7
648.00
22740.00
4075.9
650.00
26510.00
5898.2
652.00
30508.00
8008.2
Start-Elevation(ft)
5 Outlet Structures
Outlet structure 0
Orifice
name:
area (sf)
diameter or depth (in)
width for rect. (in)
coefficient
invert (ft)
multiple
discharge
Outlet structure 1
Orifice
644.00 Vol.(cy)
Low -Flow Orifice
0.049
3.000
0.000
0.600
644.000
1
into riser
name: Mid -Flow Orifice
area (sf) 0.087
diameter or depth (in) 4.000
width for rect. (in) 0.000
coefficient 0.600
invert (ft) 648.000
multiple 1
discharge into riser
Outlet structure 2
Weir
name: Emergency Spillway
length (ft) 35.000
side angle 78.460
1223.53
coefficient 3.300
invert (ft) 650.250
multiple 1
discharge through dam
Outlet structure 3
Culvert
name: Barrel
multiple 1
discharge out of riser
D (in) 30.000
h (in) 0.000
Length (ft) 76.000
Slope 0.008
Manning's n 0.013
Inlet coeff. Ke 0.500
Equation constant set 3
Invert (ft) 643.070
Outlet structure 4
Weir
name: Riser
diameter (in)
60.000
side angle
0.000
coefficient
3.300
invert (ft)
649.000
multiple
1
discharge
into riser
4 Inflow Hydrographs
Hydrograph 0
SCS
name:
Area (acres)
CN
Type
rainfall, P (in)
time of conc. (hrs)
time increment (hrs)
time limit (hrs)
fudge factor
routed
peak flow (cfs)
peak time (hrs)
volume (cy)
Hydrograph 1
SCS
1-Year 24-Hour SCS Method Storm
19.470
80.000
2
3.500
0.1800
0.0200
30.000
1.00
true
35.543
11.970
4279.362
name: 2-Year 24-Hour SCS Method Storm
Area (acres) 19.470
CN
80.000
Type 2
rainfall, P (in)
3.700
time of conc. (hrs)
0.1800
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
39.021
peak time (hrs)
11.970
volume (cy)
4698.123
Hydrograph 2
SCS
name:
10-Year 24-Hour SCS Method Storm
Area (acres)
19.470
CN
80.000
Type
2
rainfall, P (in)
5.600
time of conc. (hrs)
0.1800
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
74.336
peak time (hrs)
11.970
volume (cy)
8950.069
Hydrograph 3
SCS
name:
100-Year 24-Hour SCS Method Storm
Area (acres)
19.470
CN
80.000
Type
2
rainfall, P (in)
9.100
time of conc. (hrs)
0.1800
time increment (hrs)
0.0200
time limit (hrs)
30.000
fudge factor
1.00
routed
true
peak flow (cfs)
144.726
peak time (hrs)
11.970
volume (cy)
17425.020
OUTPUT:
Routing Method: storage -indication
Hydrograph 0
Routing Summary of Peaks: 1-Year 24-Hour SCS Method Storm
inflow
(cfs)
35.543
at
11.96
(hrs)
discharge
(cfs)
0.702
at
16.28
(hrs)
water level
(ft)
648.422
at
16.56
(hrs)
storage
(cy)
4437.189
Hydrograph 1
Routing Summary
of
Peaks: 2-Year
24-Hour
SCS
Method Storm
inflow
(cfs)
39.021
at
11.96
(hrs)
discharge
(cfs)
0.825
at
15.82
(hrs)
water level
(ft)
648.738
at
16.00
(hrs)
storage
(cy)
4715.939
Hydrograph 2
Routing Summary
of
Peaks: 10-Year
24-Hour SCS Method Storm
inflow
(cfs)
74.336
at
11.96
(hrs)
discharge
(cfs)
45.852
at
12.10
(hrs)
water level
(ft)
649.906
at
12.10
(hrs)
storage
(cy)
5806.582
Hydrograph 3
Routing Summary
of
Peaks: 100-Year
24-Hour SCS Method Storm
inflow
(cfs)
144.725
at
11.96
(hrs)
discharge
(cfs)
131.980
at
12.02
(hrs)
water level
(ft)
650.929
at
12.02
(hrs)
storage
(cy)
6841.343
Wed Jul 27 16:39:52 EDT 2016
Virginia Runoff Reduction Method Calculations
(These calculations show water quality compliance is met for the Glenbrook III Subdivision and the
future phase IV development area with the SWM Facility 2B West Pond.)
project Name: Glenbrook Phase III (Foothill Crossing VSMP Amendment N6)
Date: 1 2/14/2022
BMPDeslgn Specifications List 2013 Draft Stds & Specs
Site Information
Post -Development Project (Treatment Volume and Loads)
Land Cater lacresl
ASoils
BSails
CSails
DSoils
Totals
Forest/Open Spare lacres) — undisturbed,
protected forest/open space or reforested land
000
Me rated Test(acres) disturbed, graded for
yards or other turf tu be mowed/managed
12.50
12.50
Impervious Gainer (acres)
947
9.42
21.97
Constants
Annual RArbil(inches)
43
Target Rainfall Event(inches)
1.00
Tmal Phosphorus (TP) EMC(mp/L)
0.2fi
Tmal Nitrogen(TN) EMC(mp/L)
1.86
Target TP load(lb/acre/yr)
0.41
Pj(unidesscorrestore tacmr)
0.90
Forest/Open Space Cover (acres)
0.00
Weighted Rv(forest)
0.00
%Forest
0%
Managed Tuff Cover (acres)
12.50
Weighed Re (turf)
0.20
%Managed Tuff
52%
Impervious Carer (acres)
9.42
Re (impervious)
0.95
%Impervious
43%
Site At. (acres)
21.97
Site Re
0.52
Runoff coefficients IRA
A Sails
BSails
CSails
DSoils
FonesVOpen Space
OD2
0.03
0.04
0.05
Managed Turf
0.15
0.20
0.22
0.25
Impervious Cover
1 0.95
0.95
0.95
1 0.95
Treatment Volume
(acre-ft)
0.95M
Treatment Volume (cubic feet)
41,732
TP Load (Ib/yr)
26.22
TN Load (lb/yr)
Informational purposes Onl
182.58
data input cells
anstant values
calculation cells
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Site Results (Water Quality Compliance)
Area Checks
D.A.A
D.A.B
D.A.0
D.A.D
O.A.E
AREACHECK
FOREST/OVEN SPACE (a[)
am
0.00
0.00
am
0.00
OK.
IMPERVIOUS COVER IaQ
9.43
0.00
0.00
am
0.00
OK.
IMPERVIOUS COVER TREATED (a[)
MANAGED TURF AREA(a<)
9A3
10.36
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
OK.
OK.
MANAGED TURF AREA TREATED (aa)
10.36
0.00
aw
0.00
0.00
OK.
AREA CHECK
OK.
OK.
OK.
OK.
OK.
Site Treatment Volume (ffa)
1
Runoff Reduction Volume and TP By Drainage Area
D.A. A
D.A. B
O.A. C
D.A. D
O.A. E
TOTAL
RUNOFF REDUCTION VOLUME ACHIEVED ia3)
0
0
0
0
0
0
TP LOAD AVAILABLE FOR REMOVAL )Ib/yr
25.15
0.W
0.00
0.00
0.00
25.15
TP LOAD REDUCTION ACHIEVED (Ib/yr)
18.86
0.W
0.00
0.00
0.00
18.80
TV LOAD REMAINING IIb/yr�
6.31
0.00
0.00
0.00
0.00
6.31
NITROGEN LOAD REDUCnONACHIEVED (Ib/Yrj
21.88
Total Phosphorus
FINAL POST -DEVELOPMENT TP LOAD III, r)F
26.22
TP LOAD REDUCTION REQUIRED (Ib/yijj
17.21
TPLOADREDUCnONACHIEVED (Ib/yi)
19.80
TP WAD REMAINING (Ib/1):j
2.38
REMAINING TP LOAD REDUCTION REQUIRED IIb/yid:
0.00
"TARGET TP REDUCTION
EXCEEDED
BY 1.63 LB/YEAR"
Total Nitrogen (For Information Purposes)
POST -DEVELOPMENT LOAD (Ib/y.)
182.58
NITROGEN LOAD REDUCION ACHIEVED (Ib/yi1j
71.83
REMAINING POST -DEVELOPMENT NITROGEN LOAD jib/ yid
115.20
Virginia Runoff Reduction McMod Worksheet
Drainage Area Summary
O.A. A
D.A. B
DA C
DA D
D.A. E
Total
Forest/Open(acres)
0.00
0.00
0.00
0.00
0.00
0.00
Managed Turt(acres)
10.36
0.00
0.00
0.00
0.00
10.36
Impervious Cover(acres)
9.43
0.00
0.00
0.00
0.00
9.43
Total Area (acres)
19.T9
0.00
O.OD
0.00
0.00
19.79
Drainage Area Compliance Summary
D.A. A
D.A. B
DA C
DAD
D.A. E
Total
TP Load Reduced (lb/yr)
I 18.M
0.00
I Om
Om
1 0.00
18.80
TN Load Reduced (lb/yr)
I 71.88
0.00
I Om
Om
1 0.00
71.88
Summary Prod
Virginia Runoff Reduction McMotl WmbM1eel
Drainage Area A Summary
lLand Cover Summary
A Soils
BSoils
CSoiIs
DSails
Total
%of Total
Forest/Open (acres)
0.00
0.00
0.00
0.00
0.,
0
Managed Turf (acres)
1 0.00
1 10.36
1 0.00
I 0.00
10.36
1 52
Impervious Cover (acres)
1 0.00
1 9.43
1 0.00
I 0.00
9.43
1 48
1 19."
BMP Selections
Managetl Turt
Impervious Cover
BMP Treatment
TP Wad from
Untreated TP Load
TP Removed
TP Remaining
Downstream
Practice
Credit Area
Credit Area
Volume(ItpreRes
Upstream
to Practice, h
i bsi
)Ib/yr)
ilb/Yr)
Treatment be
(acres)
(acres)
g icbs)
Employ
Employed
13.c. Wet Pond M2 (Spec 014
10.36
9.425
40,023.47
D.DD
25.12
1 18.84
1 6.29
None
Total Impervious Cover Treated (acres)
9.43
Total Turf Area Treated (acres)
10.36
Total TP Load Reduction Achieved in D.A.
(Ib/yr)
18.84
Total TN Wad Reduction Achieved in D.A.
(lb/yr)
71.88
Summary Print
Virginia Runoff Reduotlon MCNod WmbM1eet
---------------------------------------------------------------------------------------------------------------------------------
Runoff Volume and CN Calculations
1- earstorm 2-year storm 1 10- earstorm
Target Rainfall Event (in) 3.50 3.70 5.60
Drainage Areas
RV&CN
Dainage AreaA
Drainage AmaB
Drainage AreaC
Drainage Area
Drainage Area
CN
29
0
0
0
0
RR (R3)
0
0
0
0
0
1-Year return period
RV wo RR iwslni
1.57
0.00
0.00
0.00
0.00
RV w RR iwslni
1.57
0.00
0.00
0.00
0.00
CR adjuutl
79
0
0
0
0
2-year return period
W wa RR lwsln)
1.72
0.00
0.00
0.00
0.00
RV w RR iwslni
1.72
0.00
0.00
0.00
0.00
CM atliunetl
79
0
0
0
0
1Qyeir return period
W-RRlwslni
3.32
0.00
0.00
0.00
0.00
RVw RR iwslni
3.32
0.an
0.an
0.00
0.00
CN atliuued
79
0
0
0
0
Summery Prod