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Short Version BMP Computations For worksheets 2 - 6
One Area Analysis
Albemarle County Water Protection Ordinance: Modified Simple Method
Westminster Canterbury
Plan: 6 Duplex Replacement Water Resources Area: Upper Rivanna River
Preparer: Kurt M. Gloeckner, P.E.R.L.S. Date: 25- Aug -06
Project Drainage Area Designation DA #1
L storm pollutant export in pounds, L = [P(Pj)Rv /12 ] [ C(A)2.72 ]
Rv mean runoff coefficient, Rv = 0.05 + 0.009(1)
Treat Total as Road Only
Pj small storm correction factor, 0.9
for Ease of Analysis
I percent imperviousness
P annual precipitation, 43" in Albemarle
A project area in acres in subject drainage area, A = 4.02
C pollutant concentration, mg /I or ppm target phosphorus
Use Total Areas as Shown in
f factor applied to RR
Accompanying Sheets
V required treatment volume in cy, 0.5' over imperv. area = A(I)43560(0.5/12)/27
RR required removal , L(post) - f x L(pre)
%RR removal efficiency, RR100 /L(post)
Impervious Cover Computation (values in feet & square feet)
Item
pre - development Area post - development
Area
Roads Length Width subtotal
Length Width subtotal
3207.6 22 70567.2
4059 22 89298
0 0 0
0
0
0
0 705671
0
89298
Driveways Length Width no. subtotal Length
Width no. subtotal
and walks 0 0 0 0 0
0 0 0
1 0
0
0 0
0
0
Parking Lots 1 2 3 4 1
2 3 4
0 0 0
0 1 0
0
Gravel areas Area Area
0
x0.70= 0
x0.70=
0
Structures Area no. subtotal
Area no. subtotal
0 0 0
0
0 0
0 0 0
0 0
0
0
Actively - grazed pasture & Area
Area
yards and cultivated turf x 0.08 = 0
x 0.08 =
0
Active crop land Area
Area
0 x0.25= 0
0 x0.25=
0
Other Impervious Areas
0
0
Impervious Cover 40%
51 %
I(pre)
I(post)
Rv(post) V
0.51 137.8
New Development (For Development Areas, existing impervious cover <= 20 %)
C f I (pre) * Rv(pre) L(pre) L(post) RR % RR
Area Type
0.70 1.00 20% 0.41 10.18 12.56 2.38 19%
Development Area
0.35 1.00 0% 0.41 5.09 6.28 1.19 19%
Drinking Water Watersheds
0.40 1.00 1 % 0.41 5.82 7.18 1.36 19%
Other Rural Land
* min. values
Redevelopment (For Development Areas, existing impervious cover > 20 %)
C f I (pre) * Rv(pre) L(pre) L(post) RR % RR
Area Type
0.70 0.90 20% 0.41 10.18 12.56 3.39 27%
Development Area
0.35 0.85 0% 0.41 5.09 6.28 1.95 31%
Drinking Water Watersheds
0.40 0.85 1 % 0.41 5.82 7.18 2.23 31%
Other Rural Land
Interim Manual, Page 70
rev. 16 Feb 1998 GEB
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DRAINAGE AREA
IMPERVIOUS AREA
AND POROUS AREA
i
DUPLEX
COTTAGE
REPLACEME
SOUTH EAST
QUADRANT
OF
CAMPUS
MINOR
AMENDMEN
DRAWING
NEWCOTT AGES2.DWG
JOB NUMBER
9 - 7— C)113-31
/ DA -1
3.11 AC.
,35.807.5 t 1 AC SO-FT-
39.450.30 SQ.FT.
0.81 AC.
701AL DRAINAGE AREA
175,257,52 ACO.FT.
DA -1
0.91 AC.
TOTAL DRAINAGE AREA
175,257.82 SOFT -
4.02 AC.
TOTAL IMPER'AOUS
70,739.27 SOFT.
_
TOTAL POROU FT.
104.51
2,40 ACRES
IMPER`ou
63.774.34 SQ.FT,
1.46 ACRES
IMPERVIOUS
2,661.34 SOFT.
0.06 ACRES
IMPERVIOUS
2,493
CR
6A
63,77 .
CRES
IMPERVIOUS
2,661.3 SO
0.06 ACRES
1,810.04 SQ.FT.
2,493.55 SQ•FT.
0.04 ACRES
0.06 ACRES
1.610.04 SOFT.
0.04 ACRES
too 39 7 275 Qa T
1.62 ACRES
TOTAL DRAINAGE AREA
175,257.82 SOFT -
4.02 AC.
TOTAL IMPER'AOUS
70,739.27 SOFT.
_
TOTAL POROU FT.
104.51
2,40 ACRES
Short Version BMP Computations For wmrksheets 2 - 6 Two Area Analysis
Albemarle County Water Protection Ordinance: Modified Simple Method
Westminster Canterbury
Plan: 6 Duplex Replacement Water Resources Area: Upper Rivanna River
Preparer: Kurt M. Gloeckner, P. E., P. L.S. Date: 25- Aug -06
Project Drainage Area Designation DA #1
L storm pollutant export in pounds, L = [P(Pj)Rv /12 ] [ C(A)2.72 ]
Rv mean runoff coefficient, Rv = 0.05 + 0.009(1)
Treat Total as Road Only
Pi small storm correction factor, 0.9
for Ease of Analysis
I percent imperviousness
P annual precipitation, 43" in Albemarle
A project area in acres in subject drainage area, A = 3.71
C pollutant concentration, mg /I or ppm target phosphorus
f factor applied to RR
V required treatment volume in cy, 0.5" over imperv. area = A(1)43560(0.5/12)/27
RR required removal , L(post) - f x L(pre)
%RR removal efficiency, RR100 /L(post)
Impervious Cover Computation (values in feet & square feet)
Item
pre - development Area post - development
Area
Roads Length Width subtotal
Length Width subtotal
2791.8 22 61419.6
2910.6 22 64033.2
0 0 0
0
0
0
0 61419.6
0 64033.2
Driveways Length Width no. subtotal Length
Width no, subtotal
and walks 0 0 0 0 0
0 0
0
1 0
0
0 0
0 0
Parking Lots 1 2 3 4 1
2 3
4
0 0 0
0 1
0 0
Gravel areas Area Area
0
x0.70= 0
x0.70=
0
Structures Area no. subtotal
Area no. subtotal
0 0 0
0
0 0
0 0
0
0 0
0 0
Actively- grazed pasture & Area
Area
yards and cultivated turf x 0.08 = 0
x 0.08 =
0
Active crop land Area
Area
0 x0.25= 0
0 x0.25=
0
Other Impervious Areas
0
0
Impervious Cover 38%
40%
I(pre)
I(post)
Rv(post) V
0.41 98.8
New Development (For Development Areas, existing impervious cover <= 20 %)
C f I (pre) * Rv(pre) L(pre) L(post) RR % RR
Area Type
0.70 1.00 20% 0.39 8.93 9.26 0.33 4%
Development Area
0.35 1.00 0% 0.39 4.46 4.63 0.17 4%
Drinking Water Watersheds
0.40 1.00 1 % 0.39 5.10 5.29 0.19 4%
Other Rural Land
min. values
Redevelopment (For Development Areas, existing impervious cover > 20 %)
C f I (pre) * Rv(pre) L(pre) L(post) RR % RR
Area Type
0.70 0.90 20% 0.39 8.93 9.26 1.22 13%
Development Area
0.35 0.85 0% 0.39 4.46 4.63 0.84 18%
Drinking Water Watersheds
0.40 0.85 1 % 0.39 5.10 5.29 0.95 18%
Other Rural Land
Interim Manual, Page 70 rev. 16 Feb 1998 GEB
Short Version BMP Computations For Worksheets 2 - 6
Two Area Analysis
Albemarle County Water Protection Ordinance: Modified Simple Method
Westminster Canterbury
Plan: 6 Duplex Replacement Water Resources Area: Upper Rivanna River
Preparer: Kurt M. Gloeckner, P.E.R.L.S. Date: 25- Aug -06
Project Drainage Area Designation DA #2
L storm pollutant export in pounds, L = [P(Pj)Rv /12 ] [ C(A)2.72 j
Rv mean runoff coefficient, Rv = 0.05 + 0.009(1)
Treat Total as Road Only
Pj small storm correction factor, 0.9
for Ease of Analysis
1 percent imperviousness
P annual precipitation, 43" in Albemarle
A project area in acres in subject drainage area, A = 0.85
C pollutant concentration, mg /I or ppm target phosphorus
f factor applied to RR
V required treatment volume in cy, 0.5' over imperv. area = A(1)43560(0.5/12)/27
RR required removal , L(post) - f x L(pre)
%RR removal efficiency, RR100 /L(post)
Impervious Cover Computation (values in feet & square feet)
Item
pre - development Area post - development
Area
Roads Length Width subtotal
Length Width subtotal
415.8 22 9147.6
534.6 22 11761.2
0 0 0
0
0
0
0 9147.6
0 11761.2
Driveways Length Width no. subtotal Length
Width no. subtotal
and walks 0 0 0 0 0
0 0 0
1 0
0
0 0
0 0
Parking Lots 1 2 3 4 1
2 3 4
0 0 0
0 1 0 0
Gravel areas Area Area
0
x0.70= 0
x0.70= 0
Structures Area no. subtotal
Area no. subtotal
0 0 0
0
0 0
0 0 0
0 0
0 0
Actively- grazed pasture & Area
Area
yards and cultivated turf x 0.08 = 0
x 0.08 = 0
Active crop land Area
Area
0 x0.25= 0
0 x0.25= 0
Other Impervious Areas
0
0
Impervious Cover 25%
32 0 /c
'(pre)
[(post)
Rv(post) V
0.34 18.2
New Development (For Development Areas, existing impervious cover <= 20 %)
C f I (pre) * Rv(pre) L(pre) L(post) RR % RR
Area Type
0.70 1.00 20% 0.27 1.42 1.75 0.33 19%
Development Area
0.35 1.00 0% 0.27 0.71 0.88 0.17 19%
Drinking Water Watersheds
0.40 1.00 1 % 0.27 0.81 1.00 0.19 19%
Other Rural Land
* min. values
Redevelopment (For Development Areas, existing impervious cover > 20 %)
C f I (pre) * Rv(pre) L(pre) L(post) RR % RR
Area Type
0.70 0.90 20% 0.27 1.42 1.75 0.47 27%
Development Area
0.35 0.85 0% 0.27 0.71 0.88 0.27 31%
Drinking Water Watersheds
0.40 0.85 1% 0.27 0.81 1.00 0.31 31%
Other Rural Land
Interim Manual, Page 70
rev. 16 Feb 1998 GEB
DRAINAGE AREA
IMPERVIOUS AREA
AND POROUS AREA
PRE - DEVELOPMENT
DUPLEX
COTTAGE
REPLACEMENT
SOUTH EAST
QUADRANT
OF
CAMPUS
MINOR
AMENDMENT
DRAWING
NEWCOTTAGES2.DWG
JOB NUMBER
97- 018 -31
DA -II
0.91 AC.
DRAINAGE AREA
IMPERVIOUS AREA
AND POROUS AREA
POST DEVELOPMENT
DUPLEX
COTTAGE
REPLACEMENT
SOUTH EAST
QUADRANT
OF
CAMPUS
MINOR
AMENDMENT
DRAWING
NEWCOTTAGES2.DWG
PRE - DEVELOPMENT
39,450.30 SQ.FT
0.91 AC.
36,977.61 SQ.FT
0.85 AC.
DA -II
0.85 AC.
39,450.30 SQ.FT.
0.91 AC.
30,761.79 SQ.FT.
- 0.70 ACRES
IMPERVIOUS
8,688.51 SQ.FT.
0.21 AC.
POST
DEVELOPMENT
36,977.61 SQ.FT.
0.85 AC.
25,498.26 SQ.FT.
- 0.58 ACRES
IMPERVIOUS
36,977.61 SQ.FT.
0.27 AC.
JOB NUMBER
97- 018 -31
CC � -F-
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