HomeMy WebLinkAboutSDP200700137 Calculations 2007-11-05BMP CALCULATIONS
FOR
RIVANNA PLAZA
November 5, 2007
LOCATION:
TMP 45 -109
Albemarle County, Virginia
PREPARED BY:
Dominion Development Resources, LLC
172 South Pantops Rd.
Charlottesville, VA 22911
P: 434.979 -8121
F: 434.979.1681
Short Version BMP Computations For Worksheets 2 - 6
Albemarle County Water Protection Ordinance: Modified Simple Method
Plan: Rivanna Plaza Water Resources Area:Development Area
Preparer:Domininon Development Resources Date:2- Nov -07
Project Drainage Area Designation Site
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)
Pj small storm correction factor, 0.9
1 percent imperviousness
P annual precipitation, 43" in Albemarle
A project area in acres in subject drainage area,A =3.32
C pollutant concentration, mg /I or ppm target phosphorus
f factor applied to RR
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
0 0 0 0
0 0 0 0
0 0
0 18053 0 18053
Driveways Length Width no.subtotal Length Width no.subtotal
and walks 37 5 1 185 154 5.5 1 847
14 9 1 126 94.5 7.5 1 708.75
0 0 0 0 88 17.5 1 1540
0 311 94 9.5 1 893 3988.75
Parking Lots Area 1 Area 2 Area 3 Area 4 Area 1 Area 2 Area 3 Area 4
0 0 0 48189 0 48189
Gravel areas Area 1 Area 2 subtotal Area 1 Area 2 subtotal
0 0 0 x 0.70 =0 0 0 0 x 0.70 =0
Structures Area no.subtotal Area no.subtotal
390 1 390 12500 1 12500
0 0 0 14500 1 14500
0 0 0 390 5586 1 5586 32586
Actively - grazed pasture &Area Area
yards and cultivated turf x 0.08 =0 x 0.08 =0
Active crop land Area Area
0 x 0.25 =0 0 x 0.25 =0
Other Impervious Areas Area 1 Area 2 Area 3 Area 1 Area 2 Area 3
0 0 0 0 0
Impervious Cover 13%71%
l(pre)post)
Rv(post) V
0.69 158.7
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% 0.23 4.69 14.06 9.37 67% Development Area
0.35 1.00 0% 0.17 1.70 7.03 5.33 76% Drinking Water Watersheds
0.40 1.00 1% 0.17 1.94 8.03 6.09 76% 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% 0.23 4.69 14.06 9.84 70% Development Area
0.35 0.85 0% 0.17 1.70 7.03 5.59 79% Drinking Water Watersheds
0.40 0.85 1% 0.17 1.94 8.03 6.38 79% Other Rural Land
rev. 30 May 2002 JMK