HomeMy WebLinkAboutSDP200800003 Bond ReleaseFREELAND and KAUFFMAN, INC.
EtoiwER5 • LAw-scAPE ARairECr5
BMW Service Center
Charlottesville, VA)
Removal rate computations for Catch basin Stormfilters:
Total drainage area to Catch basin Stormfilters = 0.44 AC
In, Pre - developed Condition, impervious area is 0.05 AC
Ipre = 0.05 / 0.44 = 0.1 14 = 11.4%
Lpre = 8.77 x (0.05+ 0.9x Ipre) x Cw x A
8.77 x (0.05 + 0.9 x 11.4)x0.7 x0.44
27.8
In post - developed condition, impervious area is 0.43 AC
Ipost = 0.43 / 0.44 = 0.977 = 97.7%
Lpost = 8.77 x (0.05+ 0.9x Ipost) x Cw x A
8.77x(0.05+ 0.9 x 97.7) x 0.7 x 0.44
237.6
RR = ( Lpost — f x Lpre) x 100 / Lpost
237.6 — 1 X 27.8) x 100 / 237.6
Since Ipre is more than 20 %, f value has taken as 1)
209 West Stone Avenue • Greenville, South Carolina 29609 • Telephone 864 - 233 -5497 • Fax 864- 233 -8915
FRFFLAND and KAUFFMAN, INC.
FIUGINEER5 • LANDSCAPE AlzapFCT5
BMW Service Center
Charlottesville, VA)
Removal rate computations for Filterra:
Total Drainage area to Filterra = 0.86 AC
In, Pre - developed Condition, impervious area is 0.18 AC
Ipre = 0.18 / 0.86 = 0.209 = 20.9%
Lpre = 8.77 x (0.05+ 0.9x Ipre) x Cw x A
8.77 x (0.05 + 0.9 x 20.9) x 0.7 x0.86
In post - developed condition, impervious area is 0.73 AC
Ipost = 0.73 / 0.86 = 0.849 = 84.9%
Lpost = 8.77 x (0.05+ 0.9x Ipost) x Cw x A
8.77x(0.05+ 0.9 x 84.9) x 0.7 x 0.86
403.7
RR = ( Lpost — f x Lpre) x 100 / Lpost
403.7 — 0.9 X 99.6) x 100 / 403.7
Since Ipre is more than 20 %, f value has taken as 0.9)
209 West Stone Avenue • Greenville, South Carolina 29609 • Telephone 864 - 233 -5497 • Fax 864 - 233 -8915