SW3190506_Calcs_(Sand Filter)_20190820

Sand Filter
Total Area = 5.9 acres
Impervious= 2.34 acres
%Imp= 39.7%
Rv = 0.41
WQv= 0.200 ac-ft
WQv= 8728 cu-ft
Forebay Vol = 4364 cu-ft (required)
Filtration Media Surtace Area
WQv
8728
cubic -fee[
Top of Sand
683.50
ft
WQv Elev
684.62
ft
hf
0.56
ft
df
IS
ft
k
3.5
ft/day
f
2
days
Af
1019
square feet
Af
1050
square feet
Flow Rate Ratine Curve
Sand filter surface elevation =
Water Quality Volume Elevation =
Area of Sand filter=
df =
elev.
flow
(ft)
(cfs)
683.50
0.000
683.55
0.043
683.60
0.044
683.75
0.047
684.00
0.051
684.25
0.055
684.50
0.060
685.00
0.068
686.00
0.085
687.00
0.102
688.00
0.119
689.00
0.136
690.00
0.153
Channel Protection Volume Calculation
water quality volume
average height of water above surface of bed
filter bed depth
coefficient of permeability (3.5 feet/day)
minimum required area of sand filter
area provided
Forehav Volume
Elev.
Area
Volume
(ft)
(sq.ft.)
(cu.k.)
683.50
ft
684
4825
0
684.62
ft
685
5477
5151
1050
sf
686
6156
5816.5
2.5
ft
687
6864
6510
688
15200
11032
2-year Pre=
0.886
ac-ft
2-year Pre Area =
23.77
acres
2-year Pre Q/acre =
0.037
ac-ft/acre
Subarea 001=
5.9
acres
Subarea 001 Pre =
0.220
ac-ft (2-year pre volume)
Subarea 001 Post =
1.394
ac-ft(2-year post volume)
CPv =
1.174
ac-ft (2-year pre and post difference)
CPv=
51143
cu-ft
CPv elevation =
685.82
ft
Provided 28509.5 cu-ft
Required 4364 cu-ft
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