HomeMy WebLinkAboutVJ Investments Bldg. 2 at Porky Park Sub - Drainage CalculationsDRAINAGE CALCULATIONS
FOR
VJ INVESTMENTS BLDG.
AT PORKY PARK SUBDIVISION
MERIDIAN, IDAHO
MAY 2012
NT TNGER
ENGINEERING ,
MEI # 12-008-00
2
INC.
4090 WEST STATE STREET, SUITE 29- BOISE, IDAHO - 83703 PHONE: 426-8314 FAX: 426-8319
DRAINAGE CALCULATION SUMMARY
Project: VJ linvestments Bldg. #2 at Porky Park
Project #: 12-009-00
Date: 5/15/2012
The stormwater runoff on the project site will be collected and treated via sand/ grease
traps. The stormwater will then be treated by sand filtration prior to discharging into
the receiving soils. Roof runoff will be discharged to the surface and directed to the
storm drain systems.
The runoff was calculated using a 100yr, 1 hr design storm (V runoff), for volume.
The "c" value used in calculating the runoff is based upon the amount of landscape in
the area. Roof runoff from the building is directed to drain into the systems.
SYSTEM AREA "C" Value
1 53,300 0.9
2 42,850 0.9
3 132,940 0.9
DmCalcs-VJ BLDG 2.xls Summary 1
VJ linvestments Bldg. #2 at Porky Park
Drainacie Area # 1
Area (acres): 1.22
C value: 0.90
Initial Trench Volume = 1 in x (Area (ac) x 43560cu.ft./2c) x 1ft./12in. x "C
Volume = 3998 cu. ft.
Req'd Storage Vol. = 3998 ft'
Trench Dimensions = 6 Depth (ft)
8 Width (ft)
165 Length (ft)
Storage/ft= (Vr)(D)(W) D=
= 19.2 ft2 W =
Bottom Perc/ft = (W)(Pr)(1ft/12") Vr =
= 5.33 ft2 Pr =
Trench Volume = (Length)(Storage/ft + Bottom perc/ft)
Trench Volume = 4048 ft'
Velocity in throat Flow = Q25=C*i25*a
6 ft Depth
8 ft Width
40 % Drain Rock Void Ratio
8 in./hr Percolation Rate
i25= 3.1 time of concentration <
5min (in/hr)
Q25= 3.4 cfs 1/2 per box
Velocity = 025/A A= area of throat in box
A= W*T
A= 4.00 sq. ft. A= width of box . throat opening
W= 4.00 1000 gal s/g tra[p
T= 1.00
Velocity = 0.43 ft/ sec
DrnCalcs-VJ BLDG 2.xls Area 1 2
VJ linvestments Bldg. #2 at Porky Park
Drainage Area # 2
Area (acres): 0.98
D =
C value: 0.90
Depth
Initial Trench Volume = 1 in x
(Area (ac) x 43560cu.ft./ac) x 1ft./12in. x "C
Volume =
3213.75 cu. ft.
Req'd Storage Vol. =
3214 ft'
Trench Dimensions =
6 Depth (ft)
= 8.00 ftZ
12 Width (ft)
8 in./hr
90 Length (ft)
Storage/ft = (Vr)(D)(W)
D =
6 ft
Depth
= 28.8 ft2
W =
12 ft
Width
Bottom Perc/ft = (W)(Pr)(1ft/12")
Vr =
40 %
Drain Rock Void Ratio
= 8.00 ftZ
Pr =
8 in./hr
Percolation Rate
Trench Volume = (Length)(Storage/ft + Bottom perc/ft)
Trench Volume = 3312 ft'
Velocity in throat Flow= Q25=C*i25*a i25= 3.1 time of concentration <
5min (in/hr)
Q25= 2.7 cfs
Velocity = Q25/A A= area of throat in box
A= W*T
A= 6.68 sq. ft. A= width of box . throat opening
W= 4.00 1000 gal s/g tra[p
T= 1.42 = 17"
Velocity = 0.48 ft/ sec
DmCalcs-VJ BLDG 2.xls Area 2 3
L VJ linvestments Bldg. #2 at Porky Park
Drainaae Area # 3
C value:
0.90
Initial Trench Volume =
1 in x (Area (ac) x 43560cu.ft./ac)
x 1ft./12in.
x "C"
Volume =
9970.5 cu. ft.
Req'd Storage Vol. =
9971 ft3
Trench Dimensions =
6 Depth (ft)
12 Width (ft)
275 Length (ft)
Storage/ft =
(Vr)(D)(W)
D =
6 ft
Depth
=
28.8 ft2
W =
12 ft
Width
Bottom Perc/ft=
(W)(Pr)(1ft/12")
Vr=
40 %
Drain Rock Void Ratio
=
8.00 ft2
Pr =
8 in./hr
Percolation Rate
Trench Volume = (Length) (Storage/ft + Bottom perc/ft)
Trench Volume = 10120 ft'
Velocity in throat Flow= Q21 =C*i2l*a i25= 3.1 time of concentration <
5min (in/hr)
Q25= 8.5 cfs divide between three boxes
Q25= 2.8 cfs
Velocity = Q25/A A= area of throat in box
A= W'T
A= 5.68 sq. ft. A= width of box . throat opening
W= 4.00 1000 gal s/g tra[p
T= 1.42 = 17"
Velocity = 0.50 ft/ sec
DmCalcs-VJ BLDG 2.xls Area 3 4