HomeMy WebLinkAboutVJ Investments Bldg. 2 at Porky Park Sub - Drainage Calculations (2)VlEI'# 112-008-00
DRAINAGE CALCULATIONS
FOR
VJ INVESTMENTS BLDG. 2
AT PORKY PARK SUBDIVISION
MERIDIAN, IDAHO
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4090 WEST STATE STREET, SUITE 29- BOISE, IDAHO - 83703 PHONE 428-831} FAX: 428-8319
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), forvolume.
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.
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DmCalcs-VJ BLDG 2.x1s Summary
VJ linvestments Bldg. #2 at Porky Park
Drainaae Area # t
Area (acres): 1.22
C value: 0.90
Initial Trench Volume = 1 in x (Area (ac) x 43560cu.ft./ac) 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 = Q25/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 fU sec
DrnCalcs-VJ BLDG 2.xls Area 1 2
VJ linvestments Bldg. #2 at Porky Park
Drainage Area # 2
C value: 0.90
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)
12 Width (ft)
90 Length (ft)
Storage/ft = (Vr)(D)(W) D =
28.8 ft' W =
Bottom Perc/ft=(W)(Pr)(1ft/12") Vr=
8.00 ft2 Pr =
Trench Volume = (Length)(Storage/ft + Bottom perc/ft)
Trench Volume = 3312 fe
Velocity in throat Flow = Q25=C`i25*a
6 ft
Depth
12 ft
Width
40 %
Drain Rock Void Ratio
8 in./hr
Percolation Rate
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= 5.68 sq. ft. A= width of box . throat opening
W= 4.00 1000 gal s/g tra[p
T= 1.42 = 17"
Velocity = 0.48 ft/ sec
DmCalcs-VJ BLDG 2.x1s Area 2 3
VJ linvestments Bldg. #2 at Porky Park
Drainage Area # 3
C value: 0.90
Initial Trench Volume = 1 in x (Area (ac) x 43560cu.ft./ac) x lft./121n. x "C"
Volume = 9970.5 cu. ft.
Req'd Storage Vol. = 9971 ft'
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 ft
Pr=
8 in./hr
Percolation Rate
Trench Volume = (Length)(Storagelft + Bottom perc/ft)
Trench Volume = 10120 ft'
Velocity in throat Flow = Q25=C*i25*a i25= 3.1 time of concentration <
5min (in/hr)
Qts= 8.5 cfs divide between three boxes
Q25= 2.8 cis
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
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