HomeMy WebLinkAboutOWTS Design CalculationsOWTS DESIGN CALCULATIONS:
43.6.A.4.a: Design flow values and strengths for commercial systems shall be determined from Table 6-2:
Table 6-2:
Employees
Avg GPD
BOD5 in Lbs
per day
Average
Daily Flow
(GPD)
Average
Daily BOD5
(Lbs)
Office buildings per employee per 8 -
hour shift
6
15
0.06
90
0.36
Septic Tank Size:
Design Size
(Gal):
48 Hours minimum detention
180
1000
Soil Treatment Area:
= [Design Flow (GPD)] / [LTAR (GPD per sq.ft.)]
Soil Type
Perc Rate
LTAR -
Treatment
Level 1
Soil
Treatment
Area [SF]:
LTAR -
Treatment
Level 2N
Soil
Treatment
Area [SF]:
1- Sand, loamy sand
5 to 15
0.8
112.5
0.9
100
2 - Sandy Loam, Loam, Silt Loam
16 to 25
0.6
150
0.7
128.5714286
2A - Sandy Loam, Loam, Silty clay
Loam
26 to 40
0.5
180
0.5
180
Soil Characteristics Determined by Gradation Analysis conducted by HP Kumar and Documented in 10-10-
2016 Report:
Content of Rock (> 2 mm) by Weight:
57%
Content of Sand (< 2mm and >0.075
mm)
30%
Soil Type per Table 10-1
Type 0
Soil Type of Soil < 2mm.
Type 1
Proposed Treatment Level:
TL1
Minimum 3 -ft deep unlined sand filter required
LTAR [per 11.C.2.a.(4)(i)] (GPD/SF)
1.0
Check of Sec. 11.C.2.c(3): LTAR for
Receiving Soil (Type 1) for TL3
0.9
Design LTAR:
1.0
Design Flow (GPD)
90
Soil Treatment Area [SF]:
90
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OWTS DESIGN CALCULATIONS:
Adjustments to Soil Treatment Area:
Adjusted Soil
Treatment
Area [SF]:
Adjustment for Bed Configuration
with Pressure Dosing:
1.0
90
Maximum Bed Width [ft]:
43.10.E.2.f.(1)
12
Minimum Length of Bed [ft]:
7.5
Designed Bed Width [ft]:
8
Designed Bed Length [ft]:
11.25
Area Adjustment for Factor of Safety:
1.2
Bed Length with Factor of Safety:
13.5
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