Nev. Admin. Code § 444.8361 - Absorption bed: Design criteria
1. The absorptive
area of an absorption bed must be at least 50 percent larger than the
calculated size that would be required for a standard absorption
trench.
2. The percolation rate of
the soils at the bottom of the absorption bed must not be less than 60 minutes
per inch.
3. The effective
perimeter of the area of the sidewall beneath the distribution lines, or the
depth of the aggregate, must not be less than 12 inches or more than 36 inches.
The area of the sidewall may be added to the bottom of the bed when calculating
the size of the total absorptive area of the individual sewage disposal
system.
4. An absorption bed must
not be placed on a slope if the grade of the slope is greater than 8 percent.
The bottom of the absorption bed must be level.
5. The invert of the piping for the drain
field must be not less than 12 inches or more than 48 inches below the finished
grade. The top of the absorption bed must be at least 6 inches below the
surface line of the natural soil, and a capping fill must be placed on top of
the absorption bed. The capping fill must extend at least 10 feet beyond the
perimeter of the leaching area of the absorption bed and must be placed at a
minimum depth of 12 inches above the finished grade to allow for
settling.
6. An absorption bed must
have at least two distribution lines which are separated by not less than 4
feet or more than 6 feet. The distribution lines must be level and placed not
less than 3 feet or more than 6 feet from the sidewall of the bed. If a gravity
discharge system is used, the distribution line must not be less than 4 inches
in diameter. If a pressurized distribution line is used, the line must meet the
design guidelines for a pressure distribution system as set forth in NAC
444.8394 and 444.8396.
7. A
distribution line must not be longer than 110 feet and must be placed on at
least 12 inches of clean, graded aggregate ranging in size from 3/4 to 2 1/2
inches. At least 2 inches of aggregate must cover the top of the distribution
line. Untreated building paper, straw, geotextile fabric, or any similar
covering approved by the administrative authority, must cover the aggregate,
and a backfill of soil must be placed over the covering.
8. The owner of an individual sewage disposal
system shall take such precautions as are necessary to avoid compacting the
bottom of the absorption bed. Any loose or smeared soil must be raked and
removed. No vehicles may travel on the area of the absorption bed after
excavation is completed.
9. Dosing
is required if more than 500 linear feet of distribution lines are
required.
10. The following is a
diagram of an absorption bed:
Click here to view image.
Notes
NRS 439.200, 444.650
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