Geology Reference
In-Depth Information
percolation, some local ordinances require that septic tank drains be
located at least 4 ft above underlying bedrock.
Hand auger
Timing device
Percolation tester: a particular tester known as a “Martin Perk-
Tester” consists of a base stand, a 36-in. metal rule, and an
adjustable metal rod. Electronic circuitry, powered by a dry-cell
battery, provides meter readings on an instrument panel to indicate
the water level in a percolation test hole (see Figure 17-1).
APPARATUS
AND SUPPLIES
Test holes should be bored with an auger to the required depth. If a
Martin Perk-Tester is used, the diameter of the hole may be as small as
4 in. After the hole is bored and cleaned of loose material, the bottom
should be covered with 1 to 2 in. of gravel so that it will be less likely to
become clogged with soil from the sides of the hole.
In order that “worst-case” conditions may be simulated more accu-
rately, holes should be filled with water and allowed to stand for a long
period of time (preferably overnight) before beginning a percolation test.
This allows time for the soil to become completely saturated and for soils
containing clay to swell [1].
PREPARATION
OF TEST HOLE
After a test hole has been prepared in the manner just described, the
percolation test is conducted by placing water in the hole and determining
PROCEDURE
Figure 17-1
Percolation Tester
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