N.J. Admin. Code § 7:9A-6.4 - Percolation test
(a) The following
equipment is required for the percolation test:
1. A soil auger, post-hole digger or other
means of preparing a test hole as prescribed in (b) below;
2. A knife or trowel for removing smeared or
compacted surfaces from the walls of the test hole;
3. Fine (from two to 10 millimeter in
diameter) gravel (optional);
4. A
water supply (50 gallons is generally adequate);
5. A straight board (to serve as fixed
reference point for water level measurements);
6. A clock and a ruler (12 inches or longer,
engineering scale);
7. An automatic
siphon or float valve (optional); and
8. A hole liner consisting of a 14 inch
section of slotted pipe or well screen, or a 14 inch length of one-quarter inch
hardware cloth or other similar material rolled into a tube (optional). The
hole liner shall be no smaller than two inches in diameter less than the test
hole.
(b) Percolation
tests shall not be conducted in frozen ground or in holes which have been
allowed to remain open to the atmosphere for periods greater than three days.
The required configuration of the test hole is illustrated in Figure 7 of
Appendix A. The following procedure shall be used in preparation of the test
hole.
1. Step One: Excavate a test hole
having horizontal dimensions of eight to 12 inches at a depth such that the
lower six inches of the test hole are contained entirely within the soil
horizon or layer of fill material being tested. In order to facilitate access
to the lower portion of the hole, the test hole may be excavated from the
bottom of a shallow pit provided that the vertical axis of the test hole is a
minimum of 14 inches measured from the bottom of the pit to the bottom of the
test hole.
2. Step Two: In soil
textures other than sands or loamy sands, remove smeared or compacted soil from
the sides and bottom of the test hole by inserting the tip of a knife or trowel
into the soil surface and gently prying upward and outward. Remove loose soil
from the test hole.
3. Step Three:
At this point, a one-half inch layer of fine gravel may be placed in the bottom
of the hole to protect the soil surface from disturbance or siltation when
water is added to the hole. If additional protection is desired, a hole liner
as described in (a)8 above may be placed in the hole and the space between the
liner and the sides of the hole may be filled with fine gravel.
4. Step Four: Place and secure a straight
board horizontally across the top of the test hole, as shown in Figure 7 of
Appendix A, to serve as a fixed point for depth of water measurements to be
made at appointed time intervals throughout the test.
(c) All soils, except for sandy textured
soils which meet the requirements of (d) below, shall be pre-soaked using the
following procedure. Any soil which exhibits cracks or fissures between soil
aggregates shall be pre-soaked regardless of the texture. Pre-soak as follows:
1. Fill the test hole with water and maintain
a minimum depth of 12 inches for a period of four hours by refilling as
necessary or by means of an automatic siphon or float valve.
2. At the end of four hours, cease adding
water to the hole and allow the hole to drain for a period of from 16 to 24
hours.
(d) In sandy
textured soils, including sands, loamy sands and sandy loams, where a rapid
percolation rate is anticipated, fill the test hole to a depth of 12 inches and
allow to drain completely. Refill the hole to a depth of 12 inches and record
the time required for the hole to drain completely. If this time is less than
60 minutes, the test procedure may begin as prescribed in (e) below without
further pre-soaking. If water remains in the test hole after 60 minutes, the
hole must be pre-soaked as prescribed in (c) above before proceeding with the
test.
(e) Immediately following the
pre-soak procedure (no more than 28 hours after the start of the pre-soak
procedure), the percolation rate shall be determined using the following
procedure:
1. Step One: If water remains in
the test hole after the completion of the pre-soak period, the test shall be
terminated and the percolation rate shall be reported as greater than 60
minutes per inch. If no water remains in the test hole, fill to a depth of
seven inches. At a five to 30 minute time interval, depending upon the rate of
fall, record the drop in water level to the nearest one-tenth of an inch.
Refill the hole at the end of each time interval and repeat this procedure
using the same time interval until a constant rate of fall is attained. A
constant rate of fall is attained when the difference between the highest and
lowest of three consecutive measurements is no greater than two-tenths of an
inch.
2. Step Two: Immediately
after the completion of Step One, refill the test hole to a depth of seven
inches and record the time required for exactly six inches of water to seep
away. This time divided by six will be the percolation rate in minutes per
inch.
(f) The results of
the percolation test shall be interpreted as follows:
1. When the purpose of the test is to
determine the design permeability at the level of infiltration, the slowest
percolation rate determined within the proposed disposal field shall be used
for design purposes. If any of the measured percolation rates are slower than
60 minutes per inch or faster than three minutes per inch the application shall
not be approved. A percolation rate may be the result of a single percolation
test or the average of several replicate tests, as allowed in
7:9A-6.1(e)2.
2. When the result of the test(s) is an
average percolation rate slower than 60 minutes per inch, the horizon or
substratum in question shall be considered hydraulically restrictive.
3. When the result of the test(s) is an
average percolation rate faster than three minutes per inch, the horizon or
substratum in question shall be considered excessively coarse.
4. When a seepage pit is proposed, the design
percolation rate shall be calculated by adding the products of the percolation
rate and the thickness of each individual horizon tested and dividing the
result by the total thickness of all the horizons tested. Any horizon with a
percolation rate slower than 40 minutes per inch shall be excluded from this
computation.
Notes
State regulations are updated quarterly; we currently have two versions available. Below is a comparison between our most recent version and the prior quarterly release. More comparison features will be added as we have more versions to compare.
No prior version found.