Wyoming Administrative Code › Agency 020 - Environmental Quality, Dept. of › Sub-Agency 0011 - Water Quality › Chapter 25 - SEPTIC TANKS, SOIL ABSORPTION SYSTEMS, AND OTHER SMALL WASTEWATER SYSTEMS › Appendix A - Percolation Test Procedure

Current through July 13, 2024
Section
				  1.
Purpose
(a) Percolation tests are used to determine absorption system
				  site suitability and to size the absorption system.
Section
				  2.
Procedure
(a) General Requirements:
(i) Percolation tests shall not be conducted in test holes
				  that extend into groundwater, bedrock, or frozen ground.
(ii) The percolation test shall be conducted only after the
				  soil exploration pit has been dug and examined.
(iii) A minimum of three (3) percolation test holes are
				  required.
(iv) The percolation test holes shall be spaced uniformly
				  over the proposed soil absorption system site.
(b) Preparation
(i) A twelve (12) inch diameter hole shall be dug or bored to
				  the proposed depth of the soil absorption system.
(ii) The walls shall be vertical, with the natural soil
				  surface exposed without smearing.
(iii) The sides and bottom shall be scarified with a sharp
				  pointed instrument and the loose material shall be removed from the
				  hole.
(iv) Two (2) inches of gravel or coarse sand shall be placed
				  in the bottom of the hole to prevent it from scouring and sealing during water
				  addition.
(c) Presoaking
(i) The purpose of presoaking is to have the water conditions
				  in the soil reach a stable condition similar to that which exists during
				  continual wastewater application. The minimum time of presoaking varies with
				  soil conditions but must be sufficiently long so that the water seeps away at a
				  constant rate. The following presoaking instructions are usually sufficient to
				  obtain a constant rate.
(A) Fill each hole with clear water to a level at least
				  eighteen (18) inches above the gravel or coarse sand. If the eighteen (18)
				  inches of water seeps away in eighteen (18) minutes or less, add eighteen (18)
				  inches of water a second time. If the second filling of eighteen (18) inches of
				  water seeps away in eighteen (18) minutes or less, this indicates the soil is
				  sandy and is excessively permeable. The soil absorption system shall meet the
				  requirements of Section
				  8(c).
(B) If either the first or second fillings of eighteen (18)
				  inches of water does not seep away in ninety (90) minutes, eighteen (18) inches
				  of water must be maintained in the hole for at least four (4) hours to presoak
				  the test hole. After the four (4) hours of water contact time, wait at least
				  twelve (12) hours before starting the percolation rate measurement.
(d) Percolation Rate Measurement
(i) Fill each test hole with twelve (12) inches of water and
				  allow the soil to rehydrate for fifteen (15) minutes prior to any
				  measurements.
(ii) Establish a fixed reference point to measure the
				  incremental water level drop at constant time intervals. The water level drop
				  should be measured to the nearest ? of an inch and the minimum time interval is
				  ten (10) minutes.
(iii) Refill the test hole to twelve (12) inches above the
				  gravel before starting the measurements. Continue to measure the incremental
				  water level drop at a constant time interval until a consistent incremental
				  water level drop is achieved. A consistent water level drop is achieved when
				  three (3) consecutive water level drops are within ? inches of each
				  other.
(iv) Before the water level drops below one (1) inch above
				  the gravel, refill the test hole to twelve (12) inches and continue to measure
				  the incremental water level drop.
(v) The percolation rate is calculated for each hole using
				  the following formula:
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(vi) If only three to five percolation tests are performed,
				  the design percolation rate for the absorption system is the largest rate from
				  all the holes tested. If six or more percolation tests are performed, the
				  design percolation rate for the absorption system is the average of all the
				  holes tested as determined by the above formula.
(e) The following information shall be recorded:
(i) Date(s) of test(s);
(ii) Location, diameter, and depth of each test hole;
(iii) Duration of presoak;
(iv) Time of day for beginning and end of each water-level
				  drop interval;
(v) Each water-level drop measurement;
(vi) Calculated percolation rate;
(vii) Name and signature of person performing test;
(viii) Name of owner or project name; and
(ix) Certification that the percolation test was done in
				  accordance with Wyoming Water Quality Rules and Regulations Chapter 25 Appendix
				  A.