Alabama Administrative Code › Title 420 - ALABAMA STATE BOARD OF HEALTH › Chapter 420-3-1 - ONSITE SEWAGE TREATMENT AND DISPOSAL › Site Evaluation › Section 420-3-1-.45 - Percolation Test Procedure

Current through Register Vol. 42, No. 9, June 28, 2024
(1)
				The percolation test hole shall be dug or bored to the appropriate testing
				depth according to
				420-3-1-.40 Soil Testing Depth
				Requirements, but not less than 12 inches deep. The diameter of the hole shall
				be 4 to 8 inches (except when a permeameter is used).
(2) In order to remove any glazed or
				burnished spots on the walls of the test hole, the walls shall be scratched or
				made rough so as to provide a natural soil interface for absorption. All loose
				materials shall be removed from the hole. It is recommended that a 2-inch layer
				of coarse sand or gravel be added to the hole to protect the bottom from
				scouring.
(3) A percolation test
				hole shall be filled with clear water to a minimum depth of 12 inches over the
				bottom of the hole. Water shall be added to the test hole to maintain the
				12-inch depth as often as necessary over a minimum period of 4 hours and
				preferably overnight, in order to saturate the surrounding soil.
(4) Percolation test measurements shall be
				made no later than 8 hours following the saturation process. The drop in the
				water surface shall be measured from a stable reference point at or above the
				surface, not inside the test hole, at 30-minute intervals until the completion
				of the test.
(5) After the
				saturation process, the testing professional shall adjust the water level to a
				depth of 6 inches over the bottom of the hole. From a stable reference point
				outside the test hole, the depth to the water surface shall be measured at
				30-minute intervals for a period of 4 hours, or until a minimum of three
				readings have essentially the same drop. The total variation in drop between
				three readings shall be no more than one-eighth inch.
(6) Water shall be added as necessary to
				maintain the 6 inches of water above the bottom. The drop in the water
				elevation occurring in the last 30-minute interval shall determine the
				percolation rate, provided that the absorption rate has stabilized. If there is
				more than one- eighth inch variation in drop between the last three readings,
				the test shall continue to be made at additional 30-minute intervals until the
				rate has stabilized. The rate shall be considered stabilized when the last
				three readings are the same (not exceeding one-eighth inch) after the minimum 4
				hours saturation period.
(7) Soils
				that are rated higher than moderate shrink-swell potential (plasticity index
				above 20 percent and a liquid limit greater than 50 percent) shall require a
				minimum of 24 hours of constant saturation prior to testing. See
				420-3-1-.46 Extended Saturation
				Procedure.
(8) Additional
				saturation time may be required if sufficient swelling has not occurred as
				indicated by non-representative test results.
(9) For soils that absorb the first 6 inches
				of water in less than 30 minutes following saturation, measurements on the
				water surface shall be made at 10-minute intervals over a period of 1 hour. The
				drop of water surface that occurs in the final 10 minutes shall be used to
				compute the percolation rate. Generally, these are coarse textured soils. If
				this situation occurs in other soils, the test should be relocated.
(10) The percolation rate shall be reported
				as the number of minutes required for the water surface to drop 1 inch in the
				test hole after the rate is stabilized (min/inch or MPI).
(11) A copy of all field notes for each
				percolation test attempted shall be provided to the LHD upon request.
Previous Rule .69 was renumbered .45 per certification
					 published December 30, 2022; effective February 13,
					 2023.
Author:
David Gray, Boyd Rogers, Richard
					 Smith
Statutory Authority:
Code of Ala.
					 1975
, §§
											22-2-2(4);
					 22-2-2(6);
					 22-10-1,
et
					 seq
.; 22-26-1
et seq
.