Rules & Regulations of the State of Tennessee
Title 0400 - Environment and Conservation
Subtitle 0400-48 - Water Resources (Groundwater Protection)
Chapter 0400-48-01 - Regulations To Govern Subsurface Sewage Disposal Systems (Transferred from 1200-01-06)
Section 0400-48-01-.05 - PERCOLATION TEST PROCEDURES

(1) Type of Test Holes - The holes shall be dug or bored, with horizontal dimensions from six (6) to twelve (12) inches and vertical sides to the depth as appropriate for the type of system to be installed and the house that is to be constructed.

(2) Preparation of Test Holes - Carefully scratch the bottom and sides of the holes with a knife blade or sharp pointed instrument in order to remove any smeared soil surfaces, and to provide a natural soil interface into which water may percolate. Remove all loose material from the holes. Add two (2) inches of coarse sand or fine gravel to protect the bottom from scouring and sediment.

(3) Conducting the Test - Carefully fill the holes with clear water to a minimum depth of twelve (12) inches over the gravel. No additives shall be used at any time during the percolation test procedures. In most soils, it is necessary to refill the holes by supplying a surplus reservoir of water, possibly by means of an automatic siphon, to keep water in the holes at least four (4) hours and preferably overnight. The measurement period of the test shall begin twenty-four (24) to thirty (30) hours after initial filling.

(4) Percolation Rate Measurement - Percolation rate measurement shall be made on the day following the procedure described under item (3) of the percolation test form and calculations of area required for disposal fields shall be based on Appendix II.

(5) If greater than six (6) inches of water remains in the test holes after the overnight presoaking period, adjust the depth to approximately six (6) inches over the gravel. From a fixed reference point, measure the drop in water level over a thirty (30) minute period. This drop is used to calculate the percolation rate.

(6) If six (6) inches, or less, of water remains in the holes after the overnight presoaking period, add clear water to bring the depth of water in the holes to approximately six (6) inches over the gravel. From a fixed reference point measure the drop in the water level at approximately thirty (30) minute intervals for four (4) hours, refilling to approximately six (6) inches over the gravel after each reading. The drop that occurs during the final thirty (30) minute period is used to calculate the percolation rate. The drop that occurs during prior periods provides information for possible modification of the procedure to suit local circumstances.

(7) Only percolation rates generated as the result of the complete four (4) hour measurement period will be considered valid for plat approval or permit issuance.

(8) Tests shall be conducted by an engineer or surveyor licensed in the State of Tennessee. An approved soil consultant or a registered professional environmentalist registered in the State of Tennessee may conduct percolation tests if they are not employed by a State, Regional, District, County or Municipal Department of Environment and Conservation.