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f ' TO: ENVIRONMENTAL HEALTH STAFF FROM: C. LELAND HALL , R.S. , Director RE: PERCOLATION TEST PROCEDURE DATE: SEPTEMBER 6, 1984 I. Measurements of the Percolation Test Hole. A. Diameter = 4 inches to 12 inches. B. Depth = of leach field - 36 inches. II . Preparation of the Test Hole. A. Scratch or score sides to remove any smeared soil surfaces. B. Remove loose material from hole. C. Add 2 inches of course sand or fine gravel . III. Saturation. A. Presoak Test Hole 24 hours before test by adding water a minimum of 12" over gravel . IV. Procedure #1 - if water remains in the test hole overnight. A. 24 hours after water is first added to the hole, add clear water to approximately 6 inches over the gravel . B. From a fixed reference point, measure the percolation rate over a thirty (30) minute period. C. Calculate the percolation rate in minutes per inch. V. Procedure #2 - if no water remains in test hole overnight. A. Add clear water to bring depth of water in the hole to approximately 6 inches over gravel . B. From a fixed reference point, measure the dro in water level at approximately 30 minute intervals for four (4� hours , refilling 6 inches over the gravel as necessary. C. Use the reading during the last 30 minutes of the four hour period to calculate percolation rate in minutes per inch. VI. Procedure #3 - in sandy soils (or other soils) in which the first 6 inches of water seeps away in less than 30 minutes after the overnight swelling period. A. Refill the hole to approximately 6 inches above the gravel . B. Take the readings 10 minutes apart over a one hour period. C. Use the reading obtained during the last 10 minutes to calculate percolation rate in minutes per inch. Source: Manual of Septic Tank Practice, U. S. Dept. of H.E.W. (1967)