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WONG ENGINEERS PLANNING • ENGINEERING - SURVEYING Q �g8O Q,9na�--►�- -` :t,,a I � ' 210 NORTH HUNTER STREET- STOCKTO 93 V Q0 ` n� ^�P°"L� 'i 5tg0 �2091 464-4632 Prl �.. ANCE WONG R.C.E. 14269 PERCOLATION TEST & SOIL PROFILE ANALYSIS FOR DON A. COSE On July 21, 1976 our firm made two percolation tests and augered a hole to 10 feet to determine a soil profile. See the attached graphs for the results. The percolation tests are consistent with previous tests we made in the immediate area on Dec. 12, 1975. The water level at the time of the boring was measured at 61 feet in depth. After 4 hours the water level rose to 31 feet and remained -at this level on a check made the next day. The Tracy area has had a history of high water table in open cuts caused by extensive irrigation southwest of Tracy. The slope of the ground in Tracy is approximately a foot per hundred feet from the southwest to northeast. Irrigation water pereolatea' into the ground and travels with the slope in a sandy or loamy strata perched above a relatively impervious clay layer. Note from the soil profile that from 8 to 10 feet the soil encountered is Light Brown Clayey Loam. Because of the ground slope, the traveling water is under a slight pressure. The weight of the soil above the ground water level keeps the water-level from rising. In an open cut the weight and frictional resistance between the individual grains or particles of soil is removed and hence the water rises. It was our belief that a foot or so of this soil above the water level was enough to keep the level from rising. On August 2, 19T6- three holes were sugared to the varying depths of 3 feet, 4 feet and 5 feet. After remaining open over night the 5 foot hole was the only one into which water had risen, and only to a depth of 2 inches. Much less than the 3+j feet. In actual field conditions, there will be no open cut. The leach field area will be level with the existing ground and will exert pressure and resistance on the water level and the water level will not rise. The 6f foot level is more realistically the level of the ground water which will be existing in the leach field area . t