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C. PERCOLATION TEST RESULTS The percolation tests were conducted on April 14,,12000 under U.S.E.P.A. and San Joaquin County Environmental Health guidelines. One shallow perc test boring of 24 inches was prepared in the location of the future leachfield (See Septic Plan). This test depth was stipulated by the Environmental Health Department and represents the maximum depth of the soil/effluent interface. After completion of the test boring, the bottom and sides were scarified to open smeared soil surfaces. This is a critical procedureFand must also be done at the time of leachline emplacement. The test boring was then pre-saturated with six inches of clear water. After 24 hrs, all the water had seeped away. Approximately six inches of head water was maintained during the entire four-hour test. As illustrated on the attached FIELD PERCOLATION TESTING REPORT, the perc rate for the North Leachfield (N.LT.) indicates a marginally passing percolation, as was expected due to the clay soil. The percolation rate slowed over the test interval indicating the soil became increasingly saturated. D. GROUNDWATER INFORMATION Groundwater depths and elevations are illustrated,ion maps published by the San Joaquin County Flood Control and Water Conservation District. However, due to the variability in groundwater elevations in the Tracy area, groundwater lines are�not drawn for this area. The last map denoting lines of equal elevation for the Tracy area was published in 1992 and indicate the general groundwater flow to be in a northeasterly direction, toward the San Joaquin River. The { directional flow of the groundwater should be assumed to be approximate since there are many influences on flow direction, primarily by domestic and irrigation wells. As with all groundwater tables, there will be fluctuations in elevation. Attached well logs indicate an S ft water table depth in 1987, which is nearly equal to the static water table measurement for these Studies. It is highly probable that there has not been dramatic fluctuations in groundwater elevation under the subject property for many years. The critical issue regarding the groundwater elevation is that there must be sufficient distance between the bottom of a leachline trench and the highest anticipated depth to groundwater for sufficient treatment of bacteria and viruses to occur. This is generally accepted to be five feet. Two well logs from nearby domestic wells illustrates varied geological strata of clay, sand and sandy gravel down to depths of 200 ft. From these two well logs, it can be observed that the upper zone of saturation consists of a clay-type, fine soil fraction. There is ongoing research which suggests that there may be a significant denitrification potential within aquifers composed of a fine (vs. a coarse) soil fraction. To determine the extent of nitrate impact to the underlying aquifers, two water samples were taken: The first sample was retrieved from the domestic well 40 ft north of Carmelo Avenue. This is denoted on the attached WATER ANALYSIS REPORT as "CARMELO." 3 Chesney Consulting 4