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'.,r [4] SOIL PROFILE AND PERCOLATION TESTING Because of the indigenous surface and subsurface soil properties, it was decided to dig a backhoe test pit to examine the soil strata with greater scrutiny that cannot be done with an augered boring. In addition to strata delineation, a trench pump-in test was done in conjunction with the traditional _ percolation test. For complete analysis of the subsurface sand strata which is expected to accept most of the septic effluent, a constant head permeability test was conducted on this material. Therefore, three quantitative test procedures were performed to adequately assess soil percolative capacity. The predominate soil type from existing grade to approximately 3 ft is a lean clay (CL) soil. This is the predominate soil type to this depth throughout the area. Below this clay soil is a severe cemented silts hardpan(ML-CL)which extends down to approximately 5.5 ft. Below the hardpan layer is a strata of silt material (ML). Found at approximately 13 ft below grade is a well-graded sand material with silt(SW-SM). This material extends for approximately 5 ft, where another silt layer is found down to typical seepage pit depth of 25 ft. Our percolation tests were performed in accordance with San Joaquin County Department of Environmental Health regulations. The attached Site Plan illustrates the location of the backhoe trench pit and the Field Test Data Sheet indicates perc test results. The results of the permeability test are also provided in the Appendix. The test results show fast percolation and permeability rates, which will be discussed in the Conclusions section of this report. [5] LOCAL GROUNDWATER AND SURFACE WATER INFORMATION The groundwater is located at approximately 75 ft below grade according to maps published by the Flood Control District. There was no evidence of a perched water table condition or saturated soil conditions above the referenced cemented silts hardpan after excavation of the test pit procedures, although the hardpan certainly attenuates downward percolation of water. It has been our experience from drilling in the area that this hardpan layer is quite variable in depth,thickness and continuation. The Environmental Health Department stipulated the on-site well be tested for the pesticide DBCP and nitrates. The well sampled and tested is located directly south of the residence near the existing milking parlor. Test results indicate a medium concentration of nitrate (as NOD of 26 ppm. Both DBCP and EDB were non-detect (ND). Found in the Appendix are nine Water Well Drillers Reports (Well Logs) for domestic wells along Steinegul Road. The logs illustrate a varied subsurface soil structure with intervening layers of clay, sand and gravel. There are no nearby surface waters which may be impacted from septic effluent. _ 2 vaffey Ag Aeasearck