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[3] SOIL PROFILE AND PERCOLATION TESTING Percolation tests were conducted on Parcel 1 and Parcel 2 according to San Joaquin County Department of Environmental Health regulations. The test locations are illustrated on the attached Parcel Map. Percolation test results can be found on the Field Test Data Sheet in the Appendix. One shallow perc test (42") was drilled on each of the two proposed Parcels. There was virtually no percolation in either test boring due to the severe hardpan and clay soils. Therefore, no shallow percolation tests were officially conducted. The percolation borings drilled for testing were bored to a depth of 21 feet below existing grade in an area south of the residence on proposed Parcel 1 and northeast of the shed on proposed Parcel 2. Soil structure consists of a clay (CL) throughout the shallow soil profile with a hardpan layer located at approximately 42 inches which extends to 60 inches. Under the hardpan exists a fine sandy clay (SC) with the remaining soil profile to 21 feet existing of a clay with thin gravel strata. The borings were pre- saturated the total depth, 24 hrs prior to starting the perc tests to induce worst-case saturated soil conditions. Percolation test results indicate a perc rate of 7.1 min/in for Parcel 1 and 27.3 min/in for Parcel 2. Considering the soil type these rates can be considered favorable. It is important to recognize that the percolation tests were run with the test pits at approximately 75% to 85% full. This was done to simulate worst case conditions of soil saturation throughout the soil profile of the pit. [4] LOCAL GROUNDWATER AND SURFACE WATER INFORMATION The static water table depth, or the zone of saturation is located at approximately 110 feet below grade according to the 1996 "Lines of Equal Depth" published by the San Joaquin County Flood Control District. It is possible there may be perched water table conditions under the subject property at a higher elevation that the static water level, although no perched conditions were encountered in our drilling procedures. There is no potential for septic impact to any surface waters, providing applicable distance requirements are followed. This is especially critical with the drainage ditch at the south end of the property. The property is not in the flood plain. Analysis of water drawn from the domestic well at the residence indicates a nitrate concentration of 10 ppm NO3. The Maximum Contaminant Level (MCL) for NO3 in drinking water is 45 ppm. The pesticides DBCP and EDB were not detected (ND). A nitrate concentration of 10 ppm indicates the underlying aquifers have not been significantly impacted from nitrogen contributors, such as agricultural operations, septic systems or rainfall. Additionally, there are significant clay layers which have attenuated the downward migration of nitrate. [5] CONCLUSIONS The non-existent shallow percolation rate for the subject parcel suggests there would be no effluent percolation at the leachline depths of approximately 42 inches below grade. This is due of course, to the heavy clay content soil and hardpan layer. Percolative capacity does exist at deeper depths as evidenced by the attached perc test rates. The final sewage disposal area should be dependant upon the number of bedrooms the structure on Parcel 2 will have. We are recommending �"ality ��ontrol Inspection