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CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions examined near the proposed septic disposal area for the new modular home on the Site were found to be suitable for a septic system. A satisfactory soil percolation rate of 27.8 min/in was observed in the shallow soil zone at the test location. The soil in the test location was found to be silty clay. Based on maps of recent aquifer levels, the depth of ground water is approximately 12 to 13 feet below ground surface. Live Oak excavated a ground-water boring concurrent with drilling the percolation test hole; ground water was encountered at 11.25 feet below ground surface. Ground water flows generally to the northeast in the area at a rate of approximately 5 to 11 feet per mile. Because of the percolation rate between 5.0 and 30.0 min/in encountered in the test hole, the San Joaquin County Environmental Health Department will require an eight- foot separation from the bottom of the dispersal system to ground water, unless mitigated by system design or enhancement. Based on the depth to first ground water of 11.25 feet, it is anticipated that the San Joaquin County Environmental Health Department will require the septic leach field be installed to a maximum depth of 3.25 feet below ground surface. A water sample was collected from the domestic well on the Site. Neither nitrate nor DBCP was detected in the water sample. Based on the methods and assumptions described, the nitrate loading calculation indicates that the existing and proposed future on-site septic drain field systems have the potential to cause a buildup of nitrate in the aquifer up to 10.9 mg/L-N, slightly over the MCL of 10 mg/L-N. It should be remembered that the Hantzsche and Finnemore equation is a conservative method for determining potential impacts. The clay soils may serve to limit the transportation of nitrate to the aquifer. The existing on-site well and other wells in the area do not show nitrate exceedances, and the actual nitrate loading experienced on the Site over time may be significantly less than predicted. Although Live Oak cannot make engineering recommendations, we are aware that the San Joaquin County Environmental Health Department often allows the use of standard septic systems with oversized septic tanks in cases where a 30 percent reduction would bring the nitrate loading under the MCL; the subject Site's nitrate loading result meets this criterion. Future septic system construction should follow the San Joaquin County On-Site Wastewater Treatment Systems Standards (2017) where applicable. In this area, only shallow septic systems utilizing leach lines or filter beds are permitted. LOGE 2606 Page 14