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September 27,2000 <br /> Job Number. LG00-312 <br /> Page 10 <br /> VIII. CONCLUSIONS AND RECOMMENDATIONS <br /> In conclusion,the percolation test indicated the onsite soils percolate 0.44 minutes per <br /> inch at a depth of three(3)feet. The septic permit review has shown that generally septic systems <br /> with leach lines are used in the area. No ground water was encountered in both borings. The <br /> _ most recent County ground water depth maps have shown the depth to ground water ranged <br /> between approximately 20 feet to 22 feet in 1998 at the subject site. <br /> The estimated annual nitrate concentration of percolate by the proposed facility is 9.87 <br /> mg/1-N. A ground water sample was collected from the existing water well and tested for the <br /> presence of DBCP and Nitrates. A nitrate concentration of 45.6 mg/L-NO3 exceeded the MCL of <br /> 45 mg/L-NO3(10 mg/1_­N). No DBCP's were detected. <br /> Based on the results of this study, we believe the site is suitable for use with a septic <br /> system and the proposed project will not negatively impact ground water quality provided our <br /> recommendations are followed. The recommendations for the project are as follows: <br /> 1) The use of the on-site septic system is acceptable provided that no more then 8 <br /> stafflemployees and 25 students occupy the facility in the manner described <br /> previously(6-hrs/day,M-F). Otherwise, an engineered septic system that further <br /> reduces nitrates could be utilized. We understand that the subject property is <br /> included in an area outlined in the City of Manteca's General Plan and will <br /> eventually be connected to sewer service. <br /> 2) If any large gathering or special event—exceeding the daily usage estimate—is <br /> anticipated,the use of portable chemical toilets for those events or periods is <br /> recommended. <br /> 3) Since the water sample obtained from the on-site water well contains nitrates <br /> exceeding the maximum contaminate level established at 45 mg/L-NO3 or 10 <br /> _ mg/L-N by the U.S. Environmental Protection Agency, we recommend utilizing <br /> another drinking water source such as bottled water for a drinking supply. <br /> IX. LIMITATIONS <br /> The conclusions of this report are based on the information provided regarding the <br /> existing and proposed development,the use of the subject property, and the site conditions as <br /> they existed at the time we excavated our test hole and performed the percolation test. It was <br /> ?pE RSO <br /> r <br /> Z • <br /> — d ~ <br /> mss oc� <br />