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April 3,2001 <br /> Job Number: LGO1-074 <br /> Page 1 1 <br /> VIII. CONCLUSIONS AND RECOMMENDATIONS <br /> In conclusion, a satisfactory percolation rate was achieved within a soil layer in the <br /> primary and reserve septic disposal fields. During our investigation,the soils encountered were <br /> commonly found to be a sandy clay, silty sand, and a hard pan layer. Clay soils were <br /> encountered at the surface. The septic permit review has shown that conventional septic systems <br /> with seepage pits are used in the area. The depth to ground water was found to range reciently <br /> between 64 to 70 feet. The nitrate level measured in the water well was found to be 7.6 mg/L as <br /> NO3 (1.7 mg/L-N). The Environmental Protection Agency maximum contaminate level for <br /> drinking water is 45 mg/L as NO3 and 10 mg/L-N. No DBCP was found in the ground water. <br /> The nitrate loading analysis has shown that the use of a"typical"or"standard"septic <br /> system could potentially cause a build up of nitrogen in the shallow aquifer above the maximum <br /> contaminate level of 10 mg/L-N. This is primarily due to the anticipated 740 students and <br /> facility plus visitors expected on the site Monday to Friday. To reduce the impacts of nitrates in <br /> the ground water, an onsite treatment system should be utilized. This type of system would need <br /> to obtain an average concentration of 23 mg/L-N or less prior to reaching the leach field to avoid <br /> build up of nitrates in ground water above the maximum contaminate level. <br /> Based on the results of this study, the proposed project is suitable for use with an onsite <br /> treatment (engineered septic) system discussed previously. We estimate that proposed project <br /> will not negatively impact ground water quality provided our recommendations are followed. <br /> The recommendations for the project are as follows: <br /> 1) Onsite treatment system utilizing leach lines and seepage pits or equivalent is <br /> recommended. <br /> 2) The onsite treatment system should reduce onsite waste levels of nitrate below 23 <br /> mg/L-N during active treatment. The MicroSepTec System or Orenco Advantex <br /> System appear to be capable of this level of performance. These two systems are <br /> an example of new technology available to reduce nitrates. An engineer or <br /> specialist should be consulted to select an appropriate system for the project. <br /> 3) Follow the San Joaquin County Public Health Services Sewage Standards. <br /> pE Rt ti <br /> Z � <br /> O ` <br />