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LOGE 1902: Medina NLS Addendum Page 3 <br /> March 20, 2019 <br /> with residential parcels similar in size to the subject Site, and it does not appear <br /> that water quality has been degraded substantially. <br /> • Additionally, depth to ground water beneath the Site is estimated to be 92 to 98 <br /> feet, as discussed in the original report. San Joaquin County experienced its <br /> highest recent ground-water levels in 1983 and 1999. Review of ground-water <br /> maps for these years (Plates 5 and 6) reveals that depth to water would have <br /> been approximately 68 to 72 feet during these high periods. Even assuming the <br /> most conservative (shallowest) ground-water depth, the vadose zone of the new <br /> septic system will be relatively deep, extending from the bottom of the 25-foot <br /> seepage pits to 68 feet below ground surface. Significant nitrate attenuation <br /> would be anticipated over the course of this 43-foot span. <br /> • The surface soils on the Site were observed to be silty clay with sand. Clay is <br /> known to inhibit the downward percolation of water and may mitigate nitrate as <br /> well through adhesion to the soil particles. <br /> It is our professional opinion that, based on the result of the nitrate loading calculation <br /> and the factors discussed above, septic effluent from the subject Site is unlikely to raise <br /> nitrate levels in the ground-water to above the MCL. Use of a standard septic system <br /> with leach lines and seepage pits should be permitted. <br /> Sincerely, <br /> Live Oak GeoEnvironmental, Inc. <br /> l� SS�pNAL gF� � � GFov <br /> Abigail cco, REPA �F 1p 4 <br /> O C �O pAND J.WaCH � <br /> Q 4Q DAVID J.WELCH J a No 653 <br /> NO.2151 <br /> CERTIFIED ��� <br /> ENGNEERMU <br /> (5GEOWGIST ,sem <br /> David J. Welch, CEG, CHG, PGP s 'eOFCA �\P OF CYN_ <br /> CC: Octavio Medina <br /> 5830 E. Ashley Ln. <br /> Stockton, CA 95212 <br /> Attachments: <br /> Plate 1. Recharge Calculation (Evapotranspiration Method), Holt Station <br /> Plate 2. Recharge Calculation (Evapotranspiration Method), Staten Island Station <br /> Plate 3. Nitrate Loading Calculation (Evapotranspiration Method) <br /> Plate 4. Nitrate Detections in Nearby Wells <br /> Plate 5. Depth to Water, 1983 <br /> Plate 6. Depth to Water, 1999 <br />