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LOGE 1844: Farris NLS Addendum 2 Page 3 <br /> March 21, 2019 <br /> highest recent ground-water levels in 1983 and 1999. Review of ground-water <br /> maps for these years (Plates 4 and 5) reveals that depth to water would have <br /> been approximately 40 to 42 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 10-foot <br /> sumps (if any) to 40 feet below ground surface. Significant nitrate attenuation <br /> would be anticipated over the course of this 30-foot span. For greater protection <br /> of the ground water, the customer may wish to consider a filter bed septic <br /> system; on past projects, use of these systems has been encouraged to promote <br /> denitrification. <br /> • Based on the sandy soil type present on the Site, it is likely that the infiltration of <br /> rainwater may be underestimated by the calculation shown in Plate 1. It is more <br /> likely that a large amount of the rainfall directly infiltrates through the soil, leading <br /> to more dilution of septic effluent. <br /> It is our professional opinion that, based on the factors discussed above, septic effluent <br /> from the subject Site is unlikely to contribute significantly to a build-up of nitrate in the <br /> ground water. Use of a standard septic system should be permitted. <br /> Sincerely, <br /> Live Oak GeoEnvironmental, Inc. <br /> Abigai acco, REPA Sc,�ONAL �F �pNAt- 6'EO <br /> 2Q <br /> DAVID J.VVWLCH �� pAY10 J.WELCH 'J <br /> u', Q � <br /> N0.215 65,1 <br /> CERTIFIED <br /> ENGINEERING hjUROGEOL S <br /> David J. Welch, CEG, CHG, PGPT GEGROGISI <br /> FpFCALIFo�' <br /> OF CA11`\ ✓ <br /> CC: Brittany Farris <br /> 13293 E. Louise Ave. <br /> Manteca, CA 95336 <br /> Attachments: <br /> Plate 1. Recharge Calculation (Evapotranspiration Method), Manteca Station <br /> Plate 2. Nitrate Loading Calculation (Evapotranspiration Method) <br /> Plate 3. Nitrate Detections in Nearby Wells <br /> Plate 4. Depth to Water, 1983 <br /> Plate 5. Depth to Water, 1999 <br />