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Soil Suitability and Nitrate Loading Evaluation CTE Job # 25-0726G <br />Custom Home <br />5388 Fig Road <br />Manteca, California <br />May 18, 2020 Page 7 of 9 <br />I A131. t; 8.3, <br />1NFILITRA`f"ION <br />E'ERCO1 AT ION RAI r <br />ILSI NUMBER � D[PTIE ' MATERIAL I"YPE. <br />- _ <br />RATE inln) � (t;al'ft'dav <br />- -- _._....-------- <br />- - <br />P-1 (Proposed Leach Field) 36 inches SM (Silty SAND) <br />6.6 21.5 <br />RECOMMENDED INFILTRATION RATE = <br />....... { <br />1 <br />1.0.7 <br />9.0 CONCLUSIONS <br />A suitable percolation rate for conventional onsite waste water treatment system in San Joaquin <br />County is defined as stratum capable of percolating water between 1 and 60 minutes per inch <br />(min/inch) at a depth of up to 3.5 feet below existing site grade. CTE's percolation test result at <br />the proposed leach field was 6.67 mirdinch at a depth of 36 inches which is within the acceptable <br />range for a suitable rate indicated by the San Joaquin County. However high groundwater level is <br />expected to be at approximately 9 feet depth at the site/vicinity which is less than advisable for a <br />typical 42 -inch deep dispersion field with percolation rates indicated. Highly penneable soils (e.g., <br />sands and gravels) also provide minimal treatment of the percolating wastewater and normally <br />require greater separation distances to afford proper groundwater protection. <br />Based on the above site soil conditions and test results, it is our professional opinion that site soil <br />conditions are not adequate for the use of a conventional septic tank/leach trench sewage disposal <br />system. Therefore, an alternative OWTS system is required to provide adequate vertical separation <br />between the bottom of the dispersal field and groundwater. We recommend that the OWTS should <br />consist of a shallow drip dispersal field, mounded system, or other alternative engineered system <br />should be considered. <br />The following information is from the "San Joaquin County Environmental Health Department <br />Onsite Wastewater Treatment Systems Local Agency Management Program (SJEHD LAMP, <br />April 2016). <br />VCAL.Is1C. <br />