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Soil Suitability/ Nitrate Loading Study Irerracon <br /> Thor Property ■ Stockton, CA <br /> July 19, 2018 ■ Terracon Project No. NA187029 <br /> Table 3. <br /> Summary of Percolation Tests. <br /> Percolation Percolation <br /> Test No. Comments <br /> Test Rate Test Duration <br /> Date Tested (see notes) <br /> Depth (inch) (minutes/inch) <br /> P1 Unsatisfactory <br /> June 12, 2018 42 0 30 minutes <br /> ( ) percolation rate <br /> P2 Satisfactory percolation <br /> (July 6, 2018) 300 25 240 minutes rate <br /> Note: A satisfactory percolation rate is 60 minutes per inch or less for shallow leach lines and 30 minutes per inch or less for septic <br /> pits per SJEHD,Onsite Wastewater Disposal Standards,October 2003. <br /> The completed deep percolation test form with Mr. Ahmed's verification signature is included in <br /> Appendix E of this report. <br /> 1.6.7 Discussion of Percolation Test Results <br /> The clay soils encountered in the shallow boring (3.5 feet bgs) did not demonstrate a satisfactory <br /> percolation rate for shallow leach lines possibly due to a cemented layer at lower depths. <br /> However, the clay soils in the deep boring (25.0 feet bgs) did demonstrate a satisfactory <br /> percolation rate for seepage pits. <br /> 1.6.8 Discussion of Septic System Sizing <br /> In general, septic system construction should follow the San Joaquin County On-Site Wastewater <br /> Disposal Standards where applicable. The foregoing investigation and percolation test results <br /> indicate the site consists of deep clay soils with a possible hardpan layer. Given the deeper clay <br /> layers encountered, seepage pits should be installed at the end of the leach lines as a secondary <br /> absorption measure. <br /> 2.0 NITRATE LOADING STUDY <br /> Because of concern regarding nitrate leaching into groundwater from septic systems, a nitrate <br /> loading analysis is required by the EHD for the proposed development to determine the potential <br /> concentration of percolating effluent and rain fall over the long term. Where percolating effluent <br /> leaches into the ground, groundwater quality may be impacted to some degree should the effluent <br /> reach groundwater. <br /> The method utilized for the nitrate loading analysis is based on a simple mass balance formula, <br /> discussed in a published article by Hantzsche and Finnemore (1992), which provides a <br /> convenient and simplified method to estimate long-term groundwater nitrate impacts on an area- <br /> wide basis. <br /> Responsive ■ Resourceful ■ Reliable 11 <br />