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lierracon Soil Suitability / Nitrate Loading Study <br />Buddhist Temple Proposed Dormitory • Stockton, California <br />July 11,2019 • Terracon Project No. NA177056 <br />1.6.6 Percolation Test Forms and Results <br />The completed percolation test forms are included in Appendix E of this report. A shallow <br />percolation test is defined by the EHD as being between 36 and 42 inches in depth. While a deep <br />percolation test is defined by the EHD as being between 42 inches and 25 feet in depth. The <br />percolation test must demonstrate a satisfactory percolation rate (less than or equal to 60 minutes <br />per inch drop for shallow leach lines and 30 minutes per inch or less for septic pits per SJEHD) <br />within the existing septic system disposal field of a parcel to utilize a standard septic system. <br />Details of the percolation test is summarized in the table on the following page. <br />Table 6. <br />Summary of Percolation Tests. <br />Test No. <br />Date Tested <br />Percolation <br />Test <br />Depth (feet) <br />Percolation <br />Rate <br />(minutes/inch) <br />Test Duration <br />(minutes)) <br />Comments <br />(see notes) <br />B1 (05/10/2019) 3.5 2.74 4 /I( Satisfactory <br />B2 (05/10/2019) 3.5 50 4 IR i3 Satisfactory <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 San Joaquin County Onsite Wastewater Treatment Systems Standards (END 42-014), January 2017. <br />1.6.7 Discussion of Percolation Test Results <br />Both percolation tests demonstrated satisfactory percolation rates of 2.74 minutes per inch at <br />boring B1 and 50 minutes per inch at boring B2. <br />1.6.8 Discussion of Septic System Sizing <br />Based on the favorable percolation results, the site soils appear suitable for a standard septic <br />system. In general, septic system construction should follow the San Joaquin County On-Site <br />Wastewater Treatment Systems Standards where applicable. <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 />Responsive • Resourceful • Reliable 13