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Soil Suitability / Nitrate Loading Study <br /> 11065 North Alpine Road I Stockton, California r rerracon <br /> June 30, 2026 1 Terracon Project No. NA267068 <br /> Percolation Test Procedure, recording an initial reading and final reading over a span of <br /> thirty minutes. Final readings and percolation rate calculations were performed under <br /> oversight of the EHD representative. <br /> 1.6.6. Percolation Test Forms and Results <br /> A shallow percolation test is defined by the EHD as being between 36 and 42 inches in <br /> depth, while a deep percolation test is defined by the EHD as being between 42 inches <br /> and 25 feet in depth. The shallow percolation test must demonstrate a satisfactory <br /> percolation rate of less than or equal to 60 minutes per inch drop in water level within <br /> the existing septic system disposal field of a parcel to utilize a standard septic system <br /> and 30 minutes per inch or less for septic pits. Details of the percolation tests are <br /> summarized in the table below. <br /> 1.6.6.1. 2019 Percolation Test Supplementation <br /> Percolation tests conducted as a part of this Soil Suitability Study are supplemented by <br /> percolation testing previously performed by Terracon on the site (Terracon Project No. <br /> NA197078). A total of four percolation tests (133-136) were conducted on October 31, <br /> 2019 and observed by Daria Afonskaia, EHD representative. Terracon conducted two <br /> other percolation tests (131-132) that were not observed by the EHD due to the failing <br /> percolation rates. Terracon's previous percolation testing followed percolation testing <br /> procedures within the requirements of the San Joaquin County EHD. Results of 2019 <br /> percolation tests conducted under EHD oversight are tabulated below and percolation <br /> test forms are included in Appendix E. <br /> Table 7 <br /> Summary of Percolation Test <br /> Percolation Approximate Test Comments <br /> Test No. Test Depth Percolation Rate Duration <br /> (feet bgs) (min/in) (hours) (see note) <br /> B1 25 62.5 0.5 Unsatisfactory <br /> (June 11, 2026) <br /> B2 15 50 0.5 Unsatisfactory <br /> (June 11, 2026) <br /> B3 <br /> (June 11, 2026) 3.5 0 0.5 Unsatisfactory <br /> B 3-2019 <br /> (October 31,2019) 21 27.7 4 Satisfactory <br /> 134-2019 16 0 4 Unsatisfactory <br /> (October 31,2019) <br /> B5-2019 <br /> (October 31,2019) 18 0 4 Unsatisfactory <br /> 66-2019 7 0 4 Unsatisfactory <br /> (October 31,2019) <br /> Note: A satisfactory percolation rate is 60 minutes per inch or less for shallow leach lines and 30 minutes per <br /> inch or less for septic pits per San Joaquin County Onsite Wastewater Treatment Systems Standards (EHD 42- <br /> 014), January 2017. <br /> Facilities I Environmental I Geotechnical I Materials 13 <br />