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Soil Suitability / Nitrate Loading Study Irerracon <br />JPM ■ Lathrop, California <br />May 24, 2022 m Terracon Project No. NA227026 <br />to witness the tests. The EHD representative directed Terracon to use the last reading on the <br />percolation tests to calculate the percolation rate. <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 depth. <br />While a deep percolation test is defined by the EHD as being between 42 inches and 25 feet in <br />depth. The shallow percolation test must demonstrate a satisfactory percolation rate of less than <br />or equal to 60 minutes per inch drop in water level within the existing septic system disposal field <br />of a parcel to utilize a standard septic system and 30 minutes per inch or less for septic pits. <br />Details of the percolation tests are summarized in the table below. <br />Table 7. <br />Summary of Percolation Test. <br />Test No. <br />Percolation <br />Percolation Rate <br />Approximate Test <br />Comments <br />April 12, 2022 <br />Test Depth <br />(minlin) <br />Duration <br />(hours) <br />(see note) <br />(feet) <br />131 <br />6.5 <br />1.04 <br />1.9 <br />Satisfactory <br />133 <br />3.5 <br />1.14 <br />1.9 <br />Satisfactory <br />136 <br />3.0 <br />1.43 <br />1.0 <br />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 (EHD 42-014), January 2017. <br />1.6.7 Discussion of Percolation Test Results <br />Based on the percolation tests results, the percolation test borings at 131 at 6.5 feet, B3 at 3.5 feet <br />and B6 at 3.0 feet bgs demonstrated rapid percolation rates. According to the OWTS Standards <br />Table 1.10.2, for percolation rates between 1 minute per inch and less than or equal to 5 minutes <br />per inch, a minimum 20 -foot separation is required from the bottom of the dispersal system to <br />groundwater. Groundwater was encountered at 3.83 feet bgs at boring B5 which does not appear <br />to meet the 20 -foot separation requirement from the current ground surface. <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 (OWTS) where applicable. <br />E ©, 13 <br />