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Soil Suitability/Nitrate Loading Study Irerracon <br /> Shipherd Property■ Ripon, California <br /> August 25, 2020 ■ Terracon Project No. NA207060 <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 6. <br /> Summary of Percolation Test. <br /> Test No. Percolation Test Percolation Rate Test Duration Comments <br /> Date Tested Depth feet min/in hours see note <br /> 131 <br /> 3.5 N/A N/A N/A <br /> 07/31/20 <br /> B2 Satisfactory <br /> 3.5 1.66 1.0 <br /> 07/31/20 Percolation 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 San Joaquin County Onsite Wastewater Treatment Systems Standards(EHD 42-014),January 2017. <br /> Due to the rapid percolation rate, Terracon was unable to perform percolation tests <br /> simultaneously on both boring B1 and 132; therefore, boring B2 was used to establish the <br /> percolation rate for the project. The completed percolation test form is included in Appendix E of <br /> this report. <br /> 1.6.7 Discussion of Percolation Test Results <br /> Based on the percolation tests results, Boring B2 achieved a satisfactory percolation rate of 1.66 <br /> minutes per inch suitable for standard leach fields. Table 1.10.2 of the OWTS manual indicates a <br /> minimum 20 foot soil depth is needed from the bottom of the leachfield to groundwater. <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 /> 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 /> Responsive ■ Resourceful ■ Reliable 11 <br />