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Soil Suitability/ Nitrate Loading Study <br />Lease Property ■ Acampo, California <br />December 17, 2021 Terracon Project No. NA217090 <br />Table 6. <br />Summary of Percolation Test. <br />Ircerr on <br />Test No. <br />Percolation Test <br />Percolation Rate <br />Test Duration <br />Comments <br />Date Tested <br />Depth (feet) <br />( <br />note <br />131 <br />3.5 <br />27.7 <br />4 <br />Satisfactory <br />12-07-2021 <br />Percolation Rate <br />B2 <br />* <br />Satisfactory <br />12-07-2021 <br />21 <br />3.08 <br />4 <br />Percolation Rate <br />B3 <br />Unsatisfactory <br />12-07-2021 <br />2.25 <br />250 <br />0.5 <br />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 />*Boring B2 was drilled to 21 feet bgs (refusal) and collapsed to 18 feet bgs. <br />1.6.7 Discussion of Percolation Test Results <br />Based on the percolation tests results, boring B1 at 3.5 feet bgs achieved a satisfactory <br />percolation rate of 27.7 minutes per inch. Boring 62 at 21 feet bgs demonstrated a satisfactory <br />percolation rate of 3.08 minutes per inch suitable for deep seepage pits. Table 1. 10.2 of the OWTS <br />manual indicates a minimum 20 -foot soil depth is needed from the bottom of the seepage pit to <br />groundwater. Groundwater is anticipated to be greater than 70 feet bgs which provides 45 feet <br />of separation between the bottom of the seepage pit and 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 />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 12 <br />