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Soil Suitability/ Nitrate Loading Study 1 rierracon <br />Lease Property m Acampo, California <br />December 17, 2021 Terracon Project No. NA217090 <br />2.1.2 Mass Transport Soil Properties <br />The longer the effluent remains near the surface, the more treatment is enhanced due to natural <br />processes within the soil. The percolation test has revealed that the onsite soils have a moderate <br />percolation rate at shallow depths (<3.5 feet bgs) and fast percolation rate at 21 feet bgs. <br />2.2 Groundwater Analysis <br />2.2.1 Regional Groundwater <br />A discussion of regional groundwater, including depth to groundwater is included in Section 1.4.1. <br />No significant seasonal trends were evident from the sources consulted. <br />2.2.2 Potential Ground Water Contamination Issues <br />A discussion of issues related to potential groundwater contamination is included in Section 1.4.2. <br />2.2.3 Current and Future On -Site Ground Water Uses <br />The proposed modular residence will be connected to the existing well. <br />2.3 Sources and Impact of Nitrate to Groundwater <br />2.3.1 Current Off -Site Sources of Nitrate <br />Septic systems and/or agricultural land in the area may be the most significant sources of nitrate <br />in groundwater. Septic tank usage in the vicinity is discussed in Section 1.3.5. <br />2.3.2 Contribution of Rainfall <br />An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. <br />Average precipitation and potential evapotranspiration (ETo) data was obtained from the <br />California Irrigation Management Information System (CIMIS) from the Lodi Station (042) and <br />Lodi West Station (166). The estimate first determines whether the average monthly precipitation <br />exceeds average monthly evapotranspiration (ET). If so, then the difference is potential rainfall <br />recharge. This method does not consider runoff, although due to the relatively flat nature of the <br />site, runoff should be minimal. In February 2020, the EHD approved an adjustment to the <br />evapotranspiration (ET) rate based on net rainfall recharge calculation utilizing University of <br />California (UC) plant factors (PF) for established landscape plants. Terracon calculated the ET <br />adjustment factor (actual ET) based on the anticipated commercial landscape. Refer to Appendix <br />F Water Balance Recharge Analysis for monthly precipitation and ET averages. <br />Responsive ■ Resourceful ■ Reliable 14 <br />