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Soil Suitability/Nitrate Loading Study Irerracon <br /> Shipherd Property Ripon, California <br /> August 25, 2020 Terracon Project No. NA207060 <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 rapid <br /> percolation at shallow depths (<3.5 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 home will be connected to the existing onsite domestic well. <br /> 2.3 Sources and Impact of Nitrate to Groundwater <br /> 2.3.1 Current Off-Site Sources of Nitrate <br /> Agriculture land use and septic systems in the area may be the most significant sources of nitrate <br /> in groundwater. Septic tank use 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 Manteca (070), Oakdale <br /> (194), and Ripon (249) station. The estimate first determines whether the average monthly <br /> precipitation exceeds average monthly evapotranspiration (ET). If so, then the difference is <br /> potential rainfall recharge. This method does not consider runoff, although due to the relatively <br /> flat nature of the site, runoff should be minimal. In February 2020, the EHD approved an <br /> adjustment to the evapotranspiration (ET) rate based on net rainfall recharge calculation utilizing <br /> University of California (UC) plant factors (PF) for established landscape plants. Terracon <br /> calculated the ET adjustment factor (actual ET) based on the anticipated residential landscape. <br /> Refer to Appendix F Water Balance Recharge Analysis for monthly precipitation and ET averages. <br /> Responsive ■ Resourceful ■ Reliable 13 <br />