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1 <br /> 25268 N Cherokee Lane Project No.2018-00018 Page 14 <br /> 1 <br /> 3.2 Potential Groundwater Contamination Issues ' <br /> The site is located within a rural residential subdivision and near parcels involved in <br /> agricultural practices; groundwater contamination can result from activities related to t <br /> farming practices where chemicals are applied to crops which may permeate to <br /> groundwater.The site and surrounding properties utilize septic systems;leakage from septic <br /> tanks or failed septic systems can introduce bacteria to groundwater. ' <br /> 3.3 Current and Future On-Site Groundwater Uses <br /> I <br /> There is currently no domestic well onsite. One new well to service the proposed <br /> development is currently anticipated. ' <br /> 4.0 SOURCES AND IMPACT OF NITRATE TO GROUNDWATER , <br /> 4.1 Current Off-Site Sources of Nitrate <br /> Septic systems and agriculture in the area may be the most significant sources of nitrate. In ' <br /> an attempt to determine the septic system density for the vicinity of the site, our office <br /> reviewed a recent aerial photograph available from GoogleEarthTM.We counted the clusters ' <br /> within approximately one square mile of the site, with the assumption each building cluster <br /> has one septic system.Using this method,we determined there are approximately 350 septic <br /> systems per square mile in the immediate vicinity of the site. This is a moderate amount of ' <br /> septic systems. <br /> Because there is no well onsite,no water sample to analyze nitrate as nitrogen was obtained. ' <br /> 4.2 Contribution of Rainfall <br /> An estimate of the quantity and quality of rainfall was required for the nitrate loading ' <br /> analysis. The estimate of deep percolation of rain is based on the average monthly <br /> precipitation of rain fall for Lodi, California,based on the nearest weather station to the site ' <br /> available.The estimate first determines whether the average monthly precipitation exceeds <br /> average monthly potential evapotranspiration. If so, then the difference is potential deep <br /> percolation. This method does not consider runoff. See Plate 7 for the data and calculation. ' <br /> Average potential evapotranspiration was obtained from the California Irrigation <br /> Management Information System(CIMIS).The site is located within evapotranspiration zone ' <br /> number 12,as well as the Lodi station used in the analysis. The average rain fall for the Lodi <br /> area was obtained from the Western Regional Climate Center (www.wrcc.dri.edu) and was <br /> found to be 17.27 inches per year for the years 1893 through 2015. ' <br /> P 09)-4Dfz Engineering,Inc. <br /> oa1 <br /> 26675 Bmella Bd,Galt,Ca 95632 <br /> (2091<a1-5729 <br /> w pettalogizcom <br /> 1 <br />