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33503 S Koster Road Project No.2021-00073 Page 15 <br /> The well water sample was analyzed for nitrate as nitrogen and DBCP. The analytical <br /> methods and results are included in the following table: <br /> Table 2. Laboratory Analytica Results,September 7, 2021 <br /> Analytical Well <br /> MCL <br /> Method Units Sample <br /> Nitrate (as Nitrogen) 110 <br /> DBCP E524.3 u /L ND 0.2 <br /> 1. Based on EPA's MCL (Maximum Contaminant Level). <br /> ND = non-detect to laboratory detection limit <br /> Bold indicates sample is above the MCL <br /> The laboratory report is available for review in Appendix B. <br /> 4.4 Current and Future On-Site Groundwater Uses <br /> The use of ground water for drinking water is currently utilized and further planned for the <br /> proposed development. There is currently one domestic well onsite which will serve both <br /> residential structures. <br /> 5.0 SOURCES AND IMPACT OF NITRATE TO GROUNDWATER <br /> 5.1 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 (2021) available from GoogleEarthTM. We counted the <br /> clusters within approximately one square mile of the site,with the assumption each building <br /> cluster has one septic system. Using this method,we determined there are approximately 50 <br /> septic systems per square mile in the immediate vicinity of the site. This is a low number of <br /> septic systems, with the majority of these systems located on moderately sized parcels <br /> surrounded by agricultural land. <br /> As discussed above,the domestic well was sampled for Nitrate as N; the analysis reports the <br /> groundwater is 4.3 mg/L, which is well below the EPA maximum contaminant level of 10 <br /> mg/L. <br /> 5.2 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 Tracy, California,based on the nearest weather station to the site <br /> available. The estimate first determines whether the average monthly precipitation exceeds <br /> Petralogix Engineering,InC. - <br /> 26675 BruelIa Road,Galt,Ca 95632 <br /> (209)-40o-5729 <br /> www.petralogix.com <br />