Laserfiche WebLink
33503 S Koster Road Project No. 2021-00073 P a g e | 5 <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 <br />Method Units Well <br />Sample MCL <br />Nitrate (as Nitrogen) E300.1 mg/L 4.3 10 <br />DBCP E524.3 ug/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