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Nitrate Loading Study <br />Nielsen Property Ripon, California <br />January 15, 2019 Terracon Project No. NA187066 <br />lierracon <br /> <br />2.3 Current and Future On-Site Ground Water Uses <br />It is our understanding there are no groundwater wells located on the site; therefore, a <br />groundwater sample was not collected. We further understand the site will be developed with a <br />groundwater supply well for the future residential use. <br /> <br />3.0 SOURCES AND IMPACT OF NITRATE TO GROUNDWATER <br /> <br />3.1 Current Off-Site Sources of Nitrate <br />The adjoining properties consist of agricultural land primarily orchards and rural farm structures <br />and/or residences. Terracon assumes the farm structures and/or residences are connected to <br />individual septic systems based on the absence of municipal sewer systems in the area as <br />reported on the San Joaquin County District Viewer. Therefore, off-site sources of nitrate include <br />residential septic systems, agricultural land use, and natural processes. <br />Based on information obtained from the DWR Water Data Library, between the years 1959 to <br />2012, dissolved nitrate was reported between 5 and 70.4 mg/L-N at three groundwater wells <br />located within one mile north and northeast of the site. A groundwater study titled Addressing <br />Nitrate In California's Drinking Water Technical Report 2 Nitrogen Sources and Loading to <br />Groundwater dated 2012 prepared by the University of California Davis for the Tulare Lake Basin <br />and Salinas Valley, indicated crop land contributed 96% of the human-generated nitrate sources <br />to groundwater. The study indicated other minor contributors to nitrate in groundwater included <br />waste water treatment plants, septic systems, corrals, lagoons and urban runoff. Based on the <br />groundwater study, agricultural land use on the site and vicinity is anticipated to be the highest <br />contributor to nitrates in groundwater. <br /> <br />3.2 Contribution of Rainfall <br />An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. <br />The estimate of deep percolation of rain is based on the average monthly precipitation of rain fall <br />and evapotranspiration for Ripon, California. The estimate first determines whether the average <br />monthly precipitation exceeds average monthly potential evapotranspiration. If so, then the <br />difference is potential deep percolation. This method does not consider runoff, although due to <br />the relatively flat nature of the site, runoff should be minimal. Average precipitation and potential <br />evapotranspiration were obtained from the California Irrigation Management Information System <br />(CIMIS) website. Refer to Appendix B for the data and calculation. <br />Table 2. <br />Estimate of Deep Percolation of Rain for the Site <br />Location Deep Percolation of Rain <br />Ripon 2.54 inches per year <br />Responsive • Resourceful • Reliable 5