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Nitrate Loading Study 1�erracon <br /> Landavazo Property Tracy, CA <br /> December 15, 2017 Terracon Project No. NA177067 <br /> 3.0 SOURCES AND IMPACT OF NITRATE TO GROUNDWATER <br /> 3.1 Current Off-Site Sources of Nitrate <br /> Based on a review of septic permits provided by the EHD, the adjoining properties appear to be <br /> connected to individual septic systems. Therefore, off-site sources of nitrate include residential <br /> septic systems and natural processes. There were no well or septic permits available for the site <br /> address. <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 near Tracy, 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 and the Western Regional Climate Center. Refer to Appendix B for the data and <br /> calculation. <br /> Table 1. <br /> Estimate of Deep Percolation of Rain for the Site <br /> Location Deep Percolation of Rain <br /> Tracy 2.27 inches per year <br /> Based on this method, the average deep percolation of rain for the Tracy area is estimated to be <br /> 2.27 inches/year. The nitrate concentration of rainfall is estimated to be 1 mg/L-N (Hantzsche <br /> and Finnemore, 1992). <br /> 3.3 Current On-Site Sources of Nitrate <br /> We understand the site is currently vacant; therefore, the current on-site sources of nitrate include <br /> natural processes. <br /> 3.4 Future On-Site Sources of Nitrate <br /> We understand the site is proposed to be developed with a three bedroom two-and-a-half- <br /> bathroom residence and septic system. Therefore,the future on-site sources of nitrate will include <br /> the proposed septic system and natural processes. <br /> Responsive■ Resourceful ■ Reliable 5 <br />