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Nitrate Loading Study lrerracon <br /> Rowe Property a Lodi, CA <br /> November 6, 2017 ■ Terracon Project No. NA177059 <br /> 3.0 SOURCES AND IMPACT OF NITRATE TO GROUNDWATER <br /> 3.1 Current Off-Site Sources of Nitrate <br /> The properties in the area appear to consist of agricultural land including vineyards, orchards, <br /> and row crops. One single family residence is located to the adjoining northwest of the site. Two <br /> additional residences to the north are located within 200 feet of the site. <br /> Offsite sources of nitrate include agricultural land use, residential septic systems, and natural <br /> processes. <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 Lodi, Cafrfomia. 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 Califomia 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 /> Lodi 5.76 inches per year <br /> Based on this method, the average deep percolation of rain for the Lodi area is estimated to be <br /> 5.76 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 developed with an existing three bedroom 2.5 bathroom residence and <br /> septic system; therefore, the current on-site sources of nitrate include the existing septic system <br /> and natural processes. No additional sources of nitrates besides septic effluent, groundwater, <br /> and rainfall are anticipated. <br /> 3.4 Future On-Site Sources of Nitrate <br /> We understand the site is proposed to be developed with a two bedroom 2.5 bathroom 1,500 SF <br /> residence and an additional septic system. Therefore, the future on-site sources of nitrate will <br /> include the existing septic system,the proposed additional septic system, and natural processes. <br /> Responsive ■ Resourceful ■ Reliable 5 <br />