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March 3, 2005 <br /> �IOA Project Number: F-040155A <br /> I'E 2.2 Potential Ground Water Contamination Issues <br /> A discussion of issues related to potential ground water contamination is included in Section 4.2 of <br /> the SSS.F1 <br /> /"2.3 Current and Future On-Site Ground Water Uses <br /> A description of the existing wells on the Site is included in Section 4.3 of the SSS. Ground water is <br /> currently used for residential purposes. <br /> F <br /> 3.0 SOURCES AND IMPACT OF NITRATE TO GROUND WATER <br /> F1 �`/3.1 Current Off-Site Sources of Nitrate <br /> Septic systems, agriculture, and dairies in the area may be the most significant sources of nitrate. <br /> F <br /> Septic tank use in the vicinity is discussed in Section 3.4 was found to be low. The ground water <br /> sample, discussed in Sections 4.3 through 4.6 of the SSS,was found to have a nitrate concentration <br /> of 25.4 mg/L-NO3.. This concentration indicates that the ground water aquifer is likely not <br /> experiencing nitrate leaching from various sources in the area over the long term. <br /> 1 /---'3.2 Contribution of Rainfall . <br /> An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. The <br /> estimate of deep percolation of rain is based on the average monthly precipitation of rain fall and <br /> evapotranspiration for Lodi, California. The estimate first determines whether the average monthly <br /> precipitation exceeds average monthly potential evapotranspiration. If so, then the difference is <br /> F1potential deep percolation. This method does not consider runoff. See Plate 9 for the data and <br /> calculation. <br /> F! Average potential evapotranspiration was obtained from the California Irrigation Management <br /> Information System (CIMIS)-. The average monthly rain fall for the Lodi area was obtained from <br /> the USDA Soil Conservation Service,San Joaquin County, CA.. <br /> S <br /> F Based on this method, the-average deep percolation of rain for the Lodi area is estimated to be 6.84 <br />! inches. The nitrate concentration of rain fall was estimated to be 1 mg/L-N (Hantzsche and <br /> Finnemore, 1992). <br /> R , <br /> 3.3 Current On-Site Sources of Nitrate <br /> Current on--site sources of nitrate include the current septic system for the residence. <br /> M <br /> 4 <br /> �l <br /> f <br /> 4 <br />