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JAMES D ROBINSON, PE, CEG Page 5 <br /> September 1, 2010 <br /> Project Number 2010-1015 <br /> ground water lies between 24 and 28 feet below mean sea level (54 to 58 feet below the ground <br /> surface) and flows northwest at the gradient of 3.8 feet per mile in the vicinity of the site. <br /> Ground Water Contamination Issues in the Area <br /> Potential groundwater issues in the area consist of contamination from leaching of <br /> agricultural chemicals, septic system usage and storm water infiltration. <br /> F <br /> Current and Future Groundwater Uses <br /> The site currently uses groundwater wells to provide water to the one residence and landscaping. <br /> In addition, the land east of the residences is irrigated by well water. The proposed addition of a <br /> Meeting Center will increase the water usage at the site. <br /> 3. SOURCES AND CALCULATED IMPACT OF NITRATE TO GROUNDWATER <br /> Current Off-site Sources of Nitrate <br /> Septic systems, agriculture chemical application, dairies and wineries in the area may be <br /> the most significant sources of introduction of nitrate into the groundwater. <br /> Rainfall Contribution <br /> Rainfall data was collected from the Western Regional Climate Center. Evapotranspiration data <br /> from the California Irrigation Management Information System. Data was collected from the <br /> closest station to the subject property. The data is used to determine the amount of possible <br /> percolation. On months that precipitation exceeds evapotranspiration, the additional amount of <br /> rainfall is consisted the amount which could percolate into the subsurface. For this calculation <br /> JAMES D ROBINSON,PE,CEG ENVIRONMENTAL•ENGINEERING•GEOLOGY <br /> PHONE(209)642-5445•FAX(209)740-4303 <br />