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t <br /> .. �� KLEINFELDEl2 <br />�I a <br /> File No. 20-2983-03 <br /> October 26, 1990 <br /> Il <br /> farm irrigation that would increase the annual amount of deep <br /> percolation. We have also assumed in our analysis an <br /> evapotransporation rate of approximately 3 to 4 inches. <br />�F <br /> With these assumptions, we have used an annual deep percolation <br /> rate of 6 inches in our analysis. <br /> Background Nitrate Concentration of the Deep Percolating <br /> Precipitation <br /> Very little information is available on this subject in the <br /> referenced reports. In the Chico area study the I CRWQCB used a <br /> value of 2 . 2 mg/l reflecting primarily the fact that rainwater is <br /> relatively clean. Since surface irrigation was neglected in the <br /> estimate for "r, " it was felt that the affect of the higher nitrate <br /> concentration in surface waters on the determination of Nb should <br /> also be neglected. <br /> With the above factors the calculated nitrate concentration in <br /> groundwater resulting from domestic sources and precipitation was <br /> t found to be 6. 5 mg/l. In order to evaluate whether this figure <br /> � 1 <br /> would impact the existing groundwater conditions in the study area, <br /> r it: was then important to determine the initial or background <br /> r <br /> # ' nitrate concentration in the groundwater. In this regard, we were <br />: r- furnished the results of chemical analysis on several onsite wells. <br /> This information was also presented to representatives of San <br /> Joaquin County Environmental Health and a background nitrate <br /> concentration of 30 to 35 mg/1 was approved by the County. Using <br /> the higher background value of 35 mg/1 and the calculated Nc of 6. 5 } <br /> mg/l, it can be seen that the resultant nitrate concentration is <br /> still less than the State limit of 45 mg/1. Based on this <br /> analysis, it remains our opinion that the subdivisions currently <br /> under consideration with a maximum density of one unit per acre are <br /> Copyright 1990 Kleinfetder, Inc. 6 <br />