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Mr.Jim Hoagland <br /> January 19,2004 <br /> Page 12 <br /> 6M <br /> 7.0 NITRATE LOADING ANALYSIS <br /> Because of the concern of nitrate leaching into ground water from septic systems, a nitrate <br /> loading analysis was required by the San Joaquin County Public Health Services, Environmental <br /> Health Division (PHS-EHD) for the proposed facility to measure the potential concentration of <br /> percolating effluent and rain fall over the long term. Where percolating effluent leaches into the <br /> ground, ground water quality may be impacted to some degree should the effluent reach ground <br /> .. water. <br /> The method utilized for the nitrate loading analysis is based on a simple mass balance formula, <br /> discussed in a published article by Hantzsche and Finnemore (1992) which provides a convenient <br /> and simplified method to estimate long-term ground-water nitrate impacts on an area-wide basis. <br /> .. Hantzsche and Finnemore found that over a long period of time,water quality in the upper <br /> saturated ground-water zone closely approximates the quality of percolating recharge waters. <br /> They believe that their method is a good planning tool and provides useful information to <br /> planners and local officials but with some real limitations. In their article published in Ground <br /> Water, Hantzsche and Finnemore mention that"...the equation ignores dispersion, lateral flow, <br /> and mixing with ground water flow from up-gradient areas. These processes would generally <br /> contribute to additional reduction of nitrate-nitrogen concentrations in ground water to the extent <br /> that the nitrate-nitrogen concentration of ground-water flow from up-gradient areas is lower."' <br /> `' The Hantzsche and Fennemore approach is"...a conservative(worst case) first approximation of <br /> ground-water nitrate-nitrogen concentration resulting from the combined effect of on-site sewage <br /> disposal systems and precipitation. This (the equation and approach) is for estimation of long- <br /> term effect(i.e., over years) on ground-water quality, and is not intended for prediction of <br /> seasonal changes" (Hantzsche and Finnemore, 1992). <br /> The method takes into account development area, soil denitrification factor,rainfall volume, <br /> rainfall nitrate concentration, the waste effluent quantity, and waste effluent nitrate concentration. <br /> ` The formula, assumptions and calculations used for the analysis are shown on Plates 2 through 4. <br /> The units of nitrate used in the mass balance equation are nitrate-N whose maximum drinking <br /> water contaminate level is 10 mg/L. <br /> ?pE RSo <br /> O 'L <br /> �S'Sp G♦ <br />