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UEC Document No.: R3579811 <br /> December 7, 1998 <br /> the subject site groundwater can not be reliably established without the collection of groundwater samples. <br /> It is not recommended that this analysis be performed as part of this Lot Line Adjustment process. <br /> 3.3 Groundwater Impact Analysis <br /> The groundwater impact analysis presented below has been developed by Hantzche and Finnemore to aide <br /> engineers and septic system designers /planners in assessing the long term potential impact that domestic <br /> sanitary systems may have on groundwater with respect to nitrate contamination. The simplified prediction <br /> of nitrate impacts of on-site sewage disposal systems over a defined geographical area is made by <br /> constructing a mass balance, considering only inputs from waste water and recharge of rainfall and losses <br /> due to denitrification in the soil column and the upper portion of the aquifer. The most favorable soil <br /> conditions for denitrification are (a) the abundance of organic carbon sutrate, (b) high soil moisture content, <br /> and (c) high soil pH.' Denitrification losses range from 1 to 75%, 25% being the most typical. The <br /> assumptions applied in the following analysis are on the conservative side, predicting nitrate concentration <br /> levels indicative of the worst case scenario. Essentially, the nitrate concentration reaching the upper portion <br /> of the aquifer is calculated as the weighted average of nitrate-It - <br /> i gen concentration of percolating rainfall <br /> and waste water, adjusted for expected losses;arj� <br /> t ncation. The expression for the resultant <br /> r <br /> average concentration, nr, of nitrate-nitrog 'na is given by: <br /> nr = ( I *nw *( 1 A) +R *nb ]/(I +R) <br /> Where... <br /> n„-: total nitrogen concentration in waste water [mg/liter] <br /> nb: background nitrate-nitrogen concentration of rainfall recharge at the water table [mg/liter] <br /> d: fraction of nitrogen-nitrate loss due to denitrification in the soil <br /> I: volume rate of waste water entering the soil [inches/year] <br /> R: average recharge rate of rainfall [inches/year] <br /> Hantzche and Finnemore, "Predicting Ground-Water Nitrate-Nitrogen Impacts", Ground Water Journal, <br /> Volume 30, Number 4; July-August 1992 <br /> 5 <br />