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L <br /> L May 25, 2006 <br /> NOA Project Number: E06040A <br /> L ground water flow from up-gradient areas. These processes would generally contribute to additional <br /> reduction of nitrate-nitrogen concentrations in ground water to the extent that the nitrate-nitrogen <br /> concentration of ground-water flow from up-gradient areas is lower." <br /> I <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 /> I disposal systems and precipitation. This (the equation and approach) is for estimation of long-term <br /> L effect (i.e., over years) on ground-water quality,and is not intended for prediction of seasonal <br /> changes" (Hantzsche and Finnemore, 1992). <br /> LThe method takes into account the development area, soil denitrification factor,rainfall volume, <br /> rainfall nitrate concentration,waste effluent quantity,and waste effluent nitrate concentration. The <br /> formula,assumptions and calculations used for the analysis are shown on Plates 9 and 10. The units <br /> of nitrate used in the mass balance equation ate nitrate-N,whose maximum drinking water <br /> contaminant level is 10 mg/L. <br /> I <br /> L <br /> 1.0 CHEMICAL AND PHYSICAL PROPERTIES OF SOIL <br /> L1.1 Chemical and Physical Soil Properties <br /> L <br /> For a discussion of on-site soil properties,refer to Section 5 of the SSS. <br /> I. 1.2 Mass Transport Soil Properties <br /> L Fine grained sediment and the degree of cementation can provide an added protection between <br /> percolating effluent at the surface and shallow ground water aquifers. The longer the effluent <br /> remains near the surface, the more treatment is enhanced due to natural processes within the soil. <br /> The soils on the site were silty sands with some clay. Soils of this type do not typically present a <br /> high risk of excessive mass transport of nitrate or other constituents of concern. <br /> L <br /> 2.0 GROUND WATER ANALYSIS <br /> 2.1 Regional Ground Water <br /> A discussion of regional ground water,including depth to ground water and directional ground <br /> L water gradient,is included in Section 4.1 of the SSS. No significant seasonal trends were evident <br /> from the maps consulted. <br /> t <br /> L <br /> 3 <br /> 6 <br />