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June 14,2005 <br /> NOA Project Number: E05066A <br /> and Finnemore mention that"...the equation ignores dispersion,lateral flow, and mixing with <br /> 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 /> disposal systems and precipitation. This (the equation and approach) is for estimation of long-term <br /> effect (i.e., over years) on ground-water quality,and is not intended for prediction of seasonal <br /> changes" (Hantzsche and Finnemore, 1992). <br /> The 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 through 10. The <br /> units of nitrate used in the mass balance equation are nitrate-N,whose maximum drinking water <br /> contaminant level is 10 mg/L. <br /> J/2.0 CHEMICAL AND PHYSICAL PROPERTIES OF SOIL <br /> 2.1 Chemical and Physical Soil Properties <br /> �- For a discussion of on-site soil properties,refer to Section 5 of the SSS. <br /> -*'2.2 Mass Transport Soil Properties <br /> Layered sediments or soils with higher amounts of silt and clay will typically provide an added <br /> degree of protection between percolating effluent at the surface and shallow ground water aquifers. <br /> The sandy clay soils of the site do not typically present a high risk of excessive mass transport of <br /> nitrate or other constituents of concern. <br /> 3.0 GROUND WATER ANALYSIS <br /> 3.1 Regional Ground Water <br /> A discussion of regional ground water,including depth to ground water and directional ground <br /> •• water gradient,is included in Section 4.1 of the SSS. No significant seasonal trends were evident <br /> from the maps consulted. <br /> 2 <br />