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t .,` i 4 August 5, 2005 NOA Project Number: E05098A L )/ local officials but with some real limitations. In their article published in Ground(later, Hantzsche and Finnemore mention that "...the equation ignores dispersion,lateral flow, and mixing with ground water flow from up-gradient areas. These processes would generally contribute to additional Ureduction of nitrate-nitrogen concentrations in ground water to the extent that the nitrate-nitrogen concentration of ground-water flow from up-gradient areas is lower." UThe Hantzsche and Fennemore approach is "...a conservative (worst case) first approximation of ground-water nitrate-nitrogen concentration resulting from the combined effect of on-site sewage disposal systems and precipitation. This (the equation:and approach) is for estimation of long-term !.� effect (i.e., over years) on ground-water quality, and is not intended for prediction of seasonal changes" (Hantzsche and Finnemore, 1992). The method takes into account the development area, soil denitrification factor,rainfall volume, rainfall nitrate concentration,waste effluent quantity, and waste effluent nitrate concentration. The j formula, assumptions and calculations used for the analysis are shown on Plates 9 and 10. The units of nitrate used in the mass balance equation are nitrate-N,whose maximum drinking water contaminant level is 10 mg/L. �1.0 CHEMICAL AND PHYSICAL PROPERTIES OF SOIL -1.1 Chemical and Physical Soil Properties For a discussion of on-site soilP pro erties,refer to Section 5 of the SSS. . /1.2 Mass Transport Soil Properties Layered soils and sediments, such as the some fine-grained soil layers found on the Site, typically provide a degree of protection between percolating effluent at the surface and shallow ground water aquifers. Soils of this type do not typically present a high risk of excessive mass transport of nitrate or other constituents of concern. Ll /2.0 GROUNDWATER ANALYSIS . /2.1 Regional Ground Water 1� A discussion of regional ground water,including depth to ground water and directional ground t water gradient,is included in Section 4.1 of the SSS. No significant seasonal trends were evident from the maps consulted. The depth to ground water was found to be approximately 40 and 60 feet /in the area in 1999. U {/ 2.2 Potential Ground Water Contamination Issues L-1 A discussion of issues related to potential ground water contamination is included in Section 4.2 of U2