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B. CALCULATED NITRATE-NITROGEN LOADING <br />NLS§ 3.4, 3.5, 3.6. The calculated nitrate-nitrogen impact to the soil and ultimately to the <br />groundwater is difficult to determine due to the large number of variables involved and variables <br />unknown at this time. These include: 1.) Impact from upgradient nitrate sources, 2.) Variability in <br />wastewater flows, effluent nitrogen concentrations and dilution effects from stormwater recharge, <br />3.) Changes in groundwater directional flow and elevation, 4.) And of significant importance is not <br />only the denitrification potential of the indigenous soils, but equally important is the diminished <br />nitrification potential within the soil environment. The small pore space within the high clay <br />content soil significantly reduces oxygen content, thus impeding nitrification. <br />HANTZSCHE/FI1VNEMORE EQUATION <br />1N,(1 - d)+RNI, <br />Nr = (I+R) <br />Where: <br />Nr = Resultant average concentration of nitrate-nitrogen in recharge water - (ppm NO3-N) <br />I = Volume rate of wastewater entering the soil averaged over the gross developed area in ac-ft <br />Nw = Total nitrogen concentration of wastewater in mg N/L <br />d = Fraction (%) of nitrate-nitrogen combined loss in the high clay content soil due to: <br />1.) Prevention of nitrification and 2.) The denitrification of nitrate molecules that may form. <br />R = Estimated Annual Rainfall Recharge in ac-ft <br />Nb = Background nitrate-nitrogen concentration of rainfall recharge, exclusive of wastewater influences <br />(ppm NO3-N). <br />Values and Assumptions: <br />1= 0.071 ac-ft <br />Nw = 62 mg N/L <br />d = Assume 25% due to the high percentage of clay soil (22%) found from 5 ft to 8 ft in depth that not only <br />mitigates nitrification, but also promotes denitrification of nitrate molecules that may form in the stratum from <br />0 ft to 5 ft where lower clay concentrations occur. <br />R = 5.70 ac-ft <br />Nb = Assumed to be 0.1 ppm NO,-N <br />0.071 ac-ft (62 mg NIL) (1 - 0.25) + (5.70 ac-ft x 0.1 mg/L) <br />Nr = (0.071 ac-ft + 5.70 ac-ft) <br />Nr = 0.67 ppm as nitrate-nitrogen (NO-N) <br />Page -7- <br />Chesney Consulting