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B. CALCULATED NITRATE-NITROGEN LOADING NLS§ 3.4, 3.5, 3.6. The calculated nitrate-nitrogen impact to the soil and potentially to the groundwater is difficult to determine due to the large number of variables involved and variables unknown at this time. These include: 1.) Nitrate impact from upgradient sources, 2.) Variability in wastewater flows, effluent nitrogen concentrations and dilution effects, 3.) Changes in groundwater directional flow and elevation, 4.) And the denitrification potential of the indigenous soils. HANTZSCHE/FIIVNEMORE EOUATION IN,,„ (1 - d) + R Nb Nr = (I + R) Where: Nr = Resultant average concentration of nitrate-nitrogen in recharge water - (ppm NO3-N) I = Volume rate of wastewater entering the soil averaged over the gross developed area in in/yr Nw = Total nitrogen concentration of wastewater in mg NIL d = Fraction (%) of nitrate-nitrogen combined loss in the soil due to denitrification and prevention of nitrification. R = Estimated Annual Rainfall Recharge. Nb = Background nitrate-nitrogen concentration of rainfall recharge, exclusive of wastewater influences (ppm NO3-N). Values and Assumptions: I = 2,220 gpd x 365 d/yr = 810,300 gals/yr = total WW/yr = 108,329 cu ft = 23.14 in/yr (1.93 in/mo) 1.29 Ac x 43,560 sq ft/Ac x (1 ft/12 in) Nw = 67.4 mg N/L d = The soil test results indicate a 75% decrease in soil nitrogen concentrations between the 5 ft and 20 ft depths (From 4 ppm down to 1 ppm), attributable to denitrification and attenuation of nitrification. This percentage is used in the Nr equation below. R = 8.82 in/yr. N I, = Assumed to be 0.1 ppm NO3-N 23.13 in/yr (67.4 mg NIL) (1 - 0.75) + (8.82 in/yr x 0.1 mg/L) Nr = (23.14 in/yr + 8.82 in/yr) Nr = 12.2 ppm as nitrate-nitrogen (NO3-N) or 54.4 ppm as nitrate (NO3) The calculated nitrate-nitrogen loading is theoretically 2.2 ppm over the Maximum Contaminant Level (MCL) of 10 ppm NO3-N. To mitigate this excess nitrate loading and lower the loading below the MCL, mitigation measures and procedures are discussed in the Conclusions and Recommendations Section of this Report. Pngc-z6- Chesney Consulting