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' V 12 June 2008 AGE-NC-07-1581 j Page 15 of 17 N, =The average concentration of nitrate-nitrogen in the recharged waste water parts per million of nitrate-nitrogen. I =Volume rate of wastewater entering the soil averaged over the gross developedarea(acres) in inches per year. The total wastewater volume for proposed project will be 11 gpd x 102 days of proposed operation=-1:7- ,,3-40 gallons-7.48 gallons per cubic foot='' cubic feet of wastewater. Does not accoug�'ityor evapotranspiration likely to occur. 2;35Y NW =Total nitrogen concentration of wastewater at 65 mg/L-N based on the average discharge. Accounting for the loss of mg/L-N in the septic tank at 15%: 65-15%= 55.25 and the loss from the biomat at 10%: 55.25 - 10%=49.73 mg/L-N or approximately 50 mg/L-N d = Fraction of nitrogen concentration removed from the wastewater due to denitrification within the soil (20 percent for clay type soils). R =Average rainfall rate per year: 12 inches. Nb = Background nitrate-nitrogen concentration .of rainfall recharge, from wastewater influences. Assumptions: a 3G� Z352f I= 17,340 gallons/year=2,3i-8-cubic feet wastewater/year-(3.87 acres x 43,560 feet2 12 inches) 3 3�year_14,048 = 0.165 inches/year Nw= 50 mg/L-N d=20 percent denitrification R= 12 inches/year Nb= 0.1 milligram per liter C3 N,= G. 5 inches/year(50 mg/L-N) (1-0.20) + 12 inches/year x 0.1 mg/1 (GA65-inchcs/year+ 12 inches/year) o-tdo 0.451 N,=�-8=42—.Yfr.5= 0.641 mg/L Nr=OdAl ppm nitrogen (NO3_N) Nr=13-ppm nitrate (NO3) 9.6. IMPACT OF NITROGEN LOADING FROM SITE PROJECT The Calaveras River is the most likely potential feature that could be impacted by nitrogen loading. However, the potential vertical migration of the wastewater would be greater than the potential lateral migration of over 200 feet south to the river intersection. Based on the low volume of wastewater to be generated and the significant depth to ground water,the potential vertical migration would not likely degrade the local ground water. Advanced GeoEnvironmental,Inc.