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Nue Our Lady of Sorrows Chapel Page 6 poisonings in infants have occurred following the ingestion of water containing nitrate concentrations greater than 10 mg/1 nitrate as N or 45 mg/1 nitrate as NO3. The units of nitrate in _ used in the mass balance equation are nitrate-N with a maximum drinking water contaminate level of 10 mg/l. The nitrate loading analysis estimates the concentration of nitrate-N of the septic effluent combined with rain water after denitrification before mixing with ground water. The method is based on a simple mass balance formula which takes into account soil denitrification, rain fall, and the proposed waste effluent quantity and nitrate level. Assumptions and calculations for the analysis are contained on Worksheets No. 1,2,and 3 located in the Appendix. Denitrification is the biological process in the soil whereby certain bacteria utilize the oxygen in the nitrate (NOD and release nitrogen gas (N2)to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 10%to 25%. Sites with higher clay content,moist soil conditions, and organic material denitrify about 25%or more but sites with higher sand content and fast peculation rates are estimated to denitrify about 10%. Due to the lack of fine ma erial in the 20 foot soil column examined, we estimate the denitrification factor be about'15 %. In our approach to estimate the nitrate concentration,we used the following variables in our calculation. S mmary of Anal sis and Variables Used in the Mass Balance Equation Result of Denitrification" Deep Rain Waste level' Quantity of Rain Acres Analysis Percolation discharge Concentration' (50 people) 16.49 mg/1 15% 7.86 in/yr 45 mg/1 N 250 gal/day 0.17 mg/l N 0.57 as N The results of the analysis indicates that viewing the 0.57-acre site for a period of a year, the combingd_.rain water and septic effluent after denitrification is estimated to be no greater than :49 mg/1 as N. this estimate is abo t 1.6 times greater then the maximum contaminate n ung water standar 10 mg/l as N. Since the use of the building is expected to be much 4Hantzshe N.N.,Finnemore,E.J. 1991,Predicating Ground-Water Nitrate-Nitrogen Impacts. Ground Water Vol.30,No.4. w. _