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April 20, 2004 _ <br /> NOA Project Number: E04002A - <br /> Page 12 - - <br /> 7.3 Denitrification Estimate <br /> Denitrification is an important process which occurs within the leach field whereby certain <br /> bacteria utilize the oxygen in the nitrate (NO3) and release nitrogen gas (N2)to the atmosphere. <br /> Denitrification is expressed as a percentage, and the normally accepted.range'is 10 percent to 35 <br /> percenC Soils with higher clay content, moist soil conditions; high pH;rand organic material <br /> denitrify by about 35 percent, and soils with high sand content and fast percolation rates are <br /> estimated to denitrify at a lower rate, about 10 percent to 15 percent. <br /> A denitrification factor of 25 percent was used for the Site. <br /> / 7.4 Agricultural Contribution <br /> Since the Site is not used for agriculture,no agricultural contribution has been considered for this <br /> analysis. <br /> 7.5 Nitrate Loading Scenarios <br /> r A nitrate loading scenario was performed to determine the impact from the proposed facility. <br /> The scenario utilizes-the variables discussed previously which represent the estimated conditions <br /> and uses associated with this project. The following table presents a summary of the nitrate <br /> loading calculation: - <br /> 1 <br /> Table 7. <br /> Summary of Nitrate Mass Balance Analysis. - <br /> Calculation Result T Acres :Average Effluent Leaehfield Deep Percolation <br /> (Nc)* (A) Daily Flory Concentration Denitrifi-' of Rainfall(R) <br /> (Q)(Table 2) (Nw) T -cation(d) (Plate 9) <br /> ' see Plate 10 1.4 m IL-N- . 19.9 .121 ME. 45 in L-N 25% 6.84 in <br /> * Maximum contaminate level(MCL)for Nitrate in drinking water is 10 mg/L-N. <br /> Based on the method and assumptions described, the result of the nitrate loading balance <br /> indicates the proposed development will not causFa buildup of nitrate in groundwater above 10 = . <br /> mg/L-N over the long term. <br /> s <br />