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L Id <br /> L September 10, 2004 <br /> NOA Project Number: E040104A <br /> Page 7 <br /> 3.4.2 Denitrification Estimate <br /> Denitrification is an important process which occurs within the leach field whereby certain <br /> bacteria utilize the oxygen in the nitrate (NO) and release nitrogen gas (N) to the <br /> atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is <br /> ►. 10 percent to 35 percent. Soils with higher clay content, moist soil conditions, high pH, and <br /> organic material denitrify by about 35 percent, and soils with high sand content and fast <br /> percolation rates are estimated to denitrify at a lower rate, about 10 percent to 15 percent. <br /> A denitrification factor of 25 percent was selected for the Site. <br /> 3.5 Nitrate Loading Scenario <br /> `, A nitrate loading scenario was performed to determine the impact from the proposed project. <br /> The scenario utilizes the variables discussed previously which represent the estimated <br /> conditions and uses associated with this project. The following table presents a summary of <br /> 6. the nitrate loading calculation. <br /> Table 2. <br /> Summary of Nitrate Mass Balance Analysis. <br /> Parcel Plate Result Acres Average Effluent Leachfield Deep <br /> (Nc) " (A) Daily Flow Concen- Denitrifi- Percolation of <br /> (mg/L-N) (Q)(Table 3) tration(Nw) cation(d) Rainfall(R) <br /> (gpd) (mg/L-N) (Plate 9)(in.) <br /> 1 10 18.8 2.0 560 45 25% 3.16 <br /> 2 11 18.8 2.0 560 45 25% 3.16 <br /> 6. 3 12 18.8 2.0 560 45 25% 3.16 <br /> 4 13 18.8 2.0 560 45 25% 3.16 <br /> 5 14 18.8 2.0 560 45 25% 3.16 <br /> 6 15 1.5 108.9 420 45 25% 3.16 <br /> V <br /> * Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg/L-N. <br /> 60 <br /> 7 I <br />