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L U <br /> LDecember 1, 2004 <br /> NOA Project Number: E040117A <br /> / <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 (N2) to the atmosphere. <br /> Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 <br /> percent. Soils with higher clay content, moist soil conditions,high pH, and 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 selected for the Site. <br /> f3.5 Nitrate Loading Scenario <br /> L <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 conditions <br /> 1ri and uses associated with this project. The following table presents a summary of the nitrate <br /> loading calculation for each parcel. <br /> ` Table 3. <br /> Summary of Nitrate Mass Balance Analysis. <br /> .. 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/I-N) (Plate 9)(in.) <br /> 10 5.4 4.84 382 45 25% 6.84 <br /> 11 10.1 2.51 490 45 25% 6.84 <br /> '* Maximum contaminant level(MCL)for nitrate in drinking water is 10 mg/L-N. <br /> 3.6 Impact of Nitrate Loading to Nearby Water Sources <br /> Based on the method and assumptions described, in addition to the geologic setting, we do not <br /> ` believe the proposed project will cause a build up of nitrate in the ground water above 10 <br /> mg/L-N over the long term. <br /> Since the Site is relatively flat,we do not foresee percolating effluent affecting any surface water <br /> resources. <br /> 6 <br /> 60 <br /> tr <br />