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October 11,2005 NOA Project Number: E05111B 3.4.2 Denitrification Estimate Denitrification is an important process which occurs within the leach field whereby certain bacteria utilize the oxygen in the nitrate (NO3) and release nitrogen gas (N� to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 percent. Soils with higher clay content,moist soil conditions,high pH, and organic material denitrify by about 35 percent, and soils with high sand content and fast percolation rates are estimated to denitrify at a lower rate,about 10 percent to 15 percent. A denitrification factor of 25 percent was selected for the Site. 3.5 Nitrate Loading Scenario A nitrate loading scenario was performed to determine the impact from the proposed project. The scenario utilizes the variables discussed previously which represent the estimated conditions and uses associated with this project. The following table presents a summary of the nitrate loading calculation for the different sized parcel acreage (AC) (11.5 AC, 10.0 AC, 7.2 AC, 5.0 AC,4.6 AC, 4.2 AC, 3.0 AC). Table 2. Summary of Nitrate Mass Balance Analysis. Plate Result Acres Average Daily Effluent Leachfield Deep (Nc)* (A) Flow(Q) Concen- Denitrifi- Percolation of (mg/L-N) (Table 3) tration(Nw) cation(d) Rainfall(R) (gpd) (mg/L-N) (Plate 9) (in.) 10 4.6 11.5 490 45 25% 4.67 11 5.0 10.0 490 45 25% 4.67 12 6.4 7.2 490 45 25% 4.67 13 8.2 5.0 490 45 25% 4.67 14 8.7 4.6 490 45 25% 4.67 15 9.2 4.2 490 45 25% 4.67 16 11.5* 3.0 490 45 25% 4.67 * Maximum contaminant level(MCL) for nitrate in drinking water is 10 mg/L-N. 3.6 Impact of Nitrate Loading to Nearby Water Sources Since the Site is relatively flat,we do not foresee percolating effluent affecting any surface water resources. 6