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i` <br /> L March 22, 2005 <br /> NOA Project Number. E040132A <br /> L <br /> 3.4.2 Deni&Xcadon Estimate <br /> Denitrification is an important process which occurs within the leach field whereby certain bacteria <br /> Lutilize the oxygen in the nitrate (NOS and release nitrogen gas (N� 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 /> Ldenitrify 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 /> Ldenitrification factor of 25percent was selecred'of fPie t e. <br /> 3.5 Nitrate Loading Scenario <br /> LA nitrate loading scenario was performed to determine the impact from the proposed project. The <br /> scenario utilizes the variables discussed previously which represent the estimated conditions and <br /> uses associated with this project. The following table presents a summary of the nitrate loading <br /> calculation for each parcel. <br /> Table 2 <br /> Stunmary of Niv rate ss alance Analysis. <br /> Plate Result Acresverage Dail ",Effluent Leachfield Deep <br /> (Nc)* (A) Flow(Q) ,Effluent <br /> Denitrifi- Percolation of <br /> (mg/L-N) (Table 3) tra on(Nw) cation(d) Rainfall(R) <br /> (gpd) ( g/L-N) (Plate 9)(in.) <br /> 10 2.7 20.89 490 45 25% 5.84 <br /> �. 11 2.3 27.42 490 45 % 5.84 <br /> * Maximum contaminant level(MCL) r nitrate in d g water is 10 mg/L-N. <br /> 3.6 Impact of Nitrate Loading to Nearby Water Sources <br /> l <br /> bw Based on the method and assumptions described,in addition to the geologic setting, the proposed <br /> project will likely not cause a build up of nitrate in the ground water above 10 mg/L-N on the <br /> LParcels over the long term. <br /> Since the Site is relatively flat,we do not foresee percolating effluent affecting any surface water <br /> resources. <br /> �. + <br /> j <br /> f,. <br /> L <br /> 6 <br /> L. <br />