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— December 23, 2005 <br /> NOA Project Number: E05174A <br /> !/3.4.2 DerlrtrrScation Estimate <br /> Denitrification is an important process which occurs within the leach field whereby certain bacteria <br /> .A utilize the oxygen in the nitrate (NO3) 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 /> 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 typical denitrification factor of 25 percent was selected for the Site due to the presence of low <br /> r, <br /> permeability soils. <br /> 3.5 Nitrate Loading Scenario <br /> r; <br /> A nitrate loading scenario was performed to determine the impact from the proposed project. The <br /> f 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 /> i calculation. <br /> Table 3. <br /> Summary of Nitrate Mass Balance Analysis <br /> _+ -esult Acres Average Daily Effluent Concen- Leachfield Deep Percolation of <br /> _-04r7 * (A) Flow(Q) (Table 1) tration(Nw) Denitrifi- Rainfall(R) <br /> (mg/L- (gpd) (mg/UN) cation(d) (Pl in <br /> 1.4 363.66 1,51e' 60 25% 5.76 <br /> Zaxim cont an el(MCL) for nitrate in drinking water is 10 mg/L-N. <br /> a <br /> /3.6 Impact of Nitrate Loading to Nearby Water Sources <br /> a The result of the nitrate loading balance indicates that the existing septic systems will not potentially <br /> cause a buildup of nitrate in the ground water above 10 mg/L-N over the long term. According to <br /> the Hantzsche and Fennemore equation, approach, and assumptions discussed, the potential for <br /> buildup of nitrates in the ground water was estimated to be 1.4 mg/L-N. <br /> F7" <br /> GJ <br /> 7 <br /> w : <br />