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i. <br /> `February 15, 2006 <br /> NOA=Project Number: E06006A <br /> 3.4.2 _Denitrification Estimate <br /> Denitrification is an important process which occurs within the leach field whereby certain bacteria <br /> 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 ercolation rates are <br /> g p <br /> A estimated to denitrify at a lower rate, about 10p ercent to 15 percent. <br /> f . <br /> M A denitrification factor of 10 percent was selected for the Site due to the presence of silty sands. <br /> 3 F <br /> '[[``r 3.5 Nitrate Loading Scenario <br /> i � F <br /> f JJ -A 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 (Plate 11). <br /> I, Table 3. <br /> Summaryof Nitrate Mass Balance Analysis. <br /> Result Acres Average Daily Effluent Concen- Leachfield Deep Percolation of <br /> (Ne)* (A) Flow(Q) (Table 1) tration(Nw) "'Denitrif- Rainfall(R) <br /> (mg/L-N) _-(gpd) (mg/L-N) cation(d) (Plate 10) (in.) <br /> - 4.4 14.32 ___. 841.1 60 10% 11.68 <br /> i <br /> F _ * 'Maximum contaminant level(MCL) for nitrate in drinking water is 10 mg/L-N. <br /> 3.6,T Impact of Nitrate Loading to Nearby Water Sources <br /> The result of the nitrate loadingbalance <br /> _ indicates that the proposed use should not cause a buildup <br /> of nitrate in the groundwater above 10 mg/L-N over the long term. According to the Hantzsche <br /> F1 and Fennemore equation and approach, there is a potential for a buildup of nitrates in the ground <br /> water to 4.4-mg/L-N. _ <br /> 4.0 ' DISCUSSION OF NITRATE LOADING RESULTS <br /> 4.1 Total Nitrate Impact <br /> According to the Hantzsche-and Fennemore equation and approach there is a potential for.a <br /> buildup of nitrates in the ground water to 4.4 mg/L-N over the long term;this concentration is <br /> below the safe drinking water standard. <br /> 6 <br />