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May 17, 2007 <br /> NOA Project Number: E07064A <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 percolation rates are <br /> estimated to denitrify at a lower rate, about 10 percent to 15 percent. <br /> ® A typical denitrification factor of 35 percent was selected for the site because of the fine grained <br /> �! clays that exist at the site. <br /> 3.5 Nitrate Loading Scenario <br /> 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 for the parcel <br /> Table 2. <br /> Summary of Nitrate Mass Balance Analysis. <br /> Parcel Result Acres Average Daily Effluent Leachfield Deep <br /> (Ne) * (A) Flow(Q) Concen- Denitrifi- Percolation of <br /> (mg/L-N) (Table 3) tration(Nw) cation(d) Rainfall(R) <br /> (gpd) (mg/L-N) (Plate 9) (in.) <br /> 11 1 1 2.3 12.31 104 1 85 35% 1 4.67 6,5,) <br /> * Maximum contaminant level(MCL}.foi nitrate in drinking watef is'10 mg/PtKw <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 /> 'lielieve the proposed project will-cause a'b'uild u'p o n trate in the g ound wa above 10 in N <br /> ovee long term. j <br /> - Since the site is relatively flat,we do not foresee percolating effluent affecting any surface water <br /> resources. <br /> 6 <br />