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1 <br /> C) <br /> August 5, 2005 <br /> NOA Project Number: E05098A <br /> � 3.4.2 DenitriScatrorl 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 25 percent was selected for the Site due to the presence of some <br /> fine grained surface soils. <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. <br /> Table 3. <br /> Summary of Nitrate Mass Balance Anal sis. <br /> Result Acres Average Daily Effluent Concen- Leachfield Deep Percolation of <br /> (Nc)* (A) Flow(Q) (Table 1) ttation(Nw) Denitrifi- Rainfall(R) <br /> (mg/1,N) (gpd) (mg/L-N) cation(d) (Plate 9) (in.) <br /> 1.6 79 446 60 25% 5.76 <br /> * Maximum contaminant level(MCL) for nitrate in drinking water is 10 mg/L-N. <br /> 3.6 Impact of Nitrate Loading to Nearby Water Sources <br /> The result of the nitrate loading balance indicates that the proposed development is not likely to <br /> cause a build up of nitrate in the ground water above 10 mg/L-N over the long term. The nitrate <br /> loading addresses only septic system waste water. The low expected impact is due to the large parcel <br /> size and low expected septic system waste water flow. <br /> Due to the relatively small septic use associated with the project,the potential risk of surfacing <br /> effluent effecting surface water is expected to be minimal. <br /> 6 <br />