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L <br /> L February 21,2007 <br /> NOA Project Number. E07015A <br /> L3.4.2 Denitrification Estimate <br /> 1 Denitrification is an important process which occurs within the leach field whereby certain bacteria <br /> L 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 /> 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 /> LA denitrification factor of 20 percent was selected for the Site because of the fine granted nature of <br /> the soils. <br /> 3.5 Nitrate Loading Scenario <br /> V <br /> 1 A nitrate loading scenario was performed to detemzine the impact from the proposed project. The <br /> L 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 site. <br /> 6. Table 2. <br /> Summary of Nitrate Mass Balance Analysis. <br /> Parcel Result Acres Average Daily Effluent Leachfield Deep <br /> ✓r c)* (A) Flow(Q) Concen- Denitr fii- Percolation of <br /> (m N) (Table 3) tration(Nw) cation(d) Rainfall(R) <br /> (gpd) (mg/L-N) (Plate 9) (in.) <br /> 1 4.2 22.27 272 85 20% 3.3 <br /> * Maximum c taming level(MCL) for nitrate in drinking water is 10 mg/LN. <br /> ` 3.6 Impact of Nitrate Loading to Nearby Water Sources <br /> Since the Site is relatively flat,we do not foresee percolating effluent affecting any surface water <br /> Lresources. <br /> 4.0 DISCUSSION OF NITRATE LOADING RESULTS <br /> L 4.1 Total Nitrate Impact <br /> Based on the method and assumptions described,the result of the nitrate loading balance indicates <br /> that the proposed development on the proposed parcels should not cause a build up of nitrates in <br /> L the aquifer above 10 mg/L-N. <br /> L <br /> L 6 <br /> L <br />