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July 28,2006 <br /> NOA Project Number: E06068A <br /> 4.4.2 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 denitrification factor( f 35 percent was selected for the Site due to the clayey nature of the soils. <br /> ✓4.5 Nitrate Loading Scenario <br /> LA 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 /> ins calculation for each parcel. <br /> Table 2. <br /> "p Summary of Nitrate Mass Balance Analysis. <br /> Result Average Daily Effluent Leachfield Deep <br /> Plate (Nc)* Acres Flow(Q) Concen- Denitrifi- Percolation of <br /> r. (mg/L-N) (A) (Table 3) tration(Nw) cation(d) Rainfall(R) <br /> (gpd) (mg/L-N) (Plate 9) (in.) <br /> Site 1 1.4 79 250 85 35% 5.76 <br /> * Maximum contaminant level(MCL) for nitrate in drinking water is 10 mg/1—N. <br /> V14.6 Impact of Nitrate Loading to Nearby Water Sources <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 /> the aquifer above 10 mg/L-N. <br /> Since the Site is relatively flat,we do not predict that percolating effluent will affect any surface <br /> i' water resources. <br /> r�5.0 DISCUSSION OF NITRATE LOADING RESULTS <br /> 5.1 Total Nitrate Impact <br /> r. <br /> Based on the method and assumptions described,it is our opinion that the nitrate loading <br /> calculation of the proposed development on the parcel should not cause a build up of nitrate in the <br /> 5 <br /> d <br />