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L <br /> LMay 25,2006 <br /> NOA Project Number: E06040A <br /> 3.4.2 DenibrMcation Estimate <br /> 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 (ND 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 of 35 percent was selected for the Site because of the fine grained nature of <br /> the soils. <br /> L3.5 Nitrate Loading Scenario <br /> A nitrate loading scenario was performed to determine 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 /> Table 2. <br /> —S a of Nitrate Mass Balance Anal sis. <br /> Parcel Result Acres Average Daily Effluent Leachfield Deep <br /> (Nc) * (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 /> 1 6.7 1.04 1 30 85 35% 3.3 <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 /> Since the Site is relatively flat,we do not foresee percolating effluent affecting any surface water <br /> L <br /> resources. <br /> L 4.0 DISCUSSION OF NITRATE LOADING RESULTS <br /> C 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 <br /> the aquifer above 10 mg/L-N. <br /> L <br /> 6 <br />