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L <br /> May 25,2006 <br /> NOA Project Number: E06015A <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 (NOS 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 /> 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 typical denitrification factor of 35 percent was selected for the Site because of the fine grained <br /> soils that exist at the site. <br /> L3.5 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 /> S nunary of Nitrate Mass Balance Analysis. <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 9.5 5 321 85 35% 4.67 <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 /> LBased on the method and assumptions described,in addition to the geologic setting,we do not <br /> believe the proposed project will cause a build up of nitrate in the ground water above 10 mg/L-N <br /> over the long term. <br /> LSince the Site is relatively flat,we do not foresee percolating effluent affecting any surface water <br /> resources. <br /> 4.0 DISCUSSION OF NITRATE LOADING RESULTS <br /> L4.1 Total Nitrate Impact <br /> Based on the method and assumptions described, the result of the nitrate loading balance indicates 1 <br /> that the proposed development on the proposed parcels should not cause a build up of nitrate in the <br /> 6 <br />