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..i September 30, 2007 NOA Project Number: E07147A Weighted Average for Total Nitrogen Concentration 14,700gpd x 49 mg/L-N=661,900 130gpd x 65 mg/L-N=8,490 669,990114,830 gpd=45.17 mg/L-N 3.4.2 Denitrification Estimate Denitrification is an important process which occurs within the leach field whereby certain bacteria utilize the oxygen in the nitrate (NO3) and release nitrogen gas (N� to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 percent. Soils with higher clay content,moist soil conditions,high pH, and organic material denitrify by about 35 percent, and soils with high sand content and fast percolation rates are estimated to denitrify at a lower rate,about 10 percent to 15 percent. A typical denitrification factor of 25 percent was selected for the site due to the presence of the fine- grained soils encountered on site. 3.5 Nitrate Loading Scenario A nitrate loading scenario was performed to determine the impact from the proposed project. The scenario utilizes the variables discussed previously which represent the estimated conditions and uses associated with this project. The following table presents a summary of the nitrate loading calculation. Table 3. Summary of Nitrate Mass Balance Analysis. Result Acres Average Daily Effluent Concen- Leachfield Deep Percolation of (Nc) * (A) Flow(Q) (Table 1) tration(Nw) Denitrifi- Rainfall(R) (mg/L-N) (gpd) (mg/L-N) cation(d) (Plate 9) (in.) 21.2 22.61 14,830 45.85 25% 5.76 * Maximum contaminant level(MCL) for nitrate in drinking water is 10 mg/L-N. 3.6 Impact of Nitrate Loading to Nearby Water Sources The result of the nitrate loading balance indicates that the proposed development is likely to cause a build up of nitrate in the ground water above 10 mg/L-N over the long term Due to the relatively flat surface of the subject property, the potential risk of surfacing effluent effecting surface water is expected to be minimal. 6 "004