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k' GEOTECHNICAL <br /> NEIL O. ANDERSON ENVIRONMENTAL <br /> AN D ASSOCIATES INSPECTIONS & TESTING <br /> LABORATORY SERVICES <br /> POOL ENGINEERING <br /> POST TENSION DESIGN <br /> April 7, 2006 <br /> ` NOA Project Number: E06020A <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 (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 typical denitrification factor of 20 percent was selected for the Site because of the fine grained <br /> soils that exist at the site. <br /> 3.5 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 /> ` <br /> Summary 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 1 5.2 1 45 548 47.6 20% 1.27 <br /> * Maximum contaminant level(1\1CL) for nitrate in drinking water is 10 mg/L-N. <br /> r. 3.6 Impact of Nitrate Loading to Nearby Water Sources <br /> Based 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 /> Since the Site is relatively flat,we do not foresee percolating effluent affecting any surface water <br /> resources. <br /> L <br /> 7 <br /> LLODI ■ SACRAMENTO ■ MODESTO <br /> ENVIRONMENTAL DIVISION 902 Industrial Way,Lodi,California 95240 ■209.367.3701 ■ 209.369.4228 ■www.noar. <br />