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L v <br /> LJune 10,2005 <br /> NOA Project Number: E05070A <br /> LThe daily waste water quantity is estimated to be 63 gallons per day. <br /> IThe average total nitrogen concentration of domestic waste water is normally considered to be <br /> 20-85 mg/L-N (Crites and Tchobanoglous, 1998). For the purposes of the nitrate loading estimate, <br /> the long-term average concentration for total nitrogen in waste water is estimated to be 45 mg/L-N. (3, 41 <br /> L3.4.2 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 /> L denitrify by about 35 percent,and soils with high sand content and fast percolation rates are <br /> estimated to denittfy at a lower rate, about 10 percent to 15 percent. <br /> LA denitrification factor of 15 percent was selected for 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. <br /> �- Table 2. <br /> Summary of Nitrate Mass Balance Analysis. <br /> Result Acres Average Daily Effluent Concen- Leachfield Deep Percolation of <br /> (Nc)* (A) Flow(Q) (Table 1) tration(Nw) Denitrifi- Rainfall (R) <br /> (mg/L-N) (gpd) (mg/UN) cation(d) (Plate 9)(in.) i <br /> 6 1.8 8.00 63 45 15% 4.67 <br /> * bfaximum contaminant level(MCL)for nitrate in drinking water is 10 mg/L-N. <br /> L3.6 Impact of Nitrate Loading to Nearby Water Sources <br /> The result of the nitrate loading balance indicates that the proposed development is not likely to <br /> Lcause a build up of nitrate in the ground water above 10 mg/L-N over the long term. This result is <br /> due to the large lot size and minimal predicted waste water flow. <br /> Since the Site is relatively flat,we do not foresee percolating effluent affecting any surface water <br /> resources. <br /> L <br /> 5 '.44 <br /> L <br />