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Mr. Sandi De Jong October 10,2006 Page 5 4.4 Future On-Site Sources of Nittate 4.4:1 Quantity and Qu2 tv ofDofnestic iV;?steu ster Ftnm Proposed Project See Section 3-6 for discussion of Quantity of Domestic Wa.stetvater from the proposed project '11-e average total nitrogen concentration of domestic waste water is norrmaD.y considered to be 20-85 mg/L-N with 35 to 45 mg/L-N being t`-pical (Crites and Tchobanoglous, 1998). It is esti.ma.ted ti.-int cotninezcial use will hatrc higher conccni-rations of total nitrogen w12en compared to residential use. It is estimated that the average concentration for total.nitrogen i-11 Waste water:for the project is apprositaiatcly 65 mg/L-N over the long tern. 4.4.2 Denitriftcatio.n Fstid»arr Dcnitufication is an irnportant process which occurs within the leach field whereby certain bacteria utilize the oxygen in the nitrate (NO,) and release 6twgen gas (Nj to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 percent. Soils with btgber 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.tate, about 10 percent to 15 percent A denitvficarion factor:of 30 percent was selected for the Site due to tb.e silty nature of the soils. 4.5 Nitrate Loading Scenario A nitrate loading scenatio was perfonmed to determine the impact from the proposed project_ The scenario utili7cs the variables discussed previously which represent the estunated conditions and uses associated with this project. The following table presents a summary of the nitrate loading calculation for the property. Table 2. Surma of Nitsatc Mass Balance Analysis. Average Daily Effluent LeachfiDeep Resttlt Acres Plow(Q) Concen_ Dmitri fi- Percolation of P1atc (Ne)* Denitrifi- (rrtg/i.r'�T) (A) (Table 3) tration(Nw) cation(d) Rainfall(R) (gpd) (rng/L-N) (Plate 9) (in.) 5itc 7.8 3.5 272.15 65 130% >"C * I,vLlxvmum contaminant level(MCL)for.nitrate in dtinIchig water is 10 mg/L-N.