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} l <br /> July 11, 2007 <br /> NOA Project Number: E07094A <br /> Table 2. <br /> Weighted Average of Residential / Commercial <br /> Total Nitro en Concentration <br /> 45 mg/L-N x� 770 gpd= 34,65p,mg/L-gpd <br /> 85 mg/L-N x 17.96 gpd= 1,526.6 mg/L-gpd <br /> � 34,650 m /L-gpd+ 1,526.6 m /Lrgpd =36,176.6 m /L-gPd 770 r+ 7.96_gp.�=787.96gpd <br /> 36,176.6 m /U d/ 787.96d�-45;91 m /L-N_,) <br /> I:+ <br /> Based on the weighted average of mg/L-N concentrations in the flow of waste water, it is estimated <br /> that theavemr,1 tration for total nitrogen from both sources in waste water for the project is <br /> approximately 5.91 mg/L-N over the long term. <br /> 3.4.2 Denittiffcation 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 35 percent was selected for the calculation because of the fine- <br /> grained silty clays that exist at the site. <br /> a� <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 /> F1 uses associated with this project. The following table presents a summary of the nitrate loading <br /> calculation for the parcel. <br /> Table 2. <br /> FI Summa of Nitrate Mass Balance Analysis. <br /> Parcel Result Acres Average Daily Effluent Leachfield Deep Percolation <br /> F) (Nc)* (A) Flow(Q) (Table 3) Concen- Denitrift- of Rainfall(R) <br /> (mg/L-N) (gpd) tration(Nw) cation(d) (Plate 9) (in.) <br /> (mg/L-N) <br /> 1 7.1_ J 9.86 788 45.91 35% 4.0 <br /> * Maximiiin contaminant level(NICL)for nitrate in d `hgWa-t'er is 10 mg/L-N. <br /> 0 <br /> 3 ! 7 <br /> F <br />