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• Table 6-2. Weighted Average Concentration Calculation <br /> Use Average Daily Estimated Waste Weighted Average <br /> Flow Water Quality Product <br /> Residences 980 gpd 35 mg/L-N 34,300 gpd-mg/L-N <br /> Employee 33.5 gal 85 mg/L-N 2,847.5 gpd-mg/L-N <br /> Customers 92.9 gpd 85 mg/L-N 7,896.5 gpd-mg/L-N <br /> Totals 1,106.4 gpd 45,044 gpd-mg/L-N <br /> Weighted Average 45,044 gpd-mg/L-N / 1,106.4 gpd = 40.7 mg/L-N <br /> Concentration: <br /> Denitrification Reductions <br /> Denitrification is a process that occurs in the septic system drain field whereby <br /> certain bacteria oxidize the nitrate (NO3) in the wastewater and release nitrogen <br /> gas (Nz) to the atmosphere. Due to the biologic processes in the shallow soils, <br /> nitrogen in the drain field will may undergo a reduction between 10 percent to 35 <br /> percent. Soils with higher clay content, moist soil conditions, high pH, and <br /> organic material denitrify by about 35 percent, and soils with high sand content <br /> and fast percolation rates tend to denitrify at a lower rate of about 10 percent. <br /> • A typical denitrification factor of 25 percent was selected for the Site because of <br /> the fine-grained shallow soil at the percolation test location. <br /> Nitrate Loading Estimate <br /> A nitrate loading scenario was employed to determine the impact from the <br /> proposed project to ground water. The scenario utilizes the variables discussed <br /> previously, which represent the estimated conditions and uses associated with <br /> this project. The following table presents a summary of the assumptions for the <br /> nitrate loading calculation for the Site, as presented in Plate 6-1. <br /> • LOGE 1820 Page 6-3 <br />