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LOGE 1516: Stonum Vineyards NLS Addendum Page 6 August 11, 2015 Table 3. Weighted Average Concentration Calculation Use Average Daily Estimated Waste Weighted Average Flow Water Quality Product Residential(existing) 240 gpd 45 mg/L-N 10,800 gpd-mg/L-N Potential Second Dwelling 240 gpd 45 mg/L-N 10,800 gpd-mg/L-N Unit Winery Staff 12.4 gpd 85 mg/L-N 1,054 gpd-mg/L-N Winery Customers 14.3 gpd 85 mg/L-N 1,215.5 gpd-mg/L-N Winery Events 2.7 gpd 85 mg/L-N 229.5 gpd-mg/L-N Wine Club Events 16 gpd 35 mg/L-N 560 gpd-mg/L-N Totals 525.4 gpd 24,659 gpd-mg/L-N Weighted Average 24,659 gpd-mg/L-N/ 525.4 gpd = 46.9 mg/L-N Concentration: Denitrification Reductions Denitrification is a process that occurs in the septic system drain field whereby certain bacteria oxidize the nitrate (NO3) in the waste water and release nitrogen gas (N2) to the atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain field will may undergo a reduction between 10 percent to 35 percent. Soils with higher 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 tend to denitrify at a lower rate of about 10 percent. A denitrification factor of 15 percent was selected for the Site because of the sandy nature of the soils. Nitrate Loading Estimate A nitrate loading scenario was employed to determine the impact from the proposed project to ground water. The scenario utilizes the variables discussed previously, which represent the estimated conditions and uses associated with this project. The following table presents a summary of the assumptions for the nitrate loading calculation for the Site, as presented on the attached page.