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LOGE 1605: Durst Winery NLS Addendum Page 6 March 21, 2016 Table 3. Weighted Average Concentration Calculation Use Average Daily Estimated Waste Weighted Average Flow Water Quality Product Residence 720 gpd 45 mg/L-N 32,400 gpd-mg/L-N Winery Customers 50 gpd 85 mg/L-N 4,250 gpd-mq/L-N Winery Staff(Fri.-Sun.) 7.4 gpd 85 mg/L-N 629 gpd-mg/L-N Event Customers 27.4 gpd 85 mg/L-N 2,329 gpd-mg/L-N Event Staff 1.4 gpd 85 mg/L-N 119 gpd-mg/L-N Totals 806.2 gpd 39,727 gpd-mg/L-N Weighted Average 39,727 gpd-mg/L-N/ 806.2 gpd =49.3 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 25 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.