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LOGE 1224: Heritage Oak Winery SS/NLS Addendum Page 6 November 23, 2012 Table 3. Weighted Average Concentration Calculation Use Average Daily Estimated Waste Weighted Average Flow Water Quality Product Residential (existing) 360 gpd 45 mg/L-N 16,200 gpd-mg/L-N Residential 240 gpd 45 mg/L-N 10,800 gpd-mg/L-N (potential future) Wnery Customers 110.7 gpd 85 mg/L-N 9,409.5 gpd-mg/L-N (total all days) Winery Staff 13 gpd 85 mg/L-N 1,105 gpd-mg/L-N Event Customers 26.3 gpd 85 mg/L-N 2,235.5 gpd-mg/L-N Event Staff 1.7 gpd 85 mg/L-N 144.5 gpd-mg/L-N Totals 751.7 gpd 39,894.5 gpd-mg/L-N Weighted Average 39,894.5 gpd-mglL-N / 751.7 gp = 53.1 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 (NZ) 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 typical denitrification factor Of 25 p rcent was selected for the Site because of the moderately fine-grained nature of the soil 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.