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Soil Suitability/ Nitrate Loading Study Addendum Letter 1rerracon <br /> Nostra Vita Winery Lodi, California <br /> May 20, 2019 revised June 10, 2019 Terracon Project No. NA197023 <br /> impact of the existing facility and proposed development. The scenario utilizes the variables <br /> discussed previously which represent the estimated conditions and uses associated with this <br /> project. The following table presents a summary of the nitrate loading calculation for the site <br /> based on the highest average daily flows for each the facility buildings with septic tanks. Nitrate <br /> loading scenarios were additionally calculated for the special events. A copy of the nitrate loading <br /> calculation is included in the Attachments. <br /> Table 4. <br /> Summary of Nitrate Mass Balance Equation. <br /> Septic Result Effluent Deep <br /> Leachfield <br /> (Nc)* Acres 'Average Daily Concentration Percolation <br /> Tank Land Use <br /> (mg/L- (A) Flow(Q) (gpd) (Nw) Denitrification <br /> of Rainfall <br /> No. N) (mg/L-N) (d) (R)(in) <br /> Existing Wine <br /> Tasting 3.6 45.5 650 85 25% 4.49 <br /> Building + <br /> Daily Visitors <br /> Proposed <br /> —4,000 SF <br /> 2 Wine 2.6 45.5 391 85 25% 4.49 <br /> Production <br /> Building <br /> Special 1.8 45.5 197 85 25% 4.49 <br /> Events <br /> Maximum contaminant level(MCL)for nitrate in drinking water is 10 mg/L-N. <br /> Highest average daily flow rate calculated per septic tank/building. <br /> Based on the nitrate loading balance calculation, nitrate as N levels for the existing wine tasting <br /> building is up to 5.4 mg/L-N when a special event occurs. The proposed 4,000 SF wine <br /> production building is anticipated to add 2.6 mg/L-N which increases nitrate levels to 8.0 mg/L-N, <br /> below the MCL of 10 mg/L-N. <br /> Conclusions and Recommendations <br /> In general, the parcel appears suitable for the proposed wine production building. The soils <br /> encountered on the site generally consisted of silty sand soils. A shallow percolation test <br /> conducted in August 2008 resulted in a percolation rate of 4.9 minutes per inch near the existing <br /> leachfield. A shallow percolation test conducted in May 2019 demonstrated a satisfactory <br /> percolation rate of 8.62 minutes in the preliminary leachfield. The proposed leachfield has been <br /> relocated approximately 200+feet northwest of the May 2019 percolation test location. Based on <br /> geotechnical report boring logs, Terracon anticipates the relocated leachfield will also <br /> demonstrate percolation rates similar to the most recent percolation test. <br /> Depth to groundwater is approximately 30-40 feet bgs. A groundwater sample was not collected <br /> Responsive ■ Resourceful ■ Reliable 7 <br />