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February 24, 2020 BGG Job No. G 123.02 Rainfall recharge (deep percolation of rain) is a significant factor in the nitrate loading estimate; however,data on rainfall recharge rates is not widely available. For H&F's study conducted in the Chico area,a recharge rate was calculated to be 75 percent of the average rainfall. Since the Chico area is similar geologically to San Joaquin County region, an estimated recharge rainfall was calculated for this study based upon 75 percent of annual rainfall for the project area. Rainfall data for the Escalon area were obtained from the San Joaquin County Flood Control and Water Conservation District Groundwater Report from Fall 2016. The Stockton Fire Station, the closest reported station to the site,reports the average total annual rainfall from 1941 through 2015 to be 15.6 inches. Assuming 75 percent of this rainwater percolates to the aquifer, a value of 11.7 inches of average recharge of rainfall is calculated. H&F estimates that the nitrate concentration of rainfall is approximately 1 mg/L-N. Quantity and Quality of Domestic Wastewater The proposed Zinc House Winery is anticipated to operated five days per week. A maximum of 9 employees per day is anticipated. A maximum of 40 visitors per day are expected.Approximately 150 daily guests are expected to attend four quarterly wine release events each year. The proposed winery improvements will include the conversion of an existing building for a restroom facility to contain four toilets and three lavatories. Additionally, the new winery building will have two restrooms, with a total of two toilets, one urinal, and two lavatories. The estimated sewage flow rates for various uses are available from a number of references. The uses presented below were guided by the San Joaquin County On-Site Wastewater Treatment Systems Standards(2017)and US EPA (1980). A use of 30 gallons per day for each employee is typical for an office or school day worker;this rate was used for the winery employees. A use of 20 gallons per day for each visitor or even patron is typical for bar/cocktail lounge uses. The estimated flow values discussed here should not be used for the design and sizing of the septic system. The design and sizing of the septic system should utilize the San Joaquin County Environmental Health Department On-Site Wastewater Treatment Systems Standards which incorporate peak and surge flow factors. The estimates used in the On-Site Wastewater Treatment Systems Standards may be greater than those discussed herein. The nitrate as nitrogen (N) concentration for non-showering employee use is estimated to be 85 mg/L (US EPA, 1980). This value was used in calculations for the winery employees. No contributions from crop irrigation or soil amendments are considered for the Hantzsche/Finnemore method. It is reasonably assumed that the irrigation and soil amendments would be applied at close to agronomic rates for a net balance of plant irrigation and nutrients. The following tables present the calculated maximum average daily flow for the site and weighted average concentrations: Table 1 —Average Daily Flow Calculation Use Units Rate Subtotal Reduction' Average Daily Flow Employees full-time 9 30 gal/employee 270 gpd 5/7 192.9 gpd Visitors (daily) 40 20 al/visitor 800 gpd 5/7 571.4 gpd Event Patrons 4 per ear 150 20 gal/guest 3,000 gpd 4/365 657.5 gpd Total 1 1,421.8 gpd 1 Reduction factors convert calculated flow into average daily flow over a one-year period; 5/7 converts for anticipated weekday operations. BAEZ GEOTECHNICAL GROUP Soil Suitability Study and Nitrate Loading Study-Zinc House Winery Page 7