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• Sources of Nitrate Septic systems and dairies have been found to be the most significant sources of nitrate in ground water. Orchards that require fertilization in sandy soils are also a significant source of nitrate contamination in shallow or sandy aquifers in San Joaquin County. Contribution of Rainfall An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. The Hantzsche and Finnemore method utilizes the "average recharge rate of rainfall' in calculating potential nitrate impacts to the aquifer. Not all rainfall will percolate into the aquifer; evapotranspiration, the sum of evaporation and plant transpiration, will reduce percolating effluent, especially in summer months. Rainfall recharge (deep percolation of rain) is a significant factor in the nitrate loading estimate; however, data on rainfall recharge rates are not widely available. For the Chico area, Hantzsche and Finnemore present an average rainfall of 22.5 inches per year and an estimated rainfall recharge of 16.8 inches per year; the recharge rate is calculated to be 75 percent of the average rainfall. Because the Chico area is similar geologically to San Joaquin County, for the purpose of this report Live Oak has selected 75 percent of rainfall to represent the estimated rainfall recharge for the project area. Rainfall data for the Stockton area was obtained from the Western Regional Climate • Center. The Stockton Fire Station 4 (048560), the closest active station to the Site, reports the average total annual precipitation from March of 1906 through June of 2016 to be 15.37 inches. By assuming 75 percent of this precipitation percolates to the aquifer, the value of 11.5 inches average recharge of rainfall is obtained. The nitrate concentration of rainfall was estimated to be 1 mg/L-N (Hantzsche and Finnemore). Quantity and Quality of Domestic Wastewater The proposed project is a use permit to convert an existing warehouse into a firearms manufacturing facility, retail store, and shooting range. According to the Use Permit application, the business will operate Monday through Saturday, with six employees present per day. An estimated 20 customers per day are anticipated. The estimated sewage flow rates for various uses are available from a number of references, including the San Joaquin County On-Site Wastewater Treatment Systems Standards (2016), Crites and Tchobanoglous (1998), and US EPA (1980). Crites and Tchobanoglous indicate that 13 gallons per day is typical for an industrial building employee; this rate was used for the warehouse employees. They state that 5 gallons per visitor is typical for guests at a visitor center; this rate was selected for customers at the retail store and shooting range. • LOGE 1806 Page 8