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reviewed the San Joaquin County On-Site Wastewater Treatment Systems Standards (2017), Crites and Tchobanoglous (1998), and US EPA (1980). Crites and Tchobanoglous indicate that 13 gallons per day for each employee is typical for an office or industrial worker, and 5 gallons per day per user is typical for a public lavatory; these rates were used for the facility's employee and customers. The nitrate as nitrogen (N) concentration of the employee and customer use is estimated to be 85 mg/L (US EPA, 1980). 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 here. The maximum average daily flow for the Site was estimated to be 1,547.5 gallons per day (gpd): Table 4. Average Daily Flow Calculation Use Units Rate Subtotal Reduction Average Daily Flow Employees 7.5 13 gal/person/day 97.5 gpd N/A 97.5 gpd Customers 290 gal/person/day 11450 gpd N/A 1,450 gpd Total 1,547.5 gpd Reduction factors convert calculated flow into average daily flow over a year. There is no reduction factor for this facility since it will be open seven days per week. Denitrification Reductions Denitrification is a process that occurs in the septic system drain field whereby certain bacteria oxidize the nitrate (NO3) in the wastewater and release nitrogen gas (N2) to the atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain field 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 tend to denitrify at a lower rate of about 10 percent. A denitrification factor of 35 percent was selected for the Site because of the clay soil present at the percolation test location. LOGE 2240 Page 13