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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), 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; this rate was used for the facility's employees. 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 incorporates 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 167.8 gallons per day (gpd), as calculated in the following table. Table 4. Average Daily Flow Calculation Use Units Rate Subtotal Reduction Average Daily Flow Employees, July and 75 13 gal/employee 975 gpd 2/12 162.5 gpd August Employees, holidays 3 13 gal/employee 39 gpd 7/52 5.3 gpd (7 weeks) Total 167.8 gpd Reduction factors convert calculated flow into average daily flow over a year: 2/12 converts for months per year, and 7/52 converts for weeks per year. The nitrate as nitrogen (N) concentration of the employee use is estimated to be 85 mg/L (US EPA, 1980). 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 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 tend to denitrify at a lower rate of about 10 percent. LOGE 2221 Page 11