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The estimated sewage flow rates for various uses are available from a number of <br />references. To select appropriate use values for the employees and customers of the <br />Site, Live Oak reviewed the San Joaquin County On -Site Wastewater Treatment <br />Systems Standards (2017), Crites and Tchobanoglous (1998), and US EPA (1980). <br />Crites and Tchobanoglous indicate that 13 gallons per day for each employee is typical <br />for an office or industrial worker, and 5 gallons per day per user is typical for a public <br />lavatory; these rates were used for the facility's employees and customers (visiting <br />truckers). The nitrate as nitrogen (N) concentration of the employee and customer use <br />is estimated to be 85 mg/L (US EPA, 1980). <br />The estimated flow values discussed here should not be used for the design and sizing <br />of the septic system. The design and sizing of the septic system should utilize the San <br />Joaquin County Environmental Health Department On -Site Wastewater Treatment <br />Systems Standards, which incorporates peak and surge flow factors. The estimates <br />used in the On -Site Wastewater Treatment Systems Standards may be greater than <br />those discussed here. <br />The maximum average daily flow for the Site was estimated to be 191.1 gallons per day <br />(gpd). Please see the following table: <br />Table 4. Average Daily Flow Calculation <br />Use Units Rate Subtotal Reduction/ Average Daily Flow <br />Multiplier <br />Mechanics/Office 11 13 143 gpd 5/7 102.1 gpd <br />Workers gal/person/day <br />Security Guard 1 13 gal/person/day 13 gpd 24/8 39 gpd <br />Visiting Truckers 10 gal/person/day 50 gpd None 50 gpd <br />Total 191.1 gpd <br />Reduction/multiplier factors convert calculated flow into average daily flow over a year. The factor 5/7 refers to a <br />standard M -F workweek. The factor 24/8 adjusts for a security guard present continuously rather than working an 8- <br />hourday. <br />Denitrification Reductions <br />Denitrification is a process that occurs in the septic system drain field whereby certain <br />bacteria oxidize the nitrate (NO3) in the wastewater and release nitrogen gas (N2) to the <br />atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain <br />field may undergo a reduction between 10 percent to 35 percent. Soils with higher clay <br />content, moist soil conditions, high pH, and organic material denitrify by about 35 <br />LOGE 2201 Page 11 <br />