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typical for an office or industrial worker; this rate was used for the facility's employees (Crites and Tchobanoglous, 1998). For 100 potential employees, the maximum average daily flow for the Site was estimated to be 1 ,300 gallons per day (gpd). 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 nitrate as nitrogen (N) concentration of the employee use is estimated to be 85 mg/L (US EPA, 1980). No contributions from irrigation or soil amendments are considered for the Hantzsche/Finnemore method. It is reasonably assumed that any irrigation or soil amendments would be applied at close to agronomic rates for a net balance of plant irrigation and nutrients. The average daily flow is presented in the following table: Table 3. Average Daily Flow Calculation Use Units Rate Subtotal Reduction Average Daily Flow Employee 100 13 gal/employee 1,300 gpd none 1,300 gpd (7 days) employee Total 1,300 gpd 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, while soils with high sand content and fast percolation rates tend to denitrify at lower rates. A typical denitrification factor of 25 percent was selected for the Site because of the combination of clayey and sandy soils present at the percolation test location. LOGE 1848 Page 11