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Using this method, the three-bedroom home will contribute 200 gpd, and the two- <br /> bedroom home will contribute 150 gpd. A typical residential concentration of 35 mg/L of <br /> nitrate as N was selected for the proposed residences (Crites and Tchobanoglous, <br /> 1998). <br /> The estimated sewage flow rates for various uses are available from a number of <br /> references. The commercial uses discussed here were guided by the San Joaquin <br /> County On-Site Wastewater Treatment Systems Standards (2017), Crites and <br /> Tchobanoglous (1998), and US EPA (1980). Crites and Tchobanoglous indicate that 5 <br /> gallons per day per user is typical for a public lavatory; this rate was used for the <br /> employees, who are anticipated to make only a brief stop at the Site to pick up supplies. <br /> The nitrate as nitrogen (N) concentration of the employee and customer use is <br /> 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 incorporate peak and surge flow factors. The estimates used <br /> in the On-Site Wastewater Treatment Systems Standards may be greater than those <br /> discussed here. <br /> The maximum average daily flow for the Site was estimated to be 354.3 gallons per day <br /> (gpd). Through the use of a weighted average, the average concentration of all the <br /> different effluent flows and concentrations was determined to be 35.6 mg/L-N at 354.3 <br /> gallons per day. Please see the following tables: <br /> Table 3. Average Daily Flow Calculation <br /> Use Units Rate Subtotal Reduction Average Daily <br /> Flow <br /> 3-Bedroom 3 200 gal/ 200 gpd N/A 200 gpd <br /> House bedrooms 3 bedrooms <br /> 2-Bedroom 2 150 gal/ 150 gpd N/A 150 gpd <br /> House bedrooms 2 bedrooms <br /> Employees employees 5 gal/employee 15 gal 2/7 4.3 gal <br /> Total 354.3 gpd <br /> Reduction factors convert calculated flow into average daily flow over a year: 2/7 converts for days per week that <br /> employees are present. <br /> LOGE 20-63 Page 12 <br />