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Nitrate Loading Study Flag City#4 ■ Lodi, California Irerracon September 20, 2018 ■Terracon Project No. NA187043 and up to 30 visitors and 21 truckers anticipated daily. The restrooms will consist of 2 sinks and 4 low-flow toilets. The estimated sewage flow rates for use categories are available from a number of references. The uses presented below were guided by the San Joaquin County On-Site Wastewater Disposal Standards (2003), Crites and Tchobanoglous (1998), and EPA (1980). The references indicate that 15 gallons per day is typical for each employee and 5 gallons per day for visitors, when utilizing a low-flow flush system. The following table presents the proposed septic wastewater use for the site. The rates presented from the references provide general guidance but do not always reflect a match in usage. Careful examination, professional judgment, and experience are necessary to select a reasonable flow rate estimate. The flow rates selected for the uses associated with this project are presented below. These flow rates are average daily rates over the entire year and should not be used for septic system design. These average daily rates are for nitrate loading purposes. Septic system design should take into account maximum daily rates during the season. Table 3. Typical Quantity of Effluent Total Average Quantity Category People per Person Average days of Average Daily Flow per Day (gallons) use per year Permanent (20 person x 15 gal x 365 Employees 20 *15 365 days)/ 365 days per year = 300 gpd (51 person x 5 gal x 365 Visitors 51 *5 365 days) / 365 days per year = 255 gpd Average Daily Flow 555 gallons per day Note:gpd is gallons per day. 'Value cited from the San Joaquin County On-Site Wastewater Disposal Standards(2003)6.1.15. Based on a review of Table 3, the estimated potential sewage flow rate for the proposed development is 555-gallons per day. The average total nitrogen concentration of domestic wastewater is normally considered to be 20- 85 mg/L-N with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). It is estimated that commercial use will have higher concentrations of total nitrogen when compared to residential use. It is estimated that the average concentration for total nitrogen in wastewater for the project is approximately 85 mg/L-N over the long term. Responsive ■ Resourceful ■ Reliable 7