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L LMay 25,2006 NCA Project Number: E06040A L3.4 Future On-Site Sources of Nitrate 3.4.1 Quantity and Quality ofDomestic Wastewater From Proposed Pmect LThe following discussion is for determining the long-term waste water flow generated from the proposed warehouses for the nitrate loading analysis and should not be used for septic system design purposes. Typically,use estimates for the sizing of septic systems include a peak use factor, whereas the numbers discussed here are based on long-term averages. L The wholesale warehouses are proposed to have 2-3 employees per day and will not serve customers. We understand that the warehouses are planned to be open approximately eight hours 1 per day, five days per week. ` 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 WartewaterDzposal Standards (2003), Crites and Tchobanoglous (1998), and EPA (1980).The references indicate that 14 gallons for each employee is typical for an office worker,which is suitable for a wholesale warehouse employee (Crites and Tchobanoglous, 1998). L The following table presents the septic waste water uses associated with the Site. The rates presented from the references provide general guidance but do not always reflect a match in usage. Careful examination,professional judgement, and experience are necessary to select a reasonable flow rate estimate. The flow rates selected for the uses associated with this project are presented next. I Table 1. Typical Quantity of Effluent Category Total People per Average Quantity per Average Daily Flow Day Person Per Parcel L Commercial 3 14 al/day/employee 3 em to ees* 14 d = 42 Note —gpd is gallons per day. For the subject property,the total daily waste water quantity is 42 gallons per day. A five-sevenths conversion was used to account for a five day work week. Five-sevenths of 42 gallons per day is 30 Lgallons per day averse. The average total nitrogen concentration of domestic waste water is normally considered to be 20-85 mg/L-N with 35 to 45 mg/1,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 waste water for the project is approximately 85 mg/L-N over the long term. L 5 L r