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L L, February 21,2007 NOA Project Number: E07015A ` 3.4 Future On-Site Sources of Nitrate 3.4.1 Quantity and Quality of Domestic Wastewater From Proposed Project V The following discussion is for determining the long-term waste water flow generated from the proposed construction 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. ` The equipment sales and rental office is proposed to have 5 to 10 employees per day and 40 to 50 customers per day. We understand that the office is planned to be open approximately eight hours per day, five days per week. L 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 Ox-Site Wastewater Disposal Standards L (2003), Crites and Tchobanoglous (1998),and EPA (1980).The references indicate that 13 gallons for each employee is typical for an office worker and 5 gallons for each customer. (Crites and Tchobanoglous, 1998). i 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. Table 1. Typical Quantity of Effluent Category Total People per Average Quantity per Average Daily Flow Day Person Per Parcel Customers 50 5 gal/day/customer (50 customers* 5 gpd) =250 gpd Employees 10 13 al/da /em to ee 10 employees* 13 d = 130 gpd Note —gpd is gallons per day. LFor the subject property, the total daily waste water quantity is 380 gallons per day.A five-sevenths conversion was used to account for a five day work week. Five-sevenths of 380 gallons per day is L272 gallons 12er day average. The average total nitrogen concentration of domestic waste water 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 waste water for the project is approximately 85 mg/L-N over the long term. 5 6w L