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n. September 30 2007 ri NOA Project Number: E07141A 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 Wastemvater Disposal Standards [ ! (2003), Crites and Tchobanoglous (1998), and EPA (1980). The San Joaquin County On-Site 1Vastewater Disposal Standards does not provide a flow rate for residential use. The San Joaquin F County On-Site WlastewaterDisposal Standards are based on the 1963 Manual of Septic Tank Practice. The tex ro p Crites and Tchobanoglous (1998) (Table 4-2) indicates that thetYP ical residential use rates70�ga nsrper da per person. The EPA (1980) Design Manual (Table 4-6) indicates the typieaise rate is 45 gall ns per day for a resident. Since the Crites and Tchobanoglous (1998) information is th current available, our office believes it provides the best estimate of waste water flow for the residential category. The following tables presents the potential 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 in the following table. Table 1. J Typical Quantity of Effluent Total Average Quantity Average Daily Flow Category People per Day pet Person Per Parcel Commercial --- --- \*431 gp maximum) III Residential 6 70 gal/day/person 6 residents /day*70 gpd/person=420 gpd FjBecause development is unknown,a calculation was done to determine an estimate of the maximum flow theparcel development could produce to stay at or below the EPA maximum contaminant level of 10 mg/L-N. E The maximum total daily waste water quantity for the commercial development should be equal to or below an average of 431 gpd in order to stay below the EPA maximum contaminant level�of 10 mg/L-N. The total daily waste water quantity for the residential parcels will vary depending on the number of bedrooms proposed on each parcel. We will assume each primary residence will contain three bedrooms and be occupied by four people. In addition, each parcel may contain a secondary dwelling unit which is estimated to be two bedrooms occupied by two people. Total occupation of the property would be six people. j The average total nitrogen concentration of domestic waste water is normally considered to be F1 20-85 mg/L-N with 35 mg/L-N as typical (Crites and Tchobanoglous, 1998). For the purposes of the nitrate loading estimate, the long-term average concentration for total nitrogen in waste water is estimated to be 45 mg/L-N. I I 5