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L September 10, 2004 NOA Project Number: E040104A The existing residence on the Site (Parcel 6) has two bedrooms, which have the potential to be occupied by an estimated three people. A second dwelling unit may be placed on Parcel 6 at v some point. A second dwelling unit is considered, for the purposes of this report, to be up to two bedrooms in size and dhhas thetential to be occupied by an estimated three people. VL4'7 ;, _ Therefore, a total of six residents will be used to calculate the residential septic tank usage for ca.4 k-- Parcel6. �, 4 ! For the proposed Parcels 1 through 5, Mr. Arnaudo indicated that he anticipates a four- e :p ~' bedroom house on each lot (personal communication, September 1, 2004); a four bedroom house is presumed to be occupied by up to five people over the long term. A second dwelling unit, occupied by a potential three people, could be placed on each lot as well. Therefore, a total of eight people per parcel will be used to calculate the residential septic tank usage for Parcels 1 through 5. 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 On-Site Wastewater Disposal L Standards (2003), Crites and Tchobanoglous (1998), and EPA (1980). The San Joaquin County On-Site Wastewater Disposal Standards does not provide a flow rate for residential use. The San Joaquin County On-Site Wastewater Disposal Standards are based on the 1963 Manual of Septic Tank Practice. ` The text from Crites and Tchobanoglous (1998) (Table 4-2) indicates that the typical residential use rate is 70 gallons per day. The EPA (1980) Design Manual (Table 4-6) indicates the typical use rate ss 45 gallons per day for a resident. L Since the Crites and Tchobanoglous (1998) information is the most current available, our office believes it provides the best estimate of waste water flow for the residential category. h, Therefore, the total contribution to the nitrate load from the existing residence is calculated to be 210 gallons/day. 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 in the following table. 5