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L r L November 8,2004 NOA Project Number: E040110A r L under cultivation. In addition, the fine-grained materials observed in the soil would serve to attenuate the percolation of nitrates to ground water. L3.4 Future On-Site Sources of Nitrate L3.4.1 Quantity and Quality ofDomestic Wastewater From Proposed Project The following discussion is for determining the long-term waste water flow generated from the L proposed residences 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. LFor each of the proposed parcels,Ms. Griffith indicated that she anticipates a three to five-bedroom house on each lot (personal communication, October 29,2004);for this study a foul-bedroom + home average was chosen. A four bedroom house is presumed to be occupied by up to five people Lover 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 Lresidential septic tank usage for each parcel. The estimated sewage flow rates for use categories are available from a number of references. The L uses presented below were guided by the San Joaquin County On-Site Wastewater Disposal Standards (2003), Crites and Tchobanoglous (1998),and EPA (1980). The SanJoaquin County On-Site Wastewater Disposal Standards does not provide a flow rate for residential use. The San Joaquin LCounty 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 (198 ) Design Manual (Table 4-6) indicates the typical use rate ` is 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. The following table presents the septic waste water uses associated with the Site. The rates Lpresented 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 L flow rate estimate. The flow rates selected for the uses associated with this project are presented in the following table. L L L5 L