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October 11,2005 NOA Project Number: E05111B 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. Each proposed residence is presumed toqfouro five b ooms potentially occupied by up to five people over the long term.A legal seclluig unit (SDU) up to 1,500 square feet could be / constructed on the parcel. This SDU could be occupied by up t`rthree�eople. Therefore, a maximum of seven people per parcel will be used to calculate the e�si ential septic tank usage for each parcel. This number is fairly conservative if viewed over the life of the home. 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 Standards (2003), Crites and Tchobanoglous (1998),and EPA (1980).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 is 45 gallons per day for a resident. The following tables 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 for Parcels 8-20. Total People per Average Quantity per Average Daily Flow Category Day Person Per Parcel Residential 7 70 gal/day/resident 7 residents*70 gpd/resident =490 gpd i Note —gpd is gallons per day. For all the lots, the total daily waste water quantity is estimated to be 490 gallons per day. ll 1 The average total nitrogen concentration of domestic waste water is normally considered to be 20-85 mg/L-N (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. 5