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Soil Suitability/ Nitrate Loading Study Irerracon <br /> Thor Property r Stockton, CA <br /> July 19, 2018 m Terracon Project No. NA187029 <br /> 2.3.4.1 Quantity and Quality of Wastewater from Project <br /> The following discussion is for determining the long-term wastewater flow generated from the <br /> proposed development for the nitrate loading analysis and should not be used for septic system <br /> design purposes. Typically, use estimates for the sizing of septic systems include a peak use <br /> factor, whereas the numbers discussed here are based on long-term averages. <br /> The estimated sewage flow rates for use categories are available from a number of references. <br /> The uses presented below were guided by the San Joaquin County On-Site Wastewater Disposal <br /> Standards (2003), Crites and Tchobanoglous (1998), and EPA (1980). Table 4-2 of the text from <br /> Crites and Tchobanoglous indicates that the typical residential use rate is 70-gallons per day per <br /> bedroom. The EPA Design Manual (Table 4-6) indicates the typical use rate is 45-gallons per <br /> day per resident. Based on a review of the USGS California Water Science Center California <br /> Water Use 2010 Data, average daily domestic use per capita was estimated at 69-gallons per <br /> day. Per conversations with Mr. Rodney Estrada, the EHD recommends a residential use rate of <br /> 70-gallons per person/day. Mr. Estrada additionally indicated the EHD recommends calculating <br /> the estimated sewage flow based on the number of bedrooms per residence with an average <br /> potential occupancy of two persons per bedroom. The following table presents the proposed <br /> potential septic wastewater use for the site. The flow rates selected for the uses associated with <br /> this project are based on EHD recommendations and estimated potential occupancy of 2 persons <br /> per bedroom per day. <br /> The rates presented from the references provide general guidance but do not always reflect a <br /> match in usage. Should any of the above information provided to our office change or is inconsistent <br /> with what is stated, our office shall be contacted to make any necessary modifications to our <br /> calculations. Examination and professional judgement, and experience shall be used when selecting <br /> a reasonable flowrate. The flow rates selected for the uses associated with this project are <br /> presented on the following page. <br /> Table 5. <br /> Potential Quantity of Effluent. <br /> Potential Average Average <br /> Number Number Effluent days of Potential Average Daily <br /> Category of of People Quantity per Flow <br /> use per <br /> Bedrooms per Person year (gpd*) <br /> Bedroom (gpd*) <br /> (4 bedrooms x 2 people per <br /> Proposed bedroom x 70 gal. per day x <br /> Residence 4 2 70 365 365 days per year)/365 days <br /> per year= 560 gpd <br /> Potential Average Daily Flow 560 gallons per day <br /> *gpd -gallons per day <br /> Responsive ■ Resourceful ■ Reliable 14 <br />