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Soil Suitability/ Nitrate Loading Study Irerracon <br /> Pickens Property ■ Tracy, California <br /> May 12, 2020 ■ Terracon Project No. NA207032 <br /> Table 8. <br /> Net Rainfall Recharge <br /> CIMIS Station Average Potential ET Actual ET Net Rainfall <br /> Number/ Precipitation ETO Adjustment (in/year) Recharge <br /> Location (in/year) (in/year) Factor (in/year) <br /> 167/Tracy 8.36 60.48 0.3475 21.02 3.31 <br /> Based on this method, the average net rainfall recharge for Tracy is estimated to be 3.31 <br /> inches/year. <br /> The nitrate concentration of rainfall is estimated to be 1 mg/L-N (Hantzsche and Finnemore, <br /> 1992). <br /> 2.3.3 Current On-Site Sources of Nitrate <br /> The current on-site sources of nitrate include_natural processes and the existing septic system. <br /> 2.3.4 Future On-Site Sources of Nitrate <br /> Future on-site sources of nitrate include the existing septic system, proposed septic system, and <br /> natural processes,. <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 <br /> Treatment Standards (OWTS) dated 2017, Crites and Tchobanoglous (1998), and EPA (1980). <br /> Table 4-2 of the text from Crites and Tchobanoglous indicates that the typical residential use rate <br /> is 70-gallons per day per bedroom. The EPA Design Manual (Table 4-6) indicates the typical use <br /> rate is 45-gallons per day per resident. Based on a review of the United States Geological Survey <br /> (USGS) California Water Science Center California Water Use 2010 Data, average daily domestic <br /> use per capita was estimated at 69-gallons per day. <br /> In February 2020, the EHD approved a revised calculation method for long term average <br /> discharge of waste water and recommended 100 gallons for the first bedroom and 50 gallons for <br /> each additional bedroom. <br /> The following table presents the proposed septic wastewater use for the site. The rates presented <br /> from the references provide general guidance but do not always reflect a match in usage. Should <br /> Responsive■ Resourceful ■ Reliable 14 <br />