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33503 S Koster Road Project No.2021-00073 Page 16 <br /> average monthly potential evapotranspiration. If so, then the difference is potential deep <br /> percolation. This method does not consider runoff. See Plate 7 for the data and calculation. <br /> Average potential evapotranspiration was obtained from the California Irrigation <br /> Management Information System (CIMIS).The site is located within evapotranspiration zone <br /> number 12, as well as the Tracy station (Station 048999) used in the analysis. The average <br /> rainfall for the area,as well as the average evapotranspiration data,was obtained from CIMIS <br /> (https://cimis.water.ca.gov/) where the average rain fall for the Tracy area was found to be <br /> 9.88 inches per year for years 1906 to 2016. <br /> Based on this method, the average deep percolation of rain for Tracy area is estimated to be <br /> 1.28 inches. The nitrate concentration of rain fall was estimated to be 1 mg/L-N (Hantzsche <br /> and Finnemore, 1992). <br /> 5.3 Current On-Site Sources of Nitrate <br /> The current onsite 3-bedroom residence, and associated septic system and rainfall are <br /> recognized as potential current on-site sources of nitrate. <br /> 5.4 Future On-Site Sources of Nitrate <br /> 5.4.1 Quantity and Quality of Domestic Wastewater from Proposed Project <br /> The following discussion is for determining the long-term wastewater flow anticipated from <br /> the planned residential house for the site,to be incorporated into the nitrate loading analysis. <br /> The anticipated wastewater flow determined is not intended to be used for septic system <br /> design, because septic system sizing includes a peak use factor, whereas the numbers <br /> discussed herein are based on a long-term conservative measure of estimated effluent <br /> volume. <br /> There is currently a 3-bedroom residence with associated septic system onsite. In addition, <br /> a proposed 2-bedroom, 2-bath secondary dwelling unit with a separate septic system is <br /> planned for the site. Per San Joaquin County Environmental Health requested guidelines <br /> based on previous nitrate loading studies, an average daily flow of 100 gallons for the first <br /> bedroom and 50 gallons for each additional bedroom per residence per day is estimated for <br /> the site. The following table presents the nitrate contributing septic wastewater flow rates <br /> anticipated for the site. <br /> Table 3. <br /> Typical Quantity of Effluent <br /> Average <br /> Quantity Days of <br /> Category Total per Use per Average Daily Flow <br /> Bedrooms Bedroom year Per Facility <br /> per Day <br /> al <br /> Petralogix Engineering,InC. <br /> 26675 BruelIa Road,Galt,Ca 95632 <br /> [109j-40o-5729 <br /> www.petralogix.com <br />