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Nitrate Loading Study Nielsen Property Ripon, California January 15, 2019 Terracon Project No. NA187066 lrerracon Based on this method, the average deep percolation of rain for the Ripon area is estimated to be 2.54 inches/year. The nitrate concentration of rainfall is estimated to be 1 mg/L-N (Hantzsche and Finnemore, 1992). 3.3 Current On-Site Sources of Nitrate The site is developed with an orchard; therefore, the current on-site sources of nitrate include the existing agricultural land use and natural processes. 3.4 Future On-Site Sources of Nitrate The site is proposed to be developed with an approximately 3,500-square foot (SF) four bedroom residence and septic system. Therefore, the future on-site sources of nitrate will include the proposed septic system and natural processes. 3.5 Quantity and Quality of Wastewater from Project The following discussion is for determining the long-term wastewater flow generated from the proposed development 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. 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). Table 4-2 of the text from Crites and Tchobanoglous indicates that the typical residential use rate is 70-gallons per day per bedroom. The EPA Design Manual (Table 4-6) indicates the typical use rate is 45-gallons per day per resident. Based on a review of the United States Geological Survey (USGS) California Water Science Center California Water Use 2010 Data, average daily domestic use per capita was estimated at 69-gallons per day. The EHD recommends a residential use rate of 70-gallons per person/day times two persons per bedroom. The rates presented from the references provide general guidance but do not always reflect a match in usage. Should any of the above information provided to our office change or is inconsistent with what is stated, our office shall be contacted to make any necessary modifications to our calculations. Examination and professional judgement, and experience shall be used when selecting a reasonable flowrate. The below table presents the proposed potential septic wastewater use for the site. The flow rates selected for the uses associated with this project are based on EHD recommendations and estimated double occupancy per bedroom. Responsive • Resourceful • Reliable 6