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Nitrate Loading Study Irerracon Guillermo Ramirez Property ■ Ripon, California April 29, 2019 ■ Terracon Project No. NA197019 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. Table 3. Potential Quantity of Effluent. Potential Average Number Number Effluent Average potential Average Daily Category of of People Quantity per days of Flow Bedrooms per Person u year se r (gpd*) / Bedroom (gpd*) v (4 bedrooms x 2 people per Proposed bedroom x 70 gal. per day x Residence 4 2 70 365 365 days per year)/365 days per year= 560.0 gpd Potential Average Daily Flow 560.0 gallons per day *gpd -gallons per day Based on a review of Table 3, the estimated potential sewage flow rate for the proposed future residence is 560-gallons per day. Responsive ■ Resourceful ■ Reliable 7