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Nitrate Loading Study 1 rerr�con Landavazo Property Tracy, CA December 15, 2017 Terracon Project No. NA177067 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 USGS California Water Science Center California Water Use 2010 Data, average daily domestic use per capita was estimated at 69-gallons per day. Per conversations with Mr. Estrada, the EHD recommends a residential use rate of 70- gallons per person/day. Mr. Estrada additionally indicated the EHD recommends calculating the estimated sewage flow based on the number of bedrooms per residence with an average potential occupancy of two persons per bedroom. The following 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 potential occupancy of 2 persons per bedroom per day. 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 flow rates selected for the uses associated with this project are presented on the following page. Table 2. Potential Quantity of Effluent. — Potential Average Average Number Number Effluent days of Potential Average Daily Category of of People Quantity per Flow Bedroomsuse per per Person year (gPd*) Bedroom (gpd•) (3 bedrooms x 2 people per Proposed 3 2 70 365 bedroom x 70 gal. per day x Residence 365 days per year)/365 days per year=420 gpd Potential Average Daily Flow 420.00 gallons per day 'gpd-gallons per day Responsive■ Resourceful ■ Reliable 6