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2016 to be 12.03 inches, while the Tracy Carbona Station reports average total annual precipitation from March of 1906 through May of 2016 to be 9.86 inches. Because the Site is located between these stations, an average value of 10.94 inches has been selected to represent annual precipitation at the Site. By assuming 60 percent of this precipitation percolates to the aquifer, the value of 6.56 inches average recharge of rainfall is obtained. The nitrate concentration of rainfall was estimated to be 1 mg/L-N (Hantzsche and Finnemore). Quantity and Quality of Domestic Wastewater Mr. Chashmawala proposes to construct two fourplexes on the Site; according to Mr. Gilman, each will fourplex consist of three units with three bedrooms and 2.5 bathrooms and one unit with three bedrooms and three bathrooms. Crites and Tchobanoglous (1998) list a typical flow rate of 50 to 70 gallons per person per day for an individual residence. The San Joaquin County Enviromental Health Department has indicated that maximum flow and double occupancy within each bedroom should be considered for the nitrate loading assessment; as a result, a value of 140 gallons per bedroom per day has been selected (personal communication, January 6, 2017). The estimated flow values discussed here should not be used for the design and sizing of the septic system. The design and sizing of the septic system should utilize the San Joaquin County Environmental Health Department's On-Site Wastewater Disposal Standards which incorporate peak and surge flow factors. The estimates used in the On-Site Wastewater Disposal Standards may be greater than those discussed here. Based on 24 bedrooms total at 140 gallons per bedroom per day, the maximum average daily flow for the Site was estimated to be 3,360 gallons per day (gpd). A typical residential concentration of 35 mg/L of nitrate as N is selected (Crites and Tchobanoglous, 1998). Denitrification Reductions Denitrification is a process that occurs in the septic system drain field whereby certain bacteria oxidize the nitrate (NO3) in the waste water and release nitrogen gas (N2) to the atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain field may undergo a reduction between 10 percent to 35 percent. Soils with higher clay content, moist soil conditions, high pH, and organic material denitrify by about 35 percent, and soils with high sand content and fast percolation rates tend to denitrify at a lower rate of about 10 percent. LOGE 1623 Page 9