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Rainfall recharge (deep percolation of rain) is a significant factor in the nitrate loading estimate; however, data on rainfall recharge rates are not widely available. For the Chico area, Hantzsche and Finnemore present an average rainfall of 22.5 inches per year and an estimated rainfall recharge of 16.8 inches per year; the recharge rate is calculated to be 75 percent of the average rainfall. Because the Chico area is similar geologically to San Joaquin County, for the purpose of this report Live Oak has selected 75 percent of rainfall to represent the estimated rainfall recharge for the project area. Rainfall data for the French Camp area was obtained from the Western Regional Climate Center. The Stockton Metro Airport (048558), the closest active station to the Site, reports the average total annual precipitation from October of 1948 through June of 2016 to be 13.76 inches. By assuming 75 percent of this precipitation percolates to the aquifer, the value of 10.32 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. Gomez proposes to construct a three-bedroom home on the Site. The Site is currently vacant. 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 Treatment Systems Standards (2016) which incorporate peak and surge flow factors. The estimates used in the On-Site Wastewater Treatment Systems Standards may be greater than those discussed here. Based on three bedrooms total at 140 gallons per bedroom per day, the maximum average daily flow for the Site was estimated to be 420 gallons per day (gpd). A typical residential concentration of 35 mg/L of nitrate as N was 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 • LOGE 1802 Page 6