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rainfall" in calculating potential nitrate impacts to the aquifer. Not all rainfall will <br /> percolate into the aquifer; evapotranspiration, the sum of evaporation and plant <br /> transpiration, will reduce percolating effluent, especially in summer months. <br /> Rainfall recharge (deep percolation of rain) is a significant factor in the nitrate loading <br /> estimate; however, data on rainfall recharge rates are not widely available. For the <br /> Chico area, Hantzsche and Finnemore present an average rainfall of 22.5 inches per <br /> year and an estimated rainfall recharge of 16.8 inches per year; the recharge rate is <br /> calculated to be 75 percent of the average rainfall. Because the Chico area is similar <br /> geologically to San Joaquin County, for the purpose of this report Live Oak has selected <br /> 75 percent of rainfall to represent the estimated rainfall recharge for the project area. <br /> Rainfall data for the Stockton area was obtained from the Western Regional Climate <br /> Center. The Stockton Fire Station 4 (048560), the closest active station to the Site, <br /> reports the average total annual precipitation from March 1906 through June 2016 to be <br /> 15.37 inches. By assuming 75 percent of this precipitation percolates to the aquifer, the <br /> value of 11.53 inches average recharge of rainfall is obtained. <br /> The nitrate concentration of rainfall was estimated to be 1 mg/L-N (Hantzsche and <br /> Finnemore). <br /> Quantity and Quality of Domestic Wastewater <br /> Mr. De Casas proposes to construct a three-bedroom home on the Site. The Site is <br /> currently vacant. <br /> Crites and Tchobanoglous (1998) list a typical flow rate of 50 to 70 gallons per person <br /> per day for an individual residence. The San Joaquin County Enviromental Health <br /> Department has indicated that maximum flow and double occupancy within each <br /> bedroom should be considered for the nitrate loading assessment, as a result, a value <br /> of 140 gallons per bedroom per day has been selected (personal communication, <br /> January 6, 2017). <br /> The estimated flow values discussed here should not be used for the design and sizing <br /> of the septic system. The design and sizing of the septic system should utilize the San <br /> Joaquin County Environmental Health Department's On-Site Wastewater Treatment <br /> Systems Standards (2017) which incorporate peak and surge flow factors. The <br /> estimates used in the On-Site Wastewater Treatment Systems Standards may be <br /> greater than those discussed here. <br /> Based on three bedrooms total at 140 gallons per bedroom per day, the maximum <br /> average daily flow for the Site was estimated to be 420 gallons per day (gpd). A typical <br /> residential concentration of 35 mg/L of nitrate as N was selected (Crites and <br /> Tchobanoglous, 1998). <br /> LOGE 1832 Page 6 <br />