SR0080153 SSNL - Laserfiche WebLink

Home Browse Search

Sources of Nitrate Septic systems and dairies have been found to be the most significant sources of nitrate in ground water. Orchards that require fertilization in sandy soils are also a significant source of nitrate contamination in shallow or sandy aquifers in San Joaquin County. Contribution of Rainfall An estimate of the quantity and quality of rainfall was required for the nitrate loading analysis. The Hantzsche and Finnemore method utilizes the "average recharge rate of rainfall" in calculating potential nitrate impacts to the aquifer. Not all rainfall will percolate into the aquifer; evapotranspiration, the sum of evaporation and plant transpiration, will reduce percolating effluent, especially in summer months. 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 average annual rainfall to represent the estimated rainfall recharge for the project area. Rainfall data for the Lockeford area was obtained from the Western Regional Climate Center. The Elliott station (040010), the closest active station to the Site, reports the average total annual precipitation from July 1926 through May of 2016 to be 18.27 inches. By assuming 75 percent of this precipitation percolates to the aquifer, the value of 13.70 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. Jones indicated that the proposed Ford Construction facility will employ six people Monday through Friday, and occasionally Saturday. However, because a new Ford Construction office may be built on the Site in the future, and because of the unknown nature of the other businesses which may lease portions of the Site, a value of 100 employees, seven days per week, will be used for the nitrate loading analysis. No customers are anticipated. The estimated sewage flow rates for various uses are available from a number of references. The uses presented below were guided by the San Joaquin County On-Site Wastewater Treatment Systems Standards (2017), Crites and Tchobanoglous (1998), and US EPA (1980). The references indicate that 13 gallons for each employee is LOGE 1848 Page 10