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Calculation of Alkalinity Requirement for Nitrification The nitrate-nitrogen loading calculations are contingent upon the environmental factors required for nitrification to occur. These conditions include soil pore-space oxygen content, soil temperature, pH, electrical conductivity, organic matter, cation exchange capacity, and alkalinity. Alkalinity in wastewater effluent is derived from the on-site well water, in addition to the introduction of wastes to the effluent stream. Nitrification consumes approximately 7.1 mg of alkalinity for every mg of ammonia-nitrogen(NH4-N) oxidized. Nitrification of the average Total Nitrogen(TN) concentration of 60 mg/L, as determined on Page 7, would require: 60 mg/L NH4-N x 7.1 mg CaCO3 =426 mg/L alkalinity. The alkalinity concentration tested in the well water was 334 mg/L. Therefore, there is an insufficient alkalinity in the well water for complete nitrification to readily , proceed without the introduction of wastes. E. SURFACE WATER INFORMATION Storm water drainage management will be by on-site retention. Percolating rainwater will theoretically provide a slight water table dilution effect to percolating wastewater effluent since the disposal area will be down gradient from the property itself. However, as referenced in the next Section, rainfall in comparison to evapotranspiration is minimal. Cym=tic Data: Rainfall versus Evapotranspiration LS 3.2-.-At is generally and scientifically accepted that when precipitation exceeds evapotranspiration(Eto), deep percolation of surface rainwater may occur. Evapotranspiration refers to water evaporation that takes place both at the soil surface and transpiration by plants. The following Table illustrates rainfall and evapotranspiration for the Tracy area. Precipitation data was obtained from the Soil Survey of San Joaquin County. The conservative "2 years in 10"data was used and not the"average rainfall"data. Evapotranspiration data was obtained from the California Irrigation Management Information System (CIMIS): TABLE 6 PRECIPITATION AND Eto DATA FOR TRACY, CA Month 2 Years in 10 will have more Eto Average Potential Deep precipitation than: (in/mo) Percolation(in/mo) (in/mo) (in/day) January 2.93 1.55 0.05 1.38 February 2.21 2.24 0.08 -- March 2.38 3.72 0.12 - April 1.51 1 5.10 0.17 May 0.71 6.82 0.22 -- June 2.09 7.80 0.26 Page -5-