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Calculation of Alkalinity Requirement for Nitrification The nitrate-nitrogen loading calculations on Page 8 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 domestic well water supply in addition to the introduction of wastes. 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 82 mg/L, as determined on Page 8 would require: 82 mg/L NH4-N x 7.1 mg CaCO3 = 582 mg/L alkalinity. The alkalinity in the domestic well water supply has yet to be tested for this project, but it is most likely below this concentration which would thus inhibit nitrification to an indeterminable degree. E. SURFACE WATER INFORMATION Storm water management will consist of an on-site retention basin in the extreme northwest corner of the property. Percolating stormwater may produce dilution effects to the underlying water table. Groundwater dilution effects can only be truly discerned with groundwater monitoring and modeling. According to a scientific paper authored by Shaw and Turyk(1994), reduction of nitrate concentrations in groundwater can occur primarily through dispersion, or by percolating rainwater, or a water source including effluent water recharge. Climatic Data: Rainfall versus Evapotranspiration S§3 It is generally and scientifically accepted that when precipitation exceeds spiration(Eto),deep percolation of surface rainwater may"occur. Evapotranspiration refers to water evaporation that takes place bath atthesoil 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 4 PRECIPITATION AND Eto DATA FOR TRACY,CA Month 2 Years in 10 will have more Eto Average Potential Deep precipitation than:(in/mo) (in/mo) (in/day) Percolation(in/mo) January 2.93 1.55 0.05 1.38 February 2.21 2.24 0.08 -- March 2.3 8 3.72 0.12 -- April 1.51 5.10 0.17 May 0.71 6.82 0.22 -- June 2.09 7.80 0.26 -- 5 Chesney Consulting