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i D. GROUNDWATER INFORMATION / NLS§Z.1, SSS§4.1. Groundwater depths and elevations throughout San Joaquin Coun7The illustrated on maps published by the County Flood Control and Water Conservation Dist Fall 2016 Lines of Equal Depth Map indicate the groundwater depth under the property to be approximately 45 feet below grade. This depth can certainly be attributable to the past five years of drought. It is well known that the water table has been much shallower in this locale; to depths of 10-15 ft below grade. The Fall 2016 Lines of Equal Elevation Map illustrates the groundwater directional flow to be in a northeasterly direction. NLS§2.2,3.1, SSS§2.1,4.2. Since the surrounding properties have been farmed for a number of decades,the potential for nitrate contamination to the underlying groundwater aquifers can be considered significant. l NLS§ 2.3, SSS§ 4.3, 4.4, 4.5,4.6. Th7dofncen o on-site domestic or i 'gation wells on the subject Parcel to be sampled to quantify nitrateations. Calculation of Alkalinity Requirement for Nitrification The nitrate-nitrogen loading to the underlying groundwater is 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 City of Tracy well water, in addition to the introduction of wastes. Nitrification consumes approximately 7.1 mg of alkalinity for every mg of ammonia-nitrogen(NH4 N) oxidized: rification of the average Total Nitrogen (TN) concentration of 62 mg/L, as determined Ln Page 66 would require: 62 mg/L NHa N x 7.1 mg CaCO3 =440 mg/L alkalinity. The alkalinity concentration in the City water is unknown, but certainly lower than 440 mg/L. Therefore, there is an insufficient alkalinity in the City water for complete nitrification to readily proceed without the introduction of wastes and the alkalinity within the soil environment. E. SURFACE WATER INFORMATION Storm water drainage management will be by on-site retention. Percolating rainwater will theoretically provide an indeterminable water table dilution effect to percolating wastewater effluent since the disposal area is down gradient from the south half of the property. However, as referenced in the next Section, rainfall in comparison to evapotranspiration is minimal. Climatic Data: Rainfall versus Evapotranspiration NLS§ 3.2. It 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 i California Irrigation Management Information System (CIMIS): Chesney Consulting