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D. GROUNDWATER INFORMATION NLS§2.1, SSS§4.1. Groundwater depths and elevations throughout San Joaquin County are illustrated on maps published by the County Flood Control and Water Conservation District, found in Appendix D. The most recent Lines of Equal Depth map (2016) indicates the groundwater depth to be 30 feet. The Lines of Equal Elevation depict the groundwater flow to be in a northwesterly direction toward the Delta and in-line with the San Joaquin River. SSS§2.1, 4.2. Surrounding properties have been intensely farmed for several decades. Thus, the probability for nitrate contamination in the underlying soil and groundwater can be considered significant if nitrogen fertilizers were used on this production land. However, soil and well water analyses indicate very low nitrate concentrations. Again,this may be attributable to denitrification activity. Calculation of Alkalinity Requirement for Nitrification The nitrate-nitrogen loading calculations on Pages 7 and 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 90 mg/L, as determined on Page 8 would require: 90 mg/L NH4-N x 7.1 mg CaCO3 = 639 mg/L alkalinity. The alkalinity in the domestic well water supply was tested to be an average 153 mg/L. Consequently,nitrification may be inhibited to an indeterminable degree. For comparison purposes, the average total alkalinity from the City of Stockton groundwater supplies is 158 mg/L. E. SURFACE WATER INFORMATION Storm water management consists of on-site management of runoff flows into the associated bodies of water and soil percolation. Percolating stormwater may produce dilution effects to constituents of concern, such as nitrate,within the underlying water table. 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, which is the closest data available. Precipitation data was obtained from the Soil Survey of San Joaquin Countv. 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): Chesney Consulting