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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. The 2011 Lines of Equal Depth Map indicate the groundwater depth to be approximately 30 feet below grade. The 2010 Lines of Equal Elevation Map illustrates the groundwater directional flow to be in a northerly direction. NLS§ 2.2,3.1,SSS§ 2.1,4.2. Since the subject property and surrounding properties have been intensely farmed for several decades,the potential for nitrate contamination to the upper i groundwater aquifers is significant. It is known that nitrate contamination exists in this location and has impacted the CSA-30 wells. NLS§ 2.3, SSS§4.3,4.4,4.5.4.6. As referenced, the are no ag imgatio m1 s r domestic wells to sample on the property. It is the policy of the EHD to only saon a subject property and not wells on adjoining properties to determine nitrate impact. — --- Calculation of Alkalinity Requirement for Nitrification The nitrate-nitrogen loading calculations on Page 9 of this report 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 CSA-30 well water that will be provided, in addition to the introduction of wastes to the effluent. Nitrification consumes approximately 7.1 mg of alkalinity for every mg of ammonia-nitrogen (NH;N)oxidized. Nitrification of the average Total Nitrogen(TN) concentration of 82 mg/L would require: 82 mg/L NH,-N x 7.1 mg CaCO3 =582 mg/L alkalinity. The alkalinity in the CSA-30 domestic water supply is presently unknown, but probably low and may supply insufficient alkalinity for nitrification to readily proceed. E. SURFACE WATER INFORMATION Storm water management will be by an on-site retention basin until public stormwater management services arrive. Percolating rainwater from the retention basin may theoretically provide a water table dilution effect to percolating wastewater effluent since a portion of the basin is proposed to be upgradient from the wastewater disposal area. Dilution effects can only be truly discerned with extensive 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,by percolating rainwater, or a cleaner water source including effluent water recharge. 5