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Calculation of Alkalinity Requirement for Nitrification The nitrate-nitrogen loading estimations on Pages 11 and 12 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 on-site well wAter that will be provided, in addition to the introduction of wastes. Nitrification consumes approximately f 7.1 mg of alkalinity for every mg of ammonia-nitrogen(NH4-N) oxidized. Nitrification of the average Total Nitrogen (TN) concentration of 103 mg/L, as determined on Page 10, would require: 103 mg/L NH4 N x 7.1 mg CaCO3 = 731 mg/L alkalinity. The alkalinity in the domestic water supply is presently 440 ppm, and 758 ppm in the water table. This may supply sufficient alkalinity for nitrification to occur. Mounding Analysis Reference is made to the encountered groundwater in the backhoe test pit at 7.2 feet below existing grade. This depth to groundwater can be considered shallow and may induce a phenomenon known as the "mounding effect" in which percolating effluent encounters the water table and cannot disperse laterally in a certain time period. Consequently, a mound forms under the disposal Meld creating saturated flow conditions and decreasing the distance the effluent must travel under unsaturated flow for effluent treatment to occur. This minimum distance is five feet. An equation developed by Finnemore and Hantzsche(1983) is used below to predict the long-term maximum rise of the mound. However, due to the fact that there is no proposed project, certain parameters needed for an accurate mounding analysis are unknown at this time and must be assumed or estimated. These parameters include: average daily flow, disposal area, and length of disposal field. Estimations for each of these variables are explained below in the calculations. ,�h=H+Z.=2 where: h=distance from boundary to mid-point of the long-term mound, in ft H=height of stable groundwater table above impermeable boundary, in ft Zm=long-term maximum rise of the mound, in ft Substituting known and estimated values for the variables,we find the following: H=The height of stable groundwater above an impermeable boundary is estimated to be 7.2 based upon the measured standing water depth in the backhoe test pit. Therefore, it will be assumed that a boundary exists at H= 7.2 -4.5 (Highest anticipated water table depth)=2.7 ft. Long-term maximum rise of mound is estimated at 0.5 ft. Therefore, h=2.7 + (0.5 -2)=2.95 Z,,, l A � 141 �Kh�O.Sa cy)l 4.sa where:Q—average daily flow in Jft'/day A=area of disposal field in ft' C=mounding equation constant L=length of disposal field in ft K=horizontal permeability of soil in ft/day n=mounding equation exponent S,=specific yield of receiving soil in percent t —time since the beginning of wastewater application in days 7 Chesney Consulting