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i Calculation of Alkalinity Requirement for Nitrification The nitrate-nitrogen loading estimations on Pages 14 and 15 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 7.1.'mg of alkalinity for every mg of ammonia-nitrogen(NHq N) oxidized. Nitrification of the average Total Nitrogen (TN) concentration of 113 mg/L, as determined on Page 13 would require: 113 mg/L NH4-N x 7.1 mg CaCO3 = 802 mg/L alkalinity. The alkalinity in the domestic water supply is presently 121 ppm, which may theoretically retard nitrification to an indeterminable degree! However,the water table alkalinity may be sufficient to promote nitrification. Mounding Analysis Reference is made to the encountered groundwater from the backhoe test pit at 4.5 feet below existing grade. This depth to groundwater can be considered extremely 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 frame. Consequently, a mound forms under the disposal field creating saturated flow conditions and decreasing the distance the effluent must', travel under unsaturated flow for effluent treatment to occur. An equation developed by Finnemore and Hantzsche (1983) is used below to predict the long-term maximum rise of the mound: h=H+Zm=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 4.5 based upon the measured standing water depth in the well. Therefore, it will be assumed that a boundary exists at H= 7-4.5 (Highest measured water table depth)=2.5 ft. Long-term maximum rise of mound is estimated at 0.5 ft. Therefore, h=2.5 +(0.5 -2)=2.75 Zm= L A 1 l 4 1 h)0,5. r L i-oso SY) where: Q=average daily flow in W/day — A=area of disposal field in ft2 C=mounding equation constant L=length of disposal field in ft K=horizontal permeability of soil in ft/day n=mounding equation exponent Sy=specific yield of receiving soil in percent t =time since the beginning of wastewater application in days Substituting known constants for the variables,we find: i 8 j Chesney Consulting I�