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I ~ Section 780.2I(c) Continued. Revised 11/20/80 <br />the coal aquifer. The concentration of dissolved salts will de- <br />crease rapidly with increasing distance from the source of contri- <br />bution. Dilution will continue to occur as the salt plume spreads <br />while flowing under the gradient of the piezometric surface. At a <br />given time and at a certain distance from the mine plan area, the <br />concentration of dissolved salts above the baseline level will be <br />immeasureable, and no effect of mining will be evident. An anal- <br />ysis of ground water salt loading and movement is presented below. <br />i <br />The analysis of ground water solute transport was performed using <br />the same equations and analysis as used for dispersion of. tracer <br />dye through a porous medium. First, the piezometric surface gra- <br />dient shown on Map 15, Kerr Mine Area Ground Water Hydrology was <br />used to determine the direction and rate of ground water flow <br />through the coal aquifer at selected locations. Next, the average <br />concentration of baseline total dissolved solids from Table 6, Kerr <br />Mine Area Ground Water Quality Data, was subtracted from the esti- <br />mated level of leachate solute concentration to determine the <br />initial contribution of salt to the coal aquifer. <br />The contribution concentration after 50 years of leachate movement <br />was computed for several distances from the mine plan area using a <br />two-dimensional solution of dispersion (Fried, 1975), which is <br />given below: x <br />C (x,y) Q/b e~°` Ko x2 + y2 Co <br />2'7u («iar)~ (4 c(~ ) (4a~ar ) <br />Where: Co = contribution of leachate solute minus <br />baseline ground water salt concentra- <br />tion, in mg/1 <br />C = concentration of dissolved salt at <br />point (x,y) above baseline concentra- <br />tion, in mg/1 <br />780-121 as <br />