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llconsiderable time. This is indicated by the essentially constant <br />2~concentration of salt coming out for a considerable time during <br />leaching. An analysis of the leachwater shows that magnesium and <br />4 calcium sulfates are probably causing the relatively constant ' <br />$ conductivity. The EC value is controlled by the ratio of magnesium to <br />g calcium ions in the presence of sulfate. Xhen the calcium sulfate is <br />7 essentially depleted then the concentration of the total salt in the <br />g leachwater drops. <br />g In order to predict the amount of salt that can leach out of spoil <br />LO of a given particle size distribution it was determined that the shape <br />Ll of a composite decay curve can approximate the measured curve for a <br />L2 distribution containing the same size fractions. The shape of the <br />LS composite decay curve with time for a given mixture of particle sizes <br />L4 was approximated by summing the curves of the various fractions <br />LS represented in Figa. 1 or 2 after weighting them according to the <br />L6 percentage of the total weight that ie included in each fraction. Fig. <br />l7 3 shove the measured and estimated curves for both Clenrock and <br />l8 Williams Fork material and the percentages of the various size <br />L9 fractions included in the material. The closeness of fit indicates <br />:0 that the leaching process is relatively uniform throughout the columns <br />dl~regardleas of particle size. <br />If the amount of salt leached is directly related to the surface <br />;3~area of the particles it would be expected that [he area under the < <br />.5 mm diameter curve should be at lea et 90 percent of the sum of areas <br />all the curves when weighted for percentage of [he total material <br />cause of the relative surface areas within the various size groups. <br />amount of salts leached out per unit weight of material can be <br />• <br />• <br />• <br /> <br />6 <br />