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1 Williams Fork material the larger the particles the more rapidly the 2 leachate concentration declined and the smaller the total amount of 3 salt leached as indicated by the area under the curves. It vas q expected that the amount of readily soluble salt would be related 5 directly to the particle surface area because the salts diffusing from 6 within the larger particles of the material will be negligible in 7 comparison with the salts available on the surface of the particles. g The shape of the decay curve of concentration plotted against 9 amount of leachwater (Figs. 1 and 2), when the salt supply in the spoil LO is being depleted, depends oa several mechanisms. These include ~l diffusion of ions out of porous particles, dispersion of ions within ~Zlthe pores between particles, and dissolution of soluble salts on the ~3 particle surfaces. The rate with which the water maven through the ~q pores by mass flow under the influence of gravity is much faster than l5 diffusion. Thus the contribution from diffusion is small and extended ~g over a long period of time. The shape of the curve tends toward an ~7 exponential decay. After sufficient water has leached through the ~g column the curve tends toward an electrical conductivity which is a ~g measure of the salts resulting from the dissolution of the rock matrix ;p itself. Thin may also .include the salts diffusing slowly from within E1 the larger particles. The electrical conductivity value can match t2 fairly well that measured in the stream water in the mining area above ~ the disturbance during the time of the year when there is no surface Eq runoff. Data indicating this for the Williams Fork material ae ahawn 35 in Fig. 1 were found in HcWhorter~. >g The shape of the curve for the < 0.5 mm particle size in Fig. 1 ;7 suggests that some ions are near saturation in the leach water for a 5