English

Abstract

A promising concept, known as the elevated water table, is emerging as a management and possible closure technique to limit AMD production from tailings impoundments. This prevention approach is based on the principle that tailings in the capillary zone can be maintained in a state close to full saturation which minimizes oxygen diffusion and thus limits acid generation. A parametric study was conducted to evaluate the effect of various factors on the water content profiles in reactive tailings. The results presented here show that the position of the water table has a large influence on the water content profiles and on the oxygen flux at the tailings surface. For a water table depth value smaller or equal to the tailings' air entry value (a), the degree of saturation Sr varies between 90 to 99 % at the tailings surface, covered by a sand protection layer. These high Sr values yield effective diffusion coefficient De comparable to that of O2 diffusion in water. The study also shows that the efficiency of the elevated water table concept can be negatively affected when the tailings are highly reactive.