Abstract for the 23rd World Mining Congress
To be included in the topic:
Mining, Ethics and Sustainability
Title of paper:
Feasibility of tailings reclamation for underground paste and hydraulic backfill applications
Authors:
Tarr, K. and Pratt, A. (CanmetMINING), Isagon, E. (Vale Canada Ltd.), and Poon, A. (KCBL)
Acid-producing mine tailings are present at many active and inactive mine sites and pose an
environmental liability due to the potential for acid rock drainage. Acid rock drainage originating from a
tailings pile, a waste rock pile, or exposed sulfide-rich rock, can cause discoloration and turbidity in
receiving waters, and the loading of ions mobilized by the acid can cause a decrease in aquatic flora and
fauna, and reduction in the quality of groundwater. The primary cause of acid generation is the
oxidation of sulfide minerals, predominantly pyrite and pyrrhotite.
Considerable mine tailings are being stored on surface in vast tailings impoundment areas across
Canada. In the tailings within this study, from the Sudbury, Ontario area, the sulfide mineral of primary
concern with respect to acid generation is pyrrhotite. Different tailings types show varying and
progressive degrees of oxidation correlating to their specific sulfur contents. The degree of oxidation is
determined by the relative extent to which the sulfides have reacted as well as the depth of oxidation
within the tailings.
Natural Resources Canada, CanmetMINING is dedicated to research supporting the Green Mining
Initiative, a program reducing business risks by demonstrating practices that reduce environmental
impacts. In cooperation with the Canada Mining Innovation Council (CMIC), applied research aims to
reduce land disturbance, waste volumes, and releases to the environment. By reutilizing tailings from
vast impoundment areas as a component in backfill, the potential environmental impact would be
lessened considerably, due to the reduced tonnage stored on surface long-term. From an operating
perspective, there is a need for supplemental feed for backfill from time to time. The reclamation of old
tailings for use in backfill is also driven by the fact that old tailings ponds may not be structurally stable,
and it may be more cost effective to remove the tailings than to upgrade the impoundment structure.
However it is imperative that these old tailings be fully characterized to determine their suitability for
use underground, in order to ensure the long-term integrity of the resulting backfill matrix.
A study was conducted to investigate the feasibility of tailings reclamation from old impoundment areas
as a significant component in backfill. The materials were first physically and chemically characterized,
followed by preparation of samples to determine optimal mix proportions for strength development for
both paste and hydraulic fill compliance. It was found that the amount of oxidized tailings included in
the backfill material had a profound effect on both the segregation and settling properties of the backfill
matrix, as well as the mechanical properties of the samples. The strategies for decision-making, based
on the criteria for material characterization, mining plan, and cost effectiveness are discussed.