This report presents an evaluation of the costs of applying various technologies to reactive mine
wastes in order to prevent, control or treat acid mine drainage (AMD). The reactive wastes
include either tailings or waste rock which generate, or which may generate in the future, AMD.

The AMD technologies selected for the purpose of this study include a composite soil cover,
self-sustained and maintained water covers, some combinations of these covers, a plastic liner
cover, waste removal and the long term collect and treat option with or without a simple soil (or
vegetation) cover.

The objectives of this study were to evaluate the costs of currently applied, or perceived
feasible, AMD technologies and their comparison with a reference to planning future research
directions in the AMD area, and to evaluate the financial liabilities to the Canadian mining
industry and Canadian public as related to reactive mine wastes. Because the AMD technology
costs presented in this report have been estimated with a specific reference to these two
objectives, important limitations apply to the study results if used for any other purpose. In
essence, these limitations relate to the fact that the cost of an AMD technology considered for a
waste site will depend on numerous site specific cost factors while the representative AMD
technology costs presented in this report have been estimated with the purpose of addressing a
large number of reactive waste sites.

The study has been carried out based on actual mine closure projects selected with a reference
to the study objectives. Generic tailings/waste rock disposal sites have also been considered to
address specific cost issues such as the availability of borrow materials or the area-volume ratio
in the case of a waste rock dump.

In addition to the direct costs of an AMD technology application, some incidental costs were
also accounted for in the study. The estimated costs have been compared in terms of their net
present values.

The following representative unit cost ranges have been derived for the two basic AMD
technologies (1994$/ha of tailings footprint or 1994$/tonne of waste rock):

where the values in brackets represent suggested typical (“average”) unit costs.

These unit costs have been derived with the purpose of identifying AMD technology costs of
practical significance in the sense that the majority of the actual project costs are expected to
fall into one of the representative cost ranges.

An inventory of the reactive wastes in Canada was compiled recently by MEND. Based on this
inventory and the representative costs of AMD technology applications estimated in this study,
the financial liabilities associated with the existing reactive tailings and waste rock in Canada
have been evaluated as follows (in billions of 1994 dollars):

The primary conclusion of the study is that the (unit) costs of AMD technology applications are
very site specific and can vary widely. With a reference to the considered technologies and
study cases, this is particularly true for the collect and treat option in the case of waste rock and
for the self-sustained water cover option in the case of tailings.

In general, the composite soil cover and plastic liner technologies were confirmed to be the
most expensive. From the cost perspective, it seems unlikely that these technologies would be
considered preferable for typical mine sites. The study results also indicate that it is unlikely that
a walk-away option would be selected for a major waste rock dump which generates net acidity
at the time of closure.

A number of recommendations with regard to the most desirable future research directions in
the AMD technology area have been developed based on the study findings and other
considerations. Of particular importance seems to be carrying out a research evaluation of the
performance risks associated with the implementation of various AMD technologies.

The study results indicate that the self-sustained water cover and the collect and treat
technologies may represent the best options from the perspective of the implementation costs.
Hence, in developing the recommendations with regard to future AMD research directions, an
emphasis was made on these two technologies.