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Geotechnical News • June 2016
WASTE GEOTECHNICS
Goal frequency:
90%
Success rate:
70%
Waste rock dumps and depositories
are a reality in most mines, but some
have the ability to produce chemical
reaction, and/or develop preferential
settlement that can lead to catastrophic
geotechnical failures. These have been
noted since the early days of mining,
but as our understanding of prefer-
ential air and water pathways, water
holding capacity, etc. has evolved, so
too has the reliability and stability of
these landscape features.
The high proportion of success reflects
the extensive research and trials that
have gone into the field of waste rock
physical stability. Associated failures
are highly visible and have caused
loss of life in the past. While water
quality concerns may produce severe
environmental consequences, they are
not always as visible and thus research
on chemical stability may have ranked
lower on the list of priorities. The
knowledge gap in the area of water
quality is being narrowed, but a great
deal of work still exists to be done
here.
Additional considerations and
diversified teams
It has long been said that there would
be no mining without geotechnical
engineers, but it is also true that there
would be no mine closure without
geotechnical engineers. Geotechni-
cal goals have an accumulated impact
as they directly affect the ability to
achieve all other goals (ecological,
land-use, socio-economic, and other
technical goals). For example, if
excessive erosion by wind or water is
not eliminated, then the establishment
of vegetation on that surface will be
difficult if not impossible, land-use
such as farmland or recreation will be
impeded, aesthetics will be compro-
mised, and off-site land or waterways
may have increased sediment loading
and/or contamination. It is for this
reason that so much emphasis has
been placed on geotechnical engineer-
ing and related components of closure
over the years.
At the same time, it is important to
understand the assumptions from
which geotechnical engineers base
their decisions, and the impact that
other components have on geotech-
nical features. For example, one
assumption is that waste rock dumps
and tailings impoundments remain
constant over time aside from slight
consolidation; in this respect ecolo-
gists and geochemists will readily
argue that soil properties in these land-
forms alter greatly over time (DeJong,
Tibbett, and Fourie, 2014). Input from
non-geotechnical professions can
inform how one approaches geotechni-
cal problems by fundamentally chang-
ing assumptions, so collaboration can
be key.
Geotechnical factors
have an accumulated
impact on mine closure
performance
Along the same lines, an interest-
ing finding from our survey was that
the success rate of a particular goal
is not always directly aligned with
professionals for that particular area
of specialty; for example, the greatest
success rate in achieving ecological
goals did not necessarily correspond to
the presence of ecologists on closure
teams. This tells us that it is the com-
position of a team overall that leads
to higher success rates, not just one
profession.
An unexpected finding was that of all
professions surveyed, teams with land-
scape architects were found to have
the greatest proportion of successful
outcomes: almost double that of any
other profession. It is important to
note that the broad nature of our sur-
vey made it impossible to determine
whether this was a cause and effect
relationship; however, it is an interest-
ing correlation to say the least. One
hypothesis for this is that the general-
ist nature of the landscape architecture
profession ensures oversight such that
gaps between specialists’ realms are
filled. Another hypothesis is that sites
with greater closure budgets have the
ability not only to do a more thorough
job, but also to hire more diversified
closure teams.
This is a correlation that has not
gone unnoticed: on March 30, 2016
the University of British Columbia
hosted the ‘Landscapes of Extraction
Roundtable’ which was sponsored
by BGC Engineering Inc. and UBC
Sustainability, and organized by Dirk
Van Zyl (Norman B. Keevil Institute
of Mining Engineering, UBC), Gord
McKenna (BGC), Joe Dahmen and
Kees Lokman (School of Architecture
and Landscape Architecture, UBC),
and Mickella Sjoquist (Master of
Landscape Architecture Candidate,
UBC). The event brought together
members of both the mining and land-
scape architecture community from
academia, industry, and with input
from indigenous relations special-
ists. UBC is strategically positioned
to develop these discussions, having
highly regarded mining engineering
and landscape architecture programs,
as well as a number of headquarters
of international mining companies
located in close proximity.
A number of conclusions were drawn
from the Roundtable, most notably
that:
• The mining life cycle is currently
not a cycle at all, but a line. We
need to close the gap through
better closure work and resultant
landscapes.
• The reuse of land is not a specialty
of mining companies. Perhaps
mining companies should remain
focused on mining, and land-use
specialists should focus on closure
planning aspects, in collaboration.
• If landscape architects are to be
involved, the focus needs to be
on landscape performance with
aesthetics being a natural result.
