Geotechnical News • March 2012
37
WASTE GEOTECHNICS
in the release of low SFR materials that
are difficult to reclaim (Hyndman and
Sobkowicz, 2010). Since the 1980s,
technical advances have been made
in mining and material handling and
bitumen extraction. However, finding
practical methods to control and reduce
the fluid fine tailings formation build
up has been an ongoing challenge.
Oil sands tailings regulations
The Energy Resource Conservation
Board (ERCB), Canada’s regulatory
body responsible for the oil sands
industry, has been concerned regarding
past tailings management practices,
continual accumulation of fine tailings
and the associated risks to reclama-
tion activities. As such, they elected
to regulate fluid fine tailings through
performance criterion, and in early
2009 the ERCB issued Directive 074:
Tailings Performance Criteria and
Requirements for Oil Sands Mining
Schemes. The aim of the directive is
to reduce fluid tailings accumulation
by capturing the fines in dedicated
disposal areas (DDAs) and create
trafficable surfaces for progressive
reclamation. The Directive requires
operators to submit tailings plans, tail-
ings pond status reports, disposal area
plans and compliance reports. Compli-
ance with Directive 074 can be directly
measured through specified strength
performance in the tailings deposits.
The Directive requires a minimum
undrained shear strength of 5 kPa
for tailings material deposited in the
previous year. If any material fails to
meet the 5 kPa requirement, it must be
removed or remediated. Additionally,
five years after active deposition, the
deposit must be trafficable and ready
for reclamation. The metric for “traf-
ficable” after five years requires the
deposit to have a minimum undrained
shear strength of 10 kPa. It is evident
new technologies and processes must
be developed to supplement current
tailings management plans, specifi-
cally, additional fines-management
techniques. Specification of a short-
term strength requirement may sound
like a positive exploit – at least at
first glance. However, the regulation
may inadvertently misdirect indus-
try efforts. The following discussion
attempts to explain some of the issues
and challenges.
Fine tailings management
Implementation of the ERCB’s Direc-
tive 074 has driven industry to review
current tailings management tech-
niques and investigate the numerous
alternative technologies and processes
to manage and reclaim fine tailings.
Essentially, there are three general
methods to incorporate the problem-
atic, clay dominant fine tailings into
a closure landscape. The fines can be
sequestered into the coarse tailings
matrix (CT), placed under a water cap
Figure 2. Remolded undrained shear strength of oil sand MFT.
Figure 3. Undrained shear strength of oil sands fine tailings.
