Pierre River Mine Project

WATER AENV SIRS 15 – 43
Table AENV 17-1: Comparison of ETDA Seepage Management Alternatives
Method Characteristics Sustainability
Pumping
wells
• Appropriate in gravel to
silty fine sand soils.
• Unrestricted depths using
submersible pumps.
• Costs are relatively
moderate.
Slurry wall • Appropriate in silts, sands,
gravels and cobbles.
• Depths generally limited to
40 to 60 m, depending on
soil and site conditions.
• Requires relief wells
upgradient of slurry wall.
• Costs are relatively high
for deep cut-off walls.
Clay liners • Requires large volumes of
clay.
• Requires substantial site
preparation, detailed
quality control, and
protection against dry/wet
and freeze/thaw cycles.
• Requires installation of
horizontal drains in ETDA
to alleviate ETDA pore
pressure.
• Cost is relatively high, and
can be even more costly if
clay source not close to
the ETDA site.
Synthetic
liners
• Requires intense site
preparation, detailed
quality control.
• Requires installation of
horizontal drains in ETDA
to alleviate ETDA pore
pressure.
• Cost is relatively high.
• Temporary
measure.
• Affects groundwater
flows while in
operation.
• Once pumps are
decommissioned,
the groundwater
levels and flow
directions will
recover.
• Permanent and
passive measure.
• Permanently affects
groundwater levels
and flow directions.
• Permanent and
passive measure.
• Does not affect
underlying
groundwater flows,
as seepage is
contained above
natural surface.
• Permanent and
passive measure.
• Does not affect the
underlying
groundwater flows
as seepage is
contained above
natural surface.
Performance
Efficiency
• High efficiency in
permeable soils
(gravel to silty fine
sand) as it creates a
cone of depression
that works as a
hydraulic barrier.
• High efficiency in
containing seepage
as it provides low
permeability barriers
as a result of
bentonite or clay
slurry.
• High efficiency in
containing seepage
when constructed
properly and
protected.
• High efficiency in
containing seepage
when properly
installed and
protected.
• Resistant to variety
of chemicals.
Section 12.1
Operational
Maintenance
• High. Requires
monitoring of
drawdown and
pumping rates,
systematic
adjustment of
pumping rates,
monitoring of well
efficiency and
cleanup, pump
replacement and well
replacement.
• No maintenance for
slurry wall and relief
well system.
• No maintenance
once covered by
tailings.
• No maintenance
once covered by
tailings.
Request 17b Shell describes details that demonstrate a high confidence in the likelihood of
successful mitigation of ETDA seepage water, anticipated seepage rates, and
other aspects. The predicted seepage rate from the Pierre River Mine ETDA
during operations was 240 L/s (Response 271b).
i. How was this rate determined?
12-6 Shell Canada Limited April 2010
CR029