PASTE & TAILINGS 2020
stability. The gentle 1-3% deposition slope drains
rain from the surface at mild velocities to
minimise erosion of the solids and keep the
solids exposed for continued air drying. The site
management plan did not recover rain runoff
collected in the TSF footprint but left it in the TSF
to absorb and ultimately evaporate.
Rotating active spigot locations allows drying
between layers for stability
stress P&TT is pumped a short distance to the
TSF by centrifugal pumps.
Results: TSF life and closure
The small footprint of the TSF resulted in a
relatively fast dam rise rate. The slurry pond was
near capacity when the WesTech Deep Bed Paste
Thickener was installed. A dam raise was needed
at the end of year one after the surface stack was
begun.
Over five years of operation, the dam elevation
increased over 20 m. Comparing the two
attached adjacent images, the white control
room building can be used as an elevation
reference. The surface area of the TSF
approximately doubled after five years of
spreading in the canyon. At this point, the TSF
filled to capacity, encroaching on roadways and
the paste thickener to quantify the benefits and
refinine the site management plan. A 10 m by 10 m
test site was prepared next to the TSF and was
filled to about 500 mm deep with P&TT. Due to
the very fine PSD, this non-Newtonian underflow
has the design yield stress at about 28-29 wt%
solids.
The rapid consolidation and drying allowed
foot traffic by the fourth day, despite 15 mm of
rain that day. Drying continued quickly with large
cracks developing by day seven. The attached
image shows the deposit after two rain events,
dried to significant cracking. At this point about
half of the water has evaporated.
This study showed that the rapid drying of
surface stacking and the low yield stress P&TT is
a safe and stable method of tailings disposal in a
sub-tropical climate.
Implementation
The installed 15 m diameter WesTech Deep
Bed™ thickener on a hill near the TSF effectively
dewaters to a non-Newtonian density, P&TT, and
recovers clear water for recycling. The low-yield
The surface area of the TSF approximately
doubled after five years of spreading in the
canyon
The initial spigots were placed along one side
of the TSF, forcing the pond water from the
previous pond slurry to collect near the dam
where this water was
recovered. The TSF had
relatively no standing
water after about three
months of operation.
The attached photo
shows the TSF during
the first monsoon
season.
Once the water was
collected, the spigot
placement was shifted
to other locations
around the TSF,
eventually settling on
the arrangement of
spigots located along the dam. Rotating active
spigot locations allows drying between layers for
other facilities.
The thickener allowed for the rapid drying of
non-Newtonian material throughout the life of
the TSF, and the plant was able to have quick
access to the site. The capping process quickly
followed closure of the site. IM
The capping process quickly followed closure of
the site
SEPTEMBER 2020 Supplement | International Mining P15