Geosynthetics February/March 2021 - 17

BGM in shale gas
ponds examples
The use of BGM in tailings ponds built
in very cold temperatures and harsh
weather conditions allows for an extension of the installation period during the
freezing months (i.e., -49°F [-45°C] in
February in Siberia at the Kinross Kupol
Gold Mine), which provides a quicker
return on investment by not delaying the
installation time.
In the Northwest Territories of
Canada, the Diavik Diamond Mine is
located on a 7.7-square-mile (20-km2)
island in Lac de Gras, 186 miles (300
km) northeast of Yellowknife. The mine
is owned by a subsidiary of Rio Tinto
and Aber Diamond Limited Partnership.
Average minimum and maximum daily
temperatures are around -13°F (-25°C),
and precipitation exists in different forms
of drizzle, rain, hail, sleet and snow. The
processed kimberlite containment (PKC)
retention pond was initially completed
with an HDPE geomembrane, but owners and the consultant Golder Associates
Vancouver were looking to improve the
quality and reduce the cost of the PKC
pond and other ponds. By avoiding contamination of the purity of the water of
Lac de Gras, BGM was able to present
a more economical solution by offering
a larger period of installation and welding that can tie into 5,250 feet (1,600
m) of existing HDPE. The extension
to the existing pond was to be an additional height of 16 feet (5 m). Installation
was completed by a company based in
Yellowknife that specializes in geomembrane installation in cold weather conditions, and it has appreciated BGM's
flexibility even when stored and unrolled
at -40°F (-40°C). No special precautions
inside tunnels to protect from the cold
were required during welding, which
was performed in the open air at -13°F
(-25°C). This means the installation and
welding of BGM is largely independent

of temperature and weather conditions
(Eldridge and Harman 2006).
For the installer, working with BGM
was the same at -13°F (-25°C) as it would
have been at 68°F (20°C). The geomembrane maintained its flexibility and was as
easy to install and weld at both temperatures. Even when it snowed, the installation of the geomembrane continued as
usual. BGM can thus be installed at any
time of the year. For the initial HDPE
solution, the grain size for the bedding
and cover material was specified a 2-inch
minus (50-mm minus). Tests carried out
on-site showed that a 6-inch minus (150mm minus) material could be used for
bedding and a 15.7-inch minus (400-mm
minus) could be used for cover without
damage to the BGM. The 6-inch minus
(150-mm minus) bedding material was
compacted and the surface was then
raked by hand to remove the larger particles protruding above the surface, as
is typically performed on every worksite (Figure 5 on page 16). The cover
material was then dumped along the crest
and pushed by a track loader, down the
slope over the geomembrane. The use of
relatively coarse bedding cover materials and cushion materials as well as the
elimination of the need for a protective
geotextile (not recommended in regions
that have a lot of wind) under and above
the geomembrane reduced the total cost
of construction. Only one geosynthetic
(BGM) was needed, which saved on cost
for material layers and installation time in
an extreme weather region (Elliott 2007).
In Finland, the Kiitilä Mine lies within
the Arctic climatic region. Temperatures
are cold, with an average mean monthly
temperature in July of 59°F (15°C) and in
January of 5°F (-15°C). The mean annual
air temperature at the site is 32°F (0°C).
The mine facility plan called for a small
and a large pond, for a total initial area of
133 acres (54 ha) (today, more than 247
acres [100 ha]) to receive the processed

4a

4b

4c
FIGURES 4a, 4b and 4c BGM connection to
different materials: 4a) concrete pipe; 4b) rock;
4c) concrete lining

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Geosynthetics February/March 2021

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