Figure 30. Stage 2 Stage-Storage Curve
4.3.6. Decant Pond
Deposition into the TSF will be conducted from the embankment to keep the decant pond well away
from the embankment. A suitable return water pump system will be required and may comprise a
floating pontoon pump or other suitable mobile system.
4.3.7. Seepage and Tunnel Management
A liner is required on the upstream batter of the embankment to mitigate potential seepage through the
embankment. A geomembrane liner will be required as no suitable low permeability clayey material is
found on the mine site. The liner bedding will be selectively borrowed from finer mine waste, however
as it is difficult to remove coarse particles, a more robust bituminous geomembrane membrane (BGM)
liner (BGM, Coletanche ES4) is proposed.
The BGM will need to be extended upstream of the embankment and across the valley walls to mitigate
seepage past the liner and embankment. A nominal 10mm width has been adopted at this stage,
however this is subject to further investigations to confirm the lining requirements and extents.
The stormwater tunnel inlet is within the TSF footprint is proposed to be plugged prior to embankment
construction to mitigate potential deformation or collapse of the tunnel void beneath the embankment
fill. The tunnel portal plug comprises a 1.5 m concrete plug located in competent rock approximately 5
m past the tunnel inlet. Mine spoil should then be pushed into the tunnel to backfill the inlet to support
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Wulguru Technical Services Pty Ltd – Supporting Information to Amend an Environmental Authority
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