Due to impacts from the Mount Morgan Mine, water in the Dee River not suitable for drinking or
recreation, such as swimming or fishing. The DNRMMRRD have placed signage at all crossings along
the Dee River advising no drinking, no swimming and no recreational activities.
6.2.2. Impact Assessment
The overall Heritage Minerals Project will ultimately result in improved environmental outcomes at the
Mount Morgan Mine through the excavation and placement of historical ARD generating mine waste
and redeposition into the Sandstone Gully TSF, the OCP and (if approved) the Upper Mundic Gully
TSF. This will result in the removal of the source of ARD generating material from across the site and
consolidation where modern capping and closure solutions can be employed. This will reduce impacts
from the Mount Morgan Mine to the Dee River in accordance with the State’s Rehabilitation Plan (Unger
et al, 2003) and Phase 2 Agreement.
As referenced in Section 4.3 overtopping/ environmental spill and seepage consequence categories
were considered to be “low’ for both ANCOLD and DETSI. Given the total volume capacity of both
assessed stages of the TSF, a flood included overtopping failure was deemed as non-credible. The
results of the sunny day piping failure of both the Stage 1 and Stage 2 embankment layouts indicated
that the OCP is the primary receptor of breach outflows in all scenarios with these being heavily
attenuated and controlled by its spillway discharge.
The PMP storage allowance will provide more than adequate capacity to meet the Queensland DSA
and ESS requirements. Given the total volume capacity of both assessed stages of the TSF, a flood
included overtopping failure was deemed as non-credible. These findings are important to EA
conditioning as the Upper Mundic Gully TSF does not require an operational spillway, DSA or ESS
requirements to be included in Table H3 of the EA.
The TSF design considers mitigation of impacts to groundwater through the proposed installation of a
liner on the upstream batter of the embankment to mitigate 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 liner is proposed. Piezometers are
proposed to be installed within the embankment to monitor the phreatic surface and detect potential
seepage/ discharge of contaminants. The locations of the piezometers are to be finalised during the
next design phase and are typically installed following construction of the Stage 1 embankment.
The results of the geochemical modelling provided in Table 29 indicate that the final tailings solution
analytes do no exceed any of the HILs and it is concluded that leaching from the tailings material is
benign to human health. When tailings are appropriately stored in a well maintained TSF subject to
regular inspections and monitoring, the tailings materials are generally considered benign ecological
receptors. Additional groundwater monitoring bores are proposed to be installed to monitoring for any
potential COCs.
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Wulguru Technical Services Pty Ltd – Supporting Information to Amend an Environmental Authority
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