Item
Stage 1
Stage 2
Low
It is expected that the spills from TSF will discharge in the Open pit and will be contained in the banks of the Dee River when spills from the Open pit.
General environmental harm
Same as Stage 1.
Low
No dwellings, roads or any other third- party assets are expected to be harmed. However, it is expected that the discharged outflows cause minor impacts (less than $1 million in rehabilitation/compensation) to farm supply/use downstream. This category does not include the economic losses related to the owner’s business (embankment, access roads, pits, etc.).
General economic loss or property damage
Same as Stage 1.
Overall consequence classification
Low
Low
6.4
Failure to Contain (Seepage) Consequence
6.4.1
Population at risk
No PAR is expected for both embankment stages as there no ground water bores used for water supply in the vicinity of the TSF.
6.4.2
Potential loss of life
Similarly to PAR, no PLL is expected.
6.4.3
Environmental considerations
The Mount Morgan Mine Mundic Gully Stability Assessment developed by GHD [28] provides information about the hydrogeological behaviour near Mount Morgan mine. This study identified the following: — Monitoring bore levels, along with storage data monitored from the OCP, provide and understanding of the response of waste and tailings material to rainfall infiltration — Due to its upslope location, it is assumed that seepage flows from the proposed Upper Mundic Gully TSF are directed towards the OCP. — The preferential direction of groundwater flow from the OCP is suggested to be to east towards Mundic Creek, as presented in the inferred groundwater contour map shown in Figure 6.3. — Seepage flows are expected to continue towards Mundic Creek, consistent with historical observations. Therefore, seepage interception and management systems in place are expected to be maintained. According to Figure 6.3, groundwater flow is in the direction of Dee River. It is expected that any potential seepage would be directed to Dee River and be conveyed southwards along Dee River and not impact the area east of Dee River.
Project No PS213278 Upper Mundic Gully TSF Stage 1 and 2 DBA and CCA Mount Morgan Gold Mine Heritage Minerals
WSP JUly 2025 Page 33
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