Table 6.11
Consequence Category assessment for Sandstone Gully TSF– DESI (Failure to Contain – Overtopping)
Item
Response
Low No loss of life is expected. No contamination of water used for human consumption. Low It is expected that the spills from TSF will discharge in the OCP and will be contained in the banks of the Dee River when spills from the OCP. 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.).
Harm to humans
General environmental harm
General economic loss or property damage
Overall consequence classification
Low
6.4 Failure to contain (seepage) consequence
6.4.1 Population at risk
No PAR is expected 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 [31] 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 — The preferential direction of groundwater flow from Sandstone Gully 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. Groundwater Dependent Ecosystems (GDE) data and groundwater borehole locations were retrieved from the GDE Atlas [32] and Queensland Globe [33], respectively, for the vicinity of the Mt Morgan site.
Project No PS213278 Sandstone Gully TSF Dam Break and Consequence Category Assessments Mount Morgan Gold Mine Heritage Minerals
WSP January 2025 Page 33
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