Item
DETSI Comment
How comment has been addressed
Relevant Sections in
Supporting Information
Report
considered. How will Heritage Minerals manage this interaction and potential risks?
outflow to interact with the location where the proposed Sandstone Gully TSF is to be constructed. In the worst-case scenario, where erosion progresses into a breach initiation, cascade failure of Sandstone Gully TSF would become a credible failure mode, and the overall Consequence Category of Upper Mundic Gully TSF could be elevated to “Extreme” (matching Sandstone Gully TSF). Dam break assessments will be revisited in further studies to include the final proposed Sandstone Gully TSF footprint in the hydrodynamic models to further evaluate the risks/credibility of embankment erosion and the potential for a cascade failure and a consequent CCA re-assignment. To be better informed on environmental considerations including hydrogeological behaviours of the site it is advised that the Department consider the application in it’s entirely rather than select appendices. Environmental settings and considerations are provided in Section
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Appendix C (section 6.4.3) provides details on environmental considerations such as hydrogeological behaviours of the site, however, there is limited information available (based on the application material) to confirm this determination. Also, the figure referred to does not include Upper Mundic Gully TSF
Section 5 for environmental setting and considerations and Section 5.6 for site hydrogeology
5 of the supporting information whilst site hydrogeology is discussed in section 5.6
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A detailed probable maximum flood (PMF) assessment is required and must quantify total flood volume, peak flood level and evaluate whether a spillway is required, per ANCOLD 2012 WSP
Appendix D
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The preliminary CCA classifies the Wattle Gully/Upper Mundic Gully TSF as ‘Significant’ (Stage 1) and ‘High B’ (Stage 2), per ANCOLD 2012. These ratings must inform all design, operational, and closure decisions. Figure 3.2 of appendix C depicts a spillway for ‘stage 2’, however a spillway has not been nominated within the operational design. Without a spillway, the structure is at risk of overtopping unless it can be definitely shown otherwise
Updated CCA provided as Appendix C. Design process, operational and closure considerations are underpinned by consequence categorisation and ANCOLD requirements Figure 3.2 of Appendix C depicts the proposed breach location for Upper Mundic Gully TSF that was used to inform boundary conditions to conduct the failure hydrographs.
Appendix C
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Appendix D
Spillway from design report is discussed in Section 7.7 of Appendix D
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The TSF will sit within a large multi-headed gully system with several incised channels. There is no information on bed material, bank stability or historical
Reservoir rim / basin instability is a risk for all dams but is typically a remote risk. There are recorded
Section 4.3.4
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