Mount Morgan Mine Upper Mundic Gully TSF EA Amendment

Item

Stage 1

Stage 2

Minor Some restrictions

Same as Stage 1

Impact on dam owner’s business

Minor 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. Minor It is expected that the spills from TSF will discharge in the Open pit and will be contained in Dee River banks when spills from the Open pit.

Same as Stage 1

Health and social impacts

Same as Stage 1

Environmental impacts

Low

Overall consequence classification

5.3.2.8 Environmental Spill/Failure to contain (Overtopping Consequence) – DETSI Table 29 presents the consequence category assessment for Upper Mundic Gully according to

DETSI for the “Environmental spill” scenario of both embankment stages. Table 29. Consequence Category Assessment – ANCOLD (Environmental Spill)

Item

Stage 1

Stage 2

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 Open pit and will be contained in the banks of the Dee River when spills from the Open pit. 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.).

Same as Stage 1

Harm to humans

Same as Stage 1

General environmental harm

Same as Stage 1

General economic loss or property damage

Low

Overall consequence classification

5.3.2.9 Failure to contain (Seepage) – Consequence WSP has recently completed a seepage management plan (SMP) for UMG TSF (Appendix H). The SMP aims to present an initial characterisation of potential seepage behaviour based on the current understanding of potential seepage behaviour based on the current understanding of the

Project number: 25B061

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