Table 6.7
PLL estimates according to DETSI
PLL
Stage 1
Stage 2
Mining operations
0
0
Township of Mt Morgan
0
<0.1
Itinerant
0
0
Total
<0.1
<0.1
6.2.3
Severity of Damage and Loss
The severity of loss and damage has been estimated using the maximum flood inundation and flood severity hydraulic results. The overall severity is estimated based on four categories as per ANCOLD [2]. - total infrastructure costs, impact on the dam owner’s business, health and social impacts, and environmental impacts. The resulting severities are discussed further below.
6.2.3.1
Total infrastructure costs
For both scenarios, the infrastructure costs include the replacement or repair of the failed embankment to its previous level of service and reinstatement of liners and ancillaries (pipes, etc.). The cost estimate for these works is estimated to be potentially in excess of $10 million. The impact on community infrastructure, such as the township of Mount Morgan, roads crossings, agricultural land, land use for stock, as well as the impacted dwellings is estimated to be to be less than $10 million for both Stage 1 and Stage 2 scenarios. The combined mine repair and third-party infrastructure restoration costs are expected to exceed $10 million, but less than $100 million for both stages. Therefore, the severity of damage and loss for infrastructure is classified as ‘ Medium ’ for both scenarios.
6.2.3.2
Impacts on o ’ business
Considering that Upper Mundic Gully TSF will be essential to maintain mine operations, in the event of failure of the facility, it is expected that there would be reduced services with reasonable restrictions. This could have a significant impact on financial viability in the long term. Additionally, based on reactions to recent dam failures, it is expected that there will be major loss of credibility, potentially resulting in extreme discontent from key stakeholders. This could also have political and legal implications. It is also likely that there may be community backlash, prolonging the time needed to replace the failed embankment and return to full operations. Therefore, for all scenarios, the severity of damage and loss for the impacts on the owner’s business is classified as ’ Major ’.
6.2.3.3
Health and social impacts
Flooding from a dam break would reach the township of Mt Morgan. People whose properties are damaged or destroyed will need to be compensated, as well as compensation for loss of life. Furthermore, employment within the mine may be affected under all failure scenarios. It is estimated that due to the dam break, restrictions in mine operations may result in the loss of between 50 and 100 jobs, although some staff could potentially be re-deployed in remediation roles. Additionally, it is expected that less than 100 people could be displaced/dislocated from the township of Mt Morgan as a consequence of the event.
Therefore, the health and social impacts for both scenarios have been considered to be ‘ Minor ’.
Project No PS213278 Upper Mundic Gully TSF Stage 1 and 2 DBA and CCA Mount Morgan Gold Mine Heritage Minerals
WSP JUly 2025 Page 29
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