Table 6.6
PLL estimates according to ANCOLD
PLL
Scenario 1
Scenario 2
Scenario 3
Mining operations
33.8
45.0
45.0
Township of Mt Morgan
0.1
13.8
56.7
Itinerant
< 0.1
0.3
0.8
Total
33.9
59.1
102.5
Table 6.7
PLL estimates according to DESI
PLL
Scenario 1
Scenario 2
Scenario 3
Mining operations
0
0
0
Township of Mt Morgan
< 0.1
13.5
56.7
Itinerant
0
0.3
0.83
Total
< 0.1
13.8
57.5
6.2.3 Severity of Damage and Loss The severity of loss and damage has been estimated using the maximum flood inundation and severity. 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 The infrastructure costs for all scenarios 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 (e.g., Burnett Road), agricultural land, land use for stock, as well as dwellings is estimated to be to be between $10 to 100 million for the Stage 1, and over than $100 million for Stage 3 and 5 scenarios. As the costs for the Stage 1 scenario would be between $10 to 100 million, the severity of damage and loss for infrastructure is classified as ‘ Medium ’. For the Stage 3 and 5 scenarios, estimated costs would be greater than $100 million, therefore the severity of damage and loss for infrastructure for these scenarios is classified as ‘Major’ . 6.2.3.2 Impacts on Owner’s business Considering that Sandstone 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. The impact on operations would be substantial, affecting the entire mine, including the CHPP and the Mundic Creek area. The Mundic Creek area would be affected due to the overtopping of the southern perimeter of the OPC for Scenarios 2 and 3 (Stages 3 and 5). 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.
Project No PS213278 Sandstone Gully TSF Dam Break and Consequence Category Assessments Mount Morgan Gold Mine Heritage Minerals
WSP January 2025 Page 29
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