Consequence Category
Environmental harm
High
Significant
Low
iii) significant alteration to existing ecosystems; or iv) the area of damage (including downstream effects) is likely to be at least 2 km 2 . Location such that harm (other than a different category of harm as specified above) to third party assets in the failure path would be expected to require $1 million and greater but less than $10 million in rehabilitation, compensation, repair or rectification costs.
Location such that harm (other than a different category of harm as specified above) to third party assets in the failure path would be expected to require $10 million or greater in rehabilitation, compensation, repair or rectification costs.
Location such that harm (other than a different category of harm as specified above) to third party assets in the failure path would be expected to require less than $1 million in rehabilitation, compensation, repair or rectification costs.
General economic loss or property damage
6.2
Dam Break Consequence
6.2.1
Population at risk
The definition of the population at risk (PAR) varies between the various authorities as follows:
— PAR according to ANCOLD [2], includes all people who would be directly exposed to flood waters from the dam break (within the inundation zone) — PAR for DETSI [3] does not include the mine personnel in the PAR estimates or persons located in an area with inundation depths lower than 0.3 m.
6.2.1.1
Methods and assumptions
The PAR was estimated from the number of operational personnel in buildings or other places of occupation within the failure impact zone, as well as those working or travelling through the impacted zone and by the duration of exposure (duration) of those people within the impact zone.
The PAR was estimated based on the following assumptions:
— Mining operations are active during the time of breach.
— Mine personnel location, occupancy and time of exposure within the Mine Site were provided by Heritage Minerals (via e-mail on 07/11/2024). A total of 60 are expected to be present and may potentially be exposed during inspections and operations across the mine site. Figure 6.1 presents areas potentially affected by the runout, broken down as follows:
— 30 people per day at the Process Plant and ROM Pad.
— 15 people per day at the No 2 Mill TSF.
— 15 people per day at the Mundic Red Oxide TSF.
Project No PS213278 Upper Mundic Gully TSF Stage 1 and 2 DBA and CCA Mount Morgan Gold Mine Heritage Minerals
WSP JUly 2025 Page 25
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