— Within the urban area of Mt Morgan, it was assumed that an average of two people per house affected by the flood extents are exposed during both day and night. These estimates were based on Census data presented by the Bureau of Statistics [25]. — The number of vehicles was estimated using Traffic Census data sourced from the Queensland Government [26], based on the difference between datasets retrieved from monitoring locations “30m N of Neil St” (Site Number: 60057) and “30 m N of Jeannie St” (Site Number: 61082). — No civilians are routinely expected within the mining lease; therefore, only mine personnel were considered in the impacted areas of the site. — No reductions in the PAR were considered for Sandstone Gully TSF due to limited warning/evacuation time assumed and the rapid progression of breach and outflow in the event of a failure, following ANCOLD [2] recommendations. This also accounts for the uncertainty associated with estimating the PAR and the expected rapid escalation of outflow to potentially occupied areas. 6.2.1.2 Estimation of itinerant PAR For any itinerant population along the access networks, the roads were assumed to be two-way. The PAR was estimated according to Campbell et al. [27]. The following assumptions were applied in addition to the traffic census data:
— The occupancy per light vehicle is 2 people — The occupancy per heavy vehicle is 1 person — The average vehicle speed is 60 km/hr.
6.2.1.3 Results
Table 6.4 presents the permanent and itinerant PAR for each scenario, according to ANCOLD [2].
Table 6.4
PAR estimates (ANCOLD)
PAR
Scenario 1
Scenario 2
Scenario 3
Mining operations
45
60
60
Township of Mt Morgan
14
152
350
Itinerant
0.2
1.7
2.3
Total
59.2
213.7
412.3
Table 6.5 presents the permanent and itinerant PAR for each scenario, according to DESI [3]. This methodology discounts mine personnel from the estimates.
Table 6.5
PAR estimates (DESI)
PAR
Scenario 1
Scenario 2
Scenario 3
Mining operations
0.0
0.0
0.0
Township of Mt Morgan
8
124
328
Itinerant
0.0
1.7
2.3
Total
8.0
125.7
330.3
Project No PS213278 Sandstone Gully TSF Dam Break and Consequence Category Assessments Mount Morgan Gold Mine Heritage Minerals
WSP January 2025 Page 27
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