Table 6.2
Consequence Category criteria based on PLL [2]
Incremental potential loss of life
Severity of damage and loss
Minor
Medium
Major
Catastrophic
<0.1
Very Low
Low
Significant
High C
Significant (1)
0.1 to <1
Significant
High C
High B
1 to <5
High C
High B
High A
(1)
5 to <50
High A
High A
Extreme
(1)
50 Extreme (1) With an incremental PLL equal or greater than one (1), it is unlikely damage will be minor. Similarly, with an incremental PLL in excess of 50 is unlikely damage will be classified as medium. Extreme
6.1.2 DESI guidelines
The Consequence Category based on the DESI [3] Manual has been estimated in terms of the following three failure types: 1) Failure to contain – Overtopping , spills or releases from the structure that result from loss of containment due to overtopping of the structure.
2) Dam break, collapse of the structure due to any possible cause.
3) Failure to contain – Seepage, spills, or releases to ground and/or groundwater via seepage from the floor and/or sides of the structure. The Consequence Category assessment was estimated by applying the DESI method, presented in Table 6.3, to each failure scenario.
Table 6.3
Consequence Category criteria – DESI manual
Consequence Category
Environmental harm
High
Significant
Low
Location such that people are routinely present in the failure path and if present loss of life to greater than 10 people is expected. Location such that contamination of waters (surface and/or groundwater) used for human consumption could result in the health of 20 or more people being affected.
Location such that people are routinely present in the failure path and if present loss of life to 1 person or greater, but less than 10 people is expected. Location such that contamination of waters (surface and/or groundwater) used for human consumption could result in the health of 10 or more people but less than 20 people being affected.
Location such that people are not routinely present in the failure path and loss of life is not expected. Location such that contamination of waters (surface and/or groundwater) used for human consumption could result in the health of less than 10 people being affected.
Harm to humans
Project No PS213278 Sandstone Gully TSF Dam Break and Consequence Category Assessments Mount Morgan Gold Mine Heritage Minerals
WSP January 2025 Page 24
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