Canadian Dam Association Bulletin - Fall 2017 - 25

Figure 3. Finally, Dams 2, 3, 9, 12, 13
and 14 are in bad shape, and they plot
very high in Figure 5; their pf are one
to two orders of magnitude above the
upper bound of the historical range
in Figure 3.
This last group of dams has staggeringly high probabilities of failure
because they were initially considered
as simple causeways separating two

tailings ponds. They were poorly
or not at all engineered, lacking in
monitoring and maintenance. As the
results indicate here, risk being the
combination of failure probability and
consequences, a ranking based only on
probability or consequences is totally
misleading.
A risk tolerance curve was previously developed in paragraph 4.1, and

it is shown in Figure 5 as a continuous
curved line. Within the realm of credible probabilities, Dams 6, 8, 11 and 15
will remain above the tolerance curve,
even after substantial improvements
might be implemented. This means
that those risks are unmanageable and
they will require a strategic shift.
Dams 9, 12 and 13 are also above the
tolerance curve. However, depending

Theoretical Uncertainty

1E-3

1979 (Oboni, Oboni 2013)

Slurry (Taguchi 2014)
and US (Oboni, 2013)

Historical
Uncertainty

Global Failure Probabilities

Model uncertainty (Silva et al. 2008)

Dewatered
(Taguchi 2014)

1999 (Oboni, Oboni 2013)

1E-4
1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

Individual Failure Modes Probabilities
Figure 3. A priori probability of failure for different tailings systems (slurry and dewatered) with
their basic level of uncertainty. The vertical axis displays the global failure probability, whereas the
horizontal axis shows the failure probabilities from individual failure modes.
Risk Ranking
1000000
100000
10000
Risk in ($/y)

1000
100
10

Dam 1

Dam 4

Dam 10

Dam 5

Dam 6

Dam 2

Dam 11

Dam 8

Dam 7a

Dam 15

Dam 7b

Dam 14

Dam 3

Dam 13

Dam 9

Dam 12

1
0.1

Dam

Figure 4. Decreasing risk ranking of the dam portfolio using the corporate risk matrix colouring scheme.
Risks vs Tolerance

Tolerance

1E+0

Probability per Year

1E-1
1E-2

Dam 3

Dam 9

Dam 14

Dam 13

Dam 12
Dam 2

1E-3
1E-4

Dam 10
Dam 1

1E-5
1E-6
10,000

100,000

Dam 4

Dam 7a
Dam 5

1,000,000

Dam 15

Dam 7b
Dam 8
Dam 11
Dam 6

10,000,000

100,000,000

Consequence ($)

Figure 5. Corporate risk tolerance associated with a portfolio of dams expressed as failure
probabilities pf and consequences.
Canadian Dam Association * Fall 2017

25



Table of Contents for the Digital Edition of Canadian Dam Association Bulletin - Fall 2017

Board of Directors
President’s Message
2018 Board of Directors Update
2017 CDA Awards
Screening Level Risk Assessment for a Portfolio of Tailings Dams
Dam Safety Review, Public Safety Workshops Hit the Road
CDA Events Photospread
Gardiner Dam 50th Anniversary
Jim’s Journey – Memoirs by Jim Gordon
CDA Launches Digital Editions of Guidelines
Invitation From Icold 2018 in Vienna
Icold Corner
Notice of the Annual General Meeting
Ouranos Press Release – 2017 Spring Floods in Quebec
CDA Young Professionals
CDA 2018 Conference
Time to Renew Your Membership
CDA News Brief
Buyers’ Guide and Trade List
Canadian Dam Association Bulletin - Fall 2017 - Intro
Canadian Dam Association Bulletin - Fall 2017 - cover1
Canadian Dam Association Bulletin - Fall 2017 - cover2
Canadian Dam Association Bulletin - Fall 2017 - 3
Canadian Dam Association Bulletin - Fall 2017 - 4
Canadian Dam Association Bulletin - Fall 2017 - 5
Canadian Dam Association Bulletin - Fall 2017 - 6
Canadian Dam Association Bulletin - Fall 2017 - Board of Directors
Canadian Dam Association Bulletin - Fall 2017 - 8
Canadian Dam Association Bulletin - Fall 2017 - President’s Message
Canadian Dam Association Bulletin - Fall 2017 - 10
Canadian Dam Association Bulletin - Fall 2017 - 11
Canadian Dam Association Bulletin - Fall 2017 - 12
Canadian Dam Association Bulletin - Fall 2017 - 13
Canadian Dam Association Bulletin - Fall 2017 - 2018 Board of Directors Update
Canadian Dam Association Bulletin - Fall 2017 - 2017 CDA Awards
Canadian Dam Association Bulletin - Fall 2017 - Screening Level Risk Assessment for a Portfolio of Tailings Dams
Canadian Dam Association Bulletin - Fall 2017 - 17
Canadian Dam Association Bulletin - Fall 2017 - 18
Canadian Dam Association Bulletin - Fall 2017 - 19
Canadian Dam Association Bulletin - Fall 2017 - 20
Canadian Dam Association Bulletin - Fall 2017 - 21
Canadian Dam Association Bulletin - Fall 2017 - 22
Canadian Dam Association Bulletin - Fall 2017 - 23
Canadian Dam Association Bulletin - Fall 2017 - 24
Canadian Dam Association Bulletin - Fall 2017 - 25
Canadian Dam Association Bulletin - Fall 2017 - 26
Canadian Dam Association Bulletin - Fall 2017 - 27
Canadian Dam Association Bulletin - Fall 2017 - 28
Canadian Dam Association Bulletin - Fall 2017 - 29
Canadian Dam Association Bulletin - Fall 2017 - Dam Safety Review, Public Safety Workshops Hit the Road
Canadian Dam Association Bulletin - Fall 2017 - 31
Canadian Dam Association Bulletin - Fall 2017 - 32
Canadian Dam Association Bulletin - Fall 2017 - 33
Canadian Dam Association Bulletin - Fall 2017 - CDA Events Photospread
Canadian Dam Association Bulletin - Fall 2017 - Gardiner Dam 50th Anniversary
Canadian Dam Association Bulletin - Fall 2017 - 36
Canadian Dam Association Bulletin - Fall 2017 - 37
Canadian Dam Association Bulletin - Fall 2017 - Jim’s Journey – Memoirs by Jim Gordon
Canadian Dam Association Bulletin - Fall 2017 - CDA Launches Digital Editions of Guidelines
Canadian Dam Association Bulletin - Fall 2017 - Invitation From Icold 2018 in Vienna
Canadian Dam Association Bulletin - Fall 2017 - Icold Corner
Canadian Dam Association Bulletin - Fall 2017 - 42
Canadian Dam Association Bulletin - Fall 2017 - Notice of the Annual General Meeting
Canadian Dam Association Bulletin - Fall 2017 - Ouranos Press Release – 2017 Spring Floods in Quebec
Canadian Dam Association Bulletin - Fall 2017 - 45
Canadian Dam Association Bulletin - Fall 2017 - CDA Young Professionals
Canadian Dam Association Bulletin - Fall 2017 - 47
Canadian Dam Association Bulletin - Fall 2017 - CDA 2018 Conference
Canadian Dam Association Bulletin - Fall 2017 - 49
Canadian Dam Association Bulletin - Fall 2017 - Time to Renew Your Membership
Canadian Dam Association Bulletin - Fall 2017 - CDA News Brief
Canadian Dam Association Bulletin - Fall 2017 - 52
Canadian Dam Association Bulletin - Fall 2017 - 53
Canadian Dam Association Bulletin - Fall 2017 - Buyers’ Guide and Trade List
Canadian Dam Association Bulletin - Fall 2017 - cover3
Canadian Dam Association Bulletin - Fall 2017 - cover4
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