Canadian Dam Association Bulletin - Fall 2017 - 21

i.e. hundreds to thousands of potential targets, possibly interdependent,
exposed to many possible natural and
man-made hazards. Those clients were
generally overwhelmed by the amount
of confusing information coming from
sectoral risk assessments, using fuzzy
terminology, and leading to ill-stated
risk registers.
Clients felt it was very important
to swiftly get to a screening level that
allows prioritization and immediate
mitigation of the most critical risks.
Afterwards, a road map is refined and
updated. This is in opposition to having a long and static analysis that will
delve into unnecessary details first. It
is important to find, for each portfolio,
the right balance between details and
simplifications. Superfluous details
may stop the analyses for lack of
available data and excessive costs.
Undue simplifications may defeat
the prioritization effort. Screening
does not imply the analysis is fuzzy.
To deal with the large portfolios, it
became evident that only quantitative
evaluations would reach the necessary resolution in the definition of
the priorities.

Figure 2 shows the logic flow of information within the ORE deployment,
starting from the Rich Data Context
cell located in the top left corner, all
the way down to decision-making.
Over twenty years of quantitative risk
assessments on tailings dams and other
mining macro-elements have proven
the validity of the ORE logic, and of the
underlying computational and modelling techniques. In the last five years,
a lot of effort has been devoted to portfolio analyses (Oboni and Oboni, 2013).
Attention has been paid to systemic
analysis of the causes of failure which
often include what amounts to congenital defects. These show up as pathologic
elements, decades after dam commissioning (Oboni and Oboni, 2016b, Oboni
et al., 2014). These may include:
* overly optimistic scenarios, due
to conflict of interest between the
designer and the assessor;
* complacency, caused by a too close
relationship between the assessor
and the inspector;
* poor risk assessment practices
(Oboni et al., 2013).
Hazard scenarios can be elemental or may develop in long chains of

interdependencies. They are located
under the Data Base box in the top
middle of Figure 2. A compounded or
domino effect failure has already been
mentioned for Dam 7 in Figure 1. That
type of failure leads to consequences of
a larger impact than the initiating event.
In the case history discussed in
this paper, the ORE deployment leads
to the definition of risks deriving
from all hazards, using Table 1, for
each element of the system. A single
multidimensional metric for multiple types of hazard consequences
is adapted from USEPA (1999, 2003)
and Barnthouse et al. (2000). Complex
domino scenarios due to interdependencies from multiple failures are
considered. In the present portfolio,
failure of Dam 7 could impact Dams
10, 11 and 12, as explained earlier. For
further analysis in this paper, Dam 7
has been subdivided in two scenarios,
Dam 7a (Dam 7 alone) and Dam 7b
(Dam 7 with the interdependencies).
Because of its updatable Bayesian
nature, ORE will show if risks increase
due, for example, to climate pattern
changes or to management issues, and
it will allow for alerts.

Figure 2. Optimum Risk Estimates (ORE ©Oboni Riskope Associates Inc., 2017) methodology logic.
A continuous loop of enhancements, adaptation throughout project life.
Canadian Dam Association * Fall 2017

21



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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