thomas pettersson andreas lindhe and lars rosén identification and management of risks in water...
TRANSCRIPT
Thomas PetterssonAndreas Lindhe and Lars Rosén
Identification and management of risks in water safety planning
Decision support method using multi-criteria analysis for WSP
Water Safety Conference 2010
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Presentation outline
Mainly present a stepwise (10 steps) procedure for evaluating and comparing risk-reduction options (providing decision support)
...but, also incorporate the other tools/methods developed within TECHNEAU
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Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Background
WSP make water utilities to know/understand their system better
Awareness of hazards/hazardous events Prioritization of hazards Risk reduction options suggestions
But, how to compare different measures? Cost effectiveness? Health risk reduction vs. costs of implemented measures Other benefits... (multi-criteria analysis)
Need for applicable tools and method guidance to carry out WSP (provided from the TECHNEAU project)
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Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Conceptual Structure of the Risk Management Framework and Toolbox in TECHNEAU
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Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
Decision support method in 10 steps
1) Perform a risk ranking (risk identification and estimation, P&C)
2) Identify severe risks (target risks)
3) Identify possible risk-reduction options4) Estimate risk reduction (new P and C values)
5) Define weights6) Calculate the benefit of risk reduction 7) Consider additional criteria (cost, environment etc.)
8) Determine the performance (of different criteria)
9) Calculate total performance score10)Evaluate and compare risk-reduction options
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Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 1: Perform risk ranking
Very high
High
Medium
Low
PR
OB
AB
ILIT
Y
CONSEQUENCE
Identify hazards and estimate the risk in a risk matrix (here 4x4)
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 1: Perform risk ranking
Classes representing relative;Likelihood ( P = 2(Pclass-1) )
Severity ( C = 2(Cclass-1) )
Calculate the risk as a priority number: R = P x C
8 8 16 32 64
4 4 8 16 32
2 2 4 8 16
1 1 2 4 8
1 2 4 8
Quality risk matrix
Consequence value
Pro
babi
lity
valu
e
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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TECHNEAU Hazard Database
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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12. Future risks
The structure of THDB – 12 subsystems
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 1: Perform risk ranking
Identified hazards are estimated (P and C) and added in the risk matrix
#5
#4
#2
#3
#1
Quality vs. Quantity Risks
P: Probability
C1: Quality consequencesC2: Quantity consequences
Risk (R = P x C):R1: Quality risk R2: Quantity risk
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 2: Identify target events
The severe events that must be reduced are called target events
(Here – Quality risks shown in the matrix)
#5
#4
#2
#3
#1
Event# Description P C1 C2 R1 R2
1 Pipe burst 4 4 2 16 8
2 Disinfection failure 8 4 1 32 8
3 Raw water contamination
2 8 2 16 4
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 3: Identify risk-reduction options
Pro
bab
ility
Consequence
Incr
ease
d risk
Preventive options for reduction of probability
Reduction of consequences
Combin
atio
n of p
reve
ntive
and
conse
quence
reduct
ion o
ptions
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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TECHNEAU Risk Reduction Option Database
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 4: Estimate risk reduction
Target
event
Risk Reduction option
P P’ C1C1’
C2C2’
R1R1’
R2R2’
ΔR1 ΔR2
1 1.1 4 4 4 1 2 1 16 4 8 4 12 4
1 1.2 4 1 4 1 2 1 16 1 8 1 15 7
1 1.3 4 2 4 4 2 2 16 8 8 2 8 6
'k k kR R R k = risk type (e.g. quality and quantity risk)
8 8 16 32 64
4 4 8 16 32
2 2 4 8 16
1 1 2 4 8
1 2 4 8
Risk matrix
Consequence value
Pro
babi
lity
valu
e
(Target event #1, with three different options)
New P and C values are estimated representing the situation after the options are implemented
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 5: Define weights
Are the different types of risk (quality vs. quantity) considered equally important or not?
Assign weights (v) to define the relative importance between: quality (health) risks and
quantity (interruption) risks For example:
Quality (1) and quantity (2) risk considered equally important,then v1 = v2 = 0.5
Quality risks considered more important then quantity risks,e.g. v1 = 0.7 and v2 = 0.3
Use v1 = v2 = 0.5 as default values
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 6: Calculate the benefit of risk reduction
Benefit - weigh together the two risk reductions
B = Benefit of each risk reduction option
i = # of risk-reduction
optionOption Bi
1.1 8 (=12· 0.5 + 4·0.5 = 8) 1.2 11 (=15· 0.5 + 7·0.5 =11) 1.3 7 (= 8· 0.5 + 6·0.5 = 7)
1 1 2 2 ...iB R v R v
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 7: Additional criteria
Additional criteria may be included in the analyses
Examples: Costs Environmental effects Goodwill Consumer trust Regulatory complaints ...
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 8: Determine the performance
Based on the calculated risk reduction, cost, etc., a performance score (s) is calculated by normalising the outcomes
Performance score gets a value between 0-1, where 1 is best
E.g. risk-reduction and cost (for the three options):
Option Bi si1 Costi si2
1.1 8 0.73 20 0.8 1.2 11 1 50 0.5 1.3 7 0.64 100 0
Risk reduction: si1 = Bi / max(Bi)
Cost: si2 = 1-Costi / max(Costi)
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 9: Calculate total performance score
Total performance score (si) of option i
i = risk-reduction option wm = Weight determining the relative
importance of criterion m (risk, cost, goodwill, etc...)
Assume w1 = w2 = 0.5 (i.e. risk and cost equally important)
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Step 10: Summarise results, evaluate and compare risk-reduction options
option Benefit, si1
Cost, si2 Score, si R1 R1’ R2 R2’
1.1 0.73 0.80 0.77
1.2 1 0.50 0.75
1.3 0.64 0 0.32
2.1
2.2
2.3
…
OK!
OK!
OK!
OK!
OK!
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Testing the decision support method
The method has been tested in a case study in Bergen
Method also tested in a training seminar in Pretoria (18-19 Oct 2010)
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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Summary and comments
Simple but quite powerful method to get an overview of the decision basis (for different control measures)
The overall aim is to structure the decision problem and provide transparency
This method provides support for a decision, not making decision
“Normally, I don’t believe in academic methods since it is too complicated – but this method I will test as soon as I come home (to my water utility)”
Stated by a South African water director attending the training seminar
Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia
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RA/RM Publications – TECHNEAU website
All publications are found on the TECHNEAU website
www.techneau.orgunder Publications
Thank you!