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Societal Risk Mapping: A useful extension of QRA visualisation
Hans Boot
Contents
Background: History safety legislation in the Netherlands, coloured
books, TNO
Quantitative Risk Assessment: What, Why, How
Risk definitions: Criteria INDIVIDUAL / SOCIETAL risk
Usage of risk assessment criteria in Netherlands
Using criteria for urban development planning
The concepts of societal risk maps
Different types of SR maps
What do we see? / How are they constructed?
Practical applications: experiences in several cases
Conclusions & evaluation
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Safety legislation in the Netherlands
Densely populated areas close to
industrial sites:
requires strict regulation on safety !
Already in the eighties: development
of “coloured books”: How to perform
a consequence analysis, How to
do a QRA
The obligatory safety report for
SEVESO cat2+ companies should
contain a QRA !
Currently, risk criteria also used in
“urban development planning”:
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Does urban development
invoke a SOCIETAL RISK
problem here?
Scarce space: “Do we have problems with safety in this area?
TNO and “coloured books”
TNO is “Netherlands organization for Applied Scientific Research”
Semi-governmental contract research organisation
In the 80’s and 90’s: responsible for “Yellow book” and “Green book”
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1980’s
1990’s
2000’s
2010’s
2015If we want to use models we needed them in a
software tool: this evolved to a commercial spin-
off research
Describing typical methods to predict
“Consequences” (formula’s and overview of
existing modelling approaches)
Consequence and Risk modelling
Consequence analysis: first part of QRA
(an important first step !)
Risk = Chance * Consequence ??
Risk assessment includes failure frequencies,
event probabilities & weather statistics
Quantitative Risk Assessment aims at finding a
quantitative value for the risk that you can
judge against acceptance criteria
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Consequence
analysis
Define potential
accident
scenarios
Evaluate event
consequences
Estimate potential
accident
frequencies
Estimate the
impact of events
Estimate the risk
Evaluate the risk
Identify and
prioritize
potential risk
reducing
measures
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Consequence and Risk Analysis: sources
Other sources: CCPS Guideline books
HSE publications
Local regulations ?
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Identification of
accident scenario’s
Determining physical
effects
Determining the
damage
Consequence of risk
Chance effect
Chance scenario
Chance damage
Chance of risk
Consequence Chance
Quantification of risk
Red Book
(CPR-12)
Purple Book
(CPR-18)
Yellow Book (CPR-14)
Green Book (CPR-16)
Hazid, Hazop, FMEA
Risk Reducing proposals
(NL: Handleiding Risicoberekening BEVI)
Evaluate risk
Failure freq data:Orida database
HSE (hydrocarbon
release statistics)
DNV failure freq database
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Determine the risk of (fatal) injury to employees, the public or the
environment, due to accidental release of a hazardous material,
from production, storage, handling and transport.
Judge the risk against tolerance criteria, set by
the government or by the company internally
Determination of (absolute or relative) contribution
of the risk sources to the individual (aka locational)
and/or societal risk
Purpose of risk assessment
Purpose of risk assessment and – analysis (2)
Identification of opportunities of risk reduction and their effects
Modifications in process design or operation
Mitigating measures
Modification of plant layout
Alternative options for transportation
Change in land-use planning around plant
Implement / prioritize emergency preparation and response
In The Netherlands, nowadays: important instrument in land-use
decision making
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Risk definitions in a QRA
Risk = probability of undesired outcome
In QRA for hazardous materials:
Risk = probability of fatal injury due to exposure to release
of hazardous material
Risk is a QUANTIFIED VALUE (for probability of undesired
outcome)
Risk Assessment: Calculate such a risk
value for an activity / site / area
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Risk assessment procedure
A QRA requires to perform typical basic steps
1. Identify relevant activities / units / processes
2. Define Loss of Containment cases (which scenarios can happen)
3. Assess consequences (effects & damage) for all LoCs
4. Assess frequency and likelihood of LoCs and consequences
5. Calculate risk value for process / site / area
6. Present risk in IR-contours and/or SR-curve
7. Evaluate and analyse risk
Note: IR can be used on-site and off-site,
SR always offsite (“external” safety)
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Risk criteria 1 = Individual Risk (“Locational risk”)
The risk at a location outside the premises of an establishment,
expressed as the likelihood per year that a person that is continuously
and without protection at that location, is killed as a consequence of an
event inside the establishment leading to the release of a dangerous
chemical, dangerous waste or a pesticide.
Note:
‘Establishment’ also means ‘Activity’ like transport
‘Individual Risk’ is also being referred to as ‘Locational Risk’
A value associated with a coordinate, usually presented as Iso Risk Contours
The dimension is frequency: Hz . . . but expressed as “per year”
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Calculating Individual Risk (aka Locational risk)
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Source
location
Receiver X,Y: hit by
various
wind-directions
Start with a scenario consequence analysis: which phenomena ?
Provides a lethality footprint (ellipse, cone, circular)
Determine failure frequency for Loss of Containment
Combine with “probability of wind blowing in that direction”
A receiver at a specific spot, can be hit by wind from different angles,
each time with different lethality fractions !
Combine all events and all scenarios into
total chance of dying at THAT spot
A QRA= Book-keeping chances & lethality's
Presented on a MAP as ISO RISK CONTOURS
Risk criteria 2 = Societal Risk (“Group risk”)
Cumulative probability per year that at least 10, 100 of 1000 people
will be killed as a direct result of their presence within the impact area
of an establishment and the occurrence of an event in which a
dangerous chemical, dangerous waste or a pesticide is involved.
Presented as a log/log
graph: frequency vs
number of people
(at least N victims)
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Reduction
desired
Accceptable
Unaccceptable
Calculating Societal Risk (“Group risk”)
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Same input as IR: scenarios, failure frequencies, weather/wind
statistics but also POPULATION DISTRIBUTION (geographic info)
For Societal Risk
1. For every event (scenario,wind angle) count the total number of
people lethality injured (=size of group) and store chance of this
“event” (direction with weather class) : gives a F and N
2. Cumulate ALL wind-directions, ALL weather classes into FN curve
Source
location
Within
footprint:
number
of
victims50 Number killed
cumulative
frequency
10-7
10-6
10-5
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Scenario 1
Scenario 2
Scenario 1+2
Dutch Legislation on external safety : use of criteria
Individual (or Locational) risk
Presented on map: ISO Risk Contours
No “vulnerable objects“ within 10-6 contour
Based on unprotected situation, outside,
100% presence
Strict rule: authorities are drawing lines !
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Societal risk (Group risk):
A 2 dimensional graph
Indicative “guide” values:
stationary/transport
Motivation (measures) when exceeding
or increase due to developments
Dutch Legislation on external safety
“The Societal risk” = 2D graph
Calculated by using
“geographical oriented”
scenario’s & population
distribution !!
A measure for Social Disruption
Difficult to comprehend by local
authorities and land use
planners: Where ? Why ?
Which area’s still have
development space ?
Need for Societal Risk
visualisation, displayed on a
map
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Requirements for Societal Risk maps
Which population is contributing to the societal risk ?
Which area’s do already have a SR problem ?
What is the extend of the problem ?
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Which area’s are “safer” or “less
affected” : provide possibilities for
urban development or extension
industrial activities ?
No new criteria ! Just a visualization
method based on standard
calculation
Societal Risk Maps: SR Contribution map
What if we store SR calculation results per “population grid cell”
Use standardized (Purple Book) method for calculation of SR
• Scenario list: locations, frequencies, lethal inside/outside effect definitions
• Wind/weather definition: probabilities for occurring stability classes/wind
speeds and wind directions
• Population definition: day/night, inside/outside: cell based grid
Store intermediate results to obtain “geographic oriented” information
per grid cell
• Nr of victims / lethal “response” fraction per grid cell + Frequencies
• Stored for each cell and each (sub) event that hits the cell
• Event = Scenario + Wind direction + Stability class combination
Eventually provides full “FN curve” information for each cell
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For every scenario event: store cell victims N and frequency F
Eventually provides FN curve for that cell
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N=3N=1.5
F =
1e-9
N=1.7
N=2F = 1e-6
F = 0.3e-6
F=0.6e-10
AB
C
D
Societal Risk Contribution map: How ?
Gives an illustration of relative contribution to the Societal Risk
Illustrates “Hotspots”: possible problem causing habitation
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Societal Risk Contribution map: Result
Every cell with population gets a
colour, corresponding to FN curve
Translating FN curve to colour:
“Expected value”
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F =
1e -9
, N =
400
F = 1e-6, N = 150
F = 0.3e-6
N = 50
F=0.6e-10, N = 80
For every scenario event: store total victims N and frequency F
Eventually provides FN curve per cell = SR for scenario’s hitting cell
Societal Risk Area map: How ?
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Gives an presentation of magnitude and extent of Societal Risk
Illustrates IF there is a problem, WHERE there is a problem
Societal Risk Area map: Result
Every cell gets a colour,
corresponding to its FN (=SR
affecting events)
Translating FN curve to colour:
relative to “Guide value”
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Societal Risk “Area” mapGives an indication of which areas are affected and presents the level of the risk
Societal Risk “Contribution” map
Gives indication of amount that areas
contribute to risk
Geographic presentations of SR
Experiences IJmond study
Area with fertilizer plant, steel
industry, LPG filling stations, LPG
road transport, rail transport
flammables.
Using scale 6 colours : more
distinction problem or not
Emphases LPG risks causing
problems
Growing understanding spatial
distribution risks
Rerouting of LPG transport
considered
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Experiences Terneuzen study
Area with NH3 production site,
Bromide storage, many pipelines,
road an rail transport
Urban development plans: leisure
center and educational institute
Maps are created from “receivers
point of view”: which scenario’s
are affecting me ?
Legislation: responsibility creator
source risk
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Fascinating debates about justification “cumulating” of risks (Insight)
Possibilities with map visualisation:
Simply an additional view presented on a map !
Possible to include/exclude scenarios (maps for subsets)
Compare difference after change population / change of process
Because intermediate results are stored, fast interactive evaluation of
alternative urban development plans is possible:
1. Possibility to evaluate change population distribution → what
happens with risk maps and total fN
2. Possibility to include temporary population presence with specific
inside-outside distribution (festivals, sport events etc)
3. Possibility to evaluate change of transport intensity / failure
frequency
4. Possibility to evaluate change of route’s
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Evaluate risk contribution by source
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ACN production/storage (Large) Storage of Flammables
NH3 production/storage Loading-unloading rail tank wagons
Evaluate change in transport capacity
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Transport intensity liquefied
flammable gasses reduced with
factor 10
Ind. Value
FN curve selected scenarios
All scenarios ORIG
Cat A transporten gereduceerd met factor 10
Number of fatalities
1 10 100 1,000 10,000
Fre
quency [1/y
r]
-101.0 x10
-91.0 x10
-81.0 x10
-71.0 x10
-61.0 x10
-51.0 x10
-41.0 x10
-31.0 x10
-21.0 x10
EV = 5.53e-05
NormValue = 7.14e-04
Evaluation and conclusions
The SR maps have proven their value:
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SR contribution map shows cause of
SR bottlenecks
Typical SR contribution map applications:
• Guiding emergency response planning
• Pinpointing area’s for redevelopment
/reallocation of population
SR area map shows size and level of
SR bottlenecks
Typical SR area map applications:
• Guiding urban development planning
• Pinpointing safety problems to non-
specialist (risk communication)
Evaluation and conclusions
Looking from “point of receiver” appeals, but is not obligatory
Experience of “Experts” is still required to explain “red zones”
Spatial planners: which colour means a problem ?
Safety specialists: what is behind those colours ?
It is a visualization, not a criteria: traditional graphs also required
Visualization provides supplementary view, more insight
PR contours still provide the first step: where not to build ! (no
vulnerable objects inside the 10-6 contour)
BE CAREFULL when communicating with colours
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