Managing the risks of unforseen ground conditions
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Copyright of RSK 1 Understanding and managing the risk of unforeseen ground conditions Dr George Tuckwell Director
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Encountering unforeseen ground conditions mid-project can be an expensive problem. Buried obstructions, waste, contamination, mineshafts, solution features, soft ground, landfills, storage tanks, unexploded ordnance, archaeological features and difficult geology may variously lie in wait. Buried services are often early concerns. Managing the health and safety risks means getting the right information at the right time. A well-designed investigation can pick up much more than just services at the same cost. Each project is different. This presentation covers the latest developments in surveying and geophysics with examples of how they can be tailored to understand and reduce the specific risks encountered at any particular stage in a project. A graphical approach to visualising information and risk is used to discuss the value and usefulness of different types of intrusive and geophysical site investigation data, including illustrations of when and when not to use geophysics, and, if it is used, how best to integrate it into a site investigation approach. Detailed case studies illustrate the lessons and objectives. For more information contact George Tuckwell: gtuckwell @ rsk.co.uk
Transcript of Managing the risks of unforseen ground conditions
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Understanding and managing the risk of unforeseen ground conditions
Dr George TuckwellDirector
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What do you know about your risks?
“…there are known knowns; there are things we know that we know.
There are known unknowns; that is to say there are things that we now know we don't know.
But there are also unknown unknowns; there are things we do not know we don't know.”
Donald Rumsfeld
Former US Secretary for Defence
2
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Managing the risk of unforeseen ground conditions
Thinking fast and slow
Understanding and avoiding bias
Site investigation: Information vs Risk
Case study examples
When and when not to use geophysics
How do I know the survey will work?
Wrap up
3
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Thinking fast and slow
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How cmoe your bairn is albe to udnertsnad this snetence eevn tghouh olny the frist and lsat lteteres of ecah wrod are crreoct?
Clever brains
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• While we think we observe the world, we are actually already interpreting
• We ‘fill in the blanks’ as soon as possible to minimise cognitive effort
• Judgments are made in “automatic gear”
• It is hard to turn the “lazy system” on and off (paraphrasing Kahneman)
PRACTICE TIME:
Mind minefields: Perception
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What do you see?
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What do you see?
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What do the three exibits have in common? (source: D. Kahneman)
What do you see?
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Muller-Lyer’s exp.
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• Define problem slowly to: get all the facts
formulate alternatives
weigh-up and decide
Decision making – “slow” thinking
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• Fast thinking tends to place action ahead of diagnosis of problem and to reward speed;
• Fast thinking combines causal determination with problem definition
PRACTICE TIME:
Decision making - “fast” thinking
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Example: as printed on the page, is the figure on the right larger than the figure on the left?
What do you see?
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Decisions
Paul owns shares in company A. During the past year he considered switching to stock in company B, but he decided against it. He now learns that he would have been better off by €1000 if he had switched to the stock of company B.
John owned shares in company B. During the past year he switched to stock in company A. He now learns that he would have been better off by €1000 if he had kept his stock in company B.
Who feels greater regret?
(source: Kahneman)
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Decisions
Mr Brown almost never picks up hitchhikers. Yesterday he gave a man a ride and was robbed.
Mr Smith frequently picks up hitchhikers. Yesterday he gave a man a ride and was robbed.
Who of the two will experience greater regret over the episode?
Who will be criticized most severely by others?
(source: Kahneman)
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• People expect to have stronger emotional reactions (regret included) to an outcome that is produced by action than to the same outcome when it is produced by inaction
• Biases decisions towards conventional and risk averse choices
Mind minefields: Idealized view on decision making
If this is true for site investigations – what is the risk that decision makers are averse to?
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Is there difficult ground here?
Are sites like this usually difficult?
Have I demonstrated the ground is fine?
Mind minefields: Questions we ask
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What difficult ground have I found?
Why do I think that this land might be difficult?
How can I demonstrate the ground isn’t difficult?
Mind minefields: Questions we should ask
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Understanding and
avoiding bias
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The trouble with experts
They are wrong more often than they think they are,
and by a greater margin than they would ever expect to be,
for reasons that are predictable…
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Heuristic Bias
People need to make decisions constantly, including when they are asked to make expert judgments
They do this by estimating probabilities
People employ several types of heuristics to assess probabilities
However, these heuristics often lead to significant biases in a consistent fashion
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Understanding biases decreases their effect
Summary: Heuristics and Biases
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Inspection Team Functionality
How to plan and execute a large and difficult site investigation….
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CTBT
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CTBT
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International Monitoring Stations
If a suspicious event is detected it may trigger an on-site inspection…
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OSI Inspection area
•1000 km2
•6 days to assemble a team and deploy
•72 hours to start field activities
•25 days to justify continuation
•130 days maximum
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Signatures of underground nuclear explosions
Changes caused by UNE
• radiation anomalies
• apical voids
• rubble chimney
• underground cavities
• fractures
• surface spallation (craters / retarcs)
• changes of soil density
• displacement of water table
Features related to UNE
• drill-hole (metallic) casing
• buried ferrous objects (e.g. drill pipes)
• shallow-buried cables
• construction debris
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Visual observation
Example from IFE08
Concrete platform over Bh130
Detected from the ground
Example from IFE08
Undeclared Bh51A
Detected from the air
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Equipment:• Ground high-resolution gamma
spectrometer for field and lab• Car/Airborne gamma
spectroscopy• Noble gas measurement
equipment
identiFinder gamma
spectrometer
Dose rate, finding and nuclide
identification with NaI detector
Geiger-Mueller tube for high
doses
-survey over
IFE08 IA (cps)
Gamma radiation
monitoring
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Sampling and RN identification
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Seismic Aftershock Monitoring (SAMS)
UNE aftershocks are:
• Shallower than EQ
aftershocks
• Decay more rapidly than
most EQ aftershocks
• UNE explosions may
induce aftershocks in nearby
faults
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Seismic Aftershock Monitoring (SAMS)
Example of aftershocks
magnitude:
• Magnitude -1: dropping
a brick from 1 meter
altitude
• Magnitude -2: explosion
in hard rock of 70 gr
explosive at 3 m depth
Example of event recorded by SAMS
array
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Continuation phase (geophysics) surveys
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Drilling
Last opportunity to detect relevant radionuclides if the test is contained
One chance to drill in one location
Max 130 days to fine a spot 50m across at 500-1500m depth in a 1000 sq km
The inspection team need to be efficient, justified, beyond criticism and correct
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Aspects of an OSIFinite resources
Limited time
Pressure
Scrutiny
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40 people…
• Understanding of phenomenology / knowledge about signatures
• Properly developed search logic to prioritise activities/missions
• Synergy among different technical subdisciplines
The techniques must be applied by a restricted number of inspectors in a limited amount of time:
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Difficult environmental conditions
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Pressurised working conditions
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Bad food (very bad!)
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Requirements
•A system that allows people to work effectively
•Clear purpose and direction
•Search logic that is robust
•Allow technologies to work together
•Synergy of analysis and interpretation
•Communication
•Maximisation of team resources
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What does that mean for an OSI?
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OSI in five easy steps
STEP 1
Consider the information that is available to update the logic map with IL’s and
develop questions
STEP 1
Consider the information that is available to update the logic map with IL’s and
develop questions
STEP 2
Develop missions to answer the questions from step 1
STEP 2
Develop missions to answer the questions from step 1
STEP 3
Prioritise missions according to the search logic
STEP 3
Prioritise missions according to the search logic
STEP 4
Determine which missions can be implemented with
the resources available
STEP 4
Determine which missions can be implemented with
the resources available
STEP 5
Implement the missions and collect the information
generated
STEP 5
Implement the missions and collect the information
generated
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OSI in five easy steps
STEP 1
Consider the information that is available to update the areas of interest and
develop questions
STEP 1
Consider the information that is available to update the areas of interest and
develop questions
DOConsider only the information you have
Be clear what is fact and what is interpretation
Use your expertise, intuition, and imagination
Develop questions that do not prescribe the methods used to get the answer
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OSI in five easy steps
STEP 1
Consider the information that is available to update the areas of interest and
develop questions
STEP 1
Consider the information that is available to update the areas of interest and
develop questions
DONTAssume you know things you do not yet know
Overestimate the accuracy of completeness of the information you have
Work towards an answer, do work towards the answer!
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OSI in five easy steps
STEP 2
Develop missions to answer the questions from step 1
STEP 2
Develop missions to answer the questions from step 1
DOConsider each question
Use your expertise to develop the most effective missions
Ensure each mission has clear objectives and deliverables
Carefully consider the information that the mission will deliver
• limitations
• accuracy
• risks of failure
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OSI in five easy steps
STEP 2
Develop missions to answer the questions from step 1
STEP 2
Develop missions to answer the questions from step 1
DONTDevelop missions using technologies you are not expert in
Develop missions that do not address the live questions
Develop missions that have a low liklihood of success
Over-use your ‘favourite’ technology
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OSI in five easy steps
STEP 3
Prioritise missions according to the search logic
STEP 3
Prioritise missions according to the search logic
DOObjectively consider the information that each mission will return
Ensure that the information of most value to the purpose of the investigation
Ensure time-critical missions are prioritised
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OSI in five easy steps
STEP 3
Prioritise missions according to the search logic
STEP 3
Prioritise missions according to the search logic
DONTConfuse volume of information with value
Prioritise missions unlikely to deliver the promised information
Consider the resources you have available (these are considered later!)
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OSI in five easy steps
STEP 4
Determine which missions can be implemented with
the resources available
STEP 4
Determine which missions can be implemented with
the resources available
DOAllocate resources to the missions in priority order
Combine prioritised missions where possible to make the most efficient use of resources
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OSI in five easy steps
STEP 4
Determine which missions can be implemented with
the resources available
STEP 4
Determine which missions can be implemented with
the resources available
DONTRevisit the priority of missions
Combine missions if it violates the priority order
Listen to the technical expert banging the table insisting that his technology is deployed first.
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OSI in five easy steps
STEP 5
Implement the missions and collect the information
generated
STEP 5
Implement the missions and collect the information
generated
DODeploy personnel with the appropriate expertise to undertake the mission
Stay safe!
Ensure that the mission adheres to the objectives defined
Report results clearly and concisely, and in a way that the ITL (and the world) can understand
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OSI in five easy steps
STEP 5
Implement the missions and collect the information
generated
STEP 5
Implement the missions and collect the information
generated
DONTChange (or forget!) the objectives of the mission
Take unnecessary safety risks
Confuse fact with interpretation in the report
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OSI in five easy steps
STEP 1
Consider the information that is available to update the logic map with IL’s and
develop questions
STEP 1
Consider the information that is available to update the logic map with IL’s and
develop questions
STEP 2
Develop missions to answer the questions from step 1
STEP 2
Develop missions to answer the questions from step 1
STEP 3
Prioritise missions according to the search logic
STEP 3
Prioritise missions according to the search logic
STEP 4
Determine which missions can be implemented with
the resources available
STEP 4
Determine which missions can be implemented with
the resources available
STEP 5
Implement the missions and collect the information
generated
STEP 5
Implement the missions and collect the information
generated
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Questions, answers, methods and bias
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Questions, answers, methods and bias
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Questions, answers, methods and bias
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Questions, answers, methods and bias
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Questions, answers, methods and bias
Pose questions that are independent of
the technology used to get the answer
Select an approach based on objective analysis:
•Value of the information•Relevance to the question•Risk of not returning the expected information•Cost•Time scale
Be aware of how bias will affect the outcome,
and takesteps to
minimise it
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OSI mission: linked concepts
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Commercial Site Investigation:linked concepts
Pose questions that are independent of the technology used
to get the answer
Select a technical approach, based on an objective analysis:•Value of the information•Relevance to the question•Risk of not returning the expected information•Cost•Time scale
Be aware of how bias will affect the outcome,
and takesteps to
minimise it
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Site investigation
Information vs Risk
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What do you know about your risks?
“…there are known knowns; there are things we know that we know.
There are known unknowns; that is to say there are things that we now know we don't know.
But there are also unknown unknowns; there are things we do not know we don't know.”
Donald Rumsfeld
Former US Secretary for Defence
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Management of risk and information
Know your risks
What information do you need and how do you get it?
Relate needs to survey scope and detail
The limitations of the information
Is it complete?
Is it accurate?
Information and risk conceptual maps
What do you know about where?
Is it enough to manage your risks?
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Information – what do you need to know?
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Above ground surveys
Basic appraisal drawing, with levels for flood risk assessment
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Above ground surveys
Detailed topography including tree schedule
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If the area of the target is 1/100 of the area of the site…
What are the chances of finding the target with a random set of hole locations?
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 10 20 30 40 50 60 70 80 90 100
Number of holes
Cha
nces
of
hitt
ing
Random holes
Your chances of finding things…
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If the area of the target is 1/100 of the area of the site…
What are the chances of finding the target with a regular grid of hole locations?
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 10 20 30 40 50 60 70 80 90 100
Number of holes
Ch
an
ces
of
hit
tin
g
Random holes
Regular grid
Your chances of finding things…
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It may be possible to cover the entire area in a fraction of the time with a geophysical survey
Finding things…
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• Finding something (beneath the ground surface or concealed within a structure)
• Providing reliable information across large areas
• Reducing and/or targeting intrusive investigations
When to use geophysics
Minimises the risk of unforeseen ground conditions
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Risk and information maps
Conceptualisation of risk/need for information
74
top
side
3D view
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Risk and information maps (cont.)
Tools at our disposal to gather information
75
x-section geophysicse.g. resistivity, seismic
boreholes
surface geophysicse.g. EM conductivity,
magnetics, GPR
trial pits
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Risk and information maps (cont.)
Following a detailed intrusive SI
76
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Risk and information maps (cont.)
Following a detailed intrusive SI – where do you have information?
77
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Risk and information maps (cont.)
Following a detailed intrusive SI – where does risk remain?
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Risk and information maps (cont.)
Following a detailed intrusive SI – where does risk remain?
79
How likely is it to have picked up these buried obstructions?
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Risk and information maps (cont.)
Using geophysics as a site investigation tool
80
top 3D view
side
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Risk and information maps (cont.)
Using geophysics as a site investigation tool
Find out something about everything in the near-surface
81
Surface geophysics indicates some buried structures
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Risk and information maps (cont.)
Using geophysics as a site investigation tool
Follow up with targeted trial pits, boreholes and geophysics
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Case studies and examples
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Buried services – what are your risks
HSG47
84
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Buried services – detail and scope of survey
The Survey Association (TSA) level 1 desk study
Reviews of statutory service records and other site-specific data
Borehole location clearances
Using ground penetrating radar (GPR), radiodetection, cover lifting and tracing
TSA level 4 utility survey
Full site radiodetection and cover lifting with unrecorded GPR findings marked out on ground
TSA level 5 utility survey
As above but with additional detail/accuracy in pre-agreed areas covered with recorded GPR grids and post-processing
TSA* level 6 full GPR utility survey
Radiodetection and cover lifting, with recorded GPR grids across the entire accessible site
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Buried services – what are your risks?
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Location (c.1900)
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Location (Today)
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Project Details & Scope
Further information required to improve the understanding of the buried features at the site to aid redevelopment works
Geophysical Surveying to establish -
Location, extent and depth of features indicative of potential vaults
Location of Buried Services
?
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Equipment Used - Services
Radiodetection Survey RD8000 pipe and cable locator
Cover lifting and inspection
Ground Penetrating Radar Survey Medium frequency antenna Undertaken on dense grid of orthogonal transects across the
site to build up complete 100% 3-D map of the area Limited by ground conditions (clay, rebar, made ground)
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Results - Buried ServicesSite Layout
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Results - Buried ServicesRadiodetection
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Results - Buried Services+ drainage
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Results - Buried Services+ GPR linear features
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Equipment Used - Obstructions
Ground Penetrating Radar
High frequency – slab construction
Medium frequency – services, shallow obstructions, voids
Low frequency – deeper obstructions, foundations, possible vaults
~2.5m
0.7m
Up to 5mDepth
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Example Data - Slab Thickness
Ground Penetrating Radar 1.5Ghz antenna to scan to 600mm depth
Consistent across majority of survey area
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Example Data - Foundations
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Example Data - Vaulted Areas
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Example Data - Vaulted Areas
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Example Data – Grassed Area
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Example Data – Cenotaph Detail
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Example Data – Cenotaph Pipe?
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Final Drawing
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Final DrawingFoundations
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Results - Buried ServicesVaulted basements
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Results - Buried ServicesIntegrated results
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TSA* level 1 desk study
Borehole location clearances
TSA* level 4 utility survey
TSA* level 5 utility survey
TSA* level 6 full gpr utility survey
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How to match a survey scope to your risk
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Limitations to the information
Is the information you now have
limited?
complete?
accurate?
108
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Survey quality – skills and training
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Survey quality – skills and training (cont.)
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Survey quality – skills and training (cont.)
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Geophysics as an SI tool
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Geophysics as an SI tool (cont.)
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Electromagnetic ground conductivity data
Geophysics as an SI tool (cont.)
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Geophysics as an SI tool (cont.)
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Project Example
Brownfield Site
Carrington Power CCGT
860MW gas fired combined cycle power plant on location
of former Carrington Power Station.
3km pipeline corridor from adjacent National Grid Site to CCGT.
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Case Study - Location
NG Site
Proposed power station
Pipeline route
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Case Study - Project Details
Geophysical Surveying to establish constraints along pipeline route -
Buried Services
Underground obstructions
Geophysics to compliment boreholes
Power cables (lots!) Gas pipe tracing Radar EM mapping
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Case Study - Final Interpreted Results Plan
CAD Plan Pipeline Route
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Case Study - Final Interpreted Results Plan
CAD Plan Pipeline Route Topographic
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Case Study - Final Interpreted Results Plan
CAD Plan Pipeline Route Topographic Statutory
service records
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Case Study - Final Interpreted Results Plan
CAD Plan Pipeline Route Topographic Statutory
service records Drainage
tracing
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Case Study - Final Interpreted Results Plan
CAD Plan Pipeline Route Topographic Statutory
service records Drainage
tracing Power & radio
electrolocation
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Case Study - Final Interpreted Results Plan
CAD Plan Pipeline Route Topographic Statutory
service records Drainage
tracing Power & radio
electrolocation Radar data
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Case Study - Final Interpreted Results Plan
CAD Plan Pipeline Route Topographic Statutory
service records Drainage
tracing Power & radio
electrolocation Radar data EM data
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Case Study - Final Interpreted Results Plan
CAD Plan Pipeline Route Topographic Statutory
service records Drainage
tracing Power & radio
electrolocation Radar data EM data Combined
Drawing
Multiple techniques
= More information
= Less risk
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Case Study - Intrusive Investigation
Pipes found at location and depth shown by geophysics; subsequently exposed; found to be cut at end; proven to be disused
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Case Study – Depth to bedrock & Faults
Borehole data
?
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Case Study – Depth to bedrock & Faults
P-wave refraction seismics
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Electrical resistivity and seismic data with targeted boreholes to develop a detailed ground model
Case Study – Depth to bedrock & Landfill
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Case Study – Depth to bedrock & Landfill
Ground Investigation Specialist of the Year 2012
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Closed landfill
03 Sept 2013 132
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Electrical survey of landfill
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Electrical survey of landfill (cont.)
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Integrated SI – if your site looks like this…
135
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… would this information help?
136
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When, and when not
to use geophysics
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Do I need help finding (or avoiding) my target(s)?
Do the targets represent a contrast in physical properties that may be detected?
Can one or more geophysical techniques help?Are my targets big enough?Are my targets shallow enough?Are the site conditions suitable for a successful survey?
When to use geophysics
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What are thestatistical chances
of finding it withpits/holes?
Standard intrusive SI
Standard intrusive SI
no
yes
If it is theredo we know with
confidence where itshould be?
no
yes
Standard intrusive SI
acceptable not acceptable
Doesthe brief include
finding or provingthe absence of
something?
start
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Can one or moregeophysical techniques help?
Are my targets big enough? Are my targets shallow enough?
Are the site conditions suitable fora successful survey?
Intrusive investigation
Do the targetsrepresent contrasts in
physical properties thatare detectable?
no
yes
Intrusive SIno
Integrated SI including
geophysical survey
yes
What are thestatistical chances
of finding it withpits/holes?
acceptable
not acceptable
Standard intrusive SI
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How do I know if the
survey will work?
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How do I know the survey will work?
Who is doing the geophysical survey?
Has the survey been designed by an expert to fit your information needs?
What will the survey deliver?
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Who is doing the survey?
Qualifications and experience
chartership
qualifications/demonstrable CPD
143
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Is the survey designed for YOU?
Ask some basic questions about how the survey design proposed will deliver information that addresses your risks
144
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What should the survey produce?
Ask consultants/contractors to
‘show their working’
example data annotated with interpretations
Interpretative report to support drawings
145
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How could a third party help?
Supervision
146
Peer review
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Context and interpretation
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Contact details
Hemel office
George Tuckwell, [email protected], 01442 416656
Tim Grossey, [email protected], 01442 416654
Helsby office
Stephen Owen, [email protected], 01928 728457
Paul Birtles, [email protected], 01928 728148
More information
www.environmental-geophysics.co.uk geophysical information and case studies
www.safe-ground.co.uk utility mapping and surveying
www.rsk.co.uk company website
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