Tree Risk Assessment Qualification (TRAQ) – ISA Best Management Practices

[Acer ventura]

It does, thanks.

 

Hi Paul

 

Percentages might also help, and they particularly highlight the range compressions in the matrices.

 

 

Assuming what I've posted previously is correct, and so far no one's suggested otherwise, on or off forums;

 

8 of the 16, or half, of the possible outcomes in the Risk Matrix are where there's a greater than or equal to >1/2, or 50%, Likelihood of Failure and Impact.

 

12 of the 16, or three quarters, of the possible outcomes in the Risk Matrix are where there's a greater than or equal to >1/4, or 75% Likelihood of Failure and Impact.

 

 

A Low risk rating of death is less than <1/2. In other words, a 49% risk of death is a Low risk.

 

A Moderate risk rating of death is less than <1/1. In other words, a 99% risk of death is a Moderate risk.

 

A High risk rating of death occurs when the risk is greater than or >1/2. In other words, a risk of death of 49% is not considered a High risk.

 

To compare with levels of risk in the Tolerability of Risk Framework;

 

 

Unacceptable level of risk threshold = 0.1% (1/1 000)

Tolerable risk threshold that can be imposed on the public = 0.01% (1/10 000)

Acceptable Risk = 0.0001% (1/1 000 000)

 

And an annual risk of death from tree failure is around 0.00001% (1/10 000 000)

 

Cheers

 

Acer ventura

[daltontrees]

Using my own numerical interpretations of the words used in the ISA system, I have come up with this. It's a screen shot of an Excel table, sorry of it's fuzzy.

 

It gives

severe 1/1 to 1/20

high 1/2 to 1/10,000

moderate 3/4 to 1/100,000

low 1/5 to 0

 

This is without prejudice to my own work on this subject which will hopefully explain and reconcile these apparent anomalies.

[Acer ventura]

Tolerability of Risk Framework v Risk Tolerance

With QTRA the Risk of Harm from trees can be compared to levels of tolerable and acceptable risk in the Tolerability of Risk (ToR) Framework by the risk owner/manager who makes the ‘risk management’ decision.

 

With the Risk BMP the risk owner/manager manages their acceptable level of tree risk at Extreme, High, Moderate, or Low depending on their ‘Risk Tolerance’, and this constitutes the ‘risk management’ decision.

 

I have great difficulty squaring the QTRA approach of deferring to ToR thresholds of risk as an advisory to owners/managers, with the Risk Tolerance choices in the Risk BMP. I’m going to explore what these difficulties with Risk Tolerance are, and it should hopefully stimulate more debate because the issues are not as black and white as they were with the matrices.

 

I’ll start off by looking what Risk Tolerance is, as outlined by the Risk BMP and TRAQ training manual.

 

Risk evaluation is the process of comparing the assessed risk against given risk criteria to determine the significance of the risk. This is usually done by the tree owner or risk manager' date=' sometimes in consultation with the risk assessor. You, as the risk assessor, present the level of risk that you determined, your recommended mitigation actions or options, and their associated residual risks. The tree owner or risk manager must then decide on what actions, if any, to take.

 

How people perceive risk and their need for personal safety is inherently subjective; therefore, risk tolerance and action thresholds vary among tree owners/managers. What is within the tolerance of one person may be unacceptable to another.

 

Acceptable risk is the degree of risk that is within the owner/manager’s or controlling authority’s tolerance, or that which is below a defined threshold.[/quote']

 

The Risk Tolerance difficulties will be broken down into a post per issue, to give space so a thread can run off each one if there’s interest. There are six main areas of concern, with some degree of overlap. Though it’s a lot at once, I’m going to post all six so it’s clear where the entire spectrum of difficulty lies. Each one will have a title and a one sentence summary.

 

Cheers

 

Acer ventura

[Acer ventura]

Hobson’s Choice

 

The only level of Risk Tolerance that can be reasonably chosen by the client/manager as acceptable is Low.

 

A simple way of re-framing the ranges of Risk Tolerance choice in the Risk BMP.

 

What's your Risk Tolerance for one of your children getting killed?

 

Is it Extreme, High, Moderate, or Low?

 

It’s not reasonably conceivable that anyone is going to have a Risk Tolerance to tree risk where they manage it at an Extreme or High level. The Risk BMP effectively excludes Extreme as an option, and the exclusion would also apply to High for obvious reasons, but also because the risk assessor is directed to ‘recommend mitigation measures’, and not provide ‘mitigation options’, with Extreme or High risk ratings. Realistically, a tree owner/manager’s choice of Risk Tolerance is limited to either a Moderate or Low risk rating from the outset.

 

When faced with Moderate or Low risk rating there’s then little option but to go for a Low level of acceptable risk. The reason for this is partially because when faced with such a choice it's only natural to prefer a Low level of risk. However, another driver to Low Risk Tolerance is because mitigation options showing how to lower the risk from Moderate to Low are part of the Risk BMP, TRAQ training, and included on the Basic Tree Risk Assessment Form.

 

To play out a scenario, a choice of Moderate Risk Tolerance as a Risk Management Policy has the following potential problem. After a discussion with the risk assessor about their four choices of tree risk of Severe, High, Moderate, or Low it is established the owner/manager’s Risk Tolerance is Moderate, which becomes their threshold of acceptable risk, and Tree Risk Management Policy. However, all tree reports identifying Moderate risk ratings will have mitigation options to show how the risk could have been reduced from Moderate to Low. If a Moderate risk is realised resulting in injury or death, I doubt it would be a very robust defence that the owner/manager had discharged their duty of care because their Risk Tolerance to tree risk was Moderate rather than Low. Consequently, they didn’t undertake the tree work to lower the risk from Moderate to Low, and someone got hurt or died.

 

Cheers

 

Acer ventura

Edited May 30, 2014 by Acer ventura

[Acer ventura]

Lower than Low

 

Where there is a Low risk rating there’s still scope to sell more tree work because a risk can be lower than Low.

Mitigation options, irrespective of the risk rating, are part of the Risk BMP approach. Even where the risk rating is Low mitigation options are provided. A case study on p.148 of the TRAQ Manual describes a Low risk from a dead limb over a path in an urban park. The mitigation recommendation is to ‘remove the dead limb to reduce the risk’, which lowers the risk rating from Low to Low. It’s explained that if the Risk Tolerance of the client is Low there could be even more mitigation costs for them to bear by restricting access to the path until the dead limb is removed. The owner/manager is now in a position where they’re obligated to reduce a Low risk to a Low risk if they have the budget.

 

I’ll being revisiting this case study when discussing ALARP in the next section.

 

Cheers

 

Acer ventura

[Acer ventura]

Lost in Translation

 

Risk Ratings cannot be compared to any other risks.

 

Extreme, High, Moderate, or Low risk ratings are defined by the inputs and outputs of the Risk BMP matrices, and they only have meaning within the Risk BMP. A tree owner/manager cannot compare the tree risk rating to any other risks they have to manage, or might understand. The risk ratings are effectively another language which is impossible to translate so it can be measured against established acceptable level of risk thresholds in a Risk Management Policy.

 

Cheers

 

Acer ventura

[Acer ventura]

An Imposition

 

The Risk Tolerance of those who have the risk imposed on them is not considered.

 

Where a tree, or part of a tree, has the capacity to fail outside of the owner/manager’s property, the risk is imposed on others and the risk is not solely ‘owned’ by the tree owner/manager. Tree risk being imposed in this manner is often the case where there are the highest value Targets, and consequently where there are the highest potential risks. The Risk Tolerance of those who are exposed to having the risk imposed on them is not considered.

 

Cheers

 

Acer ventura

[Acer ventura]

Is it Safe?

 

Many tree owners/ managers will not have enough knowledge about risk for the risk assessor to determine what their Risk Tolerance is to it.

 

People are notoriously bad at working out what levels of risk they are exposed to. They tend to grossly overestimate the risks of high consequence very low likelihood events such a shark attacks, plane crashes, and terrorist atrocities. And grossly underestimate much higher daily risks such as driving, diet, and household tasks. There’s a wealth of literature from behavioural economists and psychologists to demonstrate that people are simply bad at working out risks.

 

From a discussion between both parties, I think it extremely unlikely a risk assessor is sufficiently well trained, or the owner/manager has sufficient knowledge of how they ‘perceive’ risk, that either can determine what a credible Risk Tolerance is to tree risk, unless they choose Low.

 

Cheers

 

Acer ventura

[Acer ventura]

Tree Risk Assessment v Tree Risk Management Policy

 

The owners/managers Tree Risk Management Policy is being determined by the risk assessor.

 

The Risk BMP, in line with ISO 31000:2009 Risk Management – Principle and Guidelines, makes an important point about distinguishing between Risk Assessment and Risk Management. However, the risk ratings of Extreme, High, Moderate, and Low are not only Risk Assessments but are also crossing the boundary into Risk Management Policy decisions, for some of the reasons I’ve outlined in the previous posts.

 

To paraphrase this warning about risk assessors and Risk Assessments straying into Risk Management Policy by David Ball, (Professor of Risk Management Decision Analysis and Risk Management), in his book, ‘Public Safety and Risk Assessment’ (which is a great read for those of you who are interested in the subject).

 

It is sometimes not appreciated by technical persons who do risk assessments' date=' or their recruiters, that they may not be qualified, authorized, or in an intellectual position to make risk management decisions.”[/quote']

 

Those of you who are interested enough to want to explore this area, have a look at Section 5.3 ‘Establishing the Context’ of ISO 31000, and ask yourself whether the risk assessor is sufficiently trained or in a position to establish the Risk Tolerance and Risk Management Policy of the owner/manager.

 

Cheers

 

Acer ventura

[Acer ventura]

As Low As Reasonably Practicable (ALARP)

 

The QTRA approach to Tree Risk Assessment is to calculate a Risk of Harm as a probability so it can be compared to thresholds of risk in the Tolerability of Risk Framework (ToR). Owners/managers are then able to make Tree Risk Management decisions based on the thresholds and principles in ToR. One of the key elements of ToR is a region where the risk is Tolerable if it is ALARP.

 

 

There is a substantial conflict in approach between QTRA and the Risk BMP here because the Risk BMP has is no mechanism to determine whether the risk from a tree is ALARP. The consequences of not assessing whether the risk from a tree is ALARP are that the costs to the owner/manager of managing the risk from their trees are not considered. Consequently, the Tree Risk Assessment can not only be unbalanced, biased, and risk averse, but also stray into becoming a Tree Risk Management policy decision on the part of the risk assessor, causing unnecessary and disproportionate expenditure on tree work and a loss of tree-related benefits.

 

ALARP, was born out of the ‘reasonably practicable’ element in the universal common law ‘duty of care’, and international variations of the ‘occupiers' liability’. The purpose of ALARP is to recognise that when the risk from trees falls below a certain level, making trees safer involves costs in reducing the risk to an even lower level. These costs are the financial costs of the tree work, the loss in tree-related benefits, as well as additional risks from the tree work to the workers and public. Such costs should be considered and balanced against the reduction in risk to determine whether a risk is Tolerable. Otherwise, Tree Risk Management can become a disproportionate tail-chasing exercise where there is often a lower level of risk that could be achieved, with no regard to how much it might cost. To not consider ALARP is to be ‘risk averse’ and worship at the unattainable altar of safety, no matter the cost to the client. Assessing whether a risk is Tolerable and ALARP is about being ‘risk aware’, rather than ‘risk averse’, by not only seeing the elephant in the room but by weighing it.

 

 

I highlighted an example of the problems faced by the tree owner/manager when ALARP is not considered, in the Risk Tolerance section that proceeded this, in the ‘Lower Than Low’ post;

 

In summary. Case study on p.148 of the TRAQ Manual describes a Low risk from a large dead limb over a path in an urban park. The mitigation recommendation is to ‘remove the dead limb to reduce the risk’. It’s explained that if the Risk Tolerance of the client is Low there could be even more mitigation costs for them to bear by restricting access to the path until the dead limb is removed. The reasoning behind the recommendations is explained as “mitigation is easy and inexpensive”.

 

Beyond the issue of why recommend tree work that will cost money to reduce a Low risk to a Low risk. Or that if the Risk Tolerance of the owner/manager is Low even more money is spent restricting access despite the risk being Low, until the tree work is undertaken and the Low risk becomes Low. The work and restriction of access are likely to cost hundreds of dollars to manage what was already a Low risk.

 

Without consideration of ALARP there’s no mechanism to work out whether the financial costs of the restriction in access to the path and the tree work, exceed the benefits of the reduced risk. Moreover, such Tree Risk Assessment decisions have Tree Risk Management implications that any Low risk should be mitigated to a lower risk if the arborist can suggest a way of spending the owners/managers money and the funds are available.

 

Anyone got any ideas as to how to square the principles of ALARP with the Risk BMP?

 

Tomorrow I’ll start on the last section of this journey, which is looking at some of fundamental problems that are intrinsic to risk matrices. This section might offer some explanations as to what appears to be going wrong with the Risk BMP matrices. Those of you who encounter risk matrices day-to-day may find useful analysis in there.

 

Cheers

 

Acer ventura