Tree risk assessment

Why this one costs more

Because the thing you are buying is not the inspection. It is a document that has to survive being questioned, possibly years later, possibly by somebody with an interest in showing it was wrong.

That means the methodology is stated, each step of the reasoning is visible, and the conclusion is no stronger than the evidence supports. It takes longer than a condition report and it is priced accordingly.

The method

I hold the ISA Tree Risk Assessment Qualification. As far as I can find, no other consulting arborist advertising in metropolitan Melbourne publishes TRAQ or QTRA credentials, which is odd given how often these assessments decide whether a tree stands.

The assessment works through three things separately rather than collapsing them into a single impression:

• Likelihood of failure. What could fail, how likely is it, over what timeframe
• Likelihood of impacting a target. What is beneath it, how often, for how long
• Consequences. What actually happens if it does

Those combine into a risk rating with the working shown at each step. A rating without the working is an opinion with a number attached to it.

What is in the report

• Tree identification, dimensions and condition
• Site context and target occupancy, assessed rather than assumed
• Defects described specifically, with photographs
• Likelihood of failure and of impact, stated separately
• Consequences and the resulting risk rating
• Mitigation options with the residual risk after each, so removal becomes a choice rather than a default
• A recommended reinspection interval
• The matrix used, reproduced, so the rating can be checked against the method