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Tree Risk Assessment

Feel free to request a free no obligation quote from us for a tree risk assessment & report.

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Tree Risk Assessment Overview

This survey assesses the risk posed by your trees to people and property based on their species, condition, size, age, location and habitat potential, we provide management recommendations in line with BS3998 to preserve and maintain your trees safely.

On some trees it is not always possible to assess the condition of the tree from ground level. Our team are fully qualified and insured to conduct aerial tree inspections.

Method – Quantified Tree Risk Assessment QTRA

What is QTRA?

North Wales Tree Consultancy are licenced to undertake risk assessments of trees using the Quantified Tree Risk Assessment (QTRA) method, an internationally recognised methodology used as standard by UK Local Authorities. QTRA is applicable to large land areas such as schools and public gardens as well as individual trees. It can be a cost-effective way to ensure you as a landowner fulfil your legal duty of care regarding the safety of trees for which you are responsible under the Occupiers Liability Act 1984.

Why QTRA?

The QTRA method puts the risk of harm posed by trees into an easily digestible report. It is impossible to say that any tree is 100% safe, the only way to completely eliminate the risk posed by a tree is to remove it completely which is undesirable for obvious reasons. The QTRA method therefore looks at just HOW RISKY trees are relative to other risks which we publicly accept on a daily basis such as traffic, or accidental injury see table 1 to put tree risk in perspective. The method has been developed in line with the UK Health and Safety Executive (HSE) guidelines on acceptable risks to the public and property.

Table 1. Annual risk of death from various causes over entire population UK (ONS)

Cause of deathAnnual risk
Cancer1 in 387
Injury and poisoning1 in 3,137
All types of accidents and other external causes1 in 4,064
All forms of road accident1 in 16,800
Lung cancer from radon in dwellings1 in 29,000
Gas incident (fire, explosion or carbon monoxide poisoning)1 in 1,510,000
From trees1 in 10,000,000 or less if high wind incidents are excluded
from lightning1 in 18,700,000

This table helps quantify the risk that trees pose, for example you are nearly 600 times more likely to die in a traffic accident than die as result from tree failure, yet we accept this risk daily. Death from traffic or cancer is unfortunately more common and therefore tends to attract less media attention, however death from tree failure is very rare and attracts more media attention because it is unusual. This creates a public perception that trees are more dangerous than they actually are. QTRA aims to challenge the perceived risk posed by trees and promote the important environmental and social benefits of trees.

Large sites
  • Stage 1 – Zoning of the site into high, medium and low risk zones, an example of a high-risk zone is an area that has a high volume and frequency of people moving through it and or an area containing high value property such as a car park or building. By zoning the client can maximise their budget prioritise higher risk areas and not waste time and money surveying large areas of low risk.
  • Stage 2 – Produce a map of the site demarcating different risk zones and survey the agreed areas to identify any trees that pose an unacceptable risk of harm to people or property.
  • Stage 3 – Survey trees and record findings in a report and calculate the risk posed by any tree identified using QTRA software.
  • Stage 4 – Recommend appropriate management of the tree(s) to reduce the risk to an acceptable level in line with HSE guidelines
  • Stage 5 – Recommend an appropriate monitor schedule for the site that can be completed in house as evidence of legal duty of care under the Occupiers Liability Act 1984.
Individual Trees
  • Stage 1 – Conduct a visual inspection of the tree condition Identifying defects that may predispose the tree to failure.
  • Stage 2 – Record survey findings in a report and calculate the risk posed using QTRA software.
  • Stage 3 – If the risk of harm posed by the tree(s) is calculated as “broadly acceptable” as defined by the HSE, no work to the tree(s) is necessary and a monitoring schedule will be recommended that can be completed in house as evidence of legal duty of care.
  • Stage 4 – If the tree(s) poses an unacceptable risk of harm to people or property, then the report will recommend appropriate management of the tree to reduce the risk to an acceptable level in line with HSE guidelines
  • Stage 5 – Recommend an appropriate monitor schedule for the site that can be completed in house as evidence of legal duty of care under the Occupiers Liability Act 1984
Peter Gardner

Owner Of NWTC

Pete holds a BSc in Conservation with Forestry, LANTRA Professional Tree Inspector, level 2 certificate in Arb, and is a registered QTRA user. Pete has worked for over 12 years in the tree industry both as a consultant and climbing arborist and is a Professional Member of the Arboricultural Association.

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BSc, Arb, LANTRA Inspector & QTRA Registered.

Arboricultural Consultant

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