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Standardised Ash tree surveys


StephenMews
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Hi,

I have been thinking bout surveying Ash trees and coming up with a logical standardised system to do so. Ive come up with the below so far but would be keen to discuss it and open it up for some constructive criticism and sharing of ideas and experience on this one.

 

I have been trying to work a formula, which is by far complete yet. Which would work out a score which gives an urgency for the tree to be removed based on 3 factors. Ill explain what I have so far and see if it is something that can be developed into a workable idea.

-Class 1- 100-75%, 2-74-50%, 3-49-25% or 4-24-0%. based on foliage present

-Target area on a score of 4. Something like this 1 – No immediate hazard, such as a woodland. 2-low risk such as a low use pedestrian area, 3 medium risk, such as a park land tree or quiet lane, 4- high risk, such as close to buildings, busy pedestrian area or road traffic.

-Ease of dealing with the tree again out of 4. 1- Tree can be felled. 2- tree can be dismantled with no rigging and mewp access. 3- Tree can be dealt with by large machinery/mewps and rigging. 4- tree must be climbed/out of reach for mewps/cranes etc

 

These could then be multiplied together to give a score, the higher the number the more urgent. The numbers being between 1 and 64.

 

Having a system like this would be appropriate for land owners with large amounts of Ash trees and it gives a very logical order in which to approach and order the work.

 

 

Any thoughts on this?

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Your system sounds similar to that of Valid developed by David Evans whereby it becomes acceptable, tolerable, not tolerable etc.

Thing with trees, even those with ADB are all unique and what you do will depend on the targets and likelihood of failure. I’m just not too sure a score based system would work Vs a conventional survey.

Many years ago an insurance company moved to a height system for tree removal pricing which a number of contractors ditched as the height didn’t take into account the actual work involved. For example you could get a 20ft oak at the bottom of a garden with a 1100mm dbh for a couple of hundred pounds and take four guys a day or more to deal with if access was poor. To counter that you could get a 50ft ash with a 300mm dbh and post it into the chipper. Swings and roundabouts I guess

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52 minutes ago, JaySmith said:

Your system sounds similar to that of Valid developed by David Evans whereby it becomes acceptable, tolerable, not tolerable etc.

Thing with trees, even those with ADB are all unique and what you do will depend on the targets and likelihood of failure. I’m just not too sure a score based system would work Vs a conventional survey.

Many years ago an insurance company moved to a height system for tree removal pricing which a number of contractors ditched as the height didn’t take into account the actual work involved. For example you could get a 20ft oak at the bottom of a garden with a 1100mm dbh for a couple of hundred pounds and take four guys a day or more to deal with if access was poor. To counter that you could get a 50ft ash with a 300mm dbh and post it into the chipper. Swings and roundabouts I guess

It's worth thinking about, though, as a lot of ADB surveys and recommendations are not based on any systematic approach.

 

VALID has really just taken QTRA and the HSE's hierarchy of risk to get its accceptable/tolerable/unacceptable categories. A professional assessment is only possible if these terms and their legal implications are understood by the assessor.

 

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1 hour ago, StephenMews said:

Hi,

I have been thinking bout surveying Ash trees and coming up with a logical standardised system to do so. Ive come up with the below so far but would be keen to discuss it and open it up for some constructive criticism and sharing of ideas and experience on this one.

 

I have been trying to work a formula, which is by far complete yet. Which would work out a score which gives an urgency for the tree to be removed based on 3 factors. Ill explain what I have so far and see if it is something that can be developed into a workable idea.

-Class 1- 100-75%, 2-74-50%, 3-49-25% or 4-24-0%. based on foliage present

-Target area on a score of 4. Something like this 1 – No immediate hazard, such as a woodland. 2-low risk such as a low use pedestrian area, 3 medium risk, such as a park land tree or quiet lane, 4- high risk, such as close to buildings, busy pedestrian area or road traffic.

-Ease of dealing with the tree again out of 4. 1- Tree can be felled. 2- tree can be dismantled with no rigging and mewp access. 3- Tree can be dealt with by large machinery/mewps and rigging. 4- tree must be climbed/out of reach for mewps/cranes etc

 

These could then be multiplied together to give a score, the higher the number the more urgent. The numbers being between 1 and 64.

 

Having a system like this would be appropriate for land owners with large amounts of Ash trees and it gives a very logical order in which to approach and order the work.

 

 

Any thoughts on this?

I get where you are coming from, although I would be reluctant to create a new quantified system rather than applying ADB to existing risk assessment systems.

 

What you are suggesting is interesting as it included elements of severity of harm/damage, likelihood of failure, target value and cost of risk reduction. As such, it touches on proportionality and prioritisation, which are not addressed properly by any current risk assessment system. 

 

Ideally a ADB risk response should tie in with legal duty of care. Using QTRA or TRAQ would be better I think than using a new ranking system that has no values relatable to duty of care, cost of intervention or return on risk redcution.

 

Having had a go at this in theory and in practice, the answer I believe is not just in assessing the trees as they are but in forecasting rate of change and survivability. In other words, forget the current risk, what will the risk be in 6 months, or 1 year or 2 years? ADB changes probability of failure too quickly for the current probability to be the defining parameter

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I think most large landowners will be making removal decisions based on TM costs, harvesting viability, estate grouping around buildings, and economy of scale etc when seeking costs, e.g. the 5 roadside trees will get felled when the woodland behind is.

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I am warey of tick box systems, to fit the tree into the category, which is why i didnt wholly endorse Ezytreev, but then with Ezytreev i use comments much more to identify actual characters in trees. Qtra could be the answer, but then, there is always another answer 🙄 K

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