Sudden Limb Failure risks and cases

Ekka · 18th June 2007, 11:06 PM

http://www.courts.sa.gov.au/courts/e...k_v_unley.html

This is a great example of opinions by experts on gum trees probability of limb failure. In a nut shell, worried resident wants gum tree gone as it "might" fail, but loses. Lots of facts in here.

It's a long read but worth it. I applaud the SA govt regs and the way the building spec was laid down for the construction around the trees. Even had foundations changed for the trees benefit, it would be great if some-one could put up pics of the trees, the address is in the court document.

What I also like here is that it was mentioned in court that pruning and mitigation be carried out approx every 5 years @ $1500 which is considered most reasonable for retaining trees.

I also loaded a text only copy just in case the one on the net goes dead (has happened to me before)

Ekka · 18th June 2007, 11:19 PM

Now this one here is from USA and a SLD killed a guy so an investigation ensued.

http://www.sacbee.com/101/story/170150.html

What is apparent is there's some degree of VTA if you know what to look for. In my experience of SLD the branches have been too long, poor taper, poor angle of attachment/branch too horizontal. What also seems apparent is that individual trees have a history of it.

Here is another, this time an oak.
http://72.14.253.104/search?q=cache:...&ct=clnk&cd=13

Ironically the arborist here has a differing version of what causes it, lack of wind he reckons allows moisture to build up in the limb and foliage, less transpiration I suppose. But either way it appears it's a build up of moisture making the limb heavy and the limb mass itself along with how well it's attached. Below is the pic from the article I leached plus a copy of the article in text in case the link goes bad (article date was Monday - July 24, 2006).

Ekka · 18th June 2007, 11:37 PM

Here's another SA case dismissed where a person wanted to remove a gum that might drop a limb, again has some real good arb discussion as viewed by the courts.

http://www.courts.sa.gov.au/courts/e..._burnside.html

Sean Freeman · 19th June 2007, 12:37 AM

The SA courts are very good normally, and you can learn quite a bit about the role of an expert witness by reading the judgements. For those with the time here's the judgements page http://www.courts.sa.gov.au/courts/e...ent/judgments/
Together with the Qld courts I used to trawl through the relevant arb cases every two months or so before life became so time limited!!
http://www.courts.qld.gov.au/qjudgment/pe.htm

The miller case is a good one so is this one

back_v_unley.pdf

Before we get too gooey about the SA system have a read through this one

goode_v_burnside.pdf

You might recognise the names of the Arborist and the commisioner from Ekka's example....something of a back flip your honour? Courts can be treacherous places my friends.

Ekka · 19th June 2007, 01:05 AM

Well the Goode case was interesting as it came in at the subsidence angle, damage to property is what tilted the scales.

I always maintain that the right of way with trees is people and property.

With regard to the people angle they were concerned but borderline, then when the house was cracking and the soil expert concluded in his findings that trees were the major culprit the judge conceded.

An in Adelaide soil a 1m DBH and 20m tall euc will suck a lot of water out of the ground. However, in the first example I put up (1st post) the tree was retained and foundations altered to accommodate, so that guy is hanging around a while.

Interesting, I dont think root barrier would be effective at reducing subsidence anyway. The soil one side of the barrier would be contracting the other side expanding and the barrier would flex and move allowing soil movement.

Sean Freeman · 19th June 2007, 02:44 AM

Well, we're going to have to agree to disagree here since for me the ruling demonstrates one of the many issues that lead to trees being removed for no good reason. The commissioner back flips on the previous rulings he made with regards QTRA as an assessment system, he demonstartes a complete lack of understanding of the risk assessment process with regards trees generally and in relation to the mechanics of probalistic risk assessment specifically.

The evidence from Mr Nicolle is given greater creedence due to his PhD, and his being an acknowledged expert on Euc sps.

The PhD only demonstrates his ability to stay on at Uni for 10 or more years, problems with getting assignments completed on time me thinks.....as for the acknowledged expert status well cuts no ice with me since this expert still trots out the dog eared nonsense about certain species being prone to dropping limbs suddenly ie without cause or explaination...not an arguement I subscribe to at all.

The Goode decision is very dissapointing for a great number of reasons not least the above mentioned points, but also we get more unsubstantiated tripe about the role of one tree in the subsidence observed in adjacent buildings....wish I had a PhD or a doctorate degree maybe it would reduce the amount of evidence and support I have to provide for my limited specific conclusions in the reports I write week in and week out. Every situation is different, and demands the proper degree of examination before placing blame on the tree for subsidence, measuring relative soil moisture levels requires more than two or three test bores, even reactive clays are not all the same the nature of the chemical composition of the clay molecules plays a massive role in the way in which the clay responds to changing moisture levels, as does the physical structure of the soil its plasticity. I don't see anything in the court record that convinces me that Dr Mitchell's evidence outweighs Mr Nash's, except of course that the commisioner already seems to have made up his mind about the tree being the cause and the cracking bieng more than what you would expect to see in a house of that age on such soils tree or no tree.

The commissioner would do well to aquaint himself with this little known Arborist from the UK and maybe spend some of his not unsubstantial wage on the book and perhaps read it and learn something about the complexity in the relationship between vegetation and soil and moisture and subsidence.
http://www.willowmead.co.uk/

OK rant over.

Ekka · 19th June 2007, 03:51 AM

Can you put up explicitly where it's documented and proven that vegetation doesn't affect subsidence? In other words I'm looking for facts, we also have a thread on subsidence we could move these posts to.

I have been unable to prove what you are looking to prove. I draw your attention the extract below, this was given the weighting over the other guy.

Quote:

By comparison, Dr Mitchell is a specialist on the latter, having obtained a doctorate degree which involved an examination of the magnitude of soil moisture loss from the effect of trees, published a book which, inter alia, examined the role played by trees in causing soil change around footings, and having also published many papers on this topic. Dr Mitchell was the recipient of a Churchill Fellowship to study cracking in houses, and a major contributor to the development of an Australian Standard for the design of footings on expansive soil. Dr Mitchell advised the Court that, since commencing private practice in 1974, he had examined some 8,000 cracked houses, at least 6,000 of which had been affected by nearby trees.

Sean Freeman · 19th June 2007, 05:01 AM

My point is this mate, yes vegetation does have an effect....but what is it? how much wieght do you put on it and what are the specific elements of the specfic case in question?

Soils particularly clay soils react to relative moisture changes with and without the impact of vegetation. Evapotranspiration occus in all living vegetation plants move moisture from the soil but they can only do this to a certain extent....the chemical and physical nature of the soil also controls the movement of moisture up down and through the soil profile itself. The suction pressures in soil are measured in pF values, Southern and SouthWestern Australian soils studied by the Footings and Foundation Society of Victoria have been shown to retain or hold miosture at 7pF...the wilting point of native trees falls within the 3.5-4pF range these values are logarithmic, so in other words the trees cannot remove the last portion of soil moisture so critical to dramatic alterations in soil volume and compaction, other factors are at play.

It may be that in this case, the Goode case, that the tree was a major factor, but there is no evidence given to prove this...just comfy statements about the impressive resume of the expert..I would have been demanding that the expert show the evidence. As for the Australian standard for footings on expansive clay soils, would we be speaking of the same standard that talks of tree heights as an important factor in determining species suitability???

The experience documented by PG Biddle in his book "Tree root damage to buildings" of long term monitoring case studies over 20yrs after remedial work (often tree removals) for building subsidence has helped me to understand a little of the complexity that exists between soils, vegetation and the effects they can have on buildings. Hopefully such long term and balanced research will inform the changes to the UK building codes standards and regulations, and then we can wait for Oz to copy them....

I have read so much bunk written by so called experts on the ways trees are supposidly to blame without substantive evidence that I always want to see the evidence first, before the conclusion is made not the other way around.

Ekka · 19th June 2007, 02:29 PM

Boa, I still cant see any proof to the contrary just broad statements. Do you have the book and if so is there some data you can put up?

Sean Freeman · 20th June 2007, 12:13 AM

Yep got the book along with a great many others, where's your and others evidence to support broad statements that condemn trees with no substantive geotech investigation, no chemical analysis of soil type no level monitoring of both foundations and ground levels, no differentiation between tree species, evopotranspiration rates, foliar mass etc...etc.... The weight of eveidence should not be on those who want to retain healthy trees,but on those who want to remove them because their building has inadequate foundations.

Ekka · 20th June 2007, 12:46 AM

Problem is we're fighting an existing standard, you know that, so when you are up against that you need to prove the existing wrong as it is mandated correct by the system.

I had exactly this scenario recently with an engineers report.

I dont have the book and to date have not been able to get enough concrete evidence to turn that standard on it's ear although personally I do agree.

Sean Freeman · 20th June 2007, 01:52 AM

I know you feel the same way I do about this, and maybe this isn't the right spot for the debate, but what the heck since I'm typing and its a bit of a hobby horse for me....the standard is based on a very poor understanding of the biology of trees, and specifically the action and impact of root, it is based almost slavishly on the British standard which has the same idiotic base line of 1.5 x the height of the tree as the preferred distance for trees from building foundations.

We have a professional soil engineers and geotechs who make a very good living out of investigations and reports on the nature of soils in any particular area, where buidlings already exist or where buildings are planned to be built. Now to this fine body of men and women trees seem to be a total anathema, the existing standard along with local and state building regs don't help so instead of gradually getting more trees (properly) retained on new sites, and existing trees (properly) managed on existing sites we still seem to be in the trap of painting trees as the bad guys.

Trees can and do move vast amounts of water in the soil every day, but we need to recognise that movement is not simply one way (evapotranspiration) trees also lift vast quantities of water from lower in the soil profile to upper protions of the profile. Moisture gradients in the soil also lead to changes in localised moisture content....drying soils pull moisture from adjacent areas with greater moisture in other words..without the help of any vegetation.

The impact of altered relative moisture levels in a volume of soil is dependant on numerous factors previously mentioned in this thread,....and the impact that these soil changes have on buildings is also dependant on the nature of the civil works undertaken during intial subdivision and the foundations for that building.

So what am I getting at? The Goode ruling based on the evidence from the transcript is bad in so many ways, it reflects some of the fundemental misunderstandings that persist about tree roots and building movements. I'm not saying trees are never a major cause of soil volume alterations and resultant building damage...that would be silly...however I do understand enough about soil physics and chemistry to know that this simplistic model that underlies the current standards is shifting both the blame and the responsibility for subsidence from the people who alter the structure of the soil profile so fundamentally to trees that more often than not were there long before bulding on the site was even considered.

Good quality, properly installed moisture barriers (note not root barriers) have a real role in this area I think. Surround the foundations of a building by such barriers to a depth 1-2m below the excavation depth and you will effectively isolate the sub soil profile from aterations in relative moisture levels. The impact of the original cut and/or fill process and the thermal mass fluctuations created by the building will have an impact on the soil and its volume and therefore over time there will still be some buildings that still have cracking, and shortened service life span as a result.....some experts would still blame the tree 15m away in the neighbours yard for that, and if you had the same commissioner as the Goode case residing well bad luck tree.....

Ekka · 20th June 2007, 02:10 AM

I personally feel that by going the direction of cracks/subsidence/soil moisture many a tree can be condemned easily by the current standard.

From that one I had it was a regimented cemented standard.

For us as arborists to contest it we'd need mountains of hard core proof and cases. I did find a South Australian 2 year test case where meters were used in a number of locations to measure the differences around trees etc ... but for some crazy reason they used sapling trees, I mean 6' tall whip sticks only a few years old which were new street plantings.

That one concluded no influence but made a special point that the trees were small and immature, so why bloody bother!

We have done volumes of work where due to engineers reports on cracked houses they have underpinned and recommended removal of all trees within 6m of the building, no BS! Try argue with that hard core profession, also then you are in breach of a standard ...

... like some-one saying AS4373 is completely incorrect and topping is better than target cutting as the tree retains more biomass (stored sugars), replaces removed foliage, auto mulches if breakouts occur and creates habitat if decay sets in. In the natural course of tree management in the bush nature actually works better than AS4373 and this can be clearly witnessed when you consistently see the heads of the taller trees blow out.

Sean Freeman · 20th June 2007, 02:32 AM

If it comes down to an instance where you have a tree or trees that you or your client cares greatly for and the tree/s being threatened by the application of this one size fits all approach then you don't have to challenge the standard you merely have to demand that the evidence is provided. I have yet to encounter a geotech report or soil enginerring report that
1) fits the description of an adequate scientific investigation and written report
2) contains clear unequivical evidence of a tree/s being the single major factor in the building cracking/subsidence.

Now that could be due to the poor standard of reports here in Qld, how they get the money they do get for the rubbish they pass off as scientific reports is beyond me...but thats a different matter

The reports I've seen don't have enough test bores to determine the relative moisture levels across the span of the built structure and the suspect vegetation, well expensive stuff drilling holes eh!!
They don't determine the exact nature of the soil, often I suspect they pull soil type from past geotech surveys done when the particular area was being subdivided.
They don't determine what excavations (cut and fill) were done prior to the building being constructed.
They don't examine/assess the effect the original soil alterations would have had and are continuing to have (differential settlement under foundations increases over time)
They don't deteremine the suction capacity of the soil...and can't since they haven't determined the exact soil type!!
Soil plasticity is rarely mentioned, construction plans and specs are rarely referred to.

So I wouldn't bash my head on their stupid wall, but ratther lead them to the wall and invite them to make a start themselves...

As consultants we constantly have to meet minimum standards in the assessments we make and the reports we write, I expect other professions to at least meet the same performance levels.

If the LGA and the regional/state development courts are making rulings like the Goode one then we do have a hard road to walk no doubt about it, but it doesn't mean we should throw in the towel rather better arm yourself with as much info and research and understanding and challenge the inadequacies when you find them.

As I said before the tree/s may be part of the problem but unless they are almost against the building (and assuming they are healthy) removal is hardly the best solution for our communities given all we know about our environmental state of affairs.

19th June 2007, 12:37 AM	#4 (permalink)
Sean Freeman PDF King & Arborist Extrodinaire Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,645	The SA courts are very good normally, and you can learn quite a bit about the role of an expert witness by reading the judgements. For those with the time here's the judgements page http://www.courts.sa.gov.au/courts/e...ent/judgments/ Together with the Qld courts I used to trawl through the relevant arb cases every two months or so before life became so time limited!! http://www.courts.qld.gov.au/qjudgment/pe.htm The miller case is a good one so is this one back_v_unley.pdf Before we get too gooey about the SA system have a read through this one goode_v_burnside.pdf You might recognise the names of the Arborist and the commisioner from Ekka's example....something of a back flip your honour? Courts can be treacherous places my friends. __________________ Sean Trees are poems that earth writes upon the sky, We fell them down and turn them into paper, That we may record our emptiness. - Kahlil Gibran

19th June 2007, 01:05 AM	#5 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 6,869	Well the Goode case was interesting as it came in at the subsidence angle, damage to property is what tilted the scales. I always maintain that the right of way with trees is people and property. With regard to the people angle they were concerned but borderline, then when the house was cracking and the soil expert concluded in his findings that trees were the major culprit the judge conceded. An in Adelaide soil a 1m DBH and 20m tall euc will suck a lot of water out of the ground. However, in the first example I put up (1st post) the tree was retained and foundations altered to accommodate, so that guy is hanging around a while. Interesting, I dont think root barrier would be effective at reducing subsidence anyway. The soil one side of the barrier would be contracting the other side expanding and the barrier would flex and move allowing soil movement. __________________ Remember to use the "search" function, if you have answers/questions post them so everyone can benefit. Free Tree and Green Industry Link Directory Qualified Brisbane Tree Lopping Brisbane Tree Care, Consultations and Arborist Reports Forum Sponsors

19th June 2007, 02:44 AM	#6 (permalink)
Sean Freeman PDF King & Arborist Extrodinaire Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,645	Well, we're going to have to agree to disagree here since for me the ruling demonstrates one of the many issues that lead to trees being removed for no good reason. The commissioner back flips on the previous rulings he made with regards QTRA as an assessment system, he demonstartes a complete lack of understanding of the risk assessment process with regards trees generally and in relation to the mechanics of probalistic risk assessment specifically. The evidence from Mr Nicolle is given greater creedence due to his PhD, and his being an acknowledged expert on Euc sps. The PhD only demonstrates his ability to stay on at Uni for 10 or more years, problems with getting assignments completed on time me thinks.....as for the acknowledged expert status well cuts no ice with me since this expert still trots out the dog eared nonsense about certain species being prone to dropping limbs suddenly ie without cause or explaination...not an arguement I subscribe to at all. The Goode decision is very dissapointing for a great number of reasons not least the above mentioned points, but also we get more unsubstantiated tripe about the role of one tree in the subsidence observed in adjacent buildings....wish I had a PhD or a doctorate degree maybe it would reduce the amount of evidence and support I have to provide for my limited specific conclusions in the reports I write week in and week out. Every situation is different, and demands the proper degree of examination before placing blame on the tree for subsidence, measuring relative soil moisture levels requires more than two or three test bores, even reactive clays are not all the same the nature of the chemical composition of the clay molecules plays a massive role in the way in which the clay responds to changing moisture levels, as does the physical structure of the soil its plasticity. I don't see anything in the court record that convinces me that Dr Mitchell's evidence outweighs Mr Nash's, except of course that the commisioner already seems to have made up his mind about the tree being the cause and the cracking bieng more than what you would expect to see in a house of that age on such soils tree or no tree. The commissioner would do well to aquaint himself with this little known Arborist from the UK and maybe spend some of his not unsubstantial wage on the book and perhaps read it and learn something about the complexity in the relationship between vegetation and soil and moisture and subsidence. http://www.willowmead.co.uk/ OK rant over. __________________ Sean Trees are poems that earth writes upon the sky, We fell them down and turn them into paper, That we may record our emptiness. - Kahlil Gibran

19th June 2007, 05:01 AM	#8 (permalink)
Sean Freeman PDF King & Arborist Extrodinaire Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,645	My point is this mate, yes vegetation does have an effect....but what is it? how much wieght do you put on it and what are the specific elements of the specfic case in question? Soils particularly clay soils react to relative moisture changes with and without the impact of vegetation. Evapotranspiration occus in all living vegetation plants move moisture from the soil but they can only do this to a certain extent....the chemical and physical nature of the soil also controls the movement of moisture up down and through the soil profile itself. The suction pressures in soil are measured in pF values, Southern and SouthWestern Australian soils studied by the Footings and Foundation Society of Victoria have been shown to retain or hold miosture at 7pF...the wilting point of native trees falls within the 3.5-4pF range these values are logarithmic, so in other words the trees cannot remove the last portion of soil moisture so critical to dramatic alterations in soil volume and compaction, other factors are at play. It may be that in this case, the Goode case, that the tree was a major factor, but there is no evidence given to prove this...just comfy statements about the impressive resume of the expert..I would have been demanding that the expert show the evidence. As for the Australian standard for footings on expansive clay soils, would we be speaking of the same standard that talks of tree heights as an important factor in determining species suitability??? The experience documented by PG Biddle in his book "Tree root damage to buildings" of long term monitoring case studies over 20yrs after remedial work (often tree removals) for building subsidence has helped me to understand a little of the complexity that exists between soils, vegetation and the effects they can have on buildings. Hopefully such long term and balanced research will inform the changes to the UK building codes standards and regulations, and then we can wait for Oz to copy them.... I have read so much bunk written by so called experts on the ways trees are supposidly to blame without substantive evidence that I always want to see the evidence first, before the conclusion is made not the other way around. __________________ Sean Trees are poems that earth writes upon the sky, We fell them down and turn them into paper, That we may record our emptiness. - Kahlil Gibran

19th June 2007, 02:29 PM	#9 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 6,869	Boa, I still cant see any proof to the contrary just broad statements. Do you have the book and if so is there some data you can put up? __________________ Remember to use the "search" function, if you have answers/questions post them so everyone can benefit. Free Tree and Green Industry Link Directory Qualified Brisbane Tree Lopping Brisbane Tree Care, Consultations and Arborist Reports Forum Sponsors

20th June 2007, 12:13 AM	#10 (permalink)
Sean Freeman PDF King & Arborist Extrodinaire Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,645	Yep got the book along with a great many others, where's your and others evidence to support broad statements that condemn trees with no substantive geotech investigation, no chemical analysis of soil type no level monitoring of both foundations and ground levels, no differentiation between tree species, evopotranspiration rates, foliar mass etc...etc.... The weight of eveidence should not be on those who want to retain healthy trees,but on those who want to remove them because their building has inadequate foundations. __________________ Sean Trees are poems that earth writes upon the sky, We fell them down and turn them into paper, That we may record our emptiness. - Kahlil Gibran

20th June 2007, 12:46 AM	#11 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 6,869	Problem is we're fighting an existing standard, you know that, so when you are up against that you need to prove the existing wrong as it is mandated correct by the system. I had exactly this scenario recently with an engineers report. I dont have the book and to date have not been able to get enough concrete evidence to turn that standard on it's ear although personally I do agree. __________________ Remember to use the "search" function, if you have answers/questions post them so everyone can benefit. Free Tree and Green Industry Link Directory Qualified Brisbane Tree Lopping Brisbane Tree Care, Consultations and Arborist Reports Forum Sponsors

20th June 2007, 01:52 AM	#12 (permalink)
Sean Freeman PDF King & Arborist Extrodinaire Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,645	I know you feel the same way I do about this, and maybe this isn't the right spot for the debate, but what the heck since I'm typing and its a bit of a hobby horse for me....the standard is based on a very poor understanding of the biology of trees, and specifically the action and impact of root, it is based almost slavishly on the British standard which has the same idiotic base line of 1.5 x the height of the tree as the preferred distance for trees from building foundations. We have a professional soil engineers and geotechs who make a very good living out of investigations and reports on the nature of soils in any particular area, where buidlings already exist or where buildings are planned to be built. Now to this fine body of men and women trees seem to be a total anathema, the existing standard along with local and state building regs don't help so instead of gradually getting more trees (properly) retained on new sites, and existing trees (properly) managed on existing sites we still seem to be in the trap of painting trees as the bad guys. Trees can and do move vast amounts of water in the soil every day, but we need to recognise that movement is not simply one way (evapotranspiration) trees also lift vast quantities of water from lower in the soil profile to upper protions of the profile. Moisture gradients in the soil also lead to changes in localised moisture content....drying soils pull moisture from adjacent areas with greater moisture in other words..without the help of any vegetation. The impact of altered relative moisture levels in a volume of soil is dependant on numerous factors previously mentioned in this thread,....and the impact that these soil changes have on buildings is also dependant on the nature of the civil works undertaken during intial subdivision and the foundations for that building. So what am I getting at? The Goode ruling based on the evidence from the transcript is bad in so many ways, it reflects some of the fundemental misunderstandings that persist about tree roots and building movements. I'm not saying trees are never a major cause of soil volume alterations and resultant building damage...that would be silly...however I do understand enough about soil physics and chemistry to know that this simplistic model that underlies the current standards is shifting both the blame and the responsibility for subsidence from the people who alter the structure of the soil profile so fundamentally to trees that more often than not were there long before bulding on the site was even considered. Good quality, properly installed moisture barriers (note not root barriers) have a real role in this area I think. Surround the foundations of a building by such barriers to a depth 1-2m below the excavation depth and you will effectively isolate the sub soil profile from aterations in relative moisture levels. The impact of the original cut and/or fill process and the thermal mass fluctuations created by the building will have an impact on the soil and its volume and therefore over time there will still be some buildings that still have cracking, and shortened service life span as a result.....some experts would still blame the tree 15m away in the neighbours yard for that, and if you had the same commissioner as the Goode case residing well bad luck tree..... __________________ Sean Trees are poems that earth writes upon the sky, We fell them down and turn them into paper, That we may record our emptiness. - Kahlil Gibran

20th June 2007, 02:10 AM	#13 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 6,869	I personally feel that by going the direction of cracks/subsidence/soil moisture many a tree can be condemned easily by the current standard. From that one I had it was a regimented cemented standard. For us as arborists to contest it we'd need mountains of hard core proof and cases. I did find a South Australian 2 year test case where meters were used in a number of locations to measure the differences around trees etc ... but for some crazy reason they used sapling trees, I mean 6' tall whip sticks only a few years old which were new street plantings. That one concluded no influence but made a special point that the trees were small and immature, so why bloody bother! We have done volumes of work where due to engineers reports on cracked houses they have underpinned and recommended removal of all trees within 6m of the building, no BS! Try argue with that hard core profession, also then you are in breach of a standard ... ... like some-one saying AS4373 is completely incorrect and topping is better than target cutting as the tree retains more biomass (stored sugars), replaces removed foliage, auto mulches if breakouts occur and creates habitat if decay sets in. In the natural course of tree management in the bush nature actually works better than AS4373 and this can be clearly witnessed when you consistently see the heads of the taller trees blow out. __________________ Remember to use the "search" function, if you have answers/questions post them so everyone can benefit. Free Tree and Green Industry Link Directory Qualified Brisbane Tree Lopping Brisbane Tree Care, Consultations and Arborist Reports Forum Sponsors

20th June 2007, 02:32 AM	#14 (permalink)
Sean Freeman PDF King & Arborist Extrodinaire Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,645	If it comes down to an instance where you have a tree or trees that you or your client cares greatly for and the tree/s being threatened by the application of this one size fits all approach then you don't have to challenge the standard you merely have to demand that the evidence is provided. I have yet to encounter a geotech report or soil enginerring report that 1) fits the description of an adequate scientific investigation and written report 2) contains clear unequivical evidence of a tree/s being the single major factor in the building cracking/subsidence. Now that could be due to the poor standard of reports here in Qld, how they get the money they do get for the rubbish they pass off as scientific reports is beyond me...but thats a different matter The reports I've seen don't have enough test bores to determine the relative moisture levels across the span of the built structure and the suspect vegetation, well expensive stuff drilling holes eh!! They don't determine the exact nature of the soil, often I suspect they pull soil type from past geotech surveys done when the particular area was being subdivided. They don't determine what excavations (cut and fill) were done prior to the building being constructed. They don't examine/assess the effect the original soil alterations would have had and are continuing to have (differential settlement under foundations increases over time) They don't deteremine the suction capacity of the soil...and can't since they haven't determined the exact soil type!! Soil plasticity is rarely mentioned, construction plans and specs are rarely referred to. So I wouldn't bash my head on their stupid wall, but ratther lead them to the wall and invite them to make a start themselves... As consultants we constantly have to meet minimum standards in the assessments we make and the reports we write, I expect other professions to at least meet the same performance levels. If the LGA and the regional/state development courts are making rulings like the Goode one then we do have a hard road to walk no doubt about it, but it doesn't mean we should throw in the towel rather better arm yourself with as much info and research and understanding and challenge the inadequacies when you find them. As I said before the tree/s may be part of the problem but unless they are almost against the building (and assuming they are healthy) removal is hardly the best solution for our communities given all we know about our environmental state of affairs. __________________ Sean Trees are poems that earth writes upon the sky, We fell them down and turn them into paper, That we may record our emptiness. - Kahlil Gibran