AS4970 Draft| Australian Development Tree Protection

Sean Freeman

Please be aware that the draft standard has been released today..you can go to the SAI website and download the pdf for free (you need to register first). http://infostore.saiglobal.com/store...=MSWD4970ATCRD

Please everyone who is envolved in dealing with trees in any way on construction sites read this draft and if you have a comment fill out the comment form found at http://www.standards.com.au/Catalogu...ent%20Form.doc (instructions on how to fill it out and examples are included there) do submit it to the Projects Manager Chandima Nawela/Ashwini Sharma ashwini.sharma@standards.org.au

Even if you feel that the draft is fine without change please submit a comment reflecting that.

treeseer

well i tried to register but it said i was not a member of sai global so cut me off.

i must not be in with the in crowd.

also wondering how they can be selling hardcopy already if the comment period is to go for 2 months--feb 13 it says.

Sean Freeman

That is odd??

The draft is free but there are clear rules about how many copies and how they may be distributed etc...

The final full standard (if and when) will doubtless be around $75 AUS.

Eric Frei

Document uploaded and attached

Check carefully some new terminology.

What we commonly called the CRZ (Critical Root Zone) is now the SRZ (Structural Root Zone). The calculation for the SRZ is cumbersome and inconsistent with others not using DBH but using stem diameter measured immediately above root buttress.

From P17
Here's a pic of the chart which is easier than the formula.


There's also the RPZ (Root Protection Zone) which for many of us was the TPZ (Tree Protection Zone) however there can be an area further out from the RPZ included in the TPZ called the CPZ (Crown Protection Zone).

Here's how they calculate the RPZ.


Now not always have we had to protect the crown however the CPZ is 1m further out than the crown.

Source P18
Here's the overall for you to get your head around BUT IT DOES NOT SHOW THE SRZ.

Figure 1 Page 14 needs to show the SRZ


Just putting my ideas and objections in red so easier to read.

1/ Figure 1 Page 14 needs to show the SRZ

2/ No compensation or allowance for trees to grow, for example, the range of 20% to 80% of SULE is 9 x DBH for good vigour tree. If the tree is only at 25% of it's life expectency and has a 0.3m DBH trunk but could grow to 1m DBH then here's the sums.

For a 0.3m DBH tree it would get a 2.7m RPZ which is 22.9m2
For a 1.0m DBH tree it would get a 9.0m RPZ which is 254.47m2

So how could the "saved" smaller tree expect to mature when it receives less than 10% of the mature trees allocated land? This is an oversight and needs to be addressed, causes problems and early decline, interference with buildings and structures etc. So they build 1m outside the CPZ of a 21% old tree, what happens down the track as the crown grows?

3/ The calculation for the SRZ is cumbersome (the formula is a shocker!) and inconsistent with others not using DBH but using stem diameter measured immediately above root buttress.

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Attached Files

AS4970 Protection Of trees On Development Sites.pdf (1.06 MB, 551 views)

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Eric Frei

Sean, that link and the one in the PDF is dead!

I have sent an email off about it.

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Sean Freeman

Yes so did I...... :>(

Eric Frei

Just received a phone call from Ashwini and she said she'll be rectifying the broken link soon and OK'd for me to distribute copy of AS4970 which is in post 4 above.

She actually emailed me a clean copy without my down loaded details.

The idea is that all comments get pooled together on their hub for appraisal and discussion.

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MTS247

The formula and the graph seem to give diferent results.

Also no tree can have SRZ dia greater than 5m acording to the graph.

Eric Frei

Highly likely and probable.

It's been noted that as trees gain mass that mass becomes part of the stability and anchorage.

How hollow - pull test - stability tests - Wessolly - Brudi - Sterken

In all the failures (blow overs etc) that I have seen I have not seen soil upheaval further than 2.5m from the trunk of the tree, that includes huge failed Brush Box in Lamington National Park (perhaps 2m+ DBH and 60m tall)

Of course there may be exceptions.

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Sean Freeman

Here is the feedback form.
Public Comment Form.doc

Quintrex

We're supposed to use dia just above root buttress, yet Table 2 states DBH?

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Heightmaster

Sean Freeman

Just a reminder that if you want to comment you have less than two weeks to do so.

Tree Solutions

has the actual standard been released as yet ?

Eric Frei

Not that I'm aware of, thankfully.

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Sean Freeman

In the next couple of months I hope.

Eric Frei

I say thankfully as I have some reports mid way and have deviated more than 10% on the RPZ

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Tree Solutions

That would be good Sean, I think this document could be the start of something great for arboriculture in Australia.

just starting

Sean,

I heard that there were going to be some big changes ... will we get to see them and have a chance to comment before it becomes a final document or will we just have to take whatever is given to us.

Abraham

Sean Freeman

No real big changes as far as I'm aware...all the main alterations were laid out in the ISAAC conference in Newcastle 09, I have not the time this weekend but will try to put together a summary of the changes sometime soon.

The process for AS4970 is the same as any other standard so no there won't be two bites of the cherry, however there are means to raise serious objections if you have them on its release just like any other standard.

I don't think I am alone in finding even the draft standard as a real godsend for our profession, and really look forward to it becoming a full standard.

Having said that I have never been intimidated by engineers or architects, or any other profession that I have to interact with I have always found that I understand much more about their specialised field of expertise than they ever can about mine!

just starting

Sean,

I went to a talk on it in Sydneey and one of the concerns that was raised was that the distances provided for in the table were a lot bigger than would allow for the retention of many trees. I saw some paperbarks recently up your end of the world (Palm Cove) that wouldn't have been retained if the draft standards were followed, alternatively the buildings wouldn't have been built. Either situation would have been a bad outcome.

I find it hard that the standard prescribes distances rather than sticking to defining terminology and processes. What it actually says is that the standard is actually smarter than you are Sean and I am not sure that is true.

Abraham

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Eric Frei

The standard does allow for adjustment where it is supported with some validation and data.

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just starting

It certainly does. On trees of this size it suggests about 8 metres and you could argue it down to 6.4 metres. These are much closer than that. Here is another one that was even closer. Down here the councils would laugh at you if you suggested this was possible and tell you to go and redesign yet here is an example of appropriate development.

The bottom line is that if an arborist believes that it can be done AND the client is prepared to put the work in as directed by the arborist in keeping and caring for the trees then it really shouldn't be up to a standard to dictate what must be done. We should be doing things to keep trees and I fear that this standard inadvertantly implies that trees and buildings cannot go hand in hand together.

At the talk they showed a picture of a concrete and brick house on screw peers that caused almost no damage and which didn't move in reactive clays ... seems like a great way to build.

Abraham

just starting

Sorry here is the picture

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Eric Frei

Well, from my perspective the standard sets minimum requirements with a 10% deviation, if you want more than that (encroachment into the root zone) as you have suggested then you need to demonstrate how.

Now with the house on screw piers, it still changes the topography, water flow and inadvertently the soil moisture levels. Those things need to be addressed to, where the rain fell onto the soil is now a house with roof and gutters that whisk the water to the drains not the tree. Also to be considered is compaction and protection of the root zone during construction, so there's many factors at play still.

What about if the encroachment is approved due to the science of it and the tree suffers anyway? That will be on the councils neck then that "your plan" failed however they approved it .... so they'll likely be conservative.

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just starting

I thought it was like the BS 20% and 20% of that covered but you are probably right. The tree in the attached image is far too close to the building. It is inside.

What about these trees in Palm Cove? Should they have been cut down or should the buildings not have been built? According to the proposed standard it must be one of the two.

There is no doubt that the items you talk about are important and obviously they all need to be addressed but if they are addressed, and it is clear from this example that they can be, then what is the problem? Seems like they got it right at Palm Cove and that was quite some time ago. Surely we do the same thing elsewhere.

I don't know why I think this but a standard should be based on science and produce reliable results all the time otherwise it is just a set of arbitrary rules.

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just starting

Ekka,

You are right. I just found the link above and read the draft standard. Thanks! It is as you say 10% and closer if you can demonstrate that it can be done. Looks like it has been well demonstated so I guess we as arborists can throw the table out and rely on professional judgement which is what I was saying in the first place.

Whilst going through though I also found this
3.2.2.2 The RPZ of palms and other monocots, cycads and tree ferns
The RPZ of palms and other monocots, cycads and tree ferns must be 1 m outside the dripline edge of the crown.

On this basis a Phoenix would reqire a RPZ with a 4 metre radius yet I have seen them dug out with just 1 metre radius when they are transplanting them. That is an area 6.25% of the required area to protect the same palm in situ. I would have thought it was better to allow the building to come up to 1 metre from the palm than to move the palm.

Sean Freeman

I think you need to read and understand when and how Arboricultural advice is intended to fit into the development process.

Try getting hold of James Urban's work from 10/15yrs back and see just what sort of volumes trees actually require to have any kind of longevity...the approach distances in the draft standard seem quite conservative to me.

just starting

sean I didn't think that the standard talked about soil volume but I have read James' work. That said are we to assume that roots cant grow under structures particularly those that do not have a basement?

Sean Freeman

Its about delivering best practice in the management of trees not exploiting the survival capcities of particular species so some one can make more money through covering more ground with more concrete....as I said read and understand the explaination of the role of the arborist in the process of development, particularly the timing of the provision of constraints within the process.

Eric Frei

It perhaps is, the science of experience. It says minimum distances so it satisfies all scenarios perhaps, it has to provide for worst case scenario I guess.

Also your pictures from Palm Cove are soil biased (sand), over at Tangalooma there's a large gum in the middle of the restaurant with proper roof above etc and the distance from the trunk to the outside world might be 10m ... but sand is an excellent medium for roots to grow a long way plus the proximity to the ocean means roots will be able to extract ground water.

I wonder how well those trees would be going in a heavy clay. This is where the standard has to consider all scenarios or be a 1000+ page document for each and every scenario. It's a minimum distance, want to get closer then as you have show evidence of how.

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