Twin topped - peaked hoop pine | Suggestions | Subsidence?

Eric Frei

Hoop pine, Auraucaria Cunninghamii can grow to 65m tall (200') and have a DBH up to 1.5m in my experience.

This specimen is 0.5m DBH and 28m tall approximately.

The last say 6m is dual headed. Have a look. What would you do about the dual head?

This is the view from the street.


This is the view from the rear unit complex, red circle where the two tops start.


And the next two are closer ups of that twin top.

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newguy18

Well its hard to really say since i'm not familar with the species but i'll bite.Since its really to big the remove one of the leaders i'd remove all branches in between the union and bolt the union togther then cable it up higher to help strengthen it.Just my 2 cents worth.

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old schooler

rangitata

Personally Eric, I would remove the whole left side leader (photo 2) to just above the fork, to try obtain the single trunked apical dominance that this species normally has. Install a "catching" sling to protect the possible failure of the remaining leader could alos be an option.

Cheers Mike

dannyboysfc

I also say take out the left one, keep the right one.

this is not an expert oppinion, just a guess at the right thing to do.

blair duncanson

Aye, perhaps thinning some of the crossing branches, whilst still retaining shape is what i would recommend. Tricky to say without closer look at fork union. Potentially removal of one of these leaders could leave too big a wound, which through time would potentially in danger the other leader, through decay and mechanical changes but from photo two it appears that now would be the time to take one of them out without too much disturbance to the tree...ideas..

treestyle

i'd be asking why has this dual leader developed? is it the result of storm damage or has the tree choosen to naturally grow this way?

there are plenty of big old pines out there that have been lopped in the past and now have 3 - 4 codominate stems growing at the point of lopping. in my limited experience i have not yet seen a failure occur at the point of the epicormic attatchment.

this union looks to be a natural occurance not resulting from lopping or storm damage. i think it would be fine to leave as is. however from the clients point of view and in the interest of revenue raising we could find something to do to it. wether good or bad for the tree.

i'd suggest leaving all foliage so as not to change the natural movements that the stems are used to, fall arrest system could be installed for peace of mind.

worth a wander out into the bush to see how many codominate stemmed pines are naturally occurring.

Eric Frei

I'd say it's natural development.

A twist in the tail though, likely it will be cut down, not my say but they thought it was protected and got me out for a measure up and look etc.

I was geared for a save it report but doubled checked with BCC to find out NO VPO ... so they're going to cut it down most likely regardless of what I say or do (not that they need a report anymore)

They think it's part of the cause of this.

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treestyle

bastards!

Eric Frei

This is Brisbane mate ... tree hater city!

Mostly people just give a shit how big ya chipper and truck is and how cheap you are.

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treeseer

Why doesn't someone get out a pick and shovel and locate the roots nearby and find out? By simply digging and cutting, you could do more than anyone with a big truck and chipper.

re management, instead of cutting off the branches that cross the stem, why not bolt them together. This would facilitate "natural bracing", would it not?

rangitata

I get that every day Eric, the client sees a crack and the nearest tree has to be the cause, never mind the fact that we have had a record dry spell and the soil is drying out all over brisbane.

But this is a service industry in Brisbane and the customer is always right

Eric Frei

This is a double whammy of dry subsidence and wet upheaval.

Guy, as the tree is no longer protected they just cut it regardless, beside wasting my time already you'd like me to waste more?

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treeseer

O hell no, if they are hot to whack their tree instead of finding out the truth, they are beyond the help of arboriculture. Pick and shovel is not hard work really, but it'd be nuts to volunteer and arborist's time for arborphobic idiots.

It could make sense however to submit a proposal to assess the roots. They might toss it, but at least they would be made aware of the logic and simplicity of the process.

Eric Frei

They've been told verbally but now the engineers will blame the tree to.

Also, the tree was some 7m away from the building, the neighbour had a row of palms 3.7m away.

The land slopes down hill at a decent rate, just beyond their fence line (1.7m) is a 1.2m high retaining wall. With clay that means the bottom of their yard is damp. The block of units behind suffer extreme damp problems, their driveway has cracked in numerous places and we were told no more than 2.5ton on it or it will crack more. Engineers said it was like a damp river beneath due to the steep grade and water coming down, banking at the retaining wall then escaping beneath the driveway.

Talking to a builder he says when clay is extremely damp is swells, however a 3 story building pushing down on foundations is likened to this analogy.... imagine you standing in a large tub full of clay, we wet it a lot and you sink a little but what happens around you? It rises. This confirms all the slabs around the building have lifted closer to the building, moved away from the building and tilt downward. The building has sunk and the clay around risen.

Now the tree is actually helping the situation by pumping the excess water out.

This is natural subsidence resulting from poor preparation and foundation design. The building was built early 90's so the tree was there already. I estimate the tree to have been some 15m to 18m tall then, so any decent builder and geotech should have taken into consideration the mature size and built foundations accordingly.

Also the other corner of the building was same but not so bad, now the ironic part was the front of the building the same but only just slightly appearing cracks. So it's sinking at the back, where it's wettest.

But I'm just an fuggen idiot in Brisbane mate, paid worse than a shit kicker at the tip.

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Roller

Yes but the near by tree is still alive right? therefore its got to be takjing up water and only adding to the problem,..

Eric Frei

But in Brisbane where we do have clay we have a weather anomaly.

Unlike the soils of England, Melbourne and Adelaide where the winter is a typical cold wet season and summer scorching hot and dry ... Brisbane has the opposite. In Brisbane winter is mild, days are still 24C but rainfall is low and so are evaporation rates. However in summer it's humid and wet, February is not only hot but the wettest month. So the trees play less havoc with soil moisture levels in Brisbane.

In the last 3 years though the traditional summer wet season has been too dry and the soils have dried out more.

What engineers dont like is the variance the trees influencing the dry and wet.

So removing the tree means less influence on soil moisture, no more tree roots sucking the moisture out. It's a more stable environment for engineers. Like engineers would love bridges and railways etc to be a constant 21C temperature so they wouldn't have to worry about expansion and contraction of metals etc.

However we all know the vast majority (95%) of a trees root system is in the top 30cm of soil. The top 1.2m of soil is the most influenced by moisture content and heavier clays (more volatile) also mean tree roots are less likely to go deep.

It's older floating and raft style slabs that sit on the surface which get rocked around the most. A smart engineer in a clay soil will be looking to build the foundation deeper than the soil profile influence by tree, ie deeper than 1.2m

For a 3 story complex like this one in clay you'd think they would have gone a lot deeper than 1.2m .... would be interesting to know. Surely a soil test would show what the profile is, the tree was there first anyway and the tree was perhaps 15m to 20m tall then.

So in this instance I would say the engineers who built the place stuffed up. Complex was built @ 1994 and I estimate tree height then to be 15m to 20m

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treeseer

Maybe fine roots, but surely 95% of all roots are not in this layer. And fine roots do not do all the absorption--woody roots have lenticels that can suck it up.

Eric Frei

I'd say other than the immediate surrounds of the stump for sure, having seen many excavated sites and stump ground trees yeah ... here anyway. Maybe on decent soil and sand etc deeper but here, they're right up the top.

30cm is 1' you know.

Look at the vac-u-digga video, same with that paperbark, same with most here. Hey, were talking maybe trees to 2' DBH though not some 200' mountain ash.

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fosheezy

i really like mike's idea of a catching sling, i never thought about a system like that before. would some heavy-arse cobra with (potentially multiple?) shock absorbers inserted, and attached below and above the union do the trick? is that a common practice?

peace out. anton.

Sean Freeman

Not common practice but has been done, also remember cobra is not designed for that role (though it will perform very well if the correct calculations of loading are done) you have a wide range of climbing and rigging lines all rated that could perform the same task...again after calculating the absolute maximum loading and then adding 50%!

Eric Frei

Oh boy, I hit the candy today.

I had to drop in again as I was nearby, I just had to get some more data. Today I happened to meet the guy who lives in the top unit and the back property and he was living there when they built the place in 1994 with a birds eye view.

He said he was stunned by how fast they built it, he says the foundation was the same everywhere regardless of the tree. He says they poured the foundation and slab and within like 4 days the walls were getting bricked up. A number of them in the complex at the time couldn't believe how fast they whacked the place up.

He says there was no drilling holes or boring for piers, he says it was a raft foundation where the footings for the perimeter and load bearing walls was only like 2' wide and maybe 2' deep at best then lots of reo and concrete slab flushed over the top.

He says even today they're expecting the whole thing to slide down the hill. He says they simply couldn't believe the size of the place for the foundation ... but he finished in saying that he's no builder or expert just a witness, and that ever since the place was built they have suffered lots of water problems coming down the hill and drainage is not good enough on their side.

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Sean Freeman

Incredible....but sadly fairly typical...still there are those who will state as if it were irrefutable fat "No mate it is the tree, that tree there, thats what is causing the subsidence/cracking..etc...No real evidence to back up their claim just simplistic misunderstanding of
1) How soils behave after massive thermal masses are imposed on them...esp when the "soil is imported improperly stabalised fill"
2) How correct foundation design can effectively control changing subsoil conditions
3)How tree roots behave in different soil conditions
4) Where relative soil moisture levels fit into the physical behaviour of different soil types under different conditions, often complex and mixed soils.

Nah all too hard for their poor heads, just cut the tree out that'll fix it...

and please note I am not suggesting the tree does not play a part in all this, one size does not fit all, nor explain the causes of subsidence in every case.

Eric Frei

Talking about engineers and builders I found this in the news, interesting and a must read that they even today make shocking errors, like reading a measuring tape.

Interesting the last line, intimidating to make complaints about a builder who also happens to be the Chairman of the Master Builders Association.

Slab of grief for BSA head | The Courier-Mail

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Eric Frei

If in fact on a clay soil subsidence can be attributed to clay drying out and shrinking then the opposite where the clay is excessively moist and swells is called heave.

With a raft or floating slab and the weight of the building pushing down on a really moist clay two things can happen.

1/ The building sinks a little:- this in engineering circles means the soil has "inadequate bearing capacity"

2/ The other thing that can happen is heave, and parts of the building get pushed up.

Both of the examples meaning cracks.

However, like VTA to a tree I have slowly developed a watchful eye for these types of differeing scenes, because as usual the engineers/builders seldom want to criticise their own work and start pointing the finger at each other blaming each other. However on this site there's lots of the typical symptoms.

This building is cracked on ALL 4 CORNERS, yes the worst is where the tree is though but dont be so quick to blame the tree.

These next two pictures are gold, the first picture shows the slabs around the building with lots of movement.



Now in the picture below there's two possibilities.

1/ As shown by the blue arrow the building sunk a little and the clay around it rose.

2/ If the building were on piers and beams then the building might have sat still (not cracked) and the soil around heaved, however it would not be as dramatic around the perimeter of the building as it is.



Now I'm not saying this is all 100% gospel, just like a swollen trunk on a tree doesn't mean it's full of decay. But what we do see here is not only related to soil drying but the opposite, look for the heave.

It can also be that the building cracked many years ago with dry subsidence and when you inspect it was a wet year and you see signs like this, so in reality further testing has to be done but at least like in this scenario you are starting to see the tree come out of it as a scape goat.

Builders put laser levels on buildings and know where it has moved and how much. Did you know that 50mm movement or out of alignment is within tolerences and not considered bad enough to underpin. Some I have worked on have listed 110mm from fron to back, walls also aren't dead vertical anymore. It could be the building has tilted so they have the accurate instruments to measure this.

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Sean Freeman

Good use of on site observation and pics and logical reasoning backed up with a working understanding of what is happening in the subsoil under the foundations.

Here's a pic from a few years ago...defence had a road built for them across mangrove, now the bridge has pile driven pier supports didn't budge, the road despite being built on compacted base several metres high has (or rather did...all re-built now!) sunk dramatically.

Just posting this as a reminder to think beyond the tree (don't exclude it but place it in the equation appropriately)

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Eric Frei

For those privileged the report is in the confidential area, look for Hoop Pine Report.

For the rest of ya, keep learning, being nice and post more.

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