Paving around an old Ficus – Help needed Please

[Goustan BODIN]

Hi all, 

Here is the situation :

My client would like to build a hard surface road around that magnificent old Ficus religiosa (Sacred Fig).

The tree already suffers from soil compaction due to traffic on the gravel around it.

I will fight for that tree, but must be able to suggest a solution that will allow car traffic while allowing the root system to breath, drink and feed.

The way I see it now, would be to have that path/road slightly elevated above ground (like a little wooden deck maybe), wherever possible. That would allow air/rain to get to the roots, and give them space to grow.

Am afraid of the cost.

Any ideas or suggestions, please ?

[Ernst Glaeser]

The only feasable solution in such a confined situations seams to me to put a new drive way on stilts.

The surrounding planter beds are already slightly higher.

Bu placing the foundations and colums you might disturbe a few more roots, but what is this to having to loose such a beauty in due time.

[toby]

not wood.  some idiot in too heavy a vehicle will drive on it and break it.  and wood rots.

use steel.  steel sheeting (~2.5m sq x 25mm) on steel posts in concrete column at each corner.  

no matter what, I hope they have lots of money to fix this problem.

[Goustan BODIN]

still 2 weeks before presentation, keep suggestions coming !

Ernst, it is the solution I am thinking about now : some structure will also help decompact and improve soil where we ‘elevate’ the pathways. Beneficial to the tree overall.

Toby, very good point, hadnt thought about the weight yet.

thank you both :champagne: !

This tree is actually not even in the area I was entrusted to design, but knowing what my client will do, I will propose solutions beforehand : this is the most beautiful tree I know of in Bangkok, and it is well worth fighting for. 

[Mark Di Lucido]

Beautiful tree–in this case the owner should adapt the facility to accommodate this singular tree instead of the other way around. But we all know how this goes. One issue with a raised deck for vehicles would be the potential for drivers to go over the edge so a fairly stout guardrail is required. I would consider using permeable pavers for the “hard surface road”, and setting just the edges in concrete to prevent movement. You could install the concreted edges near the outer boundary of the exposed roots.

Good Luck!

[toby]

please say that a chainsaw is NOT one of the options they are considering.

[Jason T. Radice]

Would it be possible to put down a thick layer of a mulch like coarse wood chips or perhaps even rubber chips to prevent further compaction around the tree? These materials would cushion and distrubute any loads on the, as well as spring back. With the wood chips, it might possible to also put a geotextile over the wood chips and then recover with gravel. The while thing would allow water through (and some air) as well as provide some nutirents to the tree from decomposition. Of course, after a few year the wood chips will need to be replaced.

[Goustan BODIN]

If they do, I will go Greenpeace style and chain myself to the tree trunk.

[Goustan BODIN]

Good point about the guard rail : hadnt thought about that.

At first I didn’t think about the pavers option. Then, it has been suggested to me here :

http://www.linkedin.com/groupItem?view=&gid=152044&type=member&item=277526987&commentID=167552085

and the more i think about it, the more I like it, though the process is still not entirely clear to me yet.

In fact, roots, especially feeder roots, already extend much further than where the driveway will be, so laying a ‘soft enough’ surface allowing roots to still be functional underneath sounds like a good option. Then, further beyond the driveway, work the soil, mulch, etc, for the feeder roots.

Still have to investigate this option in depth, but I sure will consider it seriously.

[Goustan BODIN]

That was one of my first intuitions : was thinking of laying bundles of bamboo strips and having the surface above. Good for the roots as long as it lasts.

Problem is : what happens once the ‘mulch’ disappears ? Surface lands on roots, maybe cracks opened…

Sound like we fall back to the ‘stilts’ structure solution.

[Goustan BODIN]

obviously the best solution, didn’t even think about it…

Will start my presentation this way.

[Jason T. Radice]

Don’t use a hard surface. The gravel or stone dust goes better anyay. Every few years, you clear off the surface material, peel back the geotextileand replace the mulch. Then relay the geotextile and the granular surface. More maintenance? Sure, but worth it to keep the tree.

Another thing would be to not pave the whole area, but put down wheel paths for the cars.

 

One last one…you could try a plastic permeable paver mat that would spread the load out and still allow moisture and air transfers and leave the nice gravel look you have now. I’ve used them for fire lanes and they work very well.

http://www.invisiblestructures.com/gravelpave2.html

http://www.rkmfg.com/grassy-pavers.html

http://www.typargeosynthetics.com/products/description/porous-gravel-pavers

 

[Goustan BODIN]

Interesting products, thanks a lot Jason. We are still speaking of compaction though. And that sort of maintenance would scare any client I know of.

Let me copy here a comment which I find brilliant, given to me on another site :

Clifford Englert

Environmental Services Consultant at Seminole Consulting Arborists, LLC

Consider radial trenching with aerated tubing backfilled with larger stone under the new paving. This could allow continued root growth in, and around, the tubing if there is adequate support for the road and allowance for new root growth.

That solution, coupled with areas where fertile soil is well aerated, will do the trick for me. Now, I just hope my client will listen and not be stubborn on this…

[Rob Halpern]

What is the soil type on this site? Is it an easily compacted clay (I doubt it) or a more sandy soil (most likely). Depending on the soil and how deep that existing gravel is, there may not be much of a problem. The canopy seems a bit smaller than I would have expected with this species and that trunk.

I suppose it may be worth using an air spade to clear away the surface mix (raking out the gravel as best as possible first and protecting nearby windows, etc.), vertical mulching the root zone,  and then replacing the surface material removed with a deeper layer of gravel or structural soil. A permeable concrete layer on top then might be the best and most acceptable solution. (Just thinking out loud)

But of course as Henry said, the only real solution is to develop the courtyard and find another route for vehicles that bans them from the courtyard.

Risks from the concrete platform idea: see http://www.icfre.org/pdf_files/16%20National%20and%20International%20Collaborative%20Conservation%20Pro.pdf

[Goustan BODIN]

Hi Rob, great find, thanks a lot ! I just browsed through quickly now and will read it carefully tonight : I love these trees at Angkor Wat complex.

About the soil here : Bangkok is located on an estuary, soil is uniquely composed of fine sediments until way deep under. At ground level, it is all compacted and drenched clay : water table usually found within less than a foot deep. Just for the story, Bangkok actually sinks due to soil compaction on a large scale (used to pump drinking water from below).

Drainage on site is quite efficient : deep channels (almost 2 feet) directly connected to the river. So water table here should be a bit lower than usual.

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