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Raising Soil Grade - Protecting Existing Trees

Discussion in 'Homeowner Helper Forum' started by Farm Newbie, Jan 14, 2019.

  1. Farm Newbie

    Farm Newbie ArboristSite Lurker

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    Hello. I'm looking for advice regarding raising the soil grade around some existing trees to ensure they are protected.

    I have recently purchased some land in Laos that has been used for rice production. We are currently raising the soil grade by approximately 1 meter in preparation for future house construction.

    As it is extremely hot, I would really like to keep the existing trees for their shade and beauty, but I know nothing about ensuring the tree safety as the grade is raised around them. I have asked that the soil not be placed closer than the general overhang of the larger trees in order to try some of the techniques I have seen online regarding building a small retaining wall and filling the area close to the trees with stones for drainage and topped with soil to avoid soil compaction.

    I'm not currently in Laos which complicates things, and I have to deal with a language barrier as well. The workers say they have raised the grade right up to the tree for previous clients without problem, but I think that will lead to a long slow death. They also say if they leave the tree well open now, it will just fill with water and kill the tree that way. Also, I'm not sure when I will be back to try to finish some type of drainage/ventilation system around each tree.

    I'm attaching some pictures with an aerial map view with numbers on the largest and most important trees. You can see some before shots when the land is wet as the rice is planted, and some recent shots after the land is being raised. The soil will eventually be raised completely around each of the trees.

    Any advice would be appreciated. I don't know the type of trees, or even if they are worth saving. I can ask for better pictures if that would help.

    Thanks in advance.

    Arial View - Copy.jpg Trees Before06.jpg
     
  2. Farm Newbie

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    Here are some more before pictures from different angles.

    Trees Before01.jpeg Trees Before02.jpeg Trees Before03.jpeg Trees Before04.jpeg
     

    Attached Files:

  3. Farm Newbie

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    Here are some more during the soil grade raise. The soil will eventually surround the entire perimeter of the trees.

    Trees After01.jpeg Trees After03.jpeg Trees After05.jpeg Trees After06.jpeg Trees After07.jpeg
     
  4. Farm Newbie

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    Here are some pictures with advice on filling the tree wells. Not sure if this is a good idea or not. Any advice appreciated.

    Thanks.

    Tree.JPG Tree5.JPG Tree3.JPG
     
  5. ATH

    ATH Addicted to ArboristSite

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    That will probably keep the trees alive for longer...but not for the long term. The big issue is that roots need oxygen. They need to get that through the soil from the air above.

    Second issue I see with that: Where will the water drain to? If all of the ground above the trees is raised, the water will sit in the wells. I assume they are a species that can take flooded soil???? But how much water and for how long?

    A meter is a lot of grade change....

    Other ideas that I have seen used:
    Consider relocating the house within the parcel. Be willing to remove some of the trees knowing by doing so you are protecting the others. Leave trees to the west of the house to maximize afternoon shade.
    Is building the house on stilts an option so you don't need to fill?
    In Oklahoma City there is a tree that survived a bombing and remains as a memorial tree. They wanted to build that area up for a larger memorial...to preserve the tree, they put the platform on pilings and water underneath. It is a pretty expensive way to preserve a tree...but it works!
    Or....lift the trees. Again, not cheap, but it is possible.
     
  6. Farm Newbie

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    Thanks very much for your feedback. I am not sure of the species or even their health right now. They are probably not worth a lot of expense and effort, but if I can keep them going for a while I will try. Originally we were going to remove them all. I'll probably try something like the last 2 pictures showing radiating pipes in the tree well, and just hope for the best.
     
  7. Nick Kent

    Nick Kent ArboristSite Member

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    Do what you can, but plant new trees. I doubt those will last in the long run with such drastic grade change. And not sure what foundations consist of over there, but be careful with that build up fill if it isn’t compacted properly. My guess is houses are on stilts and not foundations or slabs anyway.
     
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  8. Farm Newbie

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    Many of the newer houses in this area have concrete slab foundations with concrete stilts due to flooding concerns. We are raising the grade to reduce the risk, but will still probably build the house on a concrete slab with stilts anyway. We'll definitely be planting new trees, but hopefully we'll be able to take advantage of the shade provided by the existing trees during the construction phase.

    Thanks for your advice!
     

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