Treated timber contaminated soil

Discussion in 'Planting, growing, nurturing Plants' started by newcroft, Feb 21, 2008.

  1. newcroft

    newcroft Junior Member

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    Hi Guys,

    I have a section of my garden where there is a treated timber post along the fence. It runs along the length of the garden bed appx 2 metres high along the top of the fence.

    I want to remove the contaminated soil, and make the soil great for veggies again. Any ideas on how deep to dig out the soil and how far from the fence line I should dig out?

    Also, I've heard that painting over the treated timber will prevent further contamination, but would that be necessary? It's over 10 yrs old and I doubt there's any of the chemical left. But if so, what would be the best way to seal it?

    Thanks in anticipation
     
  2. gardenlen

    gardenlen Group for banned users

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    just do raised beds, keep it simple hey?

    you can make them up to 2' high if you wish, but at 10"s in depth it is unlikley the plants roots will get to the original soil.

    len
     
  3. pebble

    pebble Junior Member

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    Location:
    inland Otago, NZ
    Climate:
    Inland maritime/hot/dry/frosty
    What's it treated with? What makes you think all the chemicals will have gone into the soil after 10 years?

    In NZ treated timber that is cured properly has a relatively low level of toxicity going into the surrounding environment. The arsenic and what have you will last 50 years because it stays within the wood. That's why treated wood takes longer to rot.

    If the wood wasn't cured properly before it was used then it will offgas/leach a bit but once it dries out this process stops.

    Maybe it's different in Oz?

    Paint has its own kind of toxicity.

    Len's idea is good. You can also investigate what plants will help break down the chemicals (but you would need to know what they are).

    Do you have enough room to plant a barrier crop between the post and your garden?

    Sorry, that doesn't answer your original question. What kind of soil do you have? How much rainfall? What's the ground been used for for the last 10 years?
     
  4. gardenlen

    gardenlen Group for banned users

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    it's no doubt CCA treated timber pebbles,

    now a toxic substance under EPA reg's as i believe.

    len
     
  5. pebble

    pebble Junior Member

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    Location:
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    Thanks Len. That's what we call tanalised wood here.

    I had a number of conversations in the late 90s with techincal people about leaching from tanalised wood, and the information I was given then was that there is virtually no leaching. Their rational was that they tested concentrations of arsenic over time in the wood and the concentrations were always the same. This was true even of timber in ocean water.

    However I see now that the MoH here admit that there is leaching. They say there is no health risk but they also say:

    https://www.moh.govt.nz/moh.nsf/pagesmh/680?Open

    Typical.

    I wonder if the scientists I talked to in the 90s were telling porkies.


    In the last few years there has been alot of publicity about people here getting ill from working with tanalised wood (in yards or as builders), because the wood wasn't being cured properly.


    Newcroft, there is a bit in this pdf about sealants:

    coatings
     
  6. gardenlen

    gardenlen Group for banned users

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    yes pebbles,

    those who support the product always say their is absolutley no leeching.

    then there are the others especially the EPA and why are playground built with the stuff being pulled out under secrecy and being replaced mostly with just as bad plastics??

    the way it is looking CCA treated products used in home constructions is the new fibro of the 40-50s issue, you watch even those of use with CCA fences will have problems downline with resistance by buyers wanting to buy, just like it is with fibro now.

    currently what i see or how i see it queensland is the dumping ground for CCA as timber sellers don't offer choice and near us is a huge timber yard with stock piles of it.

    of course they support whomever pays the bills.


    like gmo and chem' residues in food "they ain't looking for it are they?" as they ahve never done any human trialling fo the product for possible side effects then they cannot possibly have any parameteres to say one way or the other, if something should happen.


    len
     
  7. pebble

    pebble Junior Member

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    I'd be interested to know if old tanalised timber is a problem, of it's a new thing. The issue of people getting rashes from handling timber that hasn't been cured is a new thing here, suggesting that the greedy bastards making the stuff aren't doing their job properly now.

    I'm fairly sure that organic kiwifruit growers in NZ were allowed to use tanalised posts to grow on, that's how stable it was considered before.
     
  8. newcroft

    newcroft Junior Member

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    Really appreciate the replies guys. And Len, I've used the staw bale idea from your website to great success. I plan to do more of the same.

    So far I've been digging out from the fence line about a foot wide and a foot down. Hope that's enough. I strongly suspect that the CCA does leach and there have been plenty of posts on this forum warning about it.

    I expect that the post is probably safe now, but still want to seal it to make sure. Any ideas on what to use to seal it safely?
     
  9. gardenlen

    gardenlen Group for banned users

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    i have a couple of links on one of our pages to product made from 'lanolin' wool grease, they are aussie invention and supposed to be the best protection for wood or metal.

    most paints that will do the job all have some sort of toxins in them.

    yeh straw bale a good way to go the origianl bales are still there defining the boundries though very much rotted down.

    len
     
  10. sweetpea

    sweetpea Junior Member

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    newcroft, there are plants that will actually take heavy metals and toxins out of the soil. It's called phytoremediation, you can research that. Stinging nettles will do just that. And if you were a metals factory you could actually get those metals back out of the stinging nettles!

    But if you want to clean your soil, just toss the stinging nettles rather than compost them. Use gloves. It may take several cycles of plant growth, but it's a nice fix. :)

    Stinging nettles also do wonderful things for compost and the soil when grown in healthy soil. You just have to agree to get stung on occasion :)

    The Brassicaceae family contains a large number of hyperaccumulating species (plants that uptake heavy metals) with widest range of metals. Mustards are a good choice.

    Also Alyssum, which is probably growing freely somewhere nearby.

    https://www.ecology.kee.hu/pdf/0301_001018.pdf


    https://www.uvm.edu/~dneher/posters/01OBPC_Small.pdf
     

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