missmoo
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Joined: Wed May 30, 2012 2:30 pm

Replacing treated ties...

We just bought a house that has an existing raised gardening bed approximately 17 by 24. Two sides are constructed using what appear to be treated ties. The previous owner told us they were not treated (which I didn't believe) so I called the company that installed the bed back in 2005. He said they were treated but that he could not provide me with a cut sheet about them...based on my research, I think they are treated with copper azole? So, we are removing the ties and replacing them...My question is: should we also remove the soil adjacent to the ties? Or can we remove the ties and back fill with a new soil topping? We had a soil test done a month ago with the dirt. Is there anything I can look for in this test to tell me if the soil is contaminated? Thanks in advance!

Dillbert
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Posts: 955
Joined: Sun Apr 04, 2010 3:29 pm
Location: Central PA

there are labs that will do "heavy metal" and "organic compound" analysis. isn't cheap.

a "standard soil test" does not address any of the "treated tie" issue.

however, in a common sense regard to your question -

if the ties are treated, and "the treatment" has not leached into the surrounding soil, what is the question? basically, if you suspect the ties have leached, yes, replace the soil.

if you decide the ties have not leached, then there is no need to replace some/any of the soil.

if you suspect the ties have not leached, why replace them now? or the soil?

if you research on the web you will find huge numbers of supporting and non-supporting reports, documents, scare web sites, and head-in-the-sand websites. the point being, there are virtually no scientifically proven / accurate / reliable / take-it-to-the-bank "studies" proving anything one way or another - science is good, science is not yet that good. pretty much all of them "extrapolate" data - arsenic exposure being the "biggie" - from some other source/exposure route.

the production of CCA treated wood essentially ceased in 2004; existing inventory remained and was sold.

replacement "treatments" - without the arsenic bit - are ACQ (ammonium copper quaternary) and copper boron azole (CBA)

do note, both copper and boron are toxic on over-exposure.

certainly, "better safe than sorry" is not a bad approach - but if you're looking for absolute truth in the matter of "treated lumber/wood" - that's not available, check back in two or three centuries when the matter may become "proven"

missmoo
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Joined: Wed May 30, 2012 2:30 pm

thanks for the response. just trying to gauge if there is a standard practice. the online material is all over the place.
the ties were installed in 2005 and are in in ok shape. but, they won't stay that way forever. so I would rather replace them now before there is a bigger problem.
my local extension school does not test for heavy metals - I found only 2 that did that and they are expensive. but probably less money than excavating the perimeter of my garden bed. would this type of test tell me if the treatment has leached? is there anything else that would give me any sign of the treatment leaching? thanks.

Dillbert
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Posts: 955
Joined: Sun Apr 04, 2010 3:29 pm
Location: Central PA

there is nothing short of a heavy metal analysis to tell you whether arsenic, for example, has leached into the soil.

if you want to reply the ties with something totally non-treated, go for 6x6 hickory. that stuff lasts like near forever.



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