i don't think it will be a problem.. people (myself included) have used it to build greenhouse frames. If you are still concered you can outline the frame with the landscape plastic and pour the dirt above that...
Good Luck... Steve

pepper,
This has been a controversial issue on gardenweb for a long time. You will get answers from BOTH sides.
IMHO, Just the fact you get both answers, tells me that noone is absolutely sure.
I would never be willing to take the risks and I think just the fact you are asking, says you are concerned.
Why take the risk when there are safer alternatives?
Remember, not too long ago, everyone thought it was safe to microwave plastic. (I know, that's another thread).
Ask yourself why many school playgrounds are removing their treated wood and replacing them with safer wood or plastic. Just a thought.
Read the precautions about sawing and breathing the dust, and having to use gloves when handling it.
No thanks on the treated
Tom

This was an issue in a community garden where I had a plot some years ago. As I am a chemist I tested the soil for arsenic using x-ray fluorescence. I found a trace amount at best. The question unanswered is would more leech out over time. Personally, I doubt it. I would use it without fear. You do need to keep chidren who put their hands in the mouths away from it, as well as pets which may chew it.

The newer timbers are treated with copper, not arsenic.

birdwidow, I thought the original CCA was mainly copper, arsenic, then chromium. (in that order)

The new stuff just eliminates the arsenic & chromium and replaced it with ammonium.
Both are made with mainly copper.
Correct me if I'm wrong.
Tom

Tom:

I have no idea if you are right, or wromg, only that according to our local home center, the treated lumber that has been sold for several years now has no arsenic in it.

But I use oil based semi-transparent stain on all treated timbers, so it's really not an issue with me and the new ones seem to stain the same as the old ones did. We have given up on cedar. It's too soft, rots faster and costs too much. A few coats of stain, and you can't tell the difference looking at it anyway.

I've also never had a problem with plants in treated timber raised beds, as we always lined them with aluminum flashing to prevent soil from escaping. It may also have prevented leaching. Or, it could have been the sealer. I can't really say. But now with the copper, I had to find something else and finally settled on the extra heavy black plastic used for lining ponds.

Actually, the best timbers on our place are the RR ties that surround the barn and line the paths to the pastures. Talk about forever! Some have lain out there for over 40 years and are still sound, but it takes two strong men and a gorilla to handle them.

Hi everyone - I am new here. I want to have a vegetable garden next spring and need advice on building the structure. I want a fenced-in garden with a gate that is not too overwhelming, as I live in the suburbs and no one else has anything but grass and a few shrubs. Also, my garden will be out front since that is the only place I have sun. Can any of you tell me where I can get a plan? Can me and my husband (two city people) install it ourselves (is it difficult) or are we better off with a professional. Hope this is the right thread. I posted a similar post in the "vegetable" forum and it was removed.
Thanks
Pigeon

citypigeon-
I have no idea why a legitimate question would be removed in another forum. This forum should be a good place to post...but you should be posting your own message, rather than "hijacking" a thread on a different subject.

pigeon
it probably wasnt "removed"
This forum is kind of odd to me the way it sorts the messages (compared to other forums ive used) and I also noticed that immediately after you post, your thread may not be visible yet... check back again now and see if you can find your thread.

Any suggestions on cost-consious alternatives to PT wood? I'm needing some form of material to be the base for a 40' x 10' hoop house, going onto boggy ground.
Thanks.

I did a little research and for what i found, it looks like if you can paint the treated wood (i'm using exterior latex) then you shouldn't have any problems with leaching. I just got a bunch of big treated 2x8's for free and need to build a raised bed for some cherry trees, so i'm painting them a neutral color (brown) and filling them with good soil.

I think if you just leave it along and not eat or touch the wood, you should be fine. Also take precaution if you need to cut it, thats where you could inhale the stuff (not good).

If you're working in a greenhouse, then I doubt that the pressure treated wood would be the thing to do you in.
I'd say that's probably the least toxic thing you're going to run up against. Especially if you use some of the commercial pesticides.