Stan, some interesting reading below, it make sense given the material you are using, though I was of the same opinion of Mark, you can't get CCA as easily, I am not sure how the current ground contact material performs, CCA worked just fine, I used to handle it, crystallized CCA on the outside, wore gloves, and you don't want a splinter of this in you, or burn, eat or what have you, and I agree with it not being a good idea for playgrounds, but... people just being ignorant, fueled by some sort of activist movement directed towards the EPA, was likely the cause, I think you can order CCA though, see the links below, its still in use, but limited, and though not banned by the EPA, the wood preservative manufacturers seem to be in some sort of agreement about its limited use, as we do live in such a litigious and seemingly at times, ignorant society, no doubt as to why it went this way. ACQ and CA are the latest treatments available, I am not well versed in either, I do wonder if the ground contact preservative used today will perform the same if so, fine, but why is CCA still the choice for industrial use, it was everywhere for years and years. Same thing with creosote, fools ruined its availability, you can't dig a hole and fill it with creosote to soak logs with, like they did I am sure, its fine to use and use properly, I had some left over from years ago and applied it to the bottoms of 70's era 6"x6" x 18' posts, that have been in well drained ground for 7 years, to help prevent rot or decay, seems to work fine, no leaching ever, grass and weeds grow right up along them.