Amos, yesterday (Nov. 14) my gardening guru talked about some new kind of treated lumber for outdoor use. I didn't get the name, but I've heard about a couple lately.
Here is a link to the page to find his podcasts. The program is three hours on Sunday morning, I didn't hear the first hour or so, so if you want to listen to the last couple of hours you'll find it.

Last week on This Old House on the second half hour when they go out in the field with the various experts, the gardener put in a raised bed using beams that were treated with glass to make them quite durable without having the toxic chemicals that can leach into the soil. So you might want to look up that program also.