I removed some rail road ties from our backyard and would like to put a garden where the ties used to be.

Do I need to dig up the old dirt and replace it with new dirt or is it safe to till up the yard and plant the garden?

I have read a lot of articles about the creosote in the posts, and didn't know if anyone knew what the proper way to do things would be. I think I even read that someone said they would leech chemicals into the soil over 30 feet away.

Any good advice?