Susan Taylor Brown wrote: I am coming to terms with the fact that I can't have (and probably don't want) a pristine start.
Yup. It is what it is. You play the cards you're dealt and make it work.
I would imagine that in 10 years, you won't even remember where those railroad ties were. I had a few here in my yard when I first moved in 16 years ago, but I pulled them out so long ago, I don't even remember where they were, exactly. They were rotting and falling apart, and most of them came up easily in chunks.
When we initially moved in, I planted 3 small queen palms in that space where they ties were. Within 2 years, the trees were big and beautiful. After 10 years, I could hardly trim the dead branches off --- my 20' extension ladder was fully extended and I was standing as high as I could climb while I reached up as far as I could with my Sawzall and tried to cut the dead branches and seed pods off. So I decided to take them down. I cut those 3 massive palm trees down, used the wood for terracing on a hillside, and planted fruit trees in that space. Then I thought, "Where were those railroad ties that I dug-up so many years ago?" I couldn't find any evidence of them at all.
Palm trees have a massive root system (small pencil sized roots that web out all over --- good for holding the trees in place when they grow in sand on a beach). In that web of roots, a fungal network had clearly established itself, and after I cut those palms down, we got a flush of mushrooms every spring. So my thinking is that between the fungal growth that permeates that entire area, the years (and dozens of loads) of wood chips, and time --- any chemicals that once may of leached from those ties will have long since been rendered inert. I eat the apricots, cherimoya and plums that grow in that space without a worry in the world.
Nature has a way of healing itself. Even horribly polluted places like Chernobyl and Fukushima are returning to health (as they are going wild). Best of luck with your food forest and permie yard.