I'm very aware that railway sleepers (railroad ties in the USA) are generally filthy, poisonous things, loaded with creosote, heavy metals, dieldrin and who knows what else.
But I'm involved in developing a community food forest which must have very clear paths so people don't walk all over the place.
We can get up to 500 free sleepers, and toxicity aside, they're ideal.

So: would you say "no way, not under any circumstances"
If I could find out around about how old they are, maybe I can get more of an idea what's in them?
We plan to encourage fungi in the 300mm or so of wood mulch we'll be laying, just for general biological health.
I'm not familiar with the practicalities of mycoremediation; but let's just say we were to knowingly bring something toxic into a system (sleepers),
could encouraging fungi be a way of tying up those toxins?

We know what toxins are in them -- creosote. Natural creosote or petroleum based creosote, it's still the same mix of PAHs (polyaromatic hydrocarbons). Fungi will degrade them over time, it just takes a long, long time (on the order of decades). The reason it takes PAHs so long to degrade is that they are more than 3/4 of the way to being biochar, and biochar takes centuries to degrade. In an odd way, the bigger the PAH molecule is, the less toxic it is and the more it is like an inert piece of biochar. It's the small PAHs, with less than a dozen joined aromatic rings that are the real health hazards, and they are the ones most amenable to digestion by soil fungi.

So yes, the older they are, the more the small PAHs have been degraded by fungi and the less toxic they are overall. I would give a "yes" vote on taking the free sleepers and using them. There are others here who are a little more hesitant and will give a "no" vote, and I respect their opinion, I just think they err on the side of too much caution. If you have them mulched on both sides with lots of wood chips, I don't see how any toxins that still might be residing in the bulk of the sleeper are going to migrate out without getting metabolized by the fungi in the mulch.

John, could you char the surfaces of the railroad ties to lock in the toxins?

Bill McGee wrote:John, could you char the surfaces of the railroad ties to lock in the toxins?

Toast it with a blow torch? Yes, I suppose that would work. That's along the same line as charring the ends of fence posts so they won't rot so fast. Any mobile creosote molecules that might be inclined to wander out on a hot day will get absorbed by the char on the surface.

Brainstorming about a production run charring 500 railroad ties. Thoughts (not in order)
1. Have a trench lined with stones, urbanite, vermiculite
2. Load with chunks of hardwood
3.build a box with RR ties, have rebar to span roof and cover with RR ties
4. Light hot fire, can use leaf blowers or snail fans to stoke fire
5 go for hot burn to quickly char and gas off toxins. Workers shoould use respirators
6 use propane weed burner head to char outer ties
7 use ice pick for quality control of char depth all 6 sides
8 when inner box charred break down box, roll and use tongs to build 2nd box in trench next to 1st trench. Char other sides
9 rebuild new box, after reloading wood
10 have hoses to prevent out of control fire
11 rinse repeat, I
Could see 3 or 4 workers having a good production line Speed will improve with learning curve...thoughts?

- I would actually be more worried about the 30 or even 50 year history of weed killers used on the R.O.W. Big Al

Okay, thinking on this-
12. lots of embedded energy. Is their a permie way to stack functions in railroad tie/sleepers remediation
13 can the RR box be the horizontal exhaust for a rocket stove. Seed the exhaust path with firewood. Have a mobile feed tube that can be moved to burn both sides. Insulate with rockwool
14. Biochar can be produced for the garden path to store water.
15. A centralized burn would be quicker, but if enough workers stake out path with RR ties and dig burn tunnels as you go.
16. have path on contour with swales/berms to store water
17. Would the hot burn break down the VOC's and 50 years of dioxin/agent orange pestcides that keep all life from growing on the tracks?

I'm one of the "absolutely not" crowd. But, as a mental exercise, I'll give it a go.

I would wrap them in a couple layers of wire mesh and then trowel in a high grade hydraulic cement, to make a watertight enclosure around each unit. You'd want it to be of the same quality as the hull of a well built ferro cement boat. This should last a century.
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Railway ties are not just a toxicity concern. They are also a visual blight and on a hot day, the smell could overpower the most fragrant garden. Think of the neighborhoods where they are used. Here in Victoria, they are never seen in the upscale, tastefully done yards of Oak Bay. They are sometimes seen in South Nanaimo, an area noted for gun toting, beer swilling yokels, dressed in shorts three sizes too small, who park trucks on the front lawn and shoot beer cans. The whole place is an affront to good taste. Railway ties are a natural addition to outdoor decor. They fit in perfectly well with abandoned vehicles, old tires turned into planters, faded plastic flamingos and broken down children's ride-on toys, that a pitbull has shredded.

Dale Hodgins wrote:They are also a visual blight and on a hot day, the smell could overpower the most fragrant garden.

No self-respecting bogan (sounds like the local version of the ...subculture...you describe) would have railway sleepers at their place; in NZ, sleepers are a very 'middle class' landscaping thing.
I've never noticed a smeel. Maybe I've only been around really 'old' ones.
I sure don't think they're pretty, but 500 free sleepers, each 2.5m long sounds perfect for what I need, they're just horribly poisonous