Using railroad ties safely for raised beds

We have only about a 2% slope but our Bolar clay loam soil still tends to move downhill when wet. I knew we'd need a lot of amendment and PH correction. So when I built our garden 3 years ago I terraced with a big L (50' per side) of 2 railroad ties to prevent soil erosion during heavy rains and give us an overall level garden surface.  Anybody else in Texas will remember our 2018 "monsoon" Fall, and the ties did their job well then. We kept a path right next to the ties to prevent creosote from getting near our growing soil. Additionally, as it's on the downhill sides, any creosote runoff will move away.

Now I'm turning the walls of railroad ties into 1-sided raised beds. I plan to line them with heavy plastic sheeting so the good soil can butt right up to the ties but not touch the treated wood. Anybody else doing this?  

The ties are handy to use and I get them for only $10. They are of course many years old, as they were pulled from railroad tracks to be replaced. I don't know how many years they were out under steel tracks but maybe one of you knows. Here in Central Texas we have little water rot so it could have been 30 years or more.

I commend you for trying to protect your garden from the chemicals in the ties. Are you taking any measures to protect the surrounding soil?

John F Dean wrote:I commend you for trying to protect your garden from the chemicals in the ties. Are you taking any measures to protect the surrounding soil?

There are gravel paths on the downside. No trees except uphill.

I'm not super-toxic-paranoid by any stretch, but coal tar creosote (wood preservative in railway ties) is particularly nasty stuff.

Here is a Material Safety Data Sheet (MSDS) from a manufacturer (not an environmental activist). I invite you to consider it carefully and draw your own conclusions.
https://kmgchemicals.com/wp-content/uploads/P2_Coal_Tar_Creosote_(English).pdf

Personally, I avoid using ties in food production areas. At minimum, I would have a buffer of sand several inches wide between the ties and the plastic barrier.

Edit: Note that the MSDS is for a concentrated formulation. Even so, I think it offers valuable information when considering uses for railway ties.

Modern ink used for newspapers contains coal tar Carbon black 137, I heard. Meaning that it's not as safe to use for other purposes afterwards. Grandpa would use old newspaper to clean his car windshield.

Thanks for the info. I think I may build a sand plastic sandwich, as it were. Plastic against the ties, a couple inches of sand, then another layer of plastic, then our soil. I can't imagine the creosote would get thru that.

Way back in the 90s I was involved in the cleanup of a creosote wood treatment site for railroad ties. It was an EPA Superfund site and nobody was allowed near it without full protective gear. It's not just the toxic organic chemicals, but a lot of heavy metals. The soil from the whole site was put in a lined landfill and capped. Over time many organic toxins can be broken down by soil microorganisms, but no luck with heavy metals since they are in their final form and can't be broken down. I'm only saying this because that stuff is nasty as hell.

If you plan to have treated ties near food crops, the risk of your plastic barriers being pierced or broken down over time seem fairly high, and then seepage could occur. I've never had plastic last for more than a year in my garden back when I still tried to use it as a barrier.