Hello Edwardo82 and welcome to the madhouse.
If you are really concerned about what may be on the railway sleepers, you could always line the inside with black polythene to act as a barrier between the sleeper and the soil. Take it right down to the base of the bed, and if poss, tuck it underneath so that any moisture likely to leak out will run away from the bed rather than into it.
Hope that helps. Of course, if you are planning to grow entirely organically, then polythene will be a no no for you anyway. Whatever you use to act as a barrier will have to be impermeable so that the wood cannot contaminate the soil and I can't think of anything unless it is plastic. Somebody else may well have other ideas (in fact I guarantee it!) so hang on a little while and they'll be along soon. Sandra
If you are really concerned about what may be on the railway sleepers, you could always line the inside with black polythene to act as a barrier between the sleeper and the soil. Take it right down to the base of the bed, and if poss, tuck it underneath so that any moisture likely to leak out will run away from the bed rather than into it.
Hope that helps. Of course, if you are planning to grow entirely organically, then polythene will be a no no for you anyway. Whatever you use to act as a barrier will have to be impermeable so that the wood cannot contaminate the soil and I can't think of anything unless it is plastic. Somebody else may well have other ideas (in fact I guarantee it!) so hang on a little while and they'll be along soon. Sandra