On Mon, 08 Jun 2009 19:21:33 +0100, Jonathon wrote:

Probably something I've done wrong but yesterday I forwarded a request
for guidance on preventing tar seeping through the surface of old
railway sleepers used in the making of raised beds.

Prevention, not a lot. Live with it, hope they aren't raised beds for food
production. I'd be a little wary of the leechate getting into the crop.
And if they really are old sleepers then they are probably well soaked in
the "deposits" from trains. And I don't mean oil and grease...

--
Cheers
Dave.