[Cob] Top soil

[jane at kirstinelund.dk]

Does anyone have any experience - good or bad - with the presence of top
soil in cob? I know that you are not supposed to use it, but how bad is it
if you get a smaller amount mixed in to your cob mix?

The thing is, that we have a lot of top soil mixed piles of subsoil sand
lying around. It was kind of hard to keep apart when we digged out the
foundation (we used a machine, and the site is sloping), but it would be
nice to be able to use it.

Jane