jon.p.weaver wrote:
Do you know what? I have just been thinking to myself why I havn't
tried my SDS.. A few months back I bought some HUGE drill bits.. THey
would almost certainly do 'some' damage.. Whether it will get the stump
out, I don't know.. But its worth a try!

It won't work. However, if you drill a pilot hole down the middle
of the post, and screw a long coach screw in, you might be able
pull out the stump with a suitably drilled piece of 4" RSJ or
other sturdy lever. Your best bet may be to drill the concrete
out at the corners/sides of the posts, and then try pulling the
stump out:


OOO holes
###
### stump
###

You need a good "eye", though (the drill but won't like going
into the timber, which helps). I removed a row of posts set into
a concrete foundation (*why?*) by drilling a channel out of one
side:

---------O----------
O
###
###

--------------------

and levering in the vertical slot with a wrecking bar. Probably
won't help you, though!

Problems can happen when there are knots, dents, or whatever in
the concreted-in stump - or some silly sod has driven nails into
the stump before concreting it in! I have come across that. Grr.