Removing a coal fire back boiler

[Teamwild]

Hi There.
This is my first post here so please be gentle with me. :?

I'm in the process of removing a coal fired back boiler and the base seems to go quite deep into the ground. My question is, should I make sure it all comes out or can I just grind off the top before I brick up the fire place?

There seems to be a lot of sand as well. Is this normal?

Cheers.