Mystery photo contest #2

Well, this is a different kind of mystery photo contest. The mystery is: What is This Guy Doing To the Granite Slab in E.C. Park?

The wood carpet was rolled in this morning, and a guy in a white van started doing some kind of work with an electric power tool. (I thought maybe he was etching his initials in but checked later and no sign of that.)

Here's a picture of the stone after he finished. I'm sure there must be a second part of this production coming soon.

Does anyone know what he is doing? 

New photos added on Friday:

It looks like he just removed and replaced the center slab. Now working on re-cementing it.