Getting an BIG array from serverside to clientside, or NPCs?

[Loriel]

I am working on a mining system where at the beginning, the whole level is filled with walls. Then you use your pickaxe to dig your way through the walls, and sometimes find minerals.
How would I transfer an array that contains all of the wall/not wall info from the serverside to clientside? Or would it be better to have every "tile" as a seperate NPC?