Can I copy and store a part of the terrain?

Hello, I am working on a game with a huge map, but I notice the default ROBLOX terrain loading is not that great. What I would like to do is this:

• Take the terrain of the map and copy it locally
• Delete all of it (client side)
• Load parts of it as you get near to it

I have done this with other things in the map such as trees, homes, plants, NPCs, etc. And it has worked with incredible success to keep the server lag down, and to keep other players from having to load what you load. But the terrain is something I am having a hard time cracking, as it doesn't seem to have much scriptable customization.

Basically I want to load 250 x INF x 250 chunks of terrain onto the map, and you will be able to set the rendering distance as you wish. Most of it is designed where you do not see the rest of the world, so it wouldn't look bad anyways if it didn't go on very far. I know ROBLOX does this to an extent, but with the cost you have to lower your graphics. And also this isn't cool as if you want better graphics, you can't because your computer has to load terrain from all around the map, instead of only what you see; causing major lag.