Is in game environmental changes possible?

With unity, would i be able to somhow give the player the asbility to dig/pile dirt to change the terrain, im not really looking for an example maybe if somone knows its not possible, or if it is point me in the right direction?

If you google "Unity Terrain Deformation", this is the first result:

http://blog.almostlogical.com/2010/06/10/real-time-terrain-deformation-in-unity3d/

I've never tried it before, but it looks like it should be able to suit your needs. At the very least you can learn how they dynamically deformed the terrain.

And yes, to answer your question, it's possible.