how mining coal damages the environment?

Answer 1

Two different ways come immediately to mind: Strip Mining and Room and Pillar Mining. Strip mining requires all cover (trees, soils, etc.) to be removed so that the coal can be mined. Modern laws require the land to be "restored" to its natural state. Room and Pillar Mining is underground mining where "rooms" are excavated with "pillars" supporting the rooms. When a section has been mined the pillars are removed and the room collapses. People living above have no recourse when their homes are damaged by subsiding earth, and it cannot be good for the environment either, although I don't have any facts to support that view.

Answer 2

Mining the coal does almost no Damage just some holes in the ground ,

it is the smoke from burning the coal that does the damage and creates air polution

Answer 3

Leachate from the mine drains into surface water and subsurface containing sometimes nasty sludgy water that is high in heavy metals and acids.
More here, http://en.wikipedia.org/wiki/Acid_mine_drainage