There are two types of coal mines, surface and underground, currently producing coal in Colorado....
Surface Mines - A surface mine removes coal from excavated surface pits. The mining sequence includes vegetation removal, topsoil removal and storage, overburden removal, and coal extraction. After coal is removed, open pits are backfilled and regraded to approximate original contour, topsoil is replaced, and vegetation reestablished.
Underground Mines - An underground coal mine removes coal using mining equipment below the earth's surface. To prepare for mining, a portal faceup is constructed. Topsoil from the faceup area is removed and stored for replacement when mining is completed. An entrance tunnel is then excavated to the level of the coal seam, where coal is removed with a continuous miner or longwall miner. After coal is removed, the entrance to the mine is sealed and regraded to approximate original contour, topsoil is replaced, and vegetation reestablished.
For more information on active coal mines in Colorado, visit the Colorado Mining Association's web site.