One of the main provisions in Surface Mining Control and Reclamation Act of 1977 (SMCRA) is that during mine reclamation the mining company must attempt to return the land to its original shape. Approximate original contour is the term used by SMCRA to describe the condition the land must be left in after the mine has closed. This is important for multiple reasons. First, high walls left by mines can be safety hazards to the local populace. Second, the angle of slope affects erosion and runoff. Thirdly, rock slides could occur from steep high walls. Lastly, land values can be affected by unsightly spoil piles and high walls or landforms which are dramatically different than pre-mining conditions.

Figure: SMCRA requires all coal mines to return the land to approximate original contour (AOC) as part of their reclamation plans.