the excavation of the specific mine pit takes place on the same relatively limited site for an extended period of time;

the excavation of the specific mine pit follows a coal seam having an inclination of fifteen degrees or more from the horizontal, and continues in the same area proceeding downward with lateral expansion of the pit necessary to maintain stability or as necessary to accommodate the orderly expansion of the total mining operation;

the excavation of the specific mine pit involves the mining of more than one coal seam and mining has been initiated on the deepest coal seam contemplated to be mined in the current operation;

the amount of material removed is large in proportion to the surface area disturbed;

there is no practicable alternative method of mining the coal involved;

there is no practicable method to reclaim the land in the manner required by this chapter; and

the specific mine pit has been actually producing coal since January 1, 1972, in such manner as to meet the criteria set forth in this section, and, because of past duration of mining, is substantially committed to a mode of operation which warrants exceptions to some provisions of this subchapter.