One government surveyed section of land or up to 640 acres, whichever is the larger area, may be the subject of a coal option contract or a coal mining lease. The term of a coal option contract may not exceed one year. The term of a coal mining lease may not exceed twenty years. The acreage in a single application does not need to be contiguous. The total area of a coal option contract or a coal mining lease shall be limited to a logical mining unit as determined by the department.