In the case of strip mining operations which remove and do not replace lateral support, unless pursuant to written agreement between the operator and the adjacent property owner, the top of the consolidated material of the open cut adjacent to the property line of other property not owned or leased by the operator shall, at the time mining is completed, not be closer to such other property line than a distance of twenty-five (25) feet plus one and one-half (1 1/2) times the depth of such cut as measured from original ground surface to the top of consolidated material.