Except as hereinafter specifically provided by this act, vertical and lateral support by underlying coal for any land, easement or right of way purchased, condemned or otherwise acquired by the Commonwealth is waived, (1)(a) Whenever the State Mining Commission finds that the cost of restoring any possible subsidence or replacing any damage to structures or other improvements on such land, easement or right of way is less than the amount payable for damages for coal required to be left in place in order to furnish such vertical or lateral support, or (b) if no damages are payable by reason of the failure of the party or parties entitled thereto to institute proper proceedings to recover the same, within the period prescribed by law, whenever the owner or person entitled to remove the coal shall enter into an agreement to indemnify the Commonwealth for any damages, or reimburse it for the replacement of any structure or other improvement, which may be injured or destroyed by the removal of coal owned or adjacent to lands, easements or rights of way owned by the Commonwealth, and (2) Whenever the commission finds from the evidence before it that such waiver of support and the removal of coal will not result in loss of life or personal injury to persons properly using said land, easement or right of way.