Section 23(3)(b) in The Metro Railways (Construction Of Works) Act, 1978
(b)the construction or operation of any metro railway, the metro railway administration may, at any time after the underpinning or strengthening of such building is completed and before the expiration of a period of twelve months,-(i)in a case referred to in clause (a), from the completion of such works; and(ii)in a case referred to in clause (b), from the date on which traffic was opened in the metro railway, enter upon and survey such building and do such further underpinning or strengthening thereon as it may deem necessary.