Any permit issued shall become invalid unless the work authorized by it shall have been commenced within sixty (60) days after its issuance or if the work authorized by such permit is suspended or abandoned for a period of six (6) weeks after the time the work is commenced; provided that, for cause, one or more extensions of time for periods not exceeding sixty (60) days each may be allowed in writing by the City Engineer.
(1969 Code 155.36)