Every permit issued under the provisions of this article shall become and be void unless the excavation or other work thereby permitted to be done is commenced and thereafter diligently and continuously prosecuted within thirty (30) days from the date of issuance thereof, and if the same is not so commenced and diligently prosecuted, in the judgment of the director of public works, he/she shall have power to cancel such permit. (1954 Code §19.10; amd. 1994 Code)