After the license required by this article is issued, the licensee shall obtain a permit from the director of public works for doing any such work. All such work shall be done according to plans and specifications, grades and lines furnished by the director of public works, and shall at all times be subject to the inspection and approval of the director of public works or other persons designated for such work by him or her. Immediately upon the completion of each and every such piece of work, the contractor shall apply for and obtain from the director of public works a certificate, stating in substance that such work has been completed according to the plans and specifications, grades and lines given by him or her.
(1964 Code, § 33-12)