All excavations made within the street lines or sidewalk removed shall be subject to supervision by the Service Director. All paving, material, flagging, curbing and ballasting shall be carefully removed and preserved. After the work is completed, as contemplated by the application for the permit referred to in Section 901.02, the trench or excavation shall be refilled in accordance with the directions of the Service Director. The flagging, concrete, paving or other paving material shall be properly replaced under the supervision of the Service Director, but at the applicant's expense.