(a) The subsoil and other material must be excavated to such a depth as will allow for the required amount of material necessary for the construction of the street. After excavations have been made to the proper depth for laying the roadway, all places in the subsoil that are soft and spongy, or ditches that have not been refilled long enough to be thoroughly compact, if not compact when refilling, shall be filled with satisfactory material and tamped and rolled until they meet the approval of the urban county engineer.
(b) All portions of the roadway not compacted by the roller, such as along the curb, around manhole covers, valve covers, and other such obstructions, shall be thoroughly compacted by use of an approved type air-driven backfill tamper. Every precaution deemed necessary by the urban county engineer to protect the sewer, water and gas appurtenances, such as manholes and valve boxes, shall be taken by the contractor; and any injury to any portion of same shall be fully repaired by him, except as otherwise provided in section 17-53.