After the foregoing work has been finished and properly inspected, the back-filling shall commence without delay, and during its prosecution, and as fast as deposited in the trench, it shall be thoroughly puddled and tamped to such an extent as to render subsequent settlement of the surface practically impossible. The drain layer will be held strictly responsible for any disturbance or displacement to the roadway ballasting or paving, due to his neglect to faithfully conform to the foregoing requirements.