For the purpose of operating, constructing, maintaining or extending such waterworks, the city shall have the right to lay conduits, pipes, aqueducts or other necessary works over or under any water-course, or under and along any street, alley, lane, turnpike, road, railroad or highway within such city, but not in such manner as to obstruct the same or impede or prevent travel thereon; and the city authorities may at all times enter upon and dig up such street, alley, road or highway to lay pipes thereon, or to construct works beneath the surface thereof, but they shall cause the surface of such street, alley, road or highway to be relaid and restored to its usual state, and any damage done thereto to be repaired, and such right shall be continuous for the purpose of repairing and relaying water pipes upon like conditions.