All excavations for buildings sewers shall be adequately guarded with barricades and lights so as to protect the public from hazard. Streets, curb and gutters, sidewalks, parkways and other public property removed or damaged during the installation of the building sewer shall be repaired or replaced in a manner acceptable to the city and at the total expense of the owner. It is further agreed that any parties involved in any excavating or installation work for sewer installations as above set out, will hold the city harmless from any and all damages to persons or property resulting from or growing out of any opening or excavation or any negligent act or from any operation made within the city.