While performing the necessary work on private properties referred to in Article
IV, §
365-25 above, the City or duly authorized employees shall observe all safety rules applicable to the premises established by the owner, and the owner shall be held harmless for injury or death to the City employees, and the City shall indemnify the owner against loss or damage to its property by the City employees and against liability claims and demands for personal injury or property damage asserted against the owner and growing out of the gauging and sampling operation, except as such may be caused by negligence or failure of the owner to maintain safe conditions.