While performing the necessary work on private properties referred to in Sec. 13.13.401. above, the Director or duly authorized employees of the City shall observe all safety rules applicable to the premises established by the company, and the company shall be held harmless for injury or death to the City employees, and the City shall indemnify the company against loss or damage to its property by City employees and against liability claims and demands for the personal injury or property damage asserted against the company growing out of the gauging and sampling operation, except as such may be caused by negligence or failure of the company to maintain safe conditions as required in Sec. 13.13.611.