While performing necessary work on private properties, the Utilities Superintendent or duly authorized employees of the city shall observe all safety rules applicable to the premises established by the company, and the property owner shall be held harmless for injury or death to the city employees and the city shall indemnify the property owner against loss or damage to its property by city employees and against liability claims and demands for personal injury or property damage asserted against the company and growing out of the gauging and sampling operation, except as may be caused by negligence or failure of the company to maintain safe conditions as required in § 51.087.