Sponsors of events in Portland Civic Stadium shall maintain liability insurance against claims for damage or personal injury, including death, which may arise out of its operations in the stadium or in connection therewith. Such insurance shall afford coverage of not less than $100,000 for personal injury to each person, $300,000 for each accident or occurrence, and $50,000 for property damage; such insurance shall be without prejudice to coverage otherwise existing and shall name as additional insured the City, its officers, agents, and employees. Evidence of such insurance shall be furnished the Auditor of the City prior to the event and the same shall be kept in full force and effect throughout the full term of Stadium usage, subject to approval of the City Attorney as to sufficiency of coverage.