No permit shall be issued for any sign unless the applicant shall file a bond conditioned to save harmless the Borough from any damage or injury that might result by reason of the construction, alteration, repair, relocation, enlargement or maintenance of such sign. The amount of such bond, which shall be with corporate surety approved by the Borough Council, shall be in the sum of $5,000 to $10,000 in the case of any sign weighing 250 pounds. As an alternative to the filing of such bond, the applicant may file with the Borough a certificate issued by an insurance company setting forth that the applicant carries public liability insurance for $10,000 to $20,000 and said insurance shall be continued in full force and effect during the effective term of the permit.