If required by the superintendent of public works or by the city council, permits or any permit may be withheld upon the condition and requirement that the applicant shall furnish satisfactory proof that he has in force during the performance of the excavation work, and covering the excavation work, public liability insurance of such amount as will reasonably protect those endangered by the work, or those whose property is endangered by the work. (Ord. 280 § 8, 1969)