Every person, firm, or corporation which is granted a license or renews a license under the terms of this ordinance shall be required to maintain insurance underwritten by a company authorized to do business in this state against liability to the public in the amount as set by the City Council, and amended by resolution from time to time. Each contractor licensed under this ordinance shall maintain worker’s compensation insurance covering all employees. Proof of all required insurances shall accompany each application as certificates of insurance. This insurance shall be continuous until cancelled or shall expire March 30 of any year. These policies shall contain therein, or have attached thereto by rider, a provision that the insurer will give notice to the city at least 10 days prior to the cancellation of the policy, in the event the insurer shall elect to cancel same. Failure to maintain as above provided shall be grounds for revocation of the license issued hereunder.