The proposal shall be filed with the county clerk of the county who shall set a hearing date not less than thirty nor more than ninety days from date of filing. Notice of the hearing shall be given by certified mail addressed to the address of each land or lot owner as shown on the plat. The notice shall give the date of hearing, the amount of benefits assessed against or damages awarded to the owner so notified, and a recital that the plan for the improvement is on file and subject to inspection in the office of the clerk. If no address of a landowner is ascertainable, the county clerk shall publish a notice of the hearing as to such owner by one publication in a legal newspaper published or of general circulation in such county.