At the hearing the county board shall hear objections from any land or lot owner as to the following:
(1) Whether the project will be conducive to the public health, convenience or welfare;
(2) Assessment of benefits;
(3) Compensation for land appropriated; and
(4) Damage claimed to property affected by the improvement. Within thirty days from the date of the hearing, the county board shall make final determination of the amount of benefits to be assessed and damages to be awarded and shall decide any other objections raised at said hearing. Notice of such determination shall be given by certified mail to all parties who filed objections thereto.