The board having authority to permit the erection of a cattle guard and gateway across any highway or section line also has authority to cause the same to be removed, if the same is not kept in repair, or if in the judgment of said board, it becomes necessary to remove the cattle guard and gateway for the purpose of improving the highway or section line. If the board determines any cattle guard and gateway should be removed under this section, written notice by registered or certified mail must be sent to the occupant of the enclosure, notifying the occupant to effect such removal within thirty days from the date of mailing. If the notice is not complied with, the board, upon expiration of the period, is authorized to remove or destroy the cattle guard and gateway.