The board shall then fix a date for hearing the report which is not more than thirty nor less than twenty days after the filing, and it shall cause notice of the fact that the report has been filed, and of the date fixed for the hearing to be published by at least two publications in one or more newspapers published in the county.
On the day fixed the board shall hear the report, and it may adjourn the hearing from time to time not exceeding four weeks in all. It shall finally pass upon it, or may refer the report back to the commission for further examination and investigation, or for correction or amendment.