At the time and place specified in the order to show cause, or at such other time and place as, for good cause, is otherwise ordered by the commission, the commission shall proceed to a hearing upon the petition or order on the commission’s own motion. When the proceeding has been submitted the commission shall make and file its finding upon the question whether the use to which the property or interest therein is to be applied is a use authorized by law and whether the taking is necessary to such use, and shall make and file its written finding fixing the just compensation to be paid for the property or interest. If the commission finds that severance damages should be paid, the just compensation for such damages shall be found and stated separately. The just compensation shall be fixed by the commission as of the day on which the petition was filed or the order on the commission’s own motion was made.