On the date set for the completion of the work, or prior thereto, upon notice from the owner that the work has been completed, the Board shall cause the work to be inspected after due notice to the owner of the permit. Such inspection shall be thorough and complete, in order to determine the actual capacity of the works, their safety and efficiency. If not properly and safely constructed, the Board may require the necessary changes to be made within a reasonable time and shall not issue a certificate of completion until such changes are made. Failure to make such changes within the time required by the Board shall cause the postponement of the priority under the permit for such time as may elapse from the date for completing such changes until made to the satisfaction of the Board and applications subsequent in time shall have the benefit of such postponement of priority; provided, the Board may accept the report of inspection by a registered professional engineer.