At least 30 days before the date set by the administrative law judge the authorized officer will notify the appellant of the time and place of the hearing within or near the district. Any other person who in the opinion of the authorized officer may be directly affected by the decision on appeal will also be notified of the hearing; such person may himself appear at the hearing, or by attorney, and upon a proper showing of interest, may be recognized by the administrative law judge as an intervenor in the appeal.