(a) Any person may appear at a hearing in person or by authorized representative. A person appearing in a representative capacity may be required to prove his authority.(b) Except for good cause, the applicant or petitioner shall appear at the public hearing. Failure to so appear may be grounds for withholding consideration of a matter or for dismissal without prejudice.(c) An affidavit may be made by either the party or a representative, unless otherwise provided by statute.(d) Failure to appear at an enforcement hearing may result in a default order under §70.106 of this title (relating to Default Orders).