6 C.F.R. § 13.30 – The hearing and burden of proof.

(a) The Presiding Officer will conduct a hearing on the record in order to determine whether the Defendant is liable for a civil penalty or assessment under § 13.3 and, if so, the appropriate amount of any such civil penalty or assessment considering any aggravating or mitigating factors.
(b) The Authority will prove Defendant's liability and any aggravating factors by a preponderance of the evidence.
(c) The Defendant will prove any affirmative defenses and any mitigating factors by a preponderance of the evidence.
(d) The hearing will be open to the public unless otherwise ordered by the Presiding Officer for good cause shown.