40 CFR § 22.24
Burden of presentation; burden of persuasion; preponderance of the evidence standard
June 9, 2020
(a) The complainant has the burdens of presentation and persuasion that the violation occurred as set forth in the complaint and that the relief sought is appropriate. Following complainant's establishment of a prima facie case, respondent shall have the burden of presenting any defense to the allegations set forth in the complaint and any response or evidence with respect to the appropriate relief. The respondent has the burdens of presentation and persuasion for any affirmative defenses.
(b) Each matter of controversy shall be decided by the Presiding Officer upon a preponderance of the evidence.