40 CFR 209.6 - Answer.
(a) General. Where respondent (1) contests any material fact alleged in the complaint to constitute a violation of the Act or regulations; or (2) contends that the remedial order proposed in the complaint is inappropriate to the violation; or (3) contends that he or she is entitled to judgment as a matter of law, he or she shall file a written answer with the complainant. Any answer must be filed with the complainant within twenty (20) days after service of the complaint. Initiation of informal conferences with the Agency under § 209.19 does not add to the twenty (20) day period. The time period in which to file an answer may be extended by the Administrator upon motion.
(b) Contents of the answer. The answer shall clearly and directly admit, deny or explain each of the factual allegations contained in the complaint with regard to which respondent has any knowledge. Whenever an allegation is denied, the answer shall state briefly the facts upon which the denial is based. The answer shall also state (1) whether a hearing is requested, (2) the facts respondent intends to place at issue, and (3) the circumstances or arguments which are alleged to constitute the grounds of defense.
(c) Hearing upon the issues. A hearing upon the issues raised by the complaint and answer shall be held upon written demand of respondent.
(d) Failure to plead specifically. A respondent's failure to plead specifically to any material factual allegation contained in the complaint shall constitute an admission of such allegation.
(e) Amendment of the answer. The respondent may amend the answer upon motion granted by the administrative law judge.