40 CFR § 135.4 - Service of complaint.
(a) A citizen plaintiff shall mail a copy of a complaint filed against an alleged violator under section 505(a)(1) of the Act to the Administrator of the Environmental Protection Agency, the Regional Administrator of the EPA Region in which the violations are alleged to have occurred, and the Attorney General of the United States.
(b) The copy so served shall be of a filed, date-stamped complaint, or shall be a conformed copy of the filed complaint which indicates the assigned civil action number, accompanied by a signed statement by the plaintiff or his attorney as to when the complaint was filed.
(c) A citizen plaintiff shall mail a copy of the complaint on the same date on which the plaintiff files the complaint with the court, or as expeditiously thereafter as practicable.
(d) If the alleged violator is a Federal agency, a citizen plaintiff must serve the complaint on the United States in accordance with relevant Federal law and court rules affecting service on defendants, in addition to complying with the service requirements of this subpart.