(a) Notice of intent to file suit pursuant to section 505(a)(1) of the Act shall be served upon an alleged violator of an effluent standard or limitation under the Act, or an order issued by the Administrator or a State with respect to such a standard or limitation, in the following manner:

(1) If the alleged violator is an individual or corporation, service of notice shall be accomplished by certified mail addressed to, or by personal service upon, the owner or managing agent of the building, plant, installation, vessel, facility, or activity alleged to be in violation. A copy of the notice shall be mailed to the Administrator of the Environmental Protection Agency, the Regional Administrator of the Environmental Protection Agency for the region in which such violation is alleged to have occurred, and the chief administrative officer of the water pollution control agency for the State in which the violation is alleged to have occurred. If the alleged violator is a corporation, a copy of such notice also shall be mailed to the registered agent, if any, of such corporation in the State in which such violation is alleged to have occurred.

(2) If the alleged violator is a State or local agency, service of notice shall be accomplished by certified mail addressed to, or by personal service upon, the head of such agency. A copy of such notice shall be mailed to the chief administrative officer of the water pollution control agency for the State in which the violation is alleged to have occurred, the Administrator of the Environmental Protection Agency, and the Regional Administrator of the Environmental Protection Agency for the region in which such violation is alleged to have occurred.

(3) If the alleged violator is a Federal agency, service of notice shall be accomplished by certified mail addressed to, or by personal service upon, the head of such agency. A copy of such notice shall be mailed to the Administrator of the Environmental Protection Agency, the Regional Administrator of the Environmental Protection Agency for the region in which such violation is alleged to have occurred, the Attorney General of the United States, and the Chief administrative officer of the water pollution control agency for the State in which the violation is alleged to have occurred.

(b) Service of notice of intent to file suit pursuant to section 505(a)(2) of the Act shall be accomplished by certified mail addressed to, or by personal service upon, the Administrator, Environmental Protection Agency, Washington, DC 20460. A copy of such notice shall be mailed to the Attorney General of the United States.

(c) Notice given in accordance with the provisions of this subpart shall be deemed to have been served on the postmark date if mailed, or on the date of receipt if served personally.