45 C.F.R. § 702.17
During any proceeding held outside Washington, DC, communications to the Commission with respect to such proceeding must be made to the Chairperson or authorized Commission staff personnel in attendance. All requests for subpoenas returnable at a hearing, requests for appearance of witnesses at a hearing, and statements or other documents for inclusion in the record of a proceeding, required to be submitted in advance, must be submitted to the Chairperson, or such authorized person as the Chairperson may appoint, at an office located in the community where such hearing or proceeding is scheduled to be held. The location of such office will be set forth in all subpoenas issued under the rules in this part and in all notices prepared pursuant to § 706.2.
45 C.F.R. §702.17