50 C.F.R. § 11.15
Except where a right to request a hearing is deemed to have been waived as provided in §11.11, the respondent may, within 45 calendar days from the date of the notice of assessment referred to in §11.14, file a dated, written request for a hearing with the Hearings Division, Office of Hearings and Appeals, U.S. Department of the Interior, 801 North Quincy Street, Arlington, Virginia 22203. The request should state the respondent's preference as to the place and date for a hearing. The request must enclose a copy of the notice of violation and notice of assessment. A copy of the request shall be served upon the Director personally or by registered or certified mail, return receipt requested, at the address specified in the notice.
50 C.F.R. § 11.15