36 C.F.R. § 1120.36
(b) Any appeal must be mailed or filed in person at the address shown in § 1120.23—
(2) In the case of a partial denial, generally not later than 30 calendar days after the requestor receives all records being made available pursuant to the initial determination.
An appeal which does not meet the requirements of this paragraph may be treated either as a timely appeal or as a new request, at the option of the Freedom of Information Officer.
(c) The appeal letter must contain—