45 C.F.R. § 99.23
The Department, the Lead Agency, and any individuals or groups recognized as parties shall have the right to conduct discovery (including depositions) against opposing parties. Rules 26-37 of the Federal Rules of Civil Procedure shall apply to such proceedings; there will be no fixed rule on priority of discovery. Upon written motion, the presiding officer shall promptly rule upon any objection to such discovery action initiated pursuant to this section. The presiding officer shall also have the power to grant a protective order or relief to any party against whom discovery is sought and to restrict or control discovery so as to prevent undue delay in the conduct of the hearing. Upon the failure of any party to make discovery, the presiding officer may, at the presiding officer's discretion, issue any order and impose any sanction (other than contempt orders) authorized by rule 37 of the Federal Rules of Civil Procedure.
45 C.F.R. § 99.23