Any person who violates any provision of this chapter or any regulation or permit issued hereunder may be assessed a civil penalty by the Secretary of not more than $10,000 for each such violation. No penalty shall be assessed unless such person is given notice and opportunity for a hearing with respect to such violation. Hearings held during proceedings for the assessment of civil penalties authorized by this subsection shall be conducted in accordance with section 554 of title 5. The Secretary may issue subpoenas for the attendance and testimony of witnesses and the production of relevant papers, books, and documents, and administer oaths. Witnesses summoned shall be paid the same fees and mileage that are paid to witnesses in the courts of the United States. In case of contumacy or refusal to obey a subpoena served upon any person pursuant to this paragraph, the district court of the United States for any district in which such person is found or resides or transacts business, upon application by the United States and after notice to such person, shall have jurisdiction to issue an order requiring such person to appear and give testimony before the Secretary or to appear and produce documents before the Secretary, or both, and any failure to obey such order of the court may be punished by such court as a contempt thereof. Any civil penalty assessed may be remitted or mitigated by the Secretary for good cause shown. Upon any failure to pay a penalty assessed under this subsection, the Secretary may request the Attorney General to institute civil action in a district court of the United States for any district in which such person is found, resides, or transacts business to collect the penalty, and such court shall have jurisdiction to hear and decide any such action.