Any person who the Secretary determines, after notice and opportunity for a hearing on the record in accordance with sections 554 and 556 of title 5, is violating or has violated any provision of this chapter or any regulation of the Secretary issued hereunder, other than a violation for which a criminal penalty has been imposed under this chapter, may be assessed a civil penalty by the Secretary of not more than $10,000 for each such violation. Each offense shall be a separate violation. The amount of such civil penalty shall be assessed by the Secretary by written order, taking into account the gravity of the violation, degree of culpability, and history of prior offenses; and may be reviewed only as provided in subsection (b) of this section.