Any operator who willfully violates a mandatory health or safety standard, or knowingly violates or fails or refuses to comply with any order issued under section
814 of this title and section
817 of this title, or any order incorporated in a final decision issued under this subchapter, except an order incorporated in a decision under subsection (a)(1) or section
815
(c) of this title, shall, upon conviction, be punished by a fine of not more than $250,000, or by imprisonment for not more than one year, or by both, except that if the conviction is for a violation committed after the first conviction of such operator under this chapter, punishment shall be by a fine of not more than $500,000, or by imprisonment for not more than five years, or both.