Criminal enforcement of environmental laws is a rarity, despite relatively light evidentiary intent standards. Blatant and unquestionably deliberate violations—the "secret pipe" type—are usually the only ones we see publicized, and it is usually the low-end perpetrator who is prosecuted while the company may pay a substantial fine.
The fear of jail time, and the taint of "Lom Poc" on a resume is a much more substantial deterrent for higher-ups, but it is often viewed as so unlikely that it is not a factor taken into account. I say this, having been on both sides of these inquiries.
In 2015, the U.S. Department of Justice took a harder line on individual criminal prosecutions and on its willingness to go easy on corporations in exchange for cooperation. That was documented in the "Yates Memo" issued on September 29, 2015 (which we analyzed at the time). Under the following administration, the Yates Memo was rescinded—but it has now been revived (as DWT touched on here).
As we noted at the time of the original memo, how it will be implemented remains to be seen, but it presents the possibility of much stronger enforcement, requiring companies to make some difficult decisions as they deal with internal environmental compliance issues. Enforcement policy has always favored early self-disclosure, but a requirement that the company identify all individuals involved in the misconduct can put a lot of folks at risk.