The Commonwealth of Pennsylvania v. Exxon Mobil Corporation

Background

This case is part of consolidated multidistrict litigation concerning groundwater contamination caused by releases of gasoline containing methyl tertiary butyl ether (MTBE). Pennsylvania alleged that the defendants—including gasoline manufacturers, distributors, and sellers—were liable for actual or threatened MTBE contamination in Pennsylvania’s drinking water.

Pennsylvania moved for partial summary judgment under Federal Rule of Civil Procedure 56 on the defendants’ affirmative defenses of estoppel, waiver, assumption of risk, comparative negligence, and unclean hands. The motion concerned 70 Focus Sites. The defendants did not oppose summary judgment on the waiver, comparative-negligence, and unclean-hands defenses, but continued to oppose the motion as to estoppel and assumption of risk.

Estoppel

The defendants argued that Pennsylvania should be prevented from seeking future costs or injunctive relief for 22 sites where the Pennsylvania Department of Environmental Protection approved remedial-action completion reports. They asserted that the department’s approval letters induced them to remove equipment and abandon groundwater-monitoring wells with the understanding that they would not have to redo or continue the work.

Applying Pennsylvania law, the court explained that equitable estoppel generally requires misleading words, conduct, or silence; reasonable reliance; and no duty to inquire. A party asserting estoppel against the government must provide clear, precise, and unequivocal evidence that the government intentionally or negligently misrepresented a material fact, knew or should have known the other party would rely on it, and induced detrimental reliance.

The court held that the defendants had not made that showing. The approval letters did not promise that Pennsylvania would never bring claims or that the defendants would never have to perform or pay for additional remedial work. The letters varied in their wording, and some expressly preserved liability or enforcement rights. The court also found no evidence that Pennsylvania knew or should have known that the letters would mislead the defendants. Because no reasonable jury could find unequivocal evidence of the alleged promise, the estoppel defense could not defeat summary judgment.

Assumption of Risk

The court declined to decide whether Pennsylvania law has completely eliminated assumption of risk in negligence cases. It explained that Pennsylvania decisions leave the doctrine’s continuing availability uncertain, although the defense remains available at least in limited circumstances. The court described the relevant version of the defense as applying when a plaintiff knows and appreciates a specific risk and voluntarily encounters it, or when the plaintiff deliberately engages in conduct despite awareness of the specific risks involved.

The defendants argued that Pennsylvania assumed the risks of MTBE contamination by failing to ban MTBE, not fully implementing an MTBE action plan, adopting regulations governing corrective action, and overseeing cleanup at particular release sites. The court rejected those arguments at the summary-judgment stage. It held that, even accepting the defendants’ factual account and viewing it favorably to them, those circumstances did not show that Pennsylvania voluntarily proceeded to face the risks at issue. A government’s failure to prohibit an activity, creation or noncreation of a cleanup process, or regulation that provides protection under certain laws does not by itself create a defense to liability under all other laws.

Disposition

The court granted Pennsylvania’s February 25, 2025 motion for partial summary judgment as to the defendants’ affirmative defenses. The opinion’s conclusion states that the motion was granted; it does not separately state a different disposition for each defense. The ruling resolved the defenses addressed in this motion, not the underlying MTBE liability claims.