In Re: Methyl Tertiary Butyl Ether ("MTBE") Products Liability Litigation, 1:00-cv-01898

The Commonwealth of Pennsylvania sues dozens of gasoline manufacturers and distributors for groundwater contamination caused by methyl tertiary butyl ether (MTBE) in gasoline.
MTBE was added to gasoline for emission control but is highly soluble, migrates easily in water, and is difficult to remove from groundwater.
Pennsylvania agencies knew of MTBE risks since the mid-1980s, implemented testing and standards in the 1990s, but did not ban MTBE despite awareness of contamination and proposed legislation.
Remediation at specific sites followed a process where responsible parties sought DEP approval via Remedial Action Completion Reports (RACR), which did not provide blanket releases of liability.
The Commonwealth moved for partial summary judgment seeking to strike several affirmative defenses (estoppel, waiver, assumption of risk, comparative negligence, unclean hands), with only estoppel and assumption of risk contested by defendants for certain sites.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Estoppel	Approval letters do not create liability shield for future claims.	DEP's RACR letters induced reliance, so PA is estopped.	No promise was made; estoppel does not bar Commonwealth’s claims.
Assumption of Risk	Doctrine is inapplicable or inoperable based on Commonwealth’s actions.	Commonwealth assumed risk by regulation and failure to ban MTBE.	No evidence PA deliberately accepted risk; defense denied.

Kreutzer v. Monterey Cnty. Herald Co., 747 A.2d 358 (Pa. 2000) (equitable estoppel elements under Pennsylvania law)
Wayne Moving & Storage of N.J., Inc. v. Sch. Dist. of Phila., 625 F.3d 148 (3d Cir. 2010) (elements for equitable estoppel against the government)
Howell v. Clyde, 620 A.2d 1107 (Pa. 1993) (assumption of risk doctrine in Pennsylvania negligence cases)
Reott v. Asia Trend, Inc., 55 A.3d 1088 (Pa. 2012) (ongoing uncertainty about assumption of risk in Pennsylvania negligence law)