Burlington Northern squarely decided that where environmental harm is divisible, an individual PRP can obtain apportionment of its liability and be assigned a specific percentage share; in such instances, there will be no joint and several liability. The possibility follows from Burlington Northern that a PRP which can establish divisibility of harm might be able to show that its percentage share of liability is so small that it effectively has a complete defense to liability.

That precise issue came up in the most recent decision in the Lower Fox River Superfund matter. There, several PRPs had disposed of PCBs upgradient of an operable unit in the Lower Fox River. These PRPs argued that they could not be held liable on summary judgment because the PCBs they had discharged did not reach the operable unit in sufficient quantities to require any response action. The court rejected this argument on the ground that there was no “de minimis defense” in CERCLA and liability had been established once these PRPs acknowledged that they had discharged PCBs which had migrated in any amount to the operable unit.

In granting the government’s summary judgment motion, the low volume PRPs were deemed to be jointly and severally liable for the operable unit even though virtually all of the PCBs had come from other parties. While the practical consequence of this decision may be ameliorated if these low volume PRPs end up being assigned small contribution shares, the decision seems dubious, particularly on summary judgment. Contrary to the court’s assertion that CERCLA does not afford a de minimis defense, Burlington Northern indicates that there would be a de minimis defense if a PRP can show that the harm can be apportioned with a liability share at or near zero. At a minimium, it is a factual issue whether the harm can be apportioned, which should be sufficient to defeat summary judgment.