The U.S. Court of Appeals used the recent case of PCS Nitrogen Inc. v. Ashley II of Charleston LLC to decide when it is appropriate to rule in favor of apportionment under CERCLA.  In this case, 43 acres of land in Charleston, South Carolina were contaminated with various hazardous substances that forced Ashley II to spend almost $200,000 in remediation.  Ashley II sued PCS Nitrogen Inc. for the money it had to spend cleaning the area because PCS Nitrogen was a successor to the former owner of the contaminated land.  The district court ruled that PCS was accountable for response costs at the contaminated sites and Ashley II and other parties were responsible for an allocated part of the response costs.  This ruling was confirmed by the U.S. Court of Appeals for the Fourth Circuit who said that a reasonable basis for apportioning liability could not be reached by the parties and therefore apportionment would be inappropriate. 

In 2009 the Supreme Court oversaw the case of Burlington Northern & Santa Fe Ry. v. United States, which also dealt with apportionment.  In this case, the Supreme Court decided that “apportionment is available as an alternative to joint and several liability only when a PRP proves that ‘there is a reasonable basis for determining the contribution of each cause to a single harm.’”  Ashley II said that this decision was not ignored by the lower courts because PCS did not provide evidence to reliably inform the courts’ apportionment analysis.  The Burlington Northern case created a standard for determining if apportionment of liability under CERCLA is appropriate, and the standard must also be applied to the specifics of each case.  In the case of PCS Nitrogen, in order for there to be a reasonable basis for apportionment, two factors must be met, an ability to determined: (1) the amount of contamination contributed by each party, and (2) the amount of secondary disposal by each party.  There was significant secondary disposal at the contaminated site in Charleston, which is what differentiated this case from Burlington Northern.