A recent decision from the U.S. Court of Appeals for the D.C. Circuit rejected a challenge to U.S. EPA's decision to list a site on the National Priorities List ("NPL"), finding that although the petitioner had standing to challenge the NPL listing, it impermissibly sought to rely on information that was not contained in the administrative record and failed to demonstrate that U.S. EPA's decision to list the site was arbitrary and capricious. In CTS Corp. v. EPA, the petitioner, CTS Corporation, challenged U.S. EPA's decision to list a former manufacturing facility on the NPL. The site in question (which was the subject of an recent Supreme Court decision finding that CERCLA's Section 9658 did not preempt a state statute of repose (see CTS Corp. v. Waldburger)) was added to the NPL at least in part on the basis of groundwater contamination that had allegedly migrated from the site into an adjacent residential neighborhood. U.S. EPA conceded that but for the residential groundwater contamination, the site's Hazard Ranking System score would not have exceeded the 28.5 threshold required to list a site on the NPL. 

As part of its challenge to U.S. EPA's listing decision, CTS argued that U.S. EPA had failed to adequately investigate possible alternative sources of the residential groundwater contamination. The court rejected that argument, noting that the handful of challenges that CTS did timely raise concerning alternative sources amounted to "little more than methodological nit-picking". The court was more critical, however, of CTS's effort to present new evidence in the form of an expert report that purported to critique a prior U.S. EPA isotope analysis of the groundwater samples that were taken from the residential wells. The court rejected what the court characterized as CTS's attempt to "bypass the administrative record" noting that it was "black-letter administrative law that in an [APA] case, a reviewing court should have before it neither more nor less information than did the agency when it made its decision".  The court therefore denied CTS' petition challenge to the NPL listing.