Genuine Parts Co. v. EPA, Nos. 16-1416, 16-1418 (D.C. Cir. May 18, 2018).
The U.S. Circuit Court of Appeals for the D.C. Circuit rejected an EPA listing of a potential Superfund site on the National Priorities List (NPL) as arbitrary and capricious. Two potentially responsible parties, the owner of a former auto parts remanufacturing, degreasing, and industrial waste property, and the owner of a shopping center where dry cleaning solvents were discharged into a leaky sewer line, challenged EPA’s final agency action in placing the affected site on the NPL due to putative drinking water contamination. In assessing the site’s upper and lower aquifers, EPA determined that the aquifers were interconnected and treated them as a single hydraulic unit when applying the Hazard Ranking System (HRS) for possible NPL listing of the site. If EPA treated the aquifers as separate unconnected water bearing zones, then the final HRS score would not have qualified the site for NPL listing. EPA’s own studies, however, demonstrated that the aquifers were separated by a “confining layer” of materials with lower hydraulic conductivity that water cannot easily move through. Upon review, the D.C. Circuit vacated the NPL listing and held that EPA ignored substantial evidence and acted arbitrarily and capriciously in relying on portions of studies that supported its position regarding the interconnectivity of the aquifers, while ignoring cross sections in those studies that did not. The court also noted that while EPA’s listing decisions are highly technical and entitled to “significant deference,” conclusory explanations where there is considerable evidence in conflict do not suffice to meet the deferential standard of review.