The D.C. Circuit Court of Appeals has denied an owner’s challenge to EPA’s listing of a Toolele County, Utah, magnesium plant on CERCLA’s National Priorities List (NPL). U.S. Magnesium, LLC v. EPA, No. 09-1269 (D.C. Cir. 1/14/11). EPA completed a Hazardous Ranking System (HRS) evaluation of the plant in 2008 and calculated an HRS score of 59.18, based on air migration and soil exposure at the site. Because the score was above the threshold for inclusion on the NPL, EPA published a proposed rule proposing to list the site on the NPL. After receiving and responding to comments, the agency added the site to the NPL. 73 Fed. Reg. 51,393 (9/3/08).

U.S. Magnesium, now the site’s owner, challenged the NPL listing as “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with the law” in violation of the Administrative Procedure Act. The company claimed that EPA made four errors in calculating the HRS score and that, if the errors were corrected, the HRS score would fall below the NPL’s 28.5 threshold for listing. The court rejected the company’s argument, ruling that the process EPA used to calculate the site’s score was exactly as set forth in the HRS and the agency’s HRS Guidance Manual. After discussing in detail each of the agency’s calculations, the court denied the petition for review.