ELR Citation: 45 ELR 20076
No(s). 13-31214 (5th Cir. Apr 7, 2015)

The Fifth Circuit reversed and remanded a lower court decision ordering EPA to determine whether new water quality standards were necessary to control nitrogen and phosphorus pollution in the mainstem of the Mississippi River and the Northern Gulf of Mexico. The case arose after EPA denied environmental groups' petition to make such a necessity determination under CWA §303(c)(4). Relying on the U.S. Supreme Court's decision in Massachusetts v. EPA, 549 U.S. 497, 37 ELR 20075 (2007), in which the Court held that EPA has the statutory authority to regulate greenhouse gases under the CAA, the groups argued that EPA has a clear statutory obligation to determine one way or the other whether numeric nutrient criteria are necessary to meet the requirements of the CWA. The lower court agreed, but the Fifth Circuit reversed. In Massachusetts v. EPA, the Supreme Court stated that EPA could avoid making a threshold determination "if it provides some reasonable explanation as to why it cannot or will not exercise its discretion to determine whether they do." While the language of the CWA and that of the CAA is not identical, the structure is similar. The court therefore held that the Massachusetts v. EPA "reasonable explanation" rule applies to CWA §303(c)(4)(B). Accordingly, EPA may decline to make a necessity determination if it provides an adequate explanation, grounded in the statute, for why it has elected not to do so. On remand, therefore, the lower court must determine whether EPA's explanation for why it declined to make a necessity determination was legally sufficient.