The petitions seek review of certain effluent limitations imposed by EPA in a National Pollutant Discharge Elimination System (NPDES) permit on the discharges of Upper Blackstone Water Pollution Abatement District, a sewage treatment plant located in central Massachusetts. The District's discharges are into the headwaters of a polluted river which, in due course, flows into other rivers, and ultimately empties into Narragansett Bay.
The Appeals Court indicates that the states of Massachusetts and Rhode Island each have strong interests in the health of these waters and generally have supported the EPA's decisions during the permitting process. The District, supported by its member towns, has an interest in avoiding compliance costs associated with the permit and has challenged the effluent limitations as premature and unsupported by the scientific record.
The District first attacks a scientific model the EPA incorporated into its analysis of the nitrogen-fueled cultural eutrophication in Narragansett Bay. The District argues that this model, which was created by the University of Rhode Island's Marine Ecosystems Research Laboratory (MERL) in the 1980s to simulate water quality conditions in the Bay, is so unreliable and unrepresentative of actual Bay conditions as to entirely undermine the EPA's nitrogen analysis. The MERL model was peer-reviewed and published in a scientific journal.
In response, the Appeals Court said, "Where the agency follows the proper procedures and acts with a reasonable basis, both its choice of scientific data and interpretation and application of that data to real world conditions are entitled to deference. . . Where the EPA did rely on the MERL model, the record reflects that it fully accounted for the model's shortcomings. . . The District's argument that the MERL model should have been excluded from consideration entirely is without merit. . . The EPA also followed the proper procedures for ensuring that the model received scrutiny not only from the permittee, but from the scientific community and the public. . . The EPA's determination, based on its analysis of the evidence before it as a whole, that a nitrogen limit of 5.0 mg/L was necessary to achieve Rhode Island's water quality standards was not a 'hunch or wild guess' but a rational exercise of judgment."
The District also challenged whether the nitrogen limit was "necessary" or "sufficient." The Appeals Court said, "We reject the first claim, since the EPA expressly found that the 5.0 mg/L limit was necessary to meet state standards, and that a higher limit would not achieve those standards." On the sufficient argument, the Appeals Court said, ". . .where a complex administrative statute, like those the EPA is charged with administering, requires an agency to set a numerical standard, courts will not overturn the agency's choice of a precise figure where it falls within a 'zone of reasonableness' . . . The nitrogen limit the EPA chose here is justified by the record and within the zone of reasonableness. The District's challenges to the limit fail." Other challenges are also dismissed.