Clarke

Appellants, environmental groups and paper and pulp mills, challenge on opposing grounds the district court’s grant of summary judgment in favor of the Environmental Protection Agency (“EPA”) on appellants’ claims that the EPA violated the Clean Water Act (“Act”), 33 U.S.C. § 1251 , et seq., by establishing total maximum daily load limits for the discharge of the toxic pollutant dioxin into the Columbia River. We affirm.

FACTS AND PRIOR PROCEEDINGS

In the late 1980’s, a series of EPA-sponsored and independent biological studies revealed that high levels of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (“TCDD” or for the purposes of this appeal simply “dioxin” 1 ) were accumulating in the tissue of fish located downstream from pulp and paper mills in the Columbia River Basin. These studies also confirmed that the mills themselves were a significant source of dioxin contamination as a result of their use of chlorine-based chemicals to bleach wood and other raw materials used in the paper production cycle.

Oregon, Washington, and Idaho had already adopted applicable water quality standards under state law for waters in the Columbia Basin including the Columbia, Snake, and Willamette…