In Southern California Alliance of Publicly Owned
Treatment Works v. U.S. Environmental Protection Agency, ---
F.4th ---, No. 19-15535, 2021 WL 3412744 (9th Cir. Aug. 5, 2021),
the Ninth Circuit held that the Environmental Protection
Agency's (EPA) nonbinding guidance recommending a new
statistical method for assessing water toxicity under the Clean
Water Act (CWA) was not a reviewable final action under the
Administrative Procedures Act (APA). Instead, challenges to the
guidance must be made in the context of individual permit
decisions.
Under EPA's National Pollutant Discharge Elimination System
(NPDES) program, the CWA permitting scheme, some permit holders
must pass a whole effluent toxicity (WET) test which measures the
"aggregate effect of a discharge on aquatic
organisms." Id. EPA previously recommended
several statistical methods to satisfy the WET test requirements
and in June 2010, recommended an additional method called the Test
of Significant Toxicity
