OCTOBER TERM, 2008
NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
being done in connection with this case, at the time the opinion is issued.
The syllabus constitutes no part of the opinion of the Court but has been
prepared by the Reporter of Decisions for the convenience of the reader.
See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.
SUPREME COURT OF THE UNITED STATES
ENTERGY CORP. v. RIVERKEEPER, INC., ET AL.
CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR
THE SECOND CIRCUIT
No. 07–588. Argued December 2, 2008—Decided April 1, 2009*
Petitioners’ powerplants have “cooling water intake structures” that
threaten the environment by squashing against intake screens (“im-
pingement”) or suctioning into the cooling system (“entrainment”)
aquatic organisms from the water sources tapped to cool the plants.
Thus, the facilities are subject to regulation under the Clean Water
Act, which mandates that “[a]ny standard established pursuant to
section 1311 . . . or section 1316 . . . and applicable to a point source
shall require that the location, design, construction, and capacity of
cooling water intake structures reflect the best technology available
for minimizing adverse environmental impact.” 33 U. S. C. §1326(b).
Sections 1311 and 1316, in turn, employ a variety of “best technology”
standards to regulate effluent discharge into the Nation’s waters.
The Environmental Protection Agency (EPA) promulgated the
§1326(b) regulations at issue after nearly three decades of making
the “best technology available” determination on a case-by-case basis.
Its “Phase I” regulations govern new cooling water intake structures,
while the “Phase II” rules at issue apply to certain large existing fa-
cilities. In the latter rules, the EPA set “national performance stan-
dards,” requiring most Phase II facilities to reduce “impingement
mortality for [aquatic organisms] by 80 to 95 percent from the calcu-
lation baseline,” and requiring