Document ID: ./input/supremecourt_opinions/opinions/08pdf/07-588.pdf/07-588.pdf
Page Number: 1

(Slip Opinion) 

OCTOBER  TERM,  2008 

1 

Syllabus 

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 

Syllabus 

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  a  subset  of  facilities  to  reduce  en-
trainment  of  such  organisms  by  “60  to  90  percent  from  [that]  base-
line.”  40  CFR  §125.94(b)(1),  (2).    However,  the  EPA  expressly
declined  to  mandate  closed-cycle  cooling  systems,  or  equivalent  re-

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* Together  with  No.  07–589,  PSEG  Fossil  LLC  et al.  v.  Riverkeeper, 
Inc., et al., and No. 07–597, Utility Water Act Group v. Riverkeeper, Inc., 
et al., also on certiorari to the same court.