Plaintiffs Friends of the Earth, Inc. (FOE), Citizens Local Environmental Action Network, Inc. (CLEAN), and Sierra Club appeal an order of the district court penalizing Laidlaw Environmental Services (TOC), Inc. (Laidlaw) for violations of a National Pollutant Discharge Elimination System (NPDES) permit, arguing that the district court abused its discretion by imposing what Plaintiffs assert was an inadequate penalty. Laidlaw cross appeals, claiming, inter alia, that Plaintiffs lacked standing to institute this action because they suffered no injury in fact and that this suit should have been barred because the South Carolina Department of Health and Environmental Control (DHEC) diligently prosecuted a prior action regarding the same violations, see 33 U.S.C.A. § 1365(b)(1)(B) (West 1986). We conclude that this action is now moot; accordingly, we vacate the order of the district court and remand with instructions to dismiss.

Plaintiffs brought this enforcement action against Laidlaw1 pursuant to the citizen-suit provision of the Federal Water Pollution Control Act, see 33 U.S.C.A. § 1365(a)(1) (West 1986 & Supp.1998), alleging ongoing violations by Laidlaw of an NPDES permit and seeking imposition of monetary penalties as well as declaratory and injunctive relief and attorneys' fees and costs. After a seven-day hearing, the district court ruled that the prior suit by DHEC that Laidlaw alleged barred the current action had not been "diligently prosecuted" within the meaning of § 1365(b)(1)(B)2 and therefore would not serve to bar the present suit. See Friends of the Earth, Inc. v. Laidlaw Envtl. Servs. (TOC), Inc., 890 F. Supp. 470, 498 (D.S.C.1995). Following a bench trial, the district court found that Laidlaw had committed numerous permit violations and imposed a penalty of $405,800. See Friends of the Earth, Inc. v. Laidlaw Envtl. Servs. (TOC), Inc., 956 F. Supp. 588, 600-01, 610 (D.S.C.1997). However, because the court found that Laidlaw's violations had not harmed the environment and that Laidlaw had been in substantial compliance for several years at the time of the issuance of its final order, the court denied Plaintiffs' request for declaratory and injunctive relief. See id. at 611. In a separate order, the court stayed the time for a petition for attorney's fees until the time for appeal had expired or, if either party appealed, until the appeal was resolved. This appeal followed.II.

The Constitution provides that "[t]he judicial Power" of the federal courts of the United States extends only to specified "Cases" and "Controversies." U.S. Const. art. III, § 2, cl. 1; see In re Pruett, 133 F.3d 275, 278 (4th Cir.1997). "The doctrine of standing has always been an essential component of [the] case or controversy requirement of federal jurisdiction." Marshall v. Meadows, 105 F.3d 904, 906 (4th Cir.1997). In order to have standing, a plaintiff must have suffered an actual or threatened injury in fact; the injury must have been caused by the defendant's complained-of conduct; and the injury must be redressable by the relief sought. See Steel Co. v. Citizens for a Better Env't, --- U.S. ----, ---- - ----, 118 S. Ct. 1003, 1016-17, 140 L. Ed. 2d 210 (1998). Moreover, these elements must continue to exist at every stage of review, not merely at the time of the filing of the complaint. See Arizonans for Official English v. Arizona, 520 U.S. 43, 117 S. Ct. 1055, 1068, 137 L. Ed. 2d 170 (1997); Suarez Corp. Indus. v. McGraw, 125 F.3d 222, 228 (4th Cir.1997). Otherwise, the action becomes moot. See United States Parole Com'n v. Geraghty, 445 U.S. 388, 397, 100 S. Ct. 1202, 63 L. Ed. 2d 479 (1980) (explaining that mootness has been described as "the doctrine of standing set in a time frame: The requisite personal interest that must exist at the commencement of the litigation (standing) must continue throughout its existence (mootness)" (internal quotation marks omitted)). The continued presence of these elements ensures that the plaintiff has "such a personal stake in the outcome of the controversy as to assure that concrete adverseness which sharpens the presentation of issues." Baker v. Carr, 369 U.S. 186, 204, 82 S. Ct. 691, 7 L. Ed. 2d 663 (1962).

Here, we focus on the continued existence of the third element, redressability.3 Because Plaintiffs have not appealed the denial of declaratory and injunctive relief, the only potential relief that may be available to redress their claimed injuries is the civil penalty imposed upon Laidlaw, which would be paid to the United States Treasury. See Atlantic States Legal Found., Inc. v. Tyson Foods, Inc., 897 F.2d 1128, 1131 n. 5 (11th Cir.1990). Such penalties, however, cannot redress any injury suffered by a citizen plaintiff. See Steel Co., --- U.S. at ---- - ----, 118 S. Ct. at 1018-19.

In Steel Co., the Supreme Court held that a plaintiff lacked standing to prosecute a private enforcement action under the citizen-suit provision of the Emergency Planning and Community Right-To-Know Act of 1986, see 42 U.S.C.A. § 11046(a)(1) (West 1995), because the relief requested could not redress the injury plaintiff had allegedly suffered. See Steel Co., --- U.S. at ---- - ----, 118 S. Ct. at 1017-20. In particular, the Court noted that any civil penalties imposed would be payable to the United States Treasury and not to the plaintiff and therefore that the penalties would not benefit the plaintiff. See id. at ---- - ----, 118 S. Ct. at 1018-19. The Court reasoned that

although a suitor may derive great comfort and joy from the fact that the United States Treasury is not cheated, that a wrongdoer gets his just deserts, or that the nation's laws are faithfully enforced, that psychic satisfaction is not an acceptable Article III remedy because it does not redress a cognizable Article III injury.

Id. at ----, 118 S.Ct. at 1019.4 Applying the reasoning of Steel Co., we conclude that this action is moot because the only remedy currently available to Plaintiffs--civil penalties payable to the government--would not redress any injury Plaintiffs have suffered. We therefore vacate the order of the district court and remand with instructions to dismiss this action.5 See Arizonans for Official English, 117 S. Ct. at 1071.

VACATED AND REMANDED.