(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 

COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

CONSERVATION COUNCIL ET AL. 

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR 

THE NINTH CIRCUIT 

No. 07–984. Argued January 12, 2009—Decided June 22, 2009* 

In reviving a closed Alaska gold mine using a “froth flotation” technique, petitioner Coeur Alaska, Inc., plans to dispose of the resulting 

waste material, a rock and water mixture called “slurry,” by pumping

it into a nearby lake and then discharging purified lake water into a 

downstream creek. The Clean Water Act (CWA), inter alia, classifies 

crushed rock as a “pollutant,” §352(6); forbids its discharge “[e]xcept

as in compliance” with the Act, §301(a); empowers the Army Corps of 

Engineers (Corps) to “issue permits . . . for the discharge of . . . fill 

material,” §404(a); and authorizes the Environmental Protection 

Agency (EPA) to “issue a permit for the discharge of any pollutant,” 

“[e]xcept as provided in [§404],” §402(a). The Corps and the EPA together define “fill material” as any “material [that] has the effect of 

. . . [c]hanging the bottom elevation” of water, including “slurry . . . or

similar mining-related materials.” 40 CFR §232.2. Coeur Alaska obtained a §404 permit for the slurry discharge from the Corps and a 

§402 permit for the lake water discharge from the EPA. 

 Respondent environmental groups (collectively, SEACC) sued the 

Corps and several of its officials under the Administrative Procedure 

Act, arguing that the CWA §404 permit was not “in accordance with

law,” 5 U. S. C. §706(2)(A), because (1) Coeur Alaska should have

sought a CWA §402 permit from the EPA instead, just as it did for

the lake water discharge; and (2) the slurry discharge would violate

the “new source performance standard” the EPA had promulgated

under CWA §306(b), forbidding froth-flotation gold mines to dis-

—————— 

*Together with No. 07–990, Alaska v. Southeast Alaska Conservation 

Council et al., also on certiorari to the same court. 
2 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Syllabus 

charge “process wastewater,” which includes solid wastes, 40 CFR

§440.104(b)(1). Coeur Alaska and petitioner Alaska intervened as defendants. The District Court granted the defendants summary

judgment, but the Ninth Circuit reversed, holding that the proposed 

slurry discharge would violate the EPA’s performance standard and

§306(e). 

Held: 

1. The Corps, not the EPA, has authority to permit the slurry discharge. Pp. 9–13.

(a) By specifying that, “[e]xcept as provided in . . . [§404,]” the

EPA “may . . . issue permit[s] for the discharge of any pollutant,”

§402(a) forbids the EPA to issue permits for fill materials falling under the Corps’ §404 authority. Even if there were ambiguity on this

point, it would be resolved by the EPA’s own regulation providing 

that “[d]ischarges of . . . fill material . . . which are regulated under 

section 404” “do not require [EPA §402] permits.” 40 CFR §122.3. 

The agencies have interpreted this regulation to essentially restate

§402’s text, ibid., and the EPA has confirmed that reading before this 

Court. Because it is not “plainly erroneous or inconsistent with the 

regulation,” the Court accepts the EPA’s interpretation as correct. 

Auer v. Robbins, 519 U. S. 452, 461. Thus, the question whether the 

EPA is the proper agency to regulate the slurry discharge depends on

whether the Corps has authority to do so. If so, the EPA may not

regulate. Pp. 9–11. 

(b) Because §404(a) empowers the Corps to “issue permits . . . for 

the discharge of . . . fill material,” and the agencies’ joint regulation 

defines “fill material” to include “slurry . . . or similar mining-related

materials” having the “effect of . . . [c]hanging the bottom elevation”

of water, 40 CFR §232.2, the slurry Coeur Alaska wishes to discharge

into the lake falls well within the Corps’ §404 permitting authority,

rather than the EPA’s §402 authority. The CWA gives no indication

that Congress intended to burden industry with the confusing division of permitting authority that SEACC’s contrary reading would 

create. Pp. 11–13.

2. The Corps acted in accordance with law in issuing the slurry discharge permit to Coeur Alaska. Pp. 13–28. 

(a) The CWA alone does not resolve these cases. Pp. 14–18.

(i) SEACC contends that because the EPA’s performance standard forbids even minute solid waste discharges, 40 CFR 

§440.104(b)(1), it also forbids Coeur Alaska’s slurry discharge, 30% of 

which is solid waste, into the lake. Thus, says SEACC, the slurry

discharge is “unlawful” under CWA §306(e), which prohibits “any 

owner . . . of any new source to operate such source in violation of any

standard of performance applicable to such source.” Pp. 14–16. 
Cite as: 557 U. S. ____ (2009) 3 

Syllabus 

(ii) Petitioners and the federal agencies counter that CWA 

§404 grants the Corps authority to determine whether to issue a 

permit allowing the slurry discharge without regard to the EPA’s 

new source performance standard or §306(e)’s prohibition. Pp. 16–18.

(iii) The CWA is ambiguous on the question whether §306 applies to discharges of fill material regulated under §404. On the one 

hand, §306 provides that a discharge that violates an EPA new 

source performance standard is “unlawful”—without an exception for 

fill material. On the other hand, §404 grants the Corps blanket authority to permit the discharge of fill material—without mentioning

§306. This tension indicates that Congress has not “directly spoken”

to the “precise question” at issue. Chevron U. S. A. Inc. v. Natural 

Resources Defense Council, Inc., 467 U. S. 837, 842. P. 18. 

(b) Although the agencies’ regulations construing the CWA are 

entitled to deference if they resolve the statutory ambiguity in a reasonable manner, see Chevron, supra, at 842, the regulations bearing

on §§306 and 404, like the CWA itself, do not do so. For example,

each of the two principal regulations seems to stand on its own without reference to the other. The EPA’s performance standard contains 

no exception for fill material, and it forbids any discharge of “process

wastewater,” including solid wastes. 40 CFR §440.104(b)(1). The 

agencies’ joint regulation defining fill material includes “slurry or . . . 

similar mining-related materials,” §232.2, but contains no exception

for slurry regulated by an EPA performance standard. Additional 

regulations noted by the parties offer no basis for reconciliation.

Pp. 18–20. 

(c) In light of the ambiguities in the CWA and the pertinent regulations, the Court turns to the agencies’ subsequent interpretation of

those regulations. Auer, supra, at 461. The question at issue is addressed and resolved in a reasonable and coherent way by the two 

agencies’ practice and policy, as recited in the EPA’s internal “Regas 

Memorandum” (Memorandum), which explains that the performance 

standard applies only to the discharge of water from the lake into the

downstream creek, and not to the initial discharge of slurry into the

lake. Though the Memorandum is not subject to sufficiently formal

procedures to merit full Chevron deference, the Court defers to it because it is not “plainly erroneous or inconsistent with the regulation[s],” Auer, supra, at 461. Five factors inform that conclusion: The 

Memorandum (1) confines its own scope to closed bodies of water like

the lake here, thereby preserving a role for the performance standards; (2) guards against the possibility of evasion of those standards;

(3) employs the Corps’ expertise in evaluating the effects of fill material on the aquatic environment; (4) does not allow toxic compounds 

to be discharged into navigable waters; and (5) reconciles §§306, 402, 
4 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Syllabus 

and 404, and the regulations implementing them, better than any of 

the parties’ alternatives. The Court agrees with the parties that a

two-permit regime is contrary to the statute and regulations. Pp. 20– 

23. 

(d) The Court rejects SEACC’s contention that the Regas Memorandum is not entitled to deference because it contradicts the agencies’ published statements and prior practice. Though SEACC cites 

three such statements, its arguments are not convincing. Pp. 23–28.

(i) Although a 1986 memorandum of agreement (MOA) between the EPA and the Corps seeking to reconcile their then-differing 

“fill material” definitions suggests, as SEACC asserts, that §402 will

“normally” apply to discharges of “suspended”—i.e., solid—pollutants,

that statement is not contrary to the Regas Memorandum, which acknowledges that the EPA retains authority under §402 to regulate 

the discharge of suspended solids from the lake into downstream waters. The MOA does not address the question presented by these

cases, and answered by the Regas Memorandum, and is, in fact, consistent with the agencies’ determination that the Corps regulates all

discharges of fill material and that §306 does not apply to these discharges. Pp. 23–25. 

(ii) Despite SEACC’s assertion that the fill regulation’s preamble demonstrates that the fill rule was not intended to displace the

pre-existing froth-flotation gold mine performance standard, the preamble is consistent with the Regas Memorandum when it explicitly

notes that the EPA has “never sought to regulate fill material under

effluent guidelines,” 67 Fed. Reg. 31135. If a discharge does not qualify as fill, the EPA’s new source performance standard applies. If the 

discharge qualifies as fill, the performance standard does not apply; 

and there was no earlier agency practice or policy to the contrary.

Pp. 25–26. 

(iii) Remarks made by the two agencies in promulgating the fill

regulation, which pledge that the EPA’s “previou[s] . . . determination[s]” with regard to the application of performance standards “remain vali[d],” are not conclusive of the question at issue. The Regas 

Memorandum has followed this policy by applying the performance

standard to the discharge of water from the lake into the creek. The 

remarks do not state that the EPA will apply such standards to discharges of fill material. Pp. 26–27. 

 (iv) While SEACC cites no instance in which the EPA has applied a performance standard to a discharge of fill material, Coeur 

Alaska cites two instances in which the Corps issued a §404 permit

authorizing a mine to discharge solid waste as fill material. These 

permits illustrate that the agencies did not have a prior practice of 

applying EPA performance standards to discharges of mining wastes 
Cite as: 557 U. S. ____ (2009) 5 

Syllabus 

that qualify as fill material. Pp. 27–28. 

486 F. 3d 638, reversed and remanded. 

KENNEDY, J., delivered the opinion of the Court, in which ROBERTS, 

C. J., and THOMAS, BREYER, and ALITO, JJ., joined, and in which SCALIA, 

J., joined in part. BREYER, J., filed a concurring opinion. SCALIA, J., 

filed an opinion concurring in part and concurring in the judgment.

GINSBURG, J., filed a dissenting opinion, in which STEVENS and SOUTER, 

JJ., joined. 
_________________ 

_________________ 

Cite as: 557 U. S. ____ (2009) 1 

Opinion of the Court 

NOTICE: This opinion is subject to formal revision before publication in the

preliminary print of the United States Reports. Readers are requested to

notify the Reporter of Decisions, Supreme Court of the United States, Washington, D. C. 20543, of any typographical or other formal errors, in order

that corrections may be made before the preliminary print goes to press. 

SUPREME COURT OF THE UNITED STATES 

Nos. 07–984 and 07–990 

COEUR ALASKA, INC., PETITIONER 

07–984 v. 

SOUTHEAST ALASKA CONSERVATION COUNCIL 

ET AL. 

ALASKA, PETITIONER 

07–990 v. 

SOUTHEAST ALASKA CONSERVATION COUNCIL 

ET AL. 

ON WRITS OF CERTIORARI TO THE UNITED STATES COURT OF 

APPEALS FOR THE NINTH CIRCUIT 

[June 22, 2009] 

JUSTICE KENNEDY delivered the opinion of the Court. 

These cases require us to address two questions under 

the Clean Water Act (CWA or Act). The first is whether 

the Act gives authority to the United States Army Corps of

Engineers, or instead to the Environmental Protection 

Agency (EPA), to issue a permit for the discharge of mining waste, called slurry. The Corps of Engineers has

issued a permit to petitioner Coeur Alaska, Inc. (Coeur 

Alaska), for a discharge of slurry into a lake in Southeast 

Alaska. The second question is whether, when the Corps 

issued that permit, the agency acted in accordance with

law. We conclude that the Corps was the appropriate 

agency to issue the permit and that the permit is lawful. 

With regard to the first question, §404(a) of the CWA 
2 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

grants the Corps the power to “issue permits . . . for the 

discharge of . . . fill material.” 86 Stat. 884; 33 U. S. C. 

§1344(a). But the EPA also has authority to issue permits 

for the discharge of pollutants. Section 402 of the Act 

grants the EPA authority to “issue a permit for the discharge of any pollutant” “[e]xcept as provided in” §404. 33

U. S. C. §1342(a). We conclude that because the slurry

Coeur Alaska wishes to discharge is defined by regulation

as “fill material,” 40 CFR §232.2 (2008), Coeur Alaska

properly obtained its permit from the Corps of Engineers,

under §404, rather than from the EPA, under §402. 

The second question is whether the Corps permit is

lawful. Three environmental groups, respondents here,

sued the Corps under the Administrative Procedure Act,

arguing that the issuance of the permit by the Corps was

“not in accordance with law.” 5 U. S. C. §706(2)(A). The 

environmental groups are Southeast Alaska Conservation

Council, Sierra Club, and Lynn Canal Conservation (collectively, SEACC). The State of Alaska and Coeur Alaska 

are petitioners here.

SEACC argues that the permit from the Corps is unlawful because the discharge of slurry would violate an EPA

regulation promulgated under §306(b) of the CWA, 33

U. S. C. §1316(b). The EPA regulation, which is called a 

“new source performance standard,” forbids mines like 

Coeur Alaska’s from discharging “process wastewater” into 

the navigable waters. 40 CFR §440.104(b)(1). Coeur 

Alaska, the State of Alaska, and the federal agencies 

maintain that the Corps permit is lawful nonetheless

because the EPA’s performance standard does not apply to 

discharges of fill material. 

Reversing the judgment of the District Court, the Court

of Appeals held that the EPA’s performance standard 

applies to this discharge so that the permit from the Corps 

is unlawful. 
Cite as: 557 U. S. ____ (2009) 3 

Opinion of the Court 

I 

A 

Petitioner Coeur Alaska plans to reopen the Kensington

Gold Mine, located some 45 miles north of Juneau, Alaska. 

The mine has been closed since 1928, but Coeur Alaska 

seeks to make it profitable once more by using a technique 

known as “froth flotation.” Coeur Alaska will churn the 

mine’s crushed rock in tanks of frothing water. Chemicals 

in the water will cause gold-bearing minerals to float to

the surface, where they will be skimmed off. 

At issue is Coeur Alaska’s plan to dispose of the mixture 

of crushed rock and water left behind in the tanks. This 

mixture is called slurry. Some 30 percent of the slurry’s 

volume is crushed rock, resembling wet sand, which is

called tailings. The rest is water. 

The standard way to dispose of slurry is to pump it into 

a tailings pond. The slurry separates in the pond. Solid 

tailings sink to the bottom, and water on the surface 

returns to the mine to be used again. 

Rather than build a tailings pond, Coeur Alaska proposes to use Lower Slate Lake, located some three miles

from the mine in the Tongass National Forest. This lake 

is small—800 feet at its widest crossing, 2,000 feet at its 

longest, and 23 acres in area. See App. 138a, 212a.

Though small, the lake is 51 feet deep at its maximum. 

The parties agree the lake is a navigable water of the

United States and so is subject to the CWA. They also

agree there can be no discharge into the lake except as the

CWA and any lawful permit allow.

Over the life of the mine, Coeur Alaska intends to put 

4.5 million tons of tailings in the lake. This will raise the 

lakebed 50 feet—to what is now the lake’s surface—and 

will increase the lake’s area from 23 to about 60 acres. Id., 

at 361a (62 acres), 212a (56 acres). To contain this wider, 

shallower body of water, Coeur Alaska will dam the lake’s

downstream shore. The transformed lake will be isolated 
4 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL 

Opinion of the Court 

from other surface water. Creeks and stormwater runoff 

will detour around it. Id., at 298a. Ultimately, lakewater 

will be cleaned by purification systems and will flow from 

the lake to a stream and thence onward. Id., at 309a– 

312a. 

B 

Numerous state and federal agencies reviewed and 

approved Coeur Alaska’s plans. At issue here are actions 

by two of those agencies: the Corps of Engineers and the

EPA. 

1 

The CWA classifies crushed rock as a “pollutant.” 33 

U. S. C. §1362(6). On the one hand, the Act forbids Coeur 

Alaska’s discharge of crushed rock “[e]xcept as in compliance” with the Act. CWA §301(a), 33 U. S. C. §1311(a). 

Section 404(a) of the CWA, on the other hand, empowers

the Corps to authorize the discharge of “dredged or fill 

material.” 33 U. S. C. §1344(a). The Corps and the EPA

have together defined “fill material” to mean any “material [that] has the effect of . . . [c]hanging the bottom elevation” of water. 40 CFR §232.2. The agencies have

further defined the “discharge of fill material” to include 

“placement of . . . slurry, or tailings or similar miningrelated materials.” Ibid. 

In these cases the Corps and the EPA agree that the 

slurry meets their regulatory definition of “fill material.”

On that premise the Corps evaluated the mine’s plan for a 

§404 permit. After considering the environmental factors

required by §404(b), the Corp issued Coeur Alaska a permit to pump the slurry into Lower Slate Lake. App. 340a–

378a. 

In granting the permit the Corps followed the steps set 

forth by §404. Section 404(b) requires the Corps to consider the environmental consequences of every discharge it 
Cite as: 557 U. S. ____ (2009) 5 

Opinion of the Court 

allows. 33 U. S. C. §1344(b). The Corps must apply guidelines written by the EPA pursuant to §404(b). See ibid.; 

40 CFR pt. 230 (EPA guidelines). Applying those guidelines here, the Corps determined that Coeur Alaska’s plan

to use Lower Slate Lake as a tailings pond was the “least 

environmentally damaging practicable” way to dispose of

the tailings. App. 366a. To conduct that analysis, the 

Corps compared the plan to the proposed alternatives.

The Corps determined that the environmental damage

caused by placing slurry in the lake will be temporary. 

And during that temporary disruption, Coeur Alaska will

divert waters around the lake through pipelines built for 

this purpose. Id., at 298a. Coeur Alaska will also treat 

water flowing from the lake into downstream waters, 

pursuant to strict EPA criteria. Ibid.; see Part I–B–2, 

infra. Though the slurry will at first destroy the lake’s 

small population of common fish, that population may 

later be replaced. After mining operations are completed, 

Coeur Alaska will help “recla[im]” the lake by “[c]apping” 

the tailings with about 4 inches of “native material.” App.

361a; id., at 309a. The Corps concluded that 

“[t]he reclamation of the lake will result in more 

emergent wetlands/vegetated shallows with moderate 

values for fish habitat, nutrient recycling, carbon/detrital export and sediment/toxicant retention, 

and high values for wildlife habitat.” Id., at 361a. 

If the tailings did not go into the lake, they would be

placed on nearby wetlands. The resulting pile would rise

twice as high as the Pentagon and cover three times as 

many acres. Reply Brief for Petitioner Coeur Alaska 27. 

If it were chosen, that alternative would destroy dozens of

acres of wetlands—a permanent loss. App. 365a–366a. 

On the premise that when the mining ends the lake will 

be at least as environmentally hospitable, if not more so,

than now, the Corps concluded that placing the tailings in 
6 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

the lake will cause less damage to the environment than 

storing them above ground: The reclaimed lake will be

“more valuable to the aquatic ecosystem than a permanently filled wetland . . . that has lost all aquatic functions 

and values.” Id., at 361a; see also id., at 366a. 

2 

The EPA had the statutory authority to veto the Corps

permit, and prohibit the discharge, if it found the plan to 

have “an unacceptable adverse effect on municipal water 

supplies, shellfish beds and fishery areas . . . , wildlife, or 

recreational areas.” CWA §404(c), 33 U. S. C. §1344(c). 

After considering the Corps findings, the EPA did not veto

the Corps permit, even though, in its view, placing the 

tailings in the lake was not the “environmentally preferable” means of disposing of them. App. 300a. By declining 

to exercise its veto, the EPA in effect deferred to the judgment of the Corps on this point. 

The EPA’s involvement extended beyond the agency’s

veto consideration. The EPA also issued a permit of its 

own—not for the discharge from the mine into the lake but

for the discharge from the lake into a downstream creek. 

Id., at 287a–331a. Section 402 grants the EPA authority

to “issue a permit for the discharge of any pollutant,”

“[e]xcept as provided in [CWA §404].” 33 U. S. C. 

§1342(a). The EPA’s §402 permit authorizes Coeur Alaska

to discharge water from Lower Slate Lake into the downstream creek, subject to strict water-quality limits that

Coeur Alaska must regularly monitor. App. 303a–304a, 

309a. 

The EPA’s authority to regulate this discharge comes

from a regulation, termed a “new source performance 

standard,” that it has promulgated under authority

granted to it by §306(b) of the CWA. Section 306(b) gives

the EPA authority to regulate the amount of pollutants 

that certain categories of new sources may discharge into 
Cite as: 557 U. S. ____ (2009) 7 

Opinion of the Court 

the navigable waters of the United States. 33 U. S. C. 

§1316(b). Pursuant to this authority, the EPA in 1982

promulgated a new source performance standard restricting discharges from new froth-flotation gold mines like 

Coeur Alaska’s. The standard is stringent: It allows “no

discharge of process wastewater” from these mines. 40 

CFR §440.104(b)(1).

Applying that standard to the discharge of water from

Lower Slate Lake into the downstream creek, the EPA’s 

§402 permit sets strict limits on the amount of pollutants 

the water may contain. The permit requires Coeur Alaska

to treat the water using “reverse osmosis” to remove aluminum, suspended solids, and other pollutants. App.

298a; id., at 304a. Coeur Alaska must monitor the water 

flowing from the lake to be sure that the pollutants are

kept to low, specified minimums. Id., at 326a–330a. 

C 

SEACC brought suit against the Corps of Engineers and 

various of its officials in the United States District Court 

for the District of Alaska. The Corps permit was not in 

accordance with law, SEACC argued, for two reasons.

First, in SEACC’s view, the permit was issued by the 

wrong agency—Coeur Alaska ought to have sought a §402 

permit from the EPA, just as the company did for the 

discharge of water from the lake into the downstream

creek. See Part I–B–2, supra. Second, SEACC contended 

that regardless of which agency issued the permit, the 

discharge itself is unlawful because it will violate the EPA 

new source performance standard for froth-flotation gold 

mines. (This is the same performance standard described 

above, which the EPA has already applied to the discharge 

of water from the lake into the downstream creek. See 

ibid.) SEACC argued that this performance standard also

applies to the discharge of slurry into the lake. It contended further that the performance standard is a binding 
8 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

implementation of §306. Section 306(e) of the CWA makes 

it “unlawful” for Coeur Alaska to “operate” the mine “in 

violation of” the EPA’s performance standard. 33 U. S. C. 

§1316(e).

Coeur Alaska and the State of Alaska intervened as 

defendants. Both sides moved for summary judgment. 

The District Court granted summary judgment in favor of 

the defendants. 

The Court of Appeals for the Ninth Circuit reversed and

ordered the District Court to vacate the Corps of Engineers’ permit. Southeast Alaska Conservation Council v. 

United States Army Corps of Engs., 486 F. 3d 638, 654– 

655 (2007). The court acknowledged that Coeur Alaska’s

slurry “facially meets the Corps’ current regulatory definition of ‘fill material,’” id., at 644, because it would have 

the effect of raising the lake’s bottom elevation. But the 

court also noted that the EPA’s new source performance 

standard “prohibits discharges from froth-flotation mills.” 

Ibid. The Court of Appeals concluded that “[b]oth of the 

regulations appear to apply in this case, yet they are at

odds.” Ibid. To resolve the conflict, the court turned to 

what it viewed as “the plain language of the Clean Water 

Act.” Ibid. The court held that the EPA’s new source 

performance standard “applies to discharges from the

froth-flotation mill at Coeur Alaska’s Kensington Gold

Mine into Lower Slate Lake.” Ibid. 

In addition to the text of the CWA, the Court of Appeals

also relied on the agencies’ statements made when promulgating their current and prior definitions of “fill material.” These statements, in the Court of Appeals’ view,

demonstrated the agencies’ intent that the EPA’s new 

source performance standard govern discharges like Coeur

Alaska’s. Id., at 648–654. 

The Court of Appeals concluded that Coeur Alaska

required a §402 permit for its slurry discharge, that the 

Corps lacked authority to issue such a permit under §404, 
Cite as: 557 U. S. ____ (2009) 9 

Opinion of the Court 

and that the proposed discharge was unlawful because it 

would violate the EPA new source performance standard

and §306(e). 

The decision of the Court of Appeals in effect reallocated

the division of responsibility that the Corps and the EPA

had been following. The Court granted certiorari. 554 

U. S. ___ (2008). We now hold that the decision of the 

Court of Appeals was incorrect. 

II 

The question of which agency has authority to consider 

whether to permit the slurry discharge is our beginning

inquiry. We consider first the authority of the EPA and 

second the authority of the Corps. Our conclusion is that 

under the CWA the Corps had authority to determine

whether Coeur Alaska was entitled to the permit governing this discharge. 

A 

Section 402 gives the EPA authority to issue “permit[s]

for the discharge of any pollutant,” with one important 

exception: The EPA may not issue permits for fill material

that fall under the Corps’ §404 permitting authority. 

Section 402(a) states: 

“Except as provided in . . . [CWA §404, 33 U. S. C. 

§1344], the Administrator may . . . issue a permit for 

the discharge of any pollutant, . . . notwithstanding 

[CWA §301(a), 33 U. S. C. §1311(a)], upon condition 

that such discharge will meet either (A) all applicable

requirements under [CWA §301, 33 U. S. C. §1311(a);

CWA §302, 33 U. S. C. §1312; CWA §306, 33 U. S. C.

§1316; CWA §307, 33 U. S. C. §1317; CWA §308, 33 

U. S. C. §1318; CWA §403, 33 U. S. C. §1343], or (B) 

prior to the taking of necessary implementing actions 

relating to all such requirements, such conditions as 

the Administrator determines are necessary to carry 
10 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

out the provisions of this chapter.” 33 U. S. C. 

§1342(a)(1) (emphasis added). 

Section 402 thus forbids the EPA from exercising permitting authority that is “provided [to the Corps] in” §404. 

This is not to say the EPA has no role with respect to

the environmental consequences of fill. The EPA’s function is different, in regulating fill, from its function in

regulating other pollutants, but the agency does exercise 

some authority. Section 404 assigns the EPA two tasks in

regard to fill material. First, the EPA must write guidelines for the Corps to follow in determining whether to 

permit a discharge of fill material. CWA §404(b); 33

U. S. C. §1344(b). Second, the Act gives the EPA authority

to “prohibit” any decision by the Corps to issue a permit

for a particular disposal site. CWA §404(c); 33 U. S. C. 

§1344(c). We, and the parties, refer to this as the EPA’s

power to veto a permit. 

The Act is best understood to provide that if the Corps 

has authority to issue a permit for a discharge under §404, 

then the EPA lacks authority to do so under §402.

Even if there were ambiguity on this point, the EPA’s 

own regulations would resolve it. Those regulations provide that “[d]ischarges of dredged or fill material into 

waters of the United States which are regulated under 

section 404 of CWA” “do not require [§402] permits” from

the EPA. 40 CFR §122.3. 

In SEACC’s view, this regulation implies that some “fill

material” discharges are not regulated under §404—else,

SEACC asks, why would the regulation lack a comma

before the word “which,” and thereby imply that only a 

subset of “discharges of . . . fill material” are “regulated 

under section 404.” Ibid. 

The agencies, however, have interpreted this regulation

otherwise. In the agencies’ view the regulation essentially 

restates the text of §402, and forbids the EPA from issuing 
Cite as: 557 U. S. ____ (2009) 11 

Opinion of the Court 

permits for discharges that “are regulated under section

404.” 40 CFR §122.3(b); cf. CWA §402(a) (“[e]xcept as

provided in . . . [§404], the Administrator may . . . issue a 

permit”). Before us, the EPA confirms this reading of the 

regulation. Brief for Federal Respondents 27. The 

agency’s interpretation is not “plainly erroneous or inconsistent with the regulation”; and so we accept it as correct. 

Auer v. Robbins, 519 U. S. 452, 461 (1997) (internal quotation marks omitted).

The question whether the EPA is the proper agency to

regulate the slurry discharge thus depends on whether the 

Corps of Engineers has authority to do so. If the Corps

has authority to issue a permit, then the EPA may not do 

so. We turn to the Corps’ authority under §404. 

B 

Section 404(a) gives the Corps power to “issue permits . . . for the discharge of dredged or fill material.” 33 

U. S. C. §1344(a). As all parties concede, the slurry meets

the definition of fill material agreed upon by the agencies 

in a joint regulation promulgated in 2002. That regulation 

defines “fill material” to mean any “material [that] has the

effect of . . . [c]hanging the bottom elevation” of water—a 

definition that includes “slurry, or tailings or similar 

mining-related materials.” 40 CFR §232.2.

SEACC concedes that the slurry to be discharged meets

the regulation’s definition of fill material. Brief for Respondent SEACC et al. 20. Its concession on this point is

appropriate because slurry falls well within the central 

understanding of the term “fill,” as shown by the examples 

given by the regulation. See 40 CFR §232.2 (“Examples of

such fill material include, but are not limited to: rock, 

sand, soil, clay . . . .”). The regulation further excludes

“trash or garbage” from its definition. Ibid. SEACC expresses a concern that Coeur Alaska’s interpretation of the 

statute will lead to §404 permits authorizing the dis-
12 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

charges of other solids that are now restricted by EPA 

standards. Brief for Respondent SEACC et al. 44–45 

(listing, for example, “feces and uneaten feed,” “litter,” 

and waste produced in “battery manufacturing”). But 

these extreme instances are not presented by the cases 

now before us. If, in a future case, a discharger of one of

these solids were to seek a §404 permit, the dispositive 

question for the agencies would be whether the solid at 

issue—for instance, “feces and uneaten feed”—came 

within the regulation’s definition of “fill.” SEACC cites no 

instance in which the agencies have so interpreted their 

fill regulation. If that instance did arise, and the agencies 

were to interpret the fill regulation as SEACC fears, then 

SEACC could challenge that decision as an unlawful

interpretation of the fill regulation; or SEACC could claim 

that the fill regulation as interpreted is an unreasonable 

interpretation of §404. The difficulties are not presented 

here, however, because the slurry meets the regulation’s

definition of fill. 

Rather than challenge the agencies’ decision to define

the slurry as fill, SEACC instead contends that §404 

contains an implicit exception. According to SEACC, §404

does not authorize the Corps to permit a discharge of fill 

material if that material is subject to an EPA new source

performance standard.

But §404’s text does not limit its grant of power in this 

way. Instead, §404 refers to all “fill material” without 

qualification. Nor do the EPA regulations support 

SEACC’s reading of §404. The EPA has enacted guidelines, pursuant to §404(b), to guide the Corps permitting 

decision. 40 CFR pt. 230. Those guidelines do not strip 

the Corps of power to issue permits for fill in cases where

the fill is also subject to an EPA new source performance 

standard. 

SEACC’s reading of §404 would create numerous difficulties for the regulated industry. As the regulatory re-
Cite as: 557 U. S. ____ (2009) 13 

Opinion of the Court 

gime stands now, a discharger must ask a simple question—is the substance to be discharged fill material or 

not? The fill regulation, 40 CFR §232.2, offers a clear 

answer to that question; and under the agencies’ view, 

that answer decides the matter—if the discharge is fill, 

the discharger must seek a §404 permit from the Corps; if

not, only then must the discharger consider whether any

EPA performance standard applies, so that the discharger 

requires a §402 permit from the EPA.

Under SEACC’s interpretation, however, the discharger 

would face a more difficult problem. The discharger would 

have to ask—is the fill material also subject to one of the 

many hundreds of EPA performance standards, so that

the permit must come from the EPA, not the Corps? The 

statute gives no indication that Congress intended to

burden industry with that confusing division of permit

authority.

The regulatory scheme discloses a defined, and workable, line for determining whether the Corps or the EPA

has the permit authority. Under this framework, the 

Corps of Engineers, and not the EPA, has authority to 

permit Coeur Alaska’s discharge of the slurry. 

III 

A second question remains: In issuing the permit did the

Corps act in violation of a statutory mandate so that the 

issuance was “not in accordance with law”? 5 U. S. C. 

§706(2)(A). SEACC contends that the slurry discharge 

will violate the EPA’s new source performance standard 

and that the Corps permit is made “unlawful” by CWA 

§306(e). Petitioners and the agencies argue that the permit is lawful because the EPA performance standard, and 

§306(e), do not apply to fill material regulated by the 

Corps. In order to determine whether the Corps permit is

lawful we must answer the question: Do EPA performance

standards, and §306(e), apply to discharges of fill mate-
14 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

rial? 

We address in turn the statutory text of the CWA, the

agencies’ regulations construing it, and the EPA’s subsequent interpretation of those regulations. Because Congress has not “directly spoken” to the “precise question” of 

whether an EPA performance standard applies to discharges of fill material, the statute alone does not resolve 

the case. Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S. 837, 842 (1984). We look 

first to the agency regulations, which are entitled to deference if they resolve the ambiguity in a reasonable manner. 

Ibid.; see United States v. Mead Corp., 533 U. S. 218, 226– 

227 (2001). But the regulations, too, are ambiguous, so we

next turn to the agencies’ subsequent interpretation of 

those regulations. Id., at 234–238; Auer, 519 U. S., at 461. 

In an internal memorandum the EPA explained that its 

performance standards do not apply to discharges of fill 

material. That interpretation is not “plainly erroneous or 

inconsistent with the regulation[s],” and so we accept it as 

correct. Ibid. (internal quotation marks omitted). Though

SEACC contends that the agencies’ interpretation is not

entitled to deference because it contradicts the agencies’ 

published statements and prior practice, we disagree with

SEACC’s reading of those statements and of the regulatory record. 

A 

As for the statutory argument, SEACC claims the CWA

§404 permit is unlawful because §306(e) forbids the slurry 

discharge. Petitioners and the federal agencies, in contrast, contend that §306(e) does not apply to the slurry

discharge. 

1 

To address SEACC’s statutory argument, it is necessary 

to review the EPA’s responsibilities under the CWA. As 
Cite as: 557 U. S. ____ (2009) 15 

Opinion of the Court 

noted, §306 empowers the EPA to regulate the frothflotation gold mining industry. See 33 U. S. C. §1316(b).

Pursuant to this authority, EPA promulgated the new 

source performance standard relied upon by SEACC. The 

standard is stringent. If it were to apply here, it would

allow “no discharge of process wastewater” from the mine. 

40 CFR §440.104(b)(1).

The term “process wastewater” includes solid waste. So 

the regulation forbids not only pollutants that dissolve in 

water but also solid pollutants suspended in water—what 

the agency terms “total suspended solids,” or TSS. See 

§440.104(a) (limiting the amount of TSS from other kinds

of mines); see also EPA Development Document for Effluent Limitations Guidelines and Standards for the Ore 

Mining and Dressing Point Source Category 157–158

(Nov. 1982) (the amount of TSS in “wastewater” from

froth-flotation mines is “generally high”); id., at 175 (Table

VI–6) (measuring the amounts of TSS in samples of frothflotation mines’ discharges); id., at 194 (stating an intent

to “regulat[e]” TSS); id., at 402 (evaluating the costs of

constructing a “settling pond”); id., at 535 (concluding that 

even in mountainous regions, a froth-flotation mine will be 

able to construct a “tailings impoundment” to “provide a 

disposal area for mill tailings”). 

Were there any doubt about whether the EPA’s new 

source performance standard forbade solids as well as

soluble pollutants, the agency’s action in these cases 

would resolve it. Here, the EPA’s §402 permit authorizes 

Coeur Alaska to discharge water from Lower Slate Lake 

into a downstream creek, provided the water meets the 

quality requirements set by the performance standard. 

This demonstrates that the performance standard regulates solid waste. The EPA’s permit not only restricts the 

amount of total suspended solids, App. 327a (Table 3), but 

also forbids the mine from allowing any “floating solids” to 

flow from the lake. Id., at 328a. No party disputes the 
16 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

EPA’s authority to regulate these discharges of solid mining waste; and no party questions the validity of the EPA’s

new source performance standard when it is applicable. 

When the performance standard applies to a point

source, §306(e) makes it “unlawful” for that point source to

violate it: “[I]t shall be unlawful for any owner or operator

of any new source to operate such source in violation of 

any standard of performance applicable to such source.” 

CWA §306(e), 33 U. S. C. §1316(e).

SEACC argues that this provision, §306(e), forbids the

mine from discharging slurry into Lower Slate Lake.

SEACC contends the new source performance standard is,

in the words of §306(e), “applicable to” the mine. Both the 

text of the performance standard and the EPA’s application of it to the discharge of mining waste from Lower 

Slate Lake demonstrate that the performance standard is 

“applicable to” Coeur Alaska’s mine in some circumstances. And so, SEACC reasons, it follows that because 

the new source performance standard forbids even minute

discharges of solid waste, it also forbids the slurry discharge, 30% of which is solid waste. 

2 

For their part, the State of Alaska and the federal agencies claim that the Act is unambiguous in the opposite 

direction. They rely on §404 of the Act. As explained

above, that section authorizes the Corps of Engineers to 

determine whether to issue a permit allowing the discharge of the slurry. Petitioners and the agencies argue

that §404 grants the Corps authority to do so without 

regard to the EPA’s new source performance standard or 

the §306(e) prohibition discussed above. 

Petitioners and the agencies make two statutory arguments based on §404’s silence in regard to §306. First, 

they note that nothing in §404 requires the Corps to consider the EPA’s new source performance standard or the 
Cite as: 557 U. S. ____ (2009) 17 

Opinion of the Court 

§306(e) prohibition. That silence advances the argument 

that §404’s grant of authority to “issue permits” contradicts §306(e)’s declaration that discharges in violation of 

new source performance standards are “unlawful.”

Second, petitioners and the agencies point to §404(p), 

which protects §404 permitees from enforcement actions

by the EPA or private citizens: 

“Compliance with a permit issued pursuant to this

section . . . shall be deemed compliance, for purposes 

of sections 1319 [CWA §309] and 1365 [CWA §505] of 

this title, with sections 1311 [CWA §301], 1317 [CWA 

§307], and 1343 [CWA §403] of this title.” 33 U. S. C. 

§1344(p). 

Here again, their argument is that silence is significant. 

Section 404(p) protects the permitee from lawsuits alleging violations of CWA §301 (which bars the discharge of

“any pollutant” “except as in compliance” with the Act),

§307 (which bars the discharge of “toxic pollutants”); and 

§403 (which bars discharges into the sea). But §404(p)

does not in express terms protect the permitee from a 

lawsuit alleging a violation of §306(e) or of the EPA’s new 

source performance standards. Section 404(p)’s silence 

regarding §306 is made even more significant because a 

parallel provision in §402 does protect a §402 permitee 

from an enforcement action alleging a violation of §306. 

CWA §402(k), 33 U. S. C. §1342(k). 

In our view, Congress’ omission of §306 from §404, and 

its inclusion of §306 in §402(k), is evidence that Congress

did not intend §306(e) to apply to Corps §404 permits or to

discharges of fill material. If §306 did apply, then the

Corps would be required to evaluate each permit application for compliance with §306, and issue a permit only if it

found the discharge would comply with §306. But even if 

that finding were made, it is not clear that the §404 permitee would be protected from a suit seeking a judicial 
18 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

determination that the discharge violates §306. 

3 

The CWA is ambiguous on the question whether §306 

applies to discharges of fill material regulated under §404. 

On the one hand, §306 provides that a discharge that 

violates an EPA new source performance standard is

“unlawful”—without any exception for fill material. On 

the other hand, §404 grants the Corps blanket authority to 

permit the discharge of fill material—without any mention 

of §306. This tension indicates that Congress has not 

“directly spoken” to the “precise question” of whether §306 

applies to discharges of fill material. Chevron, 467 U. S., 

at 842. 

B 

Before turning to how the agencies have resolved that

question, we consider the formal regulations that bear on

§§306 and 404. See Mead, 533 U. S., at 234–238. The 

regulations, like the statutes, do not address the question 

whether §306, and the EPA new source performance standards promulgated under it, apply to §404 permits and the

discharges they authorize. There is no regulation, for 

example, interpreting §306(e)’s text—“standard of performance applicable to such source”—to mean that a

performance standard ceases to be “applicable” the moment the discharge qualifies as fill material, which would 

resolve the cases in petitioners’ favor. Nor is there a 

regulation providing that the Corps, in deciding whether 

to grant a permit under §404, must deny that permit if the

discharge would violate §306(e), which would decide the

cases for SEACC. 

Rather than address the tension between §§306 and 

404, the regulations instead implement the statutory 

framework without elaboration on this point. Each of the 

two principal regulations, which have been mentioned

above, seems to stand on its own without reference to the 
Cite as: 557 U. S. ____ (2009) 19 

Opinion of the Court 

other. The EPA’s new source performance standard contains no exception for fill material; and it forbids any 

discharge of “process wastewater,” a term that includes 

solid wastes. 40 CFR §440.104(b)(1); see Part III–A–1, 

supra. The agencies’ joint regulation defining fill material

is also unqualified. It includes “slurry, or tailings or similar mining-related materials” in its definition of a “discharge of fill material,” 40 CFR §232.2; and it contains no

exception for slurry that is regulated by an EPA performance standard. 

The parties point to additional regulations, but these 

provisions do not offer a clear basis of reconciliation. An 

EPA regulation, mentioned above, provides that 

“[d]ischarges of dredged or fill material into waters of the 

United States which are regulated under section 404 of

CWA” “do not require [§402] permits” from the EPA.

§122.3. As we have explained, however, this merely states 

that a permit for this discharge cannot be issued by the 

EPA. See Part II, supra. The regulation does not answer

the question whether the EPA’s new source performance

standard, and §306(e), apply to a discharge regulated by

the Corps under §404.

The agencies also direct us to the §404(b) guidelines

written by the EPA to guide the Corps permitting decision. 

See 40 CFR pt. 230. The agencies note that these guidelines do not expressly require the Corps, in issuing a

permit, to consider whether the discharge would violate 

EPA’s performance standards. Here we think failure to 

mention §306 or the EPA new source performance standards does offer some indication that these are not relevant to the §404 permit, though the argument falls short 

of being conclusive. The Corps’ own regulations require 

the agency to evaluate permit applications “for compliance

with applicable [EPA] effluent limitations.” 33 CFR 

§320.4(d) (2008). The regulations do not answer whether 

the new source performance standard is “applicable” to a 
20 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

discharge of fill material. 

C 

The regulations do not give a definitive answer to the 

question whether §306 applies to discharges regulated by

the Corps under §404, but we do find that agency interpretation and agency application of the regulations are instructive and to the point. Auer, 519 U. S., at 461. The 

question is addressed and resolved in a reasonable and 

coherent way by the practice and policy of the two agencies, all as recited in a memorandum written in May 2004

by Diane Regas, then the Director of the EPA’s Office of

Wetlands, Oceans and Watersheds, to Randy Smith, the

Director of the EPA’s regional Office of Water with responsibility over the mine. App. 141a–149a (Regas Memorandum). The Memorandum, though not subject to sufficiently formal procedures to merit Chevron deference, see 

Mead, supra, at 234–238, is entitled to a measure of deference because it interprets the agencies’ own regulatory

scheme. See Auer, supra, at 461. 

The Regas Memorandum explains: 

“As a result [of the fact that the discharge is regulated 

under §404], the regulatory regime applicable to discharges under section 402, including effluent limitations guidelines and standards, such as those applicable to gold ore mining . . . do not apply to the 

placement of tailings into the proposed impoundment 

[of Lower Slate Lake]. See 40 CFR §122.3(b).” App.

144a–145a. 

The regulation that the Memorandum cites—40 CFR

§122.3—is one we considered above and found ambiguous.

That regulation provides: “[d]ischarges of dredged or fill 

material into waters of the United States which are regulated under section 404 of CWA” “do not require [§402] 

permits.” The Regas Memorandum takes an instructive 
Cite as: 557 U. S. ____ (2009) 21 

Opinion of the Court 

interpretive step when it explains that because the discharge “do[es] not require” an EPA permit, ibid., the 

EPA’s performance standard “do[es] not apply” to the

discharge. App. 145a. The Memorandum presents a

reasonable interpretation of the regulatory regime. We 

defer to the interpretation because it is not “plainly erroneous or inconsistent with the regulation[s].” Auer, supra, 

at 461 (internal quotation marks omitted). Five factors 

inform that conclusion. 

First, the Memorandum preserves a role for the EPA’s 

performance standard. It confines the Memorandum’s 

scope to closed bodies of water, like the lake here. App.

142a–143a, n. 1. When slurry is discharged into a closed 

body of water, the Memorandum explains, the EPA’s

performance standard retains an important role in regulating the discharge into surrounding waters. The Memorandum does not purport to invalidate the EPA’s performance standard. 

Second, the Memorandum acknowledges that this is not 

an instance in which the discharger attempts to evade the 

requirements of the EPA’s performance standard. The 

Kensington Mine is not, for example, a project that smuggles a discharge of EPA-regulated pollutants into a separate discharge of Corps-regulated fill material. The instant cases do not present a process or plan designed to 

manipulate the outer boundaries of the definition of “fill

material” by labeling minute quantities of EPA-regulated 

solids as fill. The Memorandum states that when a discharge has only an “incidental filling effect,” the EPA’s

performance standard continues to govern that discharge. 

Id., at 145a. 

Third, the Memorandum’s interpretation preserves the

Corps’ authority to determine whether a discharge is in 

the public interest. See 33 CFR §320.4(a)(1); 40 CFR

§230.10. The Corps has significant expertise in making 

this determination. Applying it, the Corps determined 
22 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

that placing slurry in the lake will improve that body of

water by making it wider, shallower, and so more capable 

of sustaining aquatic life. The Corps determined, furthermore, that the alternative—a heap of tailings larger

than the Pentagon placed upon wetlands—would cause 

more harm to the environment. Because the Memorandum preserves an important role for the Corps’ expertise, 

its conclusion that the EPA’s performance standard does

not apply is a reasonable one. 

Fourth, the Regas Memorandum’s interpretation does

not allow toxic pollutants (as distinguished from other, 

less dangerous pollutants, such as slurry) to enter the

navigable waters. The EPA has regulated toxic pollutants 

under a separate provision, §307 of the CWA, and the 

EPA’s §404(b) guidelines require the Corps to deny a §404

permit for any discharge that would violate the EPA’s

§307 toxic-effluent limitations. 40 CFR §230.10(b)(2).

Fifth, as a final reason to defer to the Regas Memorandum, we find it a sensible and rational construction that 

reconciles §§306, 402, and 404, and the regulations implementing them, which the alternatives put forward by

the parties do not. SEACC’s argument, that §402 applies 

to this discharge and not §404, is not consistent with the 

statute and regulations, as already noted. See Part II, 

supra. 

The Court requested the parties to submit supplemental 

briefs addressing whether the CWA contemplated that 

both agencies would issue a permit for a discharge. 556 

U. S. ___ (2009). A two-permit regime would allow the 

EPA to apply its performance standard, while the Corps

could apply its §404(b) criteria. The parties agree, however, that a two-permit regime is contrary to the statute 

and the regulations. We conclude that this is correct. A 

two-permit regime would cause confusion, delay, expense, 

and uncertainty in the permitting process. In agreement

with all of the parties, we conclude that, when a permit is 
Cite as: 557 U. S. ____ (2009) 23 

Opinion of the Court 

required to discharge fill material, either a §402 or a §404 

permit is necessary. Here, we now hold, §404 applies, not 

§402. See Part II, supra. 

The Regas Memorandum’s interpretation of the agencies’ regulations is consistent with the regulatory scheme 

as a whole. The Memorandum preserves a role for the

EPA’s performance standards; it guards against the possibility of evasion of those standards; it employs the Corps’ 

expertise in evaluating the effects of fill material on the

aquatic environment; it does not allow toxic pollutants to 

be discharged; and we have been offered no better way to 

harmonize the regulations. We defer to the EPA’s conclusion that its performance standard does not apply to the 

initial discharge of slurry into the lake but applies only to 

the later discharge of water from the lake into the downstream creek. 

D 

SEACC argues against deference to the Regas Memorandum. In its view the Regas Memorandum is contrary 

to published agency statements and earlier agency practice. SEACC cites three agency statements: A 1986

“memorandum of understanding” between the EPA and

the Corps regarding the definition of fill material; the

preamble to the agencies’ current 2002 fill regulation; and 

comments made by the agencies in promulgating the 2002

fill regulation. These arguments are not convincing. 

1 

In 1986, to reconcile their then-differing definitions of

“fill material,” the EPA and the Corps issued a “memorandum of agreement.” 51 Fed. Reg. 8871 (MOA). The 

memorandum was not made subject to notice-andcomment procedures, but it was published in the Federal

Register. It defined the statutory term “fill material” until

the current definition took effect in 2002. Brief for Fed-
24 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

eral Respondents 30–31, n. 8. 

SEACC points to paragraph B(5) of the MOA, which

reads: 

“[A] pollutant (other than dredged material) will normally be considered by EPA and the Corps to be subject to section 402 if it is a discharge in liquid, semiliquid, or suspended form or if it is a discharge of solid 

material of a homogeneous nature normally associated with single industry wastes . . . . These materials 

include placer mining wastes, phosphate mining 

wastes, titanium mining wastes, sand and gravel

wastes, fly ash, and drilling muds. As appropriate, 

EPA and the Corps will identify additional such materials.” 51 Fed. Reg. 8872. 

It is true, as SEACC notes, that this passage suggests that 

§402 will “normally” apply to discharges of “suspended”— 

i.e., solid—pollutants. But that statement is not contrary

to the Regas Memorandum, which acknowledges that the

EPA retains authority under §402 to regulate the discharge of suspended solids from Lower Slate Lake into 

downstream waters. This passage does not address the

question presented by these cases, and answered by the

Regas Memorandum, as to whether the EPA’s performance standard applies when the discharge qualifies as fill 

material. In fact, the MOA’s preamble suggests that when 

a discharge qualifies as “fill material,” the Corps retains

authority to regulate it under §404: 

“Discharges listed in the Corps definition of ‘discharge 

of fill material,’ . . . remain subject to section 404 even 

if they occur in association with discharges of wastes

meeting the criteria in the agreement for section 402

discharges.” Id., at 8871. 

The MOA is quite consistent with the agencies’ determination that the Corps regulates all discharges of fill mate-
Cite as: 557 U. S. ____ (2009) 25 

Opinion of the Court 

rial and that §306 does not apply to these discharges. 

2 

SEACC draws our attention to the preamble of the 

current fill material regulation. 67 Fed. Reg. 31129 (2002)

(final rule). It cites the opening passages of the preamble,

which state: 

“[T]oday’s rule is generally consistent with current

agency practice and so it does not expand the types of 

discharges that will be covered under section 404.” 

Id., at 31133. 

In SEACC’s view, this passage demonstrates that the fill 

rule was not intended to displace the pre-existing frothflotation gold mine performance standard, which has been

on the books since 1982. 

The preamble goes on to say, in a section entitled “Effluent Guideline Limitations and 402 Permits”: 

“[W]e emphasize that today’s rule generally is intended to maintain our existing approach to regulating pollutants under either section 402 or 404 of the 

CWA. Effluent limitation guidelines and new source

performance standards (‘effluent guidelines’) promulgated under section 304 and 306 of the CWA establish

limitations and standards for specified wastestreams 

from industrial categories, and those limitations and

standards are incorporated into permits issued under 

section 402 of the Act. EPA has never sought to regulate fill material under effluent guidelines. Rather, 

effluent guidelines restrict discharges of pollutants 

from identified wastestreams based upon the pollutant reduction capabilities of available treatment technologies. Recognizing that some discharges (such as 

suspended or settleable solids) can have the associated effect, over time, of raising the bottom elevation

of a water due to settling of waterborne pollutants, we 
26 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

do not consider such pollutants to be ‘fill material,’ 

and nothing in today’s rule changes that view. Nor 

does today’s rule change any determination we have 

made regarding discharges that are subject to an effluent limitation guideline and standards, which will 

continue to be regulated under section 402 of the 

CWA. Similarly, this rule does not alter the manner

in which water quality standards currently apply under the section 402 or the section 404 programs.” Id., 

at 31135. 

Although the preamble asserts it does not change agency 

policy with regard to EPA performance standards and 

§402 permitting decisions, it is explicit in noting that the 

EPA has “never sought to regulate fill material under 

effluent guidelines.” Ibid. The preamble, then, is consistent with the Regas Memorandum. If a discharge does not

qualify as fill material, the EPA’s new source performance

standard applies. If the discharge qualifies as fill, the 

performance standard does not apply; and there was no

earlier agency practice or policy to the contrary. 

3 

SEACC also cites remarks made by the agencies in

response to public comments on the proposed fill material

regulation. App. 22a–127a. These remarks were incorporated by reference into the administrative record. 67 Fed. 

Reg. 31131.

Responding to a question about whether “mine tailings” 

would be “subject to section 404 regulation as opposed to 

section 402” under the 2002 fill regulation, the agencies

stated: 

“Today’s final rule clarifies that any material that has

the effect of fill is regulated under section 404 and

further that the placement of ‘overburden, slurry, or 

tailings or similar mining-related materials’ is consid-
Cite as: 557 U. S. ____ (2009) 27 

Opinion of the Court 

ered a discharge of fill material. Nevertheless, if EPA 

has previously determined that certain materials are 

subject to an [effluent limitation guideline] under specific circumstances, then that determination remains 

valid. Moreover, . . . permits issued pursuant to section 402 are intended to regulate process water and 

provide effluent limits that are protective of receiving

water quality. This distinction provides the framework for today’s rule.” App. 48a. 

This statement is not conclusive of the issue. SEACC 

notes that this response, like the regulation’s preamble, 

pledges that EPA’s “previou[s] . . . determination[s]” with

regard to the application of performance standards “remai[n] valid.” But, as noted above, the Regas Memorandum has followed this policy by applying the EPA’s performance standard to the discharge of water from the lake 

into the downstream creek. The response does not state

that the EPA will apply its performance standards to 

discharges of fill material. 

4 

The agencies’ published statements indicate adherence

to the EPA’s previous application and interpretation of its 

performance standards. SEACC cannot show that the 

agencies have changed their interpretation or application

of their regulations.

SEACC cites no instance in which the EPA has applied 

one of its performance standards to a discharge of fill

material. By contrast, Coeur Alaska cites two instances in 

which the Corps issued a §404 permit authorizing a mine

to discharge solid waste (tailings) as fill material. See 

Brief for Petitioner Coeur Alaska 40–42. SEACC objects

that those two §404 permits authorized discharges that 

used the tailings to construct useful structures—a dam in 

one case, a tailings pond in another. Here, by contrast, 

SEACC contends that the primary purpose of the dis-
28 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of the Court 

charge is to use a navigable water to dispose of waste. 

Ibid. But that objection misses the point. The two §404

permits cited by Coeur Alaska illustrate that the agencies

did not have a prior practice of applying EPA performance 

standards to discharges of mining wastes that qualify as

fill material. 

SEACC has not demonstrated that the agencies have 

changed their policy, and it cannot show that the Regas

Memorandum is contrary to the agencies’ published 

statements. 

* * * 

We accord deference to the agencies’ reasonable decision 

to continue their prior practice.

The judgment of the Court of Appeals is reversed, and

these cases are remanded for further proceedings consistent with this opinion. 

It is so ordered. 
_________________ 

_________________ 

Cite as: 557 U. S. ____ (2009) 1 

BREYER, J., concurring 

SUPREME COURT OF THE UNITED STATES 

Nos. 07–984 and 07–990 

COEUR ALASKA, INC., PETITIONER 

07–984 v. 

SOUTHEAST ALASKA CONSERVATION COUNCIL 

ET AL. 

ALASKA, PETITIONER 

07–990 v. 

SOUTHEAST ALASKA CONSERVATION COUNCIL 

ET AL. 

ON WRITS OF CERTIORARI TO THE UNITED STATES COURT OF 

APPEALS FOR THE NINTH CIRCUIT 

[June 22, 2009] 

JUSTICE BREYER, concurring. 

As I understand the Court’s opinion, it recognizes a

legal zone within which the regulating agencies might 

reasonably classify material either as “dredged or fill 

material” subject to §404 of the Clean Water Act, 33

U. S. C. §1344(a), or as a “pollutant,” subject to §§402 and 

306, 33 U. S. C. §§1342(a), 1316(a). Within this zone, the 

law authorizes the environmental agencies to classify

material as the one or the other, so long as they act within

the bounds of relevant regulations, and provided that the 

classification, considered in terms of the purposes of the

statutes and relevant regulations, is reasonable. 

This approach reflects the difficulty of applying §§402

and 306 literally to every new-source-related discharge of a

“pollutant.” The Environmental Protection Agency (EPA) 

applies §306 new source “performance standards” to a 

wide variety of discharges, ranging, for example, from 
2 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

BREYER, J., concurring

those involved in the processing of apples into apple juice 

or apple cider, 40 CFR §407.10 (2008); to the manufacturing of cement, §411.10; to the production of fresh meat 

cuts by a meat cutter, §432.60; and to the manufacture of 

pharmaceutical products by fermentation, §439.10. See 

generally 40 CFR pts. 405–471 (containing more than 800 

pages of “new source performance” and effluent limitation 

regulations). At the same time the regulations for any one 

point source often regulate numerous chemicals, minerals, 

and other substances produced by that point source; in the 

case of fermentation products, for example, the regulations 

provide performance standards for roughly 30 different 

chemicals. §439.15. These “standards of performance” 

“reflect the greatest degree of effluent reduction which the 

Administrator determines to be achievable through application of the best available demonstrated control technology . . . including, where practicable, a standard permitting no discharge of pollutants.” 33 U. S. C. §1316(a)(1).

To literally apply these performance standards so as to 

forbid the use of any of these substances as “fill,” even 

when, say, they constitute no more than trace elements in

dirt, crushed rock, or sand that is clearly being used as

“fill” to build a levee or to replace dirt removed from a lake 

bottom may prove unnecessarily strict, cf. §1362(6) (defining “pollutant” to include “rock”), to the point that such

application would undermine the objective of §404, which

foresees the use of “dredged or fill material” in certain

circumstances and with approval of the relevant agencies.

§1344. At minimum, the EPA might reasonably read the 

statute and the applicable regulations as allowing the use

of such material, say crushed rock, as “fill” in some of 

these situations. Cf. Chevron U. S. A. Inc. v. Natural 

Resources Defense Council, Inc., 467 U. S. 837, 842–844 

(1984); Auer v. Robbins, 519 U. S. 452, 461 (1997).

At the same time, I recognize the danger that JUSTICE 

GINSBURG warns against, namely, that “[w]hole categories 
Cite as: 557 U. S. ____ (2009) 3 

BREYER, J., concurring 

of regulated industries” might “gain immunity from a 

variety of pollution-control standards,” if, say, a §404-

permit applicant simply adds “sufficient solid matter” to a 

pollutant “to raise the bottom of a water body,” thereby

turning a “pollutant” governed by §306 into “fill” governed 

by §404. Post, at 7 (dissenting opinion). 

Yet there are safeguards against that occurring. For 

one thing, as the Court recognizes, see ante, at 11, it is not 

the case that any material that has the “‘effect of . . . 

[c]hanging the bottom elevation’” of the body of water is

automatically subject to §404, not §402. The EPA has 

never suggested that it would interpret the regulations so 

as to turn §404 into a loophole, permitting evasion of a

“performance standard” simply because a polluter discharges enough pollutant to raise the bottom elevation of

the body of water. For another thing, even where a matter 

is determined reasonably to be “fill” and consequently falls 

within §404, the EPA can retain an important role in the

permitting process. That is because the EPA may veto

any §404 plan that it finds has an “unacceptable adverse 

effect on municipal water supplies, shellfish beds and 

fishery areas . . . , wildlife, or recreational areas.” 

§1344(c). Finally, EPA’s decision not to apply §306, but to

allow permitting to proceed under §404, must be a reasonable decision; and court review will help assure that is so. 

5 U. S. C. §706.

In these cases, it seems to me that the EPA’s interpretation of the statute as permitting the EPA/Corps of Engineers “fill” definition to apply to the cases at hand is reasonable, hence lawful. Lower Slate Lake, located roughly 

three miles from the Kensington Gold Mine, is 51 feet 

deep, 800 feet wide, and 2,000 feet long; downstream from

the lake is Slate Creek. Faced with a difficult choice 

between creating a huge pile of slurry on nearby wetlands

or using part of the lake as a storage facility for mine

tailings, see App. 294a–298a; see also ante, at 5–8, the 
4 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

BREYER, J., concurring

EPA arrived at a compromise. On the one hand, it would 

treat mine tailings placed directly into the lake as “fill” 

under the §404 permitting program. App. 144a. The 

tailings, the EPA recognized, would have the “immediate

effect of filling the areas of water into which they are 

discharged.” Ibid. But it would also treat any spillover of

the tailings, or chemicals from the tailings, into any

nearby waterway, most particularly Slate Creek (running

out of Slate Lake) as requiring a §402 permit. The EPA’s 

§306 “performance standard” would apply and that standard insists upon no discharge of process wastewater at 

all. Id., at 145a; see also 40 CFR §440.104(b). The EPA 

reached this result because it recognized that, even though

pollutants discharged into the creek might come “in the 

form of suspended and settleable solids,” such solids would 

“have, at most, an incidental filling effect.” App. 145a.

The EPA thereby sought to apply the distinction it had

previously recognized between discharges that have the 

immediate effect of raising the bottom elevation of water,

and those that only have the “associated effect, over time,

of raising the bottom elevation of a water due to settling of 

waterborne pollutants.” See 67 Fed. Reg. 31135 (2002) 

(concluding that §402 applies to the latter); see also Brief 

for G. Tracy Mehan III as Amicus Curiae 22–23. 

I cannot say whether the EPA’s compromise represents

the best overall environmental result; but I do believe it 

amounts to the kind of detailed decision that the statutes 

delegate authority to the EPA, not the courts, to make 

(subject to the bounds of reasonableness). I believe the 

Court’s views are consistent with those I here express. 

And with that understanding, I join its opinion. 
_________________ 

_________________ 

Cite as: 557 U. S. ____ (2009) 1 

Opinion of SCALIA, J. 

SUPREME COURT OF THE UNITED STATES 

Nos. 07–984 and 07–990 

COEUR ALASKA, INC., PETITIONER 

07–984 v. 

SOUTHEAST ALASKA CONSERVATION COUNCIL 

ET AL. 

ALASKA, PETITIONER 

07–990 v. 

SOUTHEAST ALASKA CONSERVATION COUNCIL 

ET AL. 

ON WRITS OF CERTIORARI TO THE UNITED STATES COURT OF 

APPEALS FOR THE NINTH CIRCUIT 

[June 22, 2009] 

JUSTICE SCALIA, concurring in part and concurring in 

the judgment. 

I join the opinion of the Court, except for its protestation, ante, at 20, that it is not according Chevron deference 

to the reasonable interpretation set forth in the memorandum sent by the Director of the Environmental Protection

Agency’s (EPA) Office of Wetlands, Oceans and Watersheds, to the Director of the EPA’s regional Office of Water 

with responsibility over the Coeur Alaska mine—an interpretation consistently followed by both EPA and the Corps 

of Engineers, and adopted by both agencies in the proceedings before this Court. See Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S. 837 (1984). 

The opinion purports to give this agency interpretation “a

measure of deference” because it involves an interpretation

of “the agencies’ own regulatory scheme,” and “‘the regulatory regime,’” ante, at 20 (citing Auer v. Robbins, 519 
2 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

Opinion of SCALIA, J. 

U. S. 452, 461 (1997)). Auer, however, stands only for the

principle that we defer to an agency’s interpretation of its 

own ambiguous regulation. But it becomes obvious from 

the ensuing discussion that the referenced “regulatory

scheme,” and “regulatory regime” for which the Court

accepts the agency interpretation includes not just the

agencies’ own regulations but also (and indeed primarily) 

the conformity of those regulations with the ambiguous 

governing statute, which is the primary dispute here. 

Surely the Court is not adding to our already inscrutable opinion in United States v. Mead Corp., 533 U. S. 218 

(2001), the irrational fillip that an agency position which

otherwise does not qualify for Chevron deference does 

receive Chevron deference if it clarifies not just an ambiguous statute but also an ambiguous regulation. One 

must conclude, then, that if today’s opinion is not according the agencies’ reasonable and authoritative interpretation of the Clean Water Act Chevron deference, it is according some new type of deference—perhaps to be called 

in the future Coeur Alaska deference—which is identical 

to Chevron deference except for the name. 

The Court’s deference to the EPA and the Corps of 

Engineers in today’s cases is eminently reasonable. It is 

quite impossible to achieve predictable (and relatively

litigation-free) administration of the vast body of complex 

laws committed to the charge of executive agencies without the assurance that reviewing courts will accept reasonable and authoritative agency interpretation of ambiguous provisions. If we must not call that practice 

Chevron deference, then we have to rechristen the rose. 

Of course the only reason a new name is required is our

misguided opinion in Mead, whose incomprehensible 

criteria for Chevron deference have produced so much 

confusion in the lower courts* that there has now appeared 

—————— 

*Compare, e.g., Kruse v. Wells Fargo Home Mortgage, Inc., 383 F. 3d 
Cite as: 557 U. S. ____ (2009) 3 

Opinion of SCALIA, J. 

the phenomenon of Chevron avoidance—the practice of 

declining to opine whether Chevron applies or not. See 

Bressman, How Mead Has Muddled Judicial Review of 

Agency Action, 58 Vand. L. Rev. 1443, 1464 (2005). 

I favor overruling Mead. Failing that, I am pleased to 

join an opinion that effectively ignores it. 

—————— 

49, 61 (CA2 2004) (according Chevron deference to policy statements

issued by Department of Housing and Urban Development) and Schuetz v. Banc One Mortgage Corp., 292 F. 3d 1004, 1012 (CA9 2002) 

(same), with Krzalic v. Republic Title Co., 314 F. 3d 875, 881 (CA7 

2002) (denying Chevron deference to same policy statements). Compare 

American Federation of Govt. Employees, AFL–CIO, Local 446 v. 

Nicholson, 475 F. 3d 341, 353–354 (CADC 2007) (according Chevron 

deference to informal adjudication by Department of Veterans Affairs), 

with American Federation of Govt. Employees, AFL–CIO, Local 2152 v. 

Principi, 464 F. 3d 1049, 1057 (CA9 2006) (denying Chevron deference 

to similar action). It is not even clear that notice-and-comment rulemaking will assure Chevron deference to agency interpretation of an 

ambiguous statute. See Rubie’s Costume Co. v. United States, 337 F. 3d 

1350, 1355 (CA Fed. 2003) (customs classification). 
_________________ 

_________________ 

Cite as: 557 U. S. ____ (2009) 1 

GINSBURG, J., dissenting 

SUPREME COURT OF THE UNITED STATES 

Nos. 07–984 and 07–990 

COEUR ALASKA, INC., PETITIONER 

07–984 v. 

SOUTHEAST ALASKA CONSERVATION COUNCIL 

ET AL. 

ALASKA, PETITIONER 

07–990 v. 

SOUTHEAST ALASKA CONSERVATION COUNCIL 

ET AL. 

ON WRITS OF CERTIORARI TO THE UNITED STATES COURT OF 

APPEALS FOR THE NINTH CIRCUIT 

[June 22, 2009] 

JUSTICE GINSBURG, with whom JUSTICE STEVENS and 

JUSTICE SOUTER join, dissenting. 

Petitioner Coeur Alaska, Inc., proposes to discharge

210,000 gallons per day of mining waste into Lower Slate

Lake, a 23-acre subalpine lake in Tongass National Forest. The “tailings slurry” would contain concentrations of 

aluminum, copper, lead, and mercury. Over the life of the 

mine, roughly 4.5 million tons of solid tailings would enter 

the lake, raising the bottom elevation by 50 feet. It is 

undisputed that the discharge would kill all of the lake’s

fish and nearly all of its other aquatic life.1 

Coeur Alaska’s proposal is prohibited by the Environmental Protection Agency (EPA) performance standard 

—————— 

1Whether aquatic life will eventually be able to inhabit the lake

again is uncertain. Compare ante, at 5, with App. 201a–202a; and 

Southeast Alaska Conservation Council v. United States Army Corps of 

Engineers, 486 F. 3d 638, 642 (CA9 2007). 
2 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

GINSBURG, J., dissenting 

forbidding any discharge of process wastewater from new 

“froth-flotation” mills into waters of the United States. 

See 40 CFR §440.104(b)(1) (2008). Section 306 of the 

Clean Water Act directs EPA to promulgate such performance standards, 33 U. S. C. §1316(a), and declares it 

unlawful for any discharger to violate them, §1316(e).

Ordinarily, that would be the end of the inquiry. 

Coeur Alaska contends, however, that its discharge is

not subject to EPA’s regulatory regime, but is governed, 

instead, by the mutually exclusive permitting authority of 

the Army Corps of Engineers. The Corps has authority,

under §404 of the Act, §1344(a), to issue permits for discharges of “dredged or fill material.” By regulation, a 

discharge that has the effect of raising a water body’s

bottom elevation qualifies as “fill material.” See 33 CFR 

§323.2(e) (2008). Discharges properly within the Corps’ 

permitting authority, it is undisputed, are not subject to

EPA performance standards. See ante, at 20; Brief for 

Petitioner Coeur Alaska 26; Brief for Respondent Southeast Alaska Conservation Council et al. 37. 

The litigation before the Court thus presents a single

question: Is a pollutant discharge prohibited under §306 of

the Act eligible for a §404 permit as a discharge of fill 

material? In agreement with the Court of Appeals, I 

would answer no. The statute’s text, structure, and purpose all mandate adherence to EPA pollution-control

requirements. A discharge covered by a performance

standard must be authorized, if at all, by EPA. 

I 

A 

Congress enacted the Clean Water Act in 1972 “to restore and maintain the chemical, physical, and biological

integrity” of the waters of the United States. 33 U. S. C. 

§1251(a). “The use of any river, lake, stream or ocean as a 

waste treatment system,” the Act’s drafters stated, “is 
Cite as: 557 U. S. ____ (2009) 3 

GINSBURG, J., dissenting 

unacceptable.” S. Rep. No. 92–414, p. 7 (1971). Congress 

announced in the Act itself an ambitious objective: to 

eliminate, by 1985, the discharge of all pollutants into the

Nation’s navigable waters. 33 U. S. C. §1251(a).

In service of its goals, Congress issued a core command:

“[T]he discharge of any pollutant by any person shall be 

unlawful,” except in compliance with the Act’s terms. 

§1311(a). The Act’s substantive requirements—housed 

primarily in Subchapter III, “Standards and Enforcement”—establish “a comprehensive regulatory program 

supervised by an expert administrative agency,” EPA. 

Milwaukee v. Illinois, 451 U. S. 304, 317 (1981). See also 

33 U. S. C. §1251(d) (“Except as otherwise expressly provided . . . , the Administrator of [EPA] shall administer

this [Act].”).

The Act instructs EPA to establish various technologybased, increasingly stringent effluent limitations for categories of point sources. E.g., §§1311, 1314. These limitations, formulated as restrictions “on quantities, rates, and

concentrations of chemical, physical, biological, and other 

constituents,” §1362(11), were imposed to achieve national

uniformity among categories of sources. See, e.g., E. I. du 

Pont de Nemours & Co. v. Train, 430 U. S. 112, 129–130 

(1977). The limitations for a given discharge depend on 

the type of pollutant and source at issue.2 

Of key importance, new sources must meet stringent

“standards of performance” adopted by EPA under §306. 

That section makes it “unlawful for any . . . new source to 

operate . . . in violation of” an applicable performance 

—————— 

2 In addition, the Act requires States to institute comprehensive water quality standards for intrastate waters, subject to EPA approval. 

See §1313. This program supplements the technology-based standards,

serving to “prevent water quality from falling below acceptable levels”

even when point sources comply with effluent limitations. EPA v. 

California ex rel. State Water Resources Control Bd., 426 U. S. 200, 205, 

n. 12 (1976). 
4 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

GINSBURG, J., dissenting 

standard. 33 U. S. C. §1316(e) (emphasis added). In line 

with Congress’ aim “to insure . . .‘maximum feasible control of new sources,’” du Pont, 430 U. S., at 138, the preferred standard for a new source is one “‘permitting no 

discharge of pollutants,’” id., at 137–138 (quoting 33

U. S. C. §1316(a)(1) (emphasis added)). Moreover, new 

sources, unlike existing sources, are not eligible for EPAgranted variances from applicable limitations. 430 U. S., 

at 138.3 

In 1982, EPA promulgated new source performance 

standards for facilities engaged in mining, including those 

using a froth-flotation milling process. See Ore Mining

and Dressing Point Source Category Effluent Limitations

Guidelines and New Source Performance Standards, 47 

Fed. Reg. 54598 (1982). Existing mills, the Agency found, 

were already achieving zero discharge; it was therefore

practicable, EPA concluded, for new mills to do as well. 

Id., at 54602. Accordingly, under 40 CFR §440.104(b)(1),

new mines using the froth-flotation method, as Coeur

Alaska proposes to do, may not discharge wastewater

directly into waters of the United States. 

B 

The nationwide pollution-control requirements just

described are implemented through the National Pollution 

Discharge Elimination System (NPDES), a permitting 

scheme set forth in §402 and administered by EPA and the 

States. The NPDES is the linchpin of the Act, for it transforms generally applicable effluent limitations into the

individual obligations of each discharger. EPA v. Califor-

—————— 

3Even the provision allowing the President to exempt federal installations from compliance with the Act’s requirements—“if he determines 

it to be in the paramount interest of the United States to do so”—does 

not extend to new source standards: “[N]o exemption may be granted 

from the requirements of section [306] or [307] of this [Act].” 33 

U. S. C. §1323(a). 
Cite as: 557 U. S. ____ (2009) 5 

GINSBURG, J., dissenting 

nia ex rel. State Water Resources Control Bd., 426 U. S. 

200, 205 (1976). The discharge of a pollutant is generally 

prohibited unless the source has obtained a NPDES permit. E.g., EPA v. National Crushed Stone Assn., 449 U. S. 

64, 71 (1980) (“Section 402 authorizes the establishment of

the [NPDES], under which every discharger of pollutants 

is required to obtain a permit.”). 

The Act also establishes a separate permitting scheme,

administered by the Corps, for discharges of “dredged or 

fill material.” 33 U. S. C. §1344(a). Section 404 hews to 

the Corps’ established expertise in matters of navigability

and construction. The §404 program does not implement

the uniform, technology-based pollution-control standards 

set out, inter alia, in §306. Instead, §404 permits are

subject to regulatory guidelines based generally on the

impact of a discharge on the receiving environment. See 

§1344(b); ante, at 4–5. 

As the above-described statutory background indicates,

Coeur Alaska’s claim to a §404 permit carries weighty 

implications. If eligible for that permit, Coeur Alaska can 

evade the exacting performance standard prescribed by 

EPA for froth-flotation mills. It may, instead, use Lower

Slate Lake “as the settling pond and disposal site for the 

tailings.” App. 360a (Corps’ Record of Decision). 

II 

Is a pollutant discharge prohibited under §306(e) eligible to receive a §404 permit as a discharge of fill material? 

All agree on preliminary matters. Only one agency, the

Corps or EPA, can issue a permit for the discharge. See 

ante, at 10, 22. Only EPA, through the NPDES program,

issues permits that implement §306. See supra, at 2. 

Further, §306(e) and EPA’s froth-flotation performance 

standard, unless inapplicable here, bar Coeur Alaska’s

proposed discharge. See ante, at 14–15. 

No part of the statutory scheme, in my view, calls into 
6 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL 

GINSBURG, J., dissenting 

question the governance of EPA’s performance standard. 

The text of §306(e) states a clear proscription: “[I]t shall be

unlawful for any owner or operator of any new source to 

operate such source in violation of any standard of performance applicable to such source.” 33 U. S. C. §1316(e).

Under the standard of performance relevant here, “there

shall be no discharge of process wastewater to navigable 

waters from mills that use the froth-flotation process” for

mining gold. 40 CFR §440.104(b)(1). The Act imposes

these requirements without qualification.

Section 404, stating that the Corps “may issue permits”

for the discharge of “dredged or fill material,” does not 

create an exception to §306(e)’s plain command. 33 

U. S. C. §1344(a). Cf. ante, at 12. Section 404 neither 

mentions §306 nor states a contrary requirement. The Act 

can be home to both provisions, with no words added or 

omitted, so long as the category of “dredged or fill material” eligible for a §404 permit is read in harmony with 

§306. Doing so yields a simple rule: Discharges governed

by EPA performance standards are subject to EPA’s administration and receive permits under the NPDES, not

§404.

This reading accords with the Act’s structure and objectives. It retains, through the NPDES, uniform application

of the Act’s core pollution-control requirements, and it

respects Congress’ special concern for new sources. Leaving pollution-related decisions to EPA, moreover, is consistent with Congress’ delegation to that agency of primary 

responsibility to administer the Act. Most fundamental, 

adhering to §306(e)’s instruction honors the overriding 

statutory goal of eliminating water pollution, and Congress’ particular rejection of the use of navigable waters as 

waste disposal sites. See supra, at 2–3. See also 33 

U. S. C. §1324 (creating “clean lakes” program requiring 
Cite as: 557 U. S. ____ (2009) 7 

GINSBURG, J., dissenting 

States to identify and restore polluted lakes).4 

The Court’s reading, in contrast, strains credulity. A 

discharge of a pollutant, otherwise prohibited by firm

statutory command, becomes lawful if it contains sufficient solid matter to raise the bottom of a water body,

transformed into a waste disposal facility. Whole categories of regulated industries can thereby gain immunity

from a variety of pollution-control standards. The loophole

would swallow not only standards governing mining activities, see 40 CFR pt. 440 (effluent limitations and new 

source performance standards for ore mining and dressing); id., pt. 434 (coal mining); id., pt. 436 (mineral mining), but also standards for dozens of other categories of 

regulated point sources, see, e.g., id., pt. 411 (cement 

—————— 

4The Court asserts that “numerous difficulties” will ensue if a discharge governed by a new source performance standard is ineligible for 

a §404 permit. Ante, at 12. Namely, the Court notes, the discharger 

will have to determine whether a performance standard applies to it. 

Ante, at 13. That is not only the usual inquiry under the Clean Water 

Act; it is one Coeur Alaska answered, without apparent difficulty, when

it sought and obtained an EPA permit for the proposed discharge from

the lake into a downstream creek. See ante, at 6. 

JUSTICE BREYER fears that “litera[l] appl[ication]” of performance

standards would interfere with efforts “to build a levee or to replace 

dirt removed from a lake bottom,” and thus “may prove unnecessarily 

strict.” Ante, at 2 (concurring opinion). His concerns are imaginative, 

but it is questionable whether they are real. Apple juice processors,

meatcutters, cement manufacturers, and pharmaceutical producers do

not ordinarily build levees—and it is almost inconceivable that they 

would do so using the waste generated by their highly specific industrial processes. See, e.g., 40 CFR §411.10 (performance standard for

particular cement manufacturing process). Levee construction generally is undertaken by developers or government, entities not subject to

performance standards for such a project. This litigation, furthermore, 

does not illustrate the “difficulty” JUSTICE BREYER perceives. See ante, 

at 1. Coeur Alaska does not seek to build a levee or return dirt to a 

lake; it simply wants to use Lower Slate Lake as a waste disposal site. 
8 COEUR ALASKA, INC. v. SOUTHEAST ALASKA 

 CONSERVATION COUNCIL

GINSBURG, J., dissenting 

manufacturing); id., pt. 425 (leather tanning and finishing); id., pt. 432 (meat and poultry products processing).

See also Brief for American Rivers et al. as Amici Curiae 

26–27 (observing that discharges in these categories “typically contain high volumes of solids”). Providing an escape

hatch for polluters whose discharges contain solid matter,

it bears noting, is particularly perverse; the Act specifically focuses on solids as harmful pollutants. See 33 

U. S. C. §1314(a)(4) (requiring EPA to publish information 

regarding “conventional pollutants,” including “suspended

solids”); Brief for American Rivers, supra, at 28–29, and 

n. 18 (identifying over 50 effluent limitations that restrict 

total suspended solids).5 

Congress, we have recognized, does not “alter the fundamental details of a regulatory scheme in vague terms or

ancillary provisions—it does not, one might say, hide

elephants in mouseholes.” Whitman v. American Trucking 

Assns., Inc., 531 U. S. 457, 467–468 (2001). Yet an alteration of that kind is just what today’s decision imagines. 

Congress, as the Court reads the Act, silently upended, in

an ancillary permitting provision, its painstaking pollution-control scheme. See ante, at 17. Congress did so, the 

Court holds, notwithstanding the lawmakers’ stated effort 

“to restore and maintain the chemical, physical, and biological integrity” of the waters of the United States, 33 

—————— 

5The “safeguards” JUSTICE BREYER identifies are hardly reassuring. 

See ante, at 3 (concurring opinion). Given today’s decision, it is optimistic to expect that EPA or the courts will act vigorously to prevent 

evasion of performance standards. Nor is EPA’s veto power under

§404(c) of the Clean Water Act an adequate substitute for adherence to

§306. That power—exercised only a dozen times over 36 years encompassing more than one million permit applications, see Brief for American Rivers 14—hinges on a finding of “unacceptable adverse effect,” 33 

U. S. C. §1344(c). Destruction of nearly all aquatic life in a pristine

lake apparently does not qualify as “unacceptable.” Reliance on ad hoc 

vetoes, moreover, undermines Congress’ aim to install uniform waterpollution regulation. 
Cite as: 557 U. S. ____ (2009) 9 

GINSBURG, J., dissenting 

U. S. C. §1251(a); their assignment to EPA of the Herculean task of setting strict effluent limitations for many

categories of industrial sources; and their insistence that 

new sources meet even more ambitious standards, not 

subject to exception or variance. Would a rational legislature order exacting pollution limits, yet call all bets off if

the pollutant, discharged into a lake, will raise the water

body’s elevation? To say the least, I am persuaded, that 

is not how Congress intended the Clean Water Act to 

operate.

In sum, it is neither necessary nor proper to read the

statute as allowing mines to bypass EPA’s zero-discharge 

standard by classifying slurry as “fill material.” The use 

of waters of the United States as “settling ponds” for 

harmful mining waste, the Court of Appeals correctly held, 

is antithetical to the text, structure, and purpose of the

Clean Water Act. 

* * * 

For the reasons stated, I would affirm the judgment of

the Ninth Circuit.