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(Cite as: 474 U.S. 121, 106 S.Ct. 455)

Supreme Court of the United States

UNITED STATES, Petitioner

v.

RIVERSIDE BAYVIEW HOMES, INC., et al.

No. 84-701.

Argued Oct. 16, 1985.

Decided Dec. 4, 1985.

Corps of Engineers brought action to enjoin owner 

from filling wetlands without permission of the 

Corps. The District Court for the Eastern District of 

Michigan granted relief and owner appealed. The 

Court of Appeals for the Sixth Circuit, 615 F.2d 

1363, remanded. The District Court again granted 

relief and landowner again appealed. The Court of 

Appeals, 729 F.2d 391, reversed and certiorari was 

granted. The Supreme Court, Justice White, J., held 

that: (1) Corps of Engineers regulations extended 

Corps regulatory authority to wetlands, and (2) Corps 

definition of waters as including wetlands adjacent to 

navigable waters, even if not inundated or frequently 

flooded by the navigable water, was reasonable under 

the statutory authority.

Reversed.

**456 *121 Syllabus FN*

FN* 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 Lumber Co., 200 U.S. 321, 337, 26 

S.Ct. 282, 287, 50 L.Ed. 499.

The Clean Water Act prohibits any discharge of 

dredged or fill materials into “navigable waters”-

defined as the “waters of the United States”-unless 

authorized by a permit issued by the Army Corps of 

Engineers (Corps). Construing the Act to cover all 

“freshwater wetlands” that are adjacent to other covered waters, the Corps issued a regulation defining 

such wetlands as “those areas that are inundated or 

saturated by surface or ground water at a frequency 

and duration sufficient to support, and that under 

normal circumstances do support, a prevalence of 

vegetation typically adapted for life in saturated soil 

conditions.” After respondent Riverside Bayview 

Homes, Inc. (hereafter respondent), began placing fill 

materials on its property near the shores of Lake St. 

Clair, Michigan, the Corps filed suit in Federal District Court to enjoin respondent from filling its property without the Corps' permission. Finding that respondent's property was characterized by the presence of vegetation requiring saturated soil conditions 

for growth, that the source of such soil conditions 

was ground water, and that the wetland on the property was adjacent to a body of navigable water, the 

District Court held that the property was wetland 

subject to the Corps' permit authority. The Court of 

Appeals reversed, construing the Corps' regulation to 

exclude from the category of adjacent wetlands-and 

hence from that of “waters of the United States”-

wetlands that are not subject to flooding by adjacent 

navigable waters at a frequency sufficient to support 

the growth of aquatic vegetation. The court took the 

view that the Corps' authority under the Act and its 

implementing regulations must be narrowly **457

construed to avoid a taking without just compensation in violation of the Fifth Amendment. Under this 

construction, it was held that respondent's property 

was not within the Corps' jurisdiction, because its 

semi-aquatic characteristics were not the result of 

frequent flooding by the nearby navigable waters, 

and that therefore respondent was free to fill the 

property without obtaining a permit.

Held:

1. The Court of Appeals erred in concluding that a 

narrow reading of the Corps' regulatory jurisdiction 

over wetlands was necessary to avoid a taking problem. Neither the imposition of the permit requirement 

*122 itself nor the denial of a permit necessarily constitutes a taking. And the Tucker Act is available to 

provide compensation for takings that may result 

from the Corps' exercise of jurisdiction over wetlands. Pp. 458-460.

2. The District Court's findings are not clearly erroneous and plainly bring respondent's property within 

the category of wetlands and thus of the “waters of 

the United States” as defined by the regulation in 
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question. Pp. 460-461.

3. The language, policies, and history of the Clean 

Water Act compel a finding that the Corps has acted 

reasonably in interpreting the Act to require permits 

for the discharge of material into wetlands adjacent to 

other “waters of the United States.” Pp. 461-465.

729 F.2d 391 (CA6 1984), reversed.

WHITE, J., delivered the opinion for a unanimous 

Court.

Kathryn A. Oberly argued the cause for the United 

States. With her on the briefs were former Solicitor 

General Lee, Acting Solicitor General Fried, Assistant Attorney General Habicht, Deputy Solicitor 

General Claiborne, and Anne S. Almy.

Edgar B. Washburn argued the cause for respondents. 

With him on the brief was Richard K. Gienapp.*

* Briefs of amici curiae urging reversal were filed for 

the National Wildlife Federation et al. by Jerry Jackson, Frank J. Kelley, Attorney General of Michigan, 

and Louis Caruso, Solicitor General; and for the State 

of California et al. by John K. Van de Kamp, Attorney General of California, N. Gregory Taylor and 

Theodora Berger, Assistant Attorneys General, and 

Steven H. Kaufmann and David W. Hamilton, Deputy 

Attorneys General, Joseph I. Lieberman, Attorney 

General of Connecticut, Michael A. Lilly, Attorney 

General of Hawaii, Neil F. Hartigan, Attorney General of Illinois, and Jill Wine-Banks, Solicitor General, William J. Guste, Jr., Attorney General of Louisiana, Stephen H. Sachs, Attorney General of Maryland, Hubert H. Humphrey III, Attorney General of 

Minnesota, William L. Webster, Attorney General of 

Missouri, Mike Greely, Attorney General of Montana, Robert M. Spire, Attorney General of Nebraska, 

Paul Bardacke, Attorney General of New Mexico, 

Lacy H. Thornburg, Attorney General of North Carolina, Arlene Violet, Attorney General of Rhode Island, W.J. Michael Cody, Attorney General of Tennessee, Jeffrey L. Amestoy, Attorney General of 

Vermont, Charlie Brown, Attorney General of West 

Virginia, and Bronson C. La Follette, Attorney General of Wisconsin.

Briefs of amici curiae urging affirmance were filed 

for the American Petroleum Institute by Stark Ritchie

and James K. Jackson; for the Citizens of Chincoteague for a Reasonable Wetlands Policy by Richard 

R. Nageotte; for the Mid-Atlantic Developers Association by Kenneth D. McPherson; and for the Pacific 

Legal Foundation et al. by Ronald A. Zumbrun and 

Sam Kazman.

R. Sarah Compton and Robin S. Conrad filed a brief 

for the Chamber of Commerce of the United States as 

amicus curiae.

*123 Justice WHITE delivered the opinion of the 

Court.

This case presents the question whether the Clean 

Water Act (CWA), 33 U.S.C. § 1251 et seq., together 

with certain regulations promulgated under its authority by the Army Corps of Engineers, authorizes 

the Corps to require landowners to obtain permits 

from the Corps before discharging fill material into 

wetlands adjacent to navigable bodies of water and 

their tributaries.

I

[1][2] The relevant provisions of the Clean Water Act 

originated in the Federal Water Pollution Control Act 

Amendments of 1972, 86 Stat. 816, and have remained essentially unchanged since that time. Under 

§§ 301 and 502 of the Act, 33 U.S.C. §§ 1311 and 

1362, any discharge of dredged or fill materials into 

“navigable waters”-defined as the “waters of the 

United States”-is forbidden unless authorized by a 

permit issued by the Corps of Engineers pursuant to § 

404, 33 U.S.C. § 1344.

FN1 After initially construing 

the Act to cover only waters navigable in fact, in 

1975 the Corps issued interim final regulations redefining “the waters of the United States” to include not 

only actually navigable waters but also tributaries of 

such waters, interstate waters and their tributaries, 

and nonnavigable intrastate waters whose use or misuse could affect interstate commerce. *12440 

Fed.Reg. 31320 1975). More importantly for present 

purposes, the Corps construed the Act to cover all 

“freshwater wetlands” that were adjacent to other 

covered waters. A “freshwater wetland” was defined 

as an area that is “periodically inundated” and is 

“normally characterized by the prevalence of vegetation that requires saturated soil conditions for growth 

and reproduction.” 33 CFR § 209.120(d)(2)(h ) 

(1976). In 1977, the Corps refined its definition of 

wetlands by eliminating the reference to periodic 
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inundation and **458 making other minor changes. 

The 1977 definition read as follows:

FN1. With respect to certain waters, the 

Corps' authority may be transferred to States 

that have devised federally approved permit 

programs. CWA § 404(g), as added, 91 Stat. 

1600, 33 U.S.C. § 1344(g). Absent such an 

approved program, the Corps retains jurisdiction under § 404 over all “waters of the 

United States.”

“The term ‘wetlands' means those areas that are inundated or saturated by surface or ground water at a 

frequency and duration sufficient to support, and that 

under normal circumstances do support, a prevalence 

of vegetation typically adapted for life in saturated 

soil conditions. Wetlands generally include swamps, 

marshes, bogs and similar areas.” 33 CFR § 323.2(c) 

(1978).

In 1982, the 1977 regulations were replaced by substantively identical regulations that remain in force 

today. See 33 CFR § 323.2 (1985). FN2

FN2. The regulations also cover certain wetlands not necessarily adjacent to other waters. See 33 CFR §§ 323.2(a)(2) and (3) 

(1985). These provisions are not now before 

us.

Respondent Riverside Bayview Homes, Inc. (hereafter respondent), owns 80 acres of low-lying, marshy 

land near the shores of Lake St. Clair in Macomb 

County, Michigan. In 1976, respondent began to 

place fill materials on its property as part of its preparations for construction of a housing development. 

The Corps of Engineers, believing that the property 

was an “adjacent wetland” under the 1975 regulation 

defining “waters of the United States,” filed suit in 

the United States District Court for the Eastern District of Michigan, seeking to enjoin respondent from 

filling the property without the permission of the 

Corps.

*125 The District Court held that the portion of respondent's property lying below 575.5 feet above sea 

level was a covered wetland and enjoined respondent 

from filling it without a permit. Civ. No. 77-70041 

(Feb. 24, 1977) (App. to Pet. for Cert. 22a); Civ. No. 

77-70041 (June 21, 1979) (App. to Pet. for Cert. 

32a). Respondent appealed, and the Court of Appeals 

remanded for consideration of the effect of the intervening 1977 amendments to the regulation. 615 F.2d 

1363 (1980). On remand, the District Court again 

held the property to be a wetland subject to the Corps' 

permit authority. Civ. No. 77-70041 (May 10, 1981) 

(App. to Pet. for Cert. 42a).

Respondent again appealed, and the Sixth Circuit 

reversed. 729 F.2d 391 (1984). The court construed 

the Corps' regulation to exclude from the category of 

adjacent wetlands-and hence from that of “waters of 

the United States”-wetlands that were not subject to 

flooding by adjacent navigable waters at a frequency 

sufficient to support the growth of aquatic vegetation. 

The court adopted this construction of the regulation 

because, in its view, a broader definition of wetlands 

might result in the taking of private property without 

just compensation. The court also expressed its doubt 

that Congress, in granting the Corps jurisdiction to 

regulate the filling of “navigable waters,” intended to 

allow regulation of wetlands that were not the result 

of flooding by navigable waters.FN3 Under the court's 

reading of the regulation, respondent's property was 

not within the Corps' jurisdiction, because its 

semiaquatic characteristics were not the result of frequent flooding by the nearby navigable waters. Respondent was therefore free to fill the property without obtaining a permit.

FN3. In denying the Government's petition 

for rehearing, the panel reiterated somewhat 

more strongly its belief that the Corps' construction of its regulation was “overbroad 

and inconsistent with the language of the 

Act.” 729 F.2d, at 401.

*126 We granted certiorari to consider the proper 

interpretation of the Corps' regulation defining “waters of the United States” and the scope of the Corps' 

jurisdiction under the Clean Water Act, both of which 

were called into question by the Sixth Circuit's ruling. 

469 U.S. 1206, 105 S.Ct. 1166, 84 L.Ed.2d 318 

(1985). We now reverse.

II

The question whether the Corps of Engineers may 

demand that respondent obtain a permit before placing fill material on its property is primarily one of 

regulatory and statutory interpretation: we must determine whether respondent's property is an **459
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“adjacent wetland” within the meaning of the applicable regulation, and, if so, whether the Corps' jurisdiction over “navigable waters” gives it statutory 

authority to regulate discharges of fill material into 

such a wetland. In this connection, we first consider 

the Court of Appeals' position that the Corps' regulatory authority under the statute and its implementing 

regulations must be narrowly construed to avoid a 

taking without just compensation in violation of the 

Fifth Amendment.

[3] We have frequently suggested that governmental 

land-use regulation may under extreme circumstances 

amount to a “taking” of the affected property. See, 

e.g., Williamson County Regional Planning Comm'n 

v. Hamilton Bank, 473 U.S. 172, 105 S.Ct. 3108, 87 

L.Ed.2d 126 (1985); Penn Central Transportation 

Co. v. New York City, 438 U.S. 104, 98 S.Ct. 2646, 

57 L.Ed.2d 631 (1978). We have never precisely defined those circumstances, see id., at 123-128, 98 

S.Ct., at 2658-61; but our general approach was 

summed up in Agins v. Tiburon, 447 U.S. 255, 260, 

100 S.Ct. 2138, 2141, 65 L.Ed.2d 106 (1980), where 

we stated that the application of land-use regulations 

to a particular piece of property is a taking only “if 

the ordinance does not substantially advance legitimate state interests ... or denies an owner economically viable use of his land.” Moreover, we have 

made it quite clear that the mere assertion of regulatory jurisdiction by a governmental body does not 

constitute a regulatory taking. See *127Hodel v. Virginia Surface Mining & Reclamation Assn., 452 U.S. 

264, 293-297, 101 S.Ct. 2352, 2369-71, 69 L.Ed.2d 1 

(1981). The reasons are obvious. A requirement that 

a person obtain a permit before engaging in a certain 

use of his or her property does not itself “take” the 

property in any sense: after all, the very existence of 

a permit system implies that permission may be 

granted, leaving the landowner free to use the property as desired. Moreover, even if the permit is denied, there may be other viable uses available to the 

owner. Only when a permit is denied and the effect of 

the denial is to prevent “economically viable” use of 

the land in question can it be said that a taking has 

occurred.

[4][5][6] If neither the imposition of the permit requirement itself nor the denial of a permit necessarily 

constitutes a taking, it follows that the Court of Appeals erred in concluding that a narrow reading of the 

Corps' regulatory jurisdiction over wetlands was 

“necessary” to avoid “a serious taking problem.” 729 

F.2d, at 398.FN4 We have held that, in general, 

“[e]quitable relief is not available to enjoin an alleged 

taking of private property for a public use, duly authorized by law, *128 when a suit for compensation 

can be brought against the sovereign subsequent to a 

taking.” Ruckelshaus v. Monsanto Co., 467 U.S. 986, 

1016, 104 S.Ct. 2862, 2880, 81 L.Ed.2d 815 (1984)

(footnote omitted). This maxim rests on the principle 

that so long as compensation is available for those 

whose property is in fact taken, the governmental 

action is not unconstitutional. **460Williamson 

County, supra, 473 U.S., at 194-195, 105 S.Ct., at 

3120-3121. For precisely the same reason, the possibility that the application of a regulatory program 

may in some instances result in the taking of individual pieces of property is no justification for the use of 

narrowing constructions to curtail the program if 

compensation will in any event be available in those 

cases where a taking has occurred. Under such circumstances, adoption of a narrowing construction 

does not constitute avoidance of a constitutional difficulty, cf. Ashwander v. TVA, 297 U.S. 288, 341-

356, 56 S.Ct. 466, 480-87, 80 L.Ed. 688 (1936)

(Brandeis, J., concurring); it merely frustrates permissible applications of a statute or regulation.FN5

Because the Tucker Act, 28 U.S.C. § 1491, which 

presumptively supplies a means of obtaining compensation for any taking that may occur through the 

operation of a federal statute, see Ruckelshaus v. 

Monsanto Co., supra, 467 U.S., at 1017, 104 S.Ct., at 

2880 is available to provide compensation for takings 

that may result from the Corps' exercise of jurisdiction over wetlands, the Court of Appeals' fears that 

application of the Corps' permit program might result 

in a taking did not justify the court in adopting a *129

more limited view of the Corps' authority than the 

terms of the relevant regulation might otherwise support. FN6

FN4. Even were the Court of Appeals correct in concluding that a narrowing construction of the regulation is necessary to avoid 

takings of property through the application 

of the permit requirement, the construction 

adopted-which requires a showing of frequent flooding before property may be classified as a wetland-is hardly tailored to the 

supposed difficulty. Whether the denial of a 

permit would constitute a taking in any 

given case would depend upon the effect of 

the denial on the owner's ability to put the 
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property to productive use. Whether the 

property was frequently flooded would have 

no particular bearing on this question, for 

overbroad regulation of even completely 

submerged property may constitute a taking. 

See, e.g., Kaiser Aetna v. United States, 444 

U.S. 164, 100 S.Ct. 383, 62 L.Ed.2d 332 

(1979). Indeed, it may be more likely that 

denying a permit to fill frequently flooded 

property will prevent economically viable 

use of the property than denying a permit to 

fill property that is wet but not flooded. Of 

course, by excluding a large chunk of the 

Nation's wetlands from the regulatory definition, the Court of Appeals' construction 

might tend to limit the gross number of takings that the permit program would otherwise entail; but the construction adopted still 

bears an insufficiently precise relationship 

with the problem it seeks to avoid.

FN5. United States v. Security Industrial 

Bank, 459 U.S. 70, 103 S.Ct. 407, 74 

L.Ed.2d 235 (1982), in which we adopted a 

narrowing construction of a statute to avoid 

a taking difficulty, is not to the contrary. In 

that case, the problem was that there was a 

substantial argument that retroactive application of a particular provision of the Bankruptcy Code would in every case constitute a 

taking; the solution was to avoid the difficulty by construing the statute to apply only 

prospectively. Such an approach is sensible 

where it appears that there is an identifiable 

class of cases in which application of a statute will necessarily constitute a taking. As 

we have observed, this is not such a case: 

there is no identifiable set of instances in 

which mere application of the permit requirement will necessarily or even probably 

constitute a taking. The approach of adopting a limiting construction is thus unwarranted.

FN6. Because the Corps has now denied respondent a permit to fill its property, respondent may well have a ripe claim that a 

taking has occurred. On the record before 

us, however, we have no basis for evaluating 

this claim, because no evidence has been introduced that bears on the question of the 

extent to which denial of a permit to fill this 

property will prevent economically viable 

uses of the property or frustrate reasonable 

investment-backed expectations. In any 

event, this lawsuit is not the proper forum 

for resolving such a dispute: if the Corps has 

indeed effectively taken respondent's property, respondent's proper course is not to resist the Corps' suit for enforcement by denying that the regulation covers the property, 

but to initiate a suit for compensation in the 

Claims Court. In so stating, of course, we do 

not rule that respondent will be entitled to 

compensation for any temporary denial of 

use of its property should the Corps ultimately relent and allow it to be filled. We 

have not yet resolved the question whether 

compensation is a constitutionally mandated 

remedy for “temporary regulatory takings,” 

see Williamson County Planning Comm'n v. 

Hamilton Bank, 473 U.S. 172, 105 S.Ct. 

3108, 87 L.Ed.2d 126 (1985), and this case 

provides no occasion for deciding the issue.

III

[7] Purged of its spurious constitutional overtones, 

the question whether the regulation at issue requires 

respondent to obtain a permit before filling its property is an easy one. The regulation extends the Corps' 

authority under § 404 to all wetlands adjacent to 

navigable or interstate waters and their tributaries. 

Wetlands, in turn, are defined as lands that are “inundated or saturated by surface or ground water at a 

frequency and duration sufficient to support, and that 

under normal circumstances do support, a prevalence 

of vegetation typically adapted for life in saturated 

soil conditions.” 33 CFR § 323.2(c) (1985) (emphasis 

added). The plain language of the regulation refutes 

the Court of Appeals' conclusion that inundation or 

“frequent flooding” by the adjacent body of water is a 

sine qua non of a wetland under the regulation. Indeed, the regulation could hardly state more clearly 

that saturation by either surface or ground water is 

sufficient to bring an area within the category of wetlands, provided that *130 the saturation is sufficient 

to and does support wetland vegetation.

The history of the regulation underscores the absence 

of any requirement of **461 inundation. The interim 

final regulation that the current regulation replaced 
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explicitly included a requirement of “periodi[c] inundation.” 33 CFR § 209.120(d)(2)(h ) (1976). In deleting the reference to “periodic inundation” from the 

regulation as finally promulgated, the Corps explained that it was repudiating the interpretation of 

that language “as requiring inundation over a record 

period of years.” 42 Fed.Reg. 37128 (1977). In fashioning its own requirement of “frequent flooding” the 

Court of Appeals improperly reintroduced into the 

regulation precisely what the Corps had excised.FN7

FN7. The Court of Appeals seems also to 

have rested its frequent-flooding requirement on the language in the regulation stating that wetlands encompass those areas that 

“under normal circumstances do support” 

aquatic or semi-aquatic vegetation. In the 

preamble to the final regulation, the Corps 

explained that this language was intended in 

part to exclude areas characterized by the 

“abnormal presence of aquatic vegetation in 

a non-aquatic area.” 42 Fed.Reg. 37128 

(1977). Apparently, the Court of Appeals 

concluded that the growth of wetlands vegetation in soils saturated by ground water 

rather than flooded by waters emanating 

from an adjacent navigable water or its 

tributaries was “abnormal” within the meaning of the preamble. This interpretation is 

untenable in light of the explicit statements 

in both the regulation and its preamble that 

areas saturated by ground water can fall 

within the category of wetlands. It would be 

nonsensical for the Corps to define wetlands 

to include such areas and then in the same 

sentence exclude them on the ground that 

the presence of wetland vegetation in such 

areas was abnormal. Evidently, the Corps 

had something else in mind when it referred 

to “abnormal” growth of wetlands vegetation-namely, the aberrational presence of 

such vegetation in dry, upland areas.

[8] Without the nonexistent requirement of frequent 

flooding, the regulatory definition of adjacent wetlands covers the property here. The District Court 

found that respondent's property was “characterized 

by the presence of vegetation that requires saturated 

soil conditions for growth and reproduction,” *131

App. to Pet. for Cert. 24a, and that the source of the 

saturated soil conditions on the property was ground 

water. There is no plausible suggestion that these 

findings are clearly erroneous, and they plainly bring 

the property within the category of wetlands as defined by the current regulation. In addition, the court 

found that the wetland located on respondent's property was adjacent to a body of navigable water, since 

the area characterized by saturated soil conditions 

and wetland vegetation extended beyond the boundary of respondent's property to Black Creek, a navigable waterway. Again, the court's finding is not 

clearly erroneous. Together, these findings establish 

that respondent's property is a wetland adjacent to a 

navigable waterway. Hence, it is part of the “waters 

of the United States” as defined by 33 CFR § 323.2 

(1985), and if the regulation itself is valid as a construction of the term “waters of the United States” as 

used in the Clean Water Act, a question which we 

now address, the property falls within the scope of 

the Corps' jurisdiction over “navigable waters” under 

§ 404 of the Act.

IV

A

[9] An agency's construction of a statute it is charged 

with enforcing is entitled to deference if it is reasonable and not in conflict with the expressed intent of 

Congress. Chemical Manufacturers Assn. v. Natural 

Resources Defense Council, Inc., 470 U.S. 116, 125, 

105 S.Ct. 1102, 1107-1108, 84 L.Ed.2d 90 (1985); 

Chevron U.S.A. Inc. v. Natural Resources Defense 

Council, Inc., 467 U.S. 837, 842-845, 104 S.Ct. 2778, 

2781-2783, 81 L.Ed.2d 694 (1984). Accordingly, our 

review is limited to the question whether it is reasonable, in light of the language, policies, and legislative 

history of the Act for the Corps to exercise jurisdiction over wetlands adjacent to but not regularly 

flooded by rivers, streams, and other hydrographic 

features more conventionally identifiable as “waters.” FN8

FN8. We are not called upon to address the 

question of the authority of the Corps to 

regulate discharges of fill material into wetlands that are not adjacent to bodies of open 

water, see 33 CFR §§ 323.2(a)(2) and (3) 

(1985), and we do not express any opinion 

on that question.

*132 **462 On a purely linguistic level, it may ap-
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pear unreasonable to classify “lands,” wet or otherwise, as “waters.” Such a simplistic response, however, does justice neither to the problem faced by the 

Corps in defining the scope of its authority under § 

404(a) nor to the realities of the problem of water 

pollution that the Clean Water Act was intended to 

combat. In determining the limits of its power to 

regulate discharges under the Act, the Corps must 

necessarily choose some point at which water ends 

and land begins. Our common experience tells us that 

this is often no easy task: the transition from water to 

solid ground is not necessarily or even typically an 

abrupt one. Rather, between open waters and dry land 

may lie shallows, marshes, mudflats, swamps, bogsin short, a huge array of areas that are not wholly 

aquatic but nevertheless fall far short of being dry 

land. Where on this continuum to find the limit of 

“waters” is far from obvious.

[10][11] Faced with such a problem of defining the 

bounds of its regulatory authority, an agency may 

appropriately look to the legislative history and underlying policies of its statutory grants of authority. 

Neither of these sources provides unambiguous guidance for the Corps in this case, but together they do 

support the reasonableness of the Corps' approach of 

defining adjacent wetlands as “waters” within the 

meaning of § 404(a). Section 404 originated as part 

of the Federal Water Pollution Control Act Amendments of 1972, which constituted a comprehensive 

legislative attempt “to restore and maintain the 

chemical, physical, and biological integrity of the 

Nation's waters.” CWA § 101, 33 U.S.C. § 1251. 

This objective incorporated a broad, systemic view of 

the goal of maintaining and improving water quality: 

as the House Report on the legislation put it, “the 

word ‘integrity’ ... refers to a condition in which the 

natural structure and function of ecosystems is [are] 

maintained.” H.R.Rep. No. 92-911, p. 76 (1972). 

Protection of aquatic ecosystems, Congress recognized,*133 demanded broad federal authority to control pollution, for “[w]ater moves in hydrologic cycles and it is essential that discharge of pollutants be 

controlled at the source.” S.Rep. No. 92-414, p. 77

(1972), U.S.Code Cong. & Admin.News 1972, pp. 

3668, 3742.

In keeping with these views, Congress chose to define the waters covered by the Act broadly. Although 

the Act prohibits discharges into “navigable waters,” 

see CWA §§ 301(a), 404(a), 502(12), 33 U.S.C. §§ 

1311(a), 1344(a), 1362(12), the Act's definition of 

“navigable waters” as “the waters of the United 

States” makes it clear that the term “navigable” as 

used in the Act is of limited import. In adopting this 

definition of “navigable waters,” Congress evidently 

intended to repudiate limits that had been placed on 

federal regulation by earlier water pollution control 

statutes and to exercise its powers under the Commerce Clause to regulate at least some waters that 

would not be deemed “navigable” under the classical 

understanding of that term. See S.Conf.Rep. No. 92-

1236, p. 144 (1972); 118 Cong.Rec. 33756-33757 

(1972) (statement of Rep. Dingell).

Of course, it is one thing to recognize that Congress 

intended to allow regulation of waters that might not 

satisfy traditional tests of navigability; it is another to 

assert that Congress intended to abandon traditional 

notions of “waters” and include in that term “wetlands” as well. Nonetheless, the evident breadth of 

congressional concern for protection of water quality 

and aquatic ecosystems suggests that it is reasonable 

for the Corps to interpret the term “waters” to encompass wetlands adjacent to waters as more conventionally defined. Following the lead of the Environmental Protection Agency, see 38 Fed.Reg. 10834 

(1973), the Corps has determined that wetlands adjacent to navigable waters do as a general matter play a 

key role in protecting and enhancing water quality:

**463 “The regulation of activities that cause water 

pollution cannot rely on ... artificial lines ... but must 

focus on all waters that together form the entire 

aquatic system. *134 Water moves in hydrologic 

cycles, and the pollution of this part of the aquatic 

system, regardless of whether it is above or below an 

ordinary high water mark, or mean high tide line, will 

affect the water quality of the other waters within that 

aquatic system.

“For this reason, the landward limit of Federal jurisdiction under Section 404 must include any adjacent 

wetlands that form the border of or are in reasonable 

proximity to other waters of the United States, as 

these wetlands are part of this aquatic system.” 42 

Fed.Reg. 37128 (1977).

We cannot say that the Corps' conclusion that adjacent wetlands are inseparably bound up with the “waters” of the United States-based as it is on the Corps' 

and EPA's technical expertise-is unreasonable. In 
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view of the breadth of federal regulatory authority 

contemplated by the Act itself and the inherent difficulties of defining precise bounds to regulable waters, the Corps' ecological judgment about the relationship between waters and their adjacent wetlands 

provides an adequate basis for a legal judgment that 

adjacent wetlands may be defined as waters under the 

Act.

[12] This holds true even for wetlands that are not the 

result of flooding or permeation by water having its 

source in adjacent bodies of open water. The Corps 

has concluded that wetlands may affect the water 

quality of adjacent lakes, rivers, and streams even 

when the waters of those bodies do not actually inundate the wetlands. For example, wetlands that are not 

flooded by adjacent waters may still tend to drain into 

those waters. In such circumstances, the Corps has 

concluded that wetlands may serve to filter and purify water draining into adjacent bodies of water, see 

33 CFR § 320.4(b)(2)(vii) (1985), and to slow the 

flow of surface runoff into lakes, rivers, and streams 

and thus prevent flooding and erosion, see §§ 

320.4(b)(2)(iv) and (v). In addition, adjacent wetlands may “serve significant natural biological functions, including food chain production, general habitat, and nesting, *135 spawning, rearing and resting 

sites for aquatic ... species.” § 320.4(b)(2)(i). In short, 

the Corps has concluded that wetlands adjacent to 

lakes, rivers, streams, and other bodies of water may 

function as integral parts of the aquatic environment 

even when the moisture creating the wetlands does 

not find its source in the adjacent bodies of water. 

Again, we cannot say that the Corps' judgment on 

these matters is unreasonable, and we therefore conclude that a definition of “waters of the United 

States” encompassing all wetlands adjacent to other 

bodies of water over which the Corps has jurisdiction 

is a permissible interpretation of the Act. Because 

respondent's property is part of a wetland that actually abuts on a navigable waterway, respondent was 

required to have a permit in this case.FN9

FN9. Of course, it may well be that not 

every adjacent wetland is of great importance to the environment of adjoining bodies 

of water. But the existence of such cases 

does not seriously undermine the Corps' decision to define all adjacent wetlands as 

“waters.” If it is reasonable for the Corps to 

conclude that in the majority of cases, adjacent wetlands have significant effects on water quality and the aquatic ecosystem, its 

definition can stand. That the definition may 

include some wetlands that are not significantly intertwined with the ecosystem of adjacent waterways is of little moment, for 

where it appears that a wetland covered by 

the Corps' definition is in fact lacking in importance to the aquatic environment-or 

where its importance is outweighed by other 

values-the Corps may always allow development of the wetland for other uses simply 

by issuing a permit. See 33 CFR § 

320.4(b)(4) (1985).

B

Following promulgation of the Corps' interim final 

regulations in 1975, the Corps' assertion of authority 

under § 404 over waters not actually navigable engendered some congressional opposition. The controversy came to a head during Congress' consideration of the Clean Water Act of **464 1977, a major 

piece of legislation aimed at achieving “interim improvements within the existing framework” of the 

Clean Water Act. H.R.Rep. No. 95-139, pp. 1-2 

(1977). In the *136 end, however, as we shall explain, Congress acquiesced in the administrative construction.

Critics of the Corps' permit program attempted to 

insert limitations on the Corps' § 404 jurisdiction into 

the 1977 legislation: the House bill as reported out of 

committee proposed a redefinition of “navigable waters” that would have limited the Corps' authority 

under § 404 to waters navigable in fact and their adjacent wetlands (defined as wetlands periodically 

inundated by contiguous navigable waters). H.R. 

3199, 95th Cong., 1st Sess., § 16 (1977). The bill 

reported by the Senate Committee on Environment 

and Public Works, by contrast, contained no redefinition of the scope of the “navigable waters” covered 

by § 404, and dealt with the perceived problem of 

overregulation by the Corps by exempting certain 

activities (primarily agricultural) from the permit 

requirement and by providing for assumption of some 

of the Corps' regulatory duties by federally approved 

state programs. S.1952, 95th Cong., 1st Sess., § 49(b) 

(1977). On the floor of the Senate, however, an 

amendment was proposed limiting the scope of 

“navigable waters” along the lines set forth in the 
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House bill. 123 Cong.Rec. 26710-26711 (1977).

In both Chambers, debate on the proposals to narrow 

the definition of navigable waters centered largely on 

the issue of wetlands preservation. See id., at 10426-

10432 (House debate); id., at 26710-26729 (Senate 

debate). Proponents of a more limited § 404 jurisdiction contended that the Corps' assertion of jurisdiction over wetlands and other nonnavigable “waters” 

had far exceeded what Congress had intended in enacting § 404. Opponents of the proposed changes 

argued that a narrower definition of “navigable waters” for purposes of § 404 would exclude vast 

stretches of crucial wetlands from the Corps' jurisdiction, with detrimental effects on wetlands ecosystems, water quality, and the aquatic environment 

generally. The debate, particularly in the Senate, was 

lengthy. In the House, the debate ended with the 

adoption of a narrowed definition of “waters”; but in 

the Senate the limiting *137 amendment was defeated and the old definition retained. The Conference Committee adopted the Senate's approach: efforts to narrow the definition of “waters” were abandoned; the legislation as ultimately passed, in the 

words of Senator Baker, “retain[ed] the comprehensive jurisdiction over the Nation's waters exercised in 

the 1972 Federal Water Pollution Control Act.” FN10

FN10. 123 Cong.Rec. 39209 (1977); see 

also id., at 39210 (statement of Sen. Wallop); id., at 39196 (statement of Sen. 

Randolph); id., at 38950 (statement of Rep. 

Murphy); id., at 38994 (statement of Rep. 

Ambro).

[13] The significance of Congress' treatment of the 

Corps' § 404 jurisdiction in its consideration of the 

Clean Water Act of 1977 is twofold. First, the scope 

of the Corps' asserted jurisdiction over wetlands was 

specifically brought to Congress' attention, and Congress rejected measures designed to curb the Corps' 

jurisdiction in large part because of its concern that 

protection of wetlands would be unduly hampered by 

a narrowed definition of “navigable waters.” Although we are chary of attributing significance to 

Congress' failure to act, a refusal by Congress to 

overrule an agency's construction of legislation is at 

least some evidence of the reasonableness of that 

construction, particularly where the administrative 

construction has been brought to Congress' attention 

through legislation specifically designed to supplant 

it. See Bob Jones University v. United States, 461 

U.S. 574, 599-601, 103 S.Ct. 2017, 2032-34, 76 

L.Ed.2d 157 (1983); United States v. Rutherford, 442 

U.S. 544, 554, and n. 10, 99 S.Ct. 2470, 2476, and n. 

10, 61 L.Ed.2d 68 (1979).

Second, it is notable that even those who would have 

restricted the reach of the Corps' jurisdiction would 

have done so not **465 by removing wetlands altogether from the definition of “waters of the United 

States,” but only by restricting the scope of “navigable waters” under § 404 to waters navigable in fact 

and their adjacent wetlands. In amending the definition of “navigable waters” for purposes of § 404 

only, the backers of the House bill would have left 

intact the existing definition of “navigable waters” 

for purposes of § 301 of the *138 Act, which generally prohibits discharges of pollutants into navigable 

waters. As the House Report explained: “ ‘Navigable 

waters' as used in section 301 includes all of the waters of the United States including their adjacent wetlands.” H.R.Rep. No. 95-139, p. 24 (1977). Thus, 

even those who thought that the Corps' existing authority under § 404 was too broad recognized (1) that 

the definition of “navigable waters” then in force for 

both § 301 and § 404 was reasonably interpreted to 

include adjacent wetlands, (2) that the water quality 

concerns of the Clean Water Act demanded regulation of at least some discharges into wetlands, and (3) 

that whatever jurisdiction the Corps would retain 

over discharges of fill material after passage of the 

1977 legislation should extend to discharges into 

wetlands adjacent to any waters over which the Corps 

retained jurisdiction. These views provide additional 

support for a conclusion that Congress in 1977 acquiesced in the Corps' definition of waters as including 

adjacent wetlands.

Two features actually included in the legislation that 

Congress enacted in 1977 also support the view that 

the Act authorizes the Corps to regulate discharges 

into wetlands. First, in amending § 404 to allow federally approved state permit programs to supplant 

regulation by the Corps of certain discharges of fill 

material, Congress provided that the States would not 

be permitted to supersede the Corps' jurisdiction to 

regulate discharges into actually navigable waters 

and waters subject to the ebb and flow of the tide, 

“including wetlands adjacent thereto.” CWA § 

404(g)(1), 33 U.S.C. § 1344(g)(1). Here, then, Congress expressly stated that the term “waters” included 
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adjacent wetlands.FN11 Second, the *139 1977 Act 

authorized an appropriation of $6 million for completion by the Department of Interior of a “National 

Wetlands Inventory” to assist the States “in the development and operation of programs under this 

Act.” CWA § 208(i)(2), 33 U.S.C. § 1288(i)(2). The 

enactment of this provision reflects congressional 

recognition that wetlands are a concern of the Clean 

Water Act and supports the conclusion that in defining the waters covered by the Act to include wetlands, the Corps is “implementing congressional policy rather than embarking on a frolic of its own.” Red 

Lion Broadcasting Co. v. FCC, 395 U.S. 367, 375, 89 

S.Ct. 1794, 1799, 23 L.Ed.2d 371 (1969).

FN11. To be sure, § 404(g)(1) does not conclusively determine the construction to be 

placed on the use of the term “waters” elsewhere in the Act (particularly in § 502(7), 

which contains the relevant definition of 

“navigable waters”); however, in light of the 

fact that the various provisions of the Act 

should be read in pari materia, it does at 

least suggest strongly that the term “waters” 

as used in the Act does not necessarily exclude “wetlands.”

C

We are thus persuaded that the language, policies, 

and history of the Clean Water Act compel a finding 

that the Corps has acted reasonably in interpreting the 

Act to require permits for the discharge of fill material into wetlands adjacent to the “waters of the 

United States.” The regulation in which the Corps has 

embodied this interpretation by its terms includes the 

wetlands on respondent's property within the class of 

waters that may not be filled without a permit; and, as 

we have seen, there is no reason to interpret the regulation more narrowly than its terms would indicate. 

Accordingly, the judgment of the Court of Appeals is

Reversed.

U.S.Mich.,1985.

U.S. v. Riverside Bayview Homes, Inc.

474 U.S. 121, 106 S.Ct. 455, 23 ERC 1561, 88 

L.Ed.2d 419, 54 USLW 4027, 16 Envtl. L. Rep. 

20,086