opinion: Mr. Justice Douglas
  delivered the opinion of the Court.
  This is a suit by the United States to enjoin respondent companies from depositing industrial solids in the Calumet River (which flows out of Lake Michigan and connects eventually with the Mississippi) without first obtaining a permit from the Chief of Engineers of the Army providing conditions for the removal of the deposits and to order and direct them to restore the depth of the channel to 21 feet by removing portions of existing deposits.
  The District Court found that the Calumet was used by vessels requiring a 21-foot draft, and that that depth has been maintained by the Corps of Engineers. Respondents, who operate mills on the banks of the river for the production of iron and related products, use large quantities of the water from the river, returning it through numerous sewers. The processes they use create industrial waste containing various solids. A substantial quantity of these solids is recovered in settling basins but, according to the findings, many fine particles are discharged into the river and they flocculate into larger units and are deposited in the river, bottom. Soundings show a progressive decrease in the depth of the river in the vicinity of respondents’ mills. But respondents have refused, since 1951, the demand of the Corps of Engineers that they dredge that portion of the river. The shoaling conditions being created in the vicinity of these plants were found by the District Court to be created by the waste discharged from the mills of respondents. This shoaling was found to have reduced the depth of the channel to 17 feet in some places and to 12 feet in others. The District Court made findings which credited respondents with 81.5% of the waste deposited in the channel, and it allocated that in various proportions among the three respondents. See 155 F. Supp. 442.
  The Court of Appeals did not review the sufficiency of evidence. It dealt only with questions of law and directed that the complaint be dismissed. 264 F. 2d 289. The case is here on a petition for a writ of certiorari which we granted because of the public importance of the questions tendered. 359 U. S. 1010.
  Section 10 of the Rivers and Harbors Act of 1899, 30 Stat. 1121, 1151, as amended, 33 U. S. C. § 403, provides in part:
  “That the creation of any obstruction not affirmatively authorized by Congress, to the navigable capacity of any of the waters of the United States is hereby prohibited; . . .” (Italics added.)
  The section goes on to outlaw various structures “in” any navigable waters except those initiated by plans recommended by the Chief of Engineers and authorized by the Secretary of the Army. Section 10 then states that “it shall not be lawful to excavate or fill, or in any manner to alter or modify the . . . capacity of . . . the channel of any navigable water of the United States, unless the work has been recommended by the Chief of Engineers and authorized by the Secretary of the Army prior to beginning the same.”
  A criminal penalty is added by § 12; and § 12 further provides that the United States may sue to have “any structures or parts of structures erected” in violation of the Act removed. Section 17 directs the Department of Justice to “conduct the legal proceedings necessary to enforce” the provisions of the Act, including § 10.
  Section 13 forbids the discharge of “any refuse matter of any kind or description whatever other than that flow.-ing from streets and sewers and passing therefrom in a liquid state, into any navigable water of the United States”; but § 13 grants authority to the Secretary of the Army to permit such deposits under conditions prescribed by him.
  Our conclusions are that the industrial deposits placed by respondents in the Calumet have, on the findings of the District Court, created an “obstruction” within the meaning of § 10 of the Act and are discharges not exempt under § 13. We also conclude that the District Court was authorized to grant the relief.
  The history of federal control over obstructions to the navigable capacity of our rivers and harbors goes back to Willamette Iron Bridge Co. v. Hatch, 125 U. S. 1, 8, where the Court held “there is no common law of the United States” which prohibits “obstructions” in our navigable rivers. Congress acted promptly, forbidding by § 10 of the Rivers and Harbors Act of 1890, 26 Stat. 426, 454, “the creation of any obstruction, not affirmatively authorized by law, to the navigable capacity” of any waters of the United States. The 1899 Act followed a report to Congress by the Secretary of War, which at the direction of Congress, 29 Stat. 234, contained a compilation and revision of existing laws relating to navigable waters. The 1899 Act was said to contain “no essential changes in the existing law.” Certainly so far as outlawry of any “obstructions” in navigable rivers is concerned there was no change relevant to our present problem.
  It is argued that “obstruction” means some kind of structure. The design of § 10 should be enough to refute that argument, since the ban of “any obstruction,” unless approved by Congress, appears in the first part of § 10, followed by a semicolon and another provision which bans various kinds of structures unless authorized by the Secretary of the Army.
  The reach of § 10 seems plain. Certain types of structures, enumerated in the second clause, may not be erected “in” any navigable river without approval by the Secretary of the Army. Nor may excavations or fills, described in the third clause, that alter or modify “the course, location, condition, or capacity of” a navigable river be made unless “the work” has been approved by the Secretary of the Army. There is, apart from these particularized invasions of navigable rivers, which the Secretary of the Army may approve, the generalized first clause which prohibits “the creation of any obstruction not affirmatively authorized by Congress, to the navigable capacity” of such rivers. We can only conclude that Congress planned to ban any type of “obstruction,” not merely those specifically made subject to approval by the Secretary of the Army. It seems, moreover, that the first clause being specifically aimed at “navigable capacity” serves an end that may at times be broader than those served by the other clauses. Some structures mentioned in the second clause may only deter movements in commerce, falling short of adversely affecting navigable capacity. And navigable capacity of a waterway may conceivably be affected by means other than the excavations and fills mentioned in the third clause. We would need to strain hard to conclude that the only obstructions banned by § 10 are those enumerated in the second and third clauses. In short, the first clause is aimed at protecting “navigable capacity,” though it is adversely affected in ways other than those specified in the other clauses.
  There is an argument that § 10 of the 1890 Act, 26 Stat. 454, which was the predecessor of the section with which we are now concerned, used the words “any obstruction” in the narrow sense, embracing only the prior enumeration of obstructions in the preceding sections of the Act. The argument is a labored one which we do not stop to refute step by step. It is unnecessary to do so, for the Court in United States v. Rio Grande Irrigation Co., 174 U. S. 690, 708, decided not long after the 1890 Act became effective, gave the concept of “obstruction,” as used in § 10, a broad sweep: “It is not a prohibition of any obstruction to the navigation, but any obstruction to the navigable capacity, and anything, wherever done or however done, within the limits of the jurisdiction of the United States which tends to destroy the navigable capacity of one of the navigable waters of the United States, is within the terms of the prohibition.” This broad construction given § 10 of the 1890 Act was carried over to § 10 of the 1899 Act in Sanitary District v. United States, 266 U. S. 405, 429, the Court citing United States v. Rio Grande Irrigation Co., supra, with approval and saying that § 10 of the 1899 Act was “a broad expression of policy in unmistakable terms, advancing upon” § 10 of the 1890 Act.
  The decision in Sanitary District v. United States, supra, seems to us to be decisive. There the Court affirmed a decree enjoining the diversion of water from Lake Michigan through this same river. Mr. Justice Holmes, writing for the Court, did not read § 10 narrowly but in the spirit in which Congress moved to fill the gap created by Willamette Iron Bridge Co. v. Hatch, supra. That which affects the water level may, he said, amount to an “obstruction” within the meaning of § 10:
  “Evidence is sufficient, if evidence is necessary, to show that a withdrawal of water on the scale directed by the statute of Illinois threatens and will affect the level of the Lakes, and that is a matter which cannot be done without the consent of the United States, even were there no international covenant in the case.” Sanitary District v. United States, supra, 426.
  “There is neither reason nor opportunity for a construction that would not cover the present case. As now applied it concerns a change in the condition of the Lakes and the Chicago River, admitted to be navigable, and, if that be necessary, an obstruction to their navigable capacity . . . .” Id., at 429.
  It is said that that case is distinguishable because it involved the erections of “structures,” prohibited by the second clause of § 10. The “structures” erected, however, were not “in” navigable waters. The Sanitary District had reversed the flow of the Chicago River, “formerly a little stream flowing into Lake Michigan,” 266 U. S., at 424, and used it as a sluiceway to draw down the waters of the Great Lakes to a dangerous degree. Moreover, the Court did not rely on the second clause of § 10 but on the first and the third. Id., at 428. The decree in that case did not run against any “structure”; it merely enjoined the diversion of water from Lake Michigan in excess of 250,000 cubic feet per minute.
  That broad construction of § 10 was reaffirmed in Wisconsin v. Illinois, 278 U. S. 367, 414, another case involving the reduction of the water level of the Great Lakes by means of withdrawals through the Chicago River. And the Court, speaking through Chief Justice Taft (id., at 406, 414, 417), made clear that it adhered to what Mr. Justice Holmes had earlier said, “This withdrawal is prohibited by Congress, except so far as it may be authorized by the Secretary of War.” Satnitary District v. United States, supra, at 429.
  The teaching of those cases is that the term “obstruction” as used in § 10 is broad enough to include diminution of the navigable capacity of a waterway by means not included in the second or third clauses. In the Sanitary District case it was caused by lowering the water level. Here it is caused by clogging the channel with deposits of inorganic solids. Each affected the navigable “capacity” of the river. The concept of “obstruction” which was broad enough to include the former seems to us plainly adequate to include the latter.
  As noted, § 13 bans the discharge in any navigable water of “any refuse matter of any kind or description whatever other than that flowing from streets and sewers and passing therefrom in a liquid state.” The materials carried here are “industrial solids,” as the District Court found. The particles creating the present obstruction were in suspension, not in solution. Articles in suspension, such as organic matter in sewage, may undergo chemical change. Others settle out. All matter in suspension is not saved by the exception clause in § 13. Refuse flowing from “sewers” in a “liquid state” means to us “sewage.” Any doubts are resolved by a consistent administrative construction which refused to give immunity to industrial wastes resulting in the deposit of solids in the very river in question. The fact that discharges from streets and sewers may contain some articles in suspension that settle out and potentially impair navigability is no reason for us to enlarge the group to include these industrial discharges. We follow the line Congress has drawn and cannot accept the invitation to broaden the exception in § 13 because other matters “in a liquid state” might logically have been treated as favorably as sewage is treated. We read the 1899 Act charitably in light of the purpose to be served. The philosophy of the statement of Mr. Justice Holmes in New Jersey v. New York, 283 U. S. 336, 342, that “A river is more than an amenity, it is a treasure,” forbids a narrow, cramped reading either of § 13 or of § 10.
  The Court of Appeals concluded that even if violations were shown, no relief by injunction is permitted. Yet § 17 provides, as we have seen, that “the Department of Justice shall conduct the legal proceedings necessary to enforce” the provisions of the Act, including § 10. It is true that § 12 in specifically providing for relief by injunction refers only to the removal of “structures” erected in violation of the Act (see United States v. Bigan, 274 F. 2d 729), while § 10 of the 1890 Act provided for the enjoining of any “obstruction.” Here again Sanitary District v. United States, supra, is answer enough. It was argued in that case that relief by injunction was restricted to removal of “structures.” See 266 U. S., at 408. But the Court replied, “The Attorney General by virtue of his office may bring this proceeding and no statute is necessary to authorize the suit.” Id., at 426. The authority cited was United States v. San Jacinto Tin Co., 125 U. S. 273, where a suit was brought by the Attorney General to set aside a fraudulent patent to public lands. The Court held that the Attorney General could bring suit, even though Congress had not given specific authority. The test was whether the United States had an interest to protect or defend. Section 10 of the present Act defines the interest of the United States which the injunction serves. Protection of the water level of the Great Lakes through injunctive relief, Sanitary District v. United States, supra, is precedent enough for ordering that the navigable capacity of the Calumet River be restored. The void which was left by Willamette Iron Bridge Co. v. Hatch, supra, need not be filled by detailed codes which provide for every contingency. Congress has legislated and made its purpose clear; it has provided enough federal law in § 10 from which appropriate remedies may be fashioned even though they rest on inferences. Otherwise we impute to Congress a futility inconsistent with the great design of this legislation. This is for us the meaning of Sanitary District v. United States, supra, on this procedural point.
  Since the Court of Appeals dealt only with these questions of law and not with subsidiary questions raised by the appeal, we remand the case to it for proceedings in conformity with this opinion.
  Reversed.
  Memorandum of
  A House Report contains similar animadversions. H. R. Rep. No. 1345, 83d Cong., 2d Sess., p. 10.
  Section 10 provides in full:
  “That the creation of any obstruction not affirmatively authorized by Congress, to the navigable capacity of any of the waters of the United States is hereby prohibited; and if shall not be lawful to build or commence the building of any wharf, pier, dolphin, boom, weir, breakwater, bulkhead, jetty, or other structures in any port, roadstead, haven, harbor, canal, navigable river, or other water of the United States, outside established harbor lines, or where no harbor lines have been established, except on plans recommended by the Chief of Engineers and authorized by the Secretary of the Army; and it shall not be lawful to excavate or fill, or in any manner to alter or modify the course, location, condition, or capacity of, any port, roadstead, haven, harbor, canal, lake, harbor of refuge, or inclosure within the limits of any breakwater, or of the channel of any navigable water of the United States, unless the work has been recommended by the Chief of Engineers and authorized by the Secretary of the Army prior to beginning the same.”
  H. R. Doc. No. 293, 54th Cong., 2d Sess.
  32 Cong. Rec., Pt. 3, p. 2923, which reports the statement by the House Conferees. For the discussion in the Senate see 32 Cong. Rec. 2296-2298.
  We have a rather precise history of administrative construction of the 1899 Act as it applies to the deposit of solids in the Calumet River by mills located on it. The Army Engineers, beginning in 1909, warned a steel company of the accumulation of solids from industrial wastes being poured into the Calumet. In 1918, 1920, 1924, 1927, 1928, 1931, and 1937 the District Engineer required these deposits to be removed. An improvement in the Calumet was authorized by the Act of August 30, 1935, 49 Stat. 1028, 1036, on the basis of a report from the Army Engineers. See H. R. Doc. No. 494, 72d Cong., 2d Sess. The costs were computed on the basis that shoals created by the deposit of solids would be removed by the company creating them. The report states, at p. 24, “It is assumed, in this estimate, that the shoal adjacent to the outer bulkhead of the Illinois Steel Co. will be removed by that company to the depth of 21 feet originally provided by the United States.”
  This long-standing administrative construction, while not conclusive of course, is entitled to “great weight” even though it arose out of cases “settled by consent rather than in litigation.” Federal Trade Comm’n v. Mandel Brothers, Inc., 359 U. S. 385, 391.
  For references in public documents to this administrative construction see H. R. Doc. No. 237, 63d Cong., 1st Sess., pp. 77, 160; S. Rep. No. 66, 68th Cong., 1st Sess., p. 2; H. R. Doc. No. 494, 72d Cong., 2d Sess., pp. 24, 34; S. Rep. No. 2225, 74th Cong., 2d Sess., p. 2; Hearings, Civil Functions, Department of the Army Appropriations for 1955, Subcommittee of House Committee on Appropriations, 83d Cong., 2d Sess., Pt. 1, pp. 695-696; H. R. Rep. No. 1345, 83d Cong., 2d Sess., p. 10.
  H. R. Doc. No. 417, 69th Cong., 1st Sess., p. 9, states:
  “In some instances the organic solid matter in sewage and wastes causes temporary shoaling in the vicinity of the point of discharge, but in most cases of this kind nature eventually decomposes this organic matter and rectifies the condition. In a few instances, where large quantities of sewage are discharged into sluggish and restricted waters, overpollution results and the oxygen content remains insufficient to enable nature to break up the solids. In such cases permanent shoaling in the vicinity of the point of discharge results and dredging must be resorted to. As a rule such dredging is well attended to by municipal authorities.”
  The “main ground” advanced was the interest of the United States in removing obstructions to commerce. 266 U. S., at 426. Another ground was a treaty with Great Britain. Id., at 425-426. But these were alternative grounds, the treaty rights being treated as lesser or subordinate interests. Id., at 426.
  See Comment, Substantive and Remedial Problems in Preventing Interferences with Navigation: The Republic Steel Case, 59 Col. L. Rev. 1065, 1079.