public interest in maintaining unimpeded access to the navigable waters of the United States. The appropriate test for determining the geographic limits of navigable wate .D.Va.1960) (“[W]here in the judgement of Congress, or its agents, a structure appears in a navigable stream whieh may affect the regulation of commerce, it is subject to the dominant power to cause the removal of such structure, even though the structure be ‘private property’ and originally not unlawful.”), aff'd 295 F.2d 91 (4th Cir.1961). The government may require substantial and expensive alterations to be made to lawfully created structures when they are found to interfere with access to navigable waters. See Monongahela Bridge Co. v. United States, 216 U.S. 177, 194, 30 S.Ct. 356, 360-61, 54 L.Ed. 435 (1910) (<HOLDING>); Union Bridge Co. v. United States, 204 U.S.
holding that government has right to remove unreasonable obstructions to navigation and may order removal of bridge holding that review of an original removal decision and a subsequent removal order are distinct holding that government may recover expenses incurred in removal of lawfully erected bridge piers found to be obstruction under section 403 holding that any defect in removal procedure must be cured within the 30day removal period or it is fatal to the removal and defendants failure to attach exhibits to the notice of removal within that time required remand holding that wjaiver of the right to remove must be clear and unequivocal  and that standard was not met by an agreement in which defendants consented to filing of suit in state court but which did not address removal