Porter could not get many of his ironclads over the falls at Alexandria. Colonel Joseph Bailey designed Bailey's Dam, to which Banks soon gave night-and-day attention. Several boats got through before a partial dam collapse. An extra upriver dam provided additional water depth, allowing the march to resume. When the Federals left Alexandria, the town went up in flames, the origins of which are disputed. Because the Confederates had already burned most of the cotton, many speculators at Alexandria were disappointed.