This from WSJ online:

8:47 p.m.: How long would it take, with unlimited funds, to build levees around New Orleans to withstand a Category 5 hurricane? Three to five years, according to Col. Richard P. Wagenaar, district engineer for the U.S. Army Corps of Engineers in New Orleans, when asked the question by Bill O’Reilly on Fox News. “We just can’t go out and built a concrete wall around the city of New Orleans,” he said, noting that environmental, economic and cultural compromises would need to be made.