Mississippi River water levels drop to historic lows
The U.S. Army Corps of Engineers is constructing a 1,500-foot-wide underwater levee in the Mississippi River to prevent saltwater from threatening drinking water. Officials say record low water levels and flow rates are allowing saltwater from the Gulf of Mexico to push upriver. Cameron McWhirter, a reporter for The Wall Street Journal who has covered the issue, joined CBS News to discuss what's behind it and how it impacts the U.S. economy.