A steam pipe explosion rocks New Yorkers on a summer day in Midtown Manhattan. Boston's Big Dig highway project suffers a major setback when sections of a tunnel ceiling fall onto the roadway. Rush hour in Minnesota turns deadly, as a bridge plunges into the Mississippi River. An air show in Mannheim, Germany comes to a tragic end when a Chinook helicopter crashes along the Autobahn killing 46 people. A tanker truck explodes on an Oakland freeway overpass, causing the structure to collapse. And a mud volcano near a natural gas drilling site erupts in Indonesia, leaving villages buried 16 feet deep. We'll explore what engineering and structural failures caused these events, and the changes the catastrophes have wrought.