The Spill at Dan River, Disrupting Cancer, The City of Music

Lesley Stahl reports on how the nation's biggest energy company is handling 100 million tons of coal ash waste in North Carolina; Sanjay Gupta profiles billionaire surgeon Patrick Soon-Shiong who discusses unconventional ways of treating cancer; Bill Whitaker travels to Cremona, Italy, to visit artisans who are crafting violins the way Antonio Stradivari did 300 years ago.