This video segment adapted from NOVA: "Poison in the Rockies" discusses how abandoned mines have contaminated rivers in the Rocky Mountains. Beginning in the 1850s, prospectors dug deep mines in the Colorado Rockies in search of precious metals. Today, more than 15,000 abandoned metal mines have filled with acidic water that carries away heavy metals like lead, cadmium, and zinc into mountain streams. In small quantities, some metals are essential to life, but in larger quantities they are toxic. Some newer mines include safeguards to make them more environmentally sound. A background essay, discussion questions, and standards correlations are also provided.