Imagine a siege of hydrocarbons spewing from deep below ground, polluting water and air, sickening animals and threatening the health of unsuspecting Americans. And no one knows how long it will last. No, we're not talking about BP's gulf oil spill. We're talking about hydraulic fracturing of natural gas deposits. Fracking, as the practice is also known, may be coming to a drinking well or a water system near you. It involves blasting water, sand and chemicals, many of them toxic, into underground rock to extract oil or gas. Gasland," a compelling documentary on HBO ..., traces hydraulic fracturing across 34 states from California to Louisiana to Pennsylvania. The expos by filmmaker Josh Fox, alternately chilling and darkly humorous, won the 2010 Sundance Film Festival's special jury prize for documentary. It details how former Vice President Dick Cheney, in partnership with the energy industry and drilling companies such as his former employer, Halliburton Corp., successfully pressured Congress in 2005 to exempt fracking from the Safe Drinking Water Act, the Clean Air Act and other environmental laws. Each well requires the high-pressure injection of a cocktail of nearly 600 chemicals, including known carcinogens and neurotoxins, diluted in 1 million to 7 million gallons of water. Some 450,000 wells have been drilled nationwide.