Each day, 300 million gallons of polluted mine water enters Pennsylvania streams and rivers, turning many of them into dead zones unable to support aquatic life.
At the same time, drilling companies use up to 5 million gallons of fresh water for every natural-gas well they frack.
State environmental officials and coal region lawmakers are hoping Pennsylvania's newest extractive industry can help clean up a giant mess left by the last one. They're encouraging drillers to use tainted coal mine water to hydraulically fracture gas wells in the Marcellus Shale formation.
They say that would divert pollution from streams and rivers that now run orange with mine drainage and would reduce the drillers' reliance on fresh water.
Drainage from abandoned mines is one of the state's worst environmental headaches, impairing 5,500 miles of waterways.