PHILADELPHIA A national conservation group on Tuesday declared the 444-mile Susquehanna River in New York, Pennsylvania and Maryland to be the nation's most endangered due to use of a gas drilling method known as hydraulic fracturing in the region.
The so-called fracking process extracts natural gas trapped in shale formations by blasting a mix of water, sand and chemicals into the rock. The subject of intense debate, fracking is feared by critics as contaminating water supplies.
Second on the list of endangered waterways, compiled by American Rivers, was Alaska's Bristol Bay, threatened by copper and gold mining, followed by the Roanoke River in Virginia and North Carolina, threatened by uranium mining, it said.
The Susquehanna River, which originates near Cooperstown, New York and flows south to the Chesapeake Bay, passes through parts of New York and Pennsylvania where the gas industry is tapping into shale formations.
"Fracking (as the method is known) poses one of the greatest risks our nation's rivers have faced in decades," said Andrew Fahlund, senior vice president of American Rivers. "We are taking a major gamble on the clean drinking water for millions of Americans."
Some 6.2 million people depend on the Susquehanna for drinking water, according to an estimate by the attorney general of Maryland.
Kathryn Klaber, president of the industry group called the Marcellus Shale Coalition, said American Rivers "is seeking nothing more than to undercut the responsible development of clean-burning, job-creating natural gas."
Commenting on the American Rivers report, a spokesman for the Pennsylvania Department of Environmental Protection said: "There has been no evidence of frac water entering the Susquehanna.
"Additionally, sampling across the state, including the Susquehanna, has shown no levels of concern for radioactivity and other contaminants," said the statement issued by DEP press aide Kevin Sunday.
Jessie Thomas-Blate, manager of the endangered rivers project for American Rivers, said being on the list does not necessarily mean a river is heavily polluted but that it is under threat.
On Tuesday, the Pennsylvania DEP said it was fining major natural gas producer Chesapeake Energy more than $1 million for contamination of ground water and for a tank fire.
Also on the list was the Chicago River in Illinois, threatened by sewage pollution; the Yuba River in California, threatened by hydropower dams and the Green River in Washington, threatened by exploratory drilling and mine development, the group said.
Rounding out the list was the Hoback River in Wyoming, threatened by natural gas extraction, the Black Warrior River in Alabama, threatened by coal mining, the St. Croix River in Minnesota and Wisconsin, threatened by rollback of protections and the Ozark National Scenic Riverways in Missouri, threatened by overuse and poor management, it said.
The group also gave a special mention to the Mississippi River, saying it was threatened by outdated flood management.
(Editing by Ellen Wulfhorst, Greg McCune and Peter Bohan)