The U.S. Environmental Protection Agency said on Tuesday it has the legal power to block permits for so-called mountaintop coal mines, a move that could affect hundreds of mining operations. The EPA voiced concerns about the controversial mining practice and said it could veto permits issued by the U.S. Army Corps of Engineers if the mines would permanently impair water quality by fouling valley streams. This could affect hundreds of operations where mining permits have been sought or granted. Deborah Zabarenko reports for Reuters March 24, 2009.