PHOENIX (AP) - Groundwater pumping by the operator of the Black Mesa coal mine in northeastern Arizona threatens the water supply for the Navajo and Hopi tribes more than the government admits and a new federal permit should be denied, an environmental group says.

The Natural Resources Defense Council says a review of federal monitoring data shows that the aquifer under the Navajo Nation is being damaged by pumping of the Peabody Western Coal Co. Wells levels are dropping, springs are drying up, and there are signs that water is being contaminated, said David Beckman, a senior attorney with the NRDC.

Peabody also is asking for permission to greatly increase the amount of water it pumps from the aquifer, the NRDC said.

"Not only has Peabody's water use been massive by any stretch of the imagination, but in their application they are applying to use even more water," Beckman said.

But a spokeswoman for Peabody disputed the findings, saying extensive studies over more than 30 years have shown that the aquifer is "healthy and robust." Beth Sutton also said the application for a so-called life-of-mine permit only asks to use the water on an interim basis, until another supply can be secured.

"The claims have long been refuted by long term studies," she said of the NRDC study. "The issues are mainly moot."

Regardless, the mine, the power company it supplies and the leaders of the Indian tribes where it sits all agree that a new water source is needed and have been working for years to secure it, Sutton said.

The mine, in the heart of the Navajo Nation, provides coal to Southern California Edison's massive Mohave Generating Station near Laughlin, Nev.

The plant, the mine and a 273-mile pipeline that carries coal slurry between the two has been shut down since Jan. 1 because SCE did not upgrade its pollution control devices as required by the 1999 settlement of a lawsuit brought by consortium of environment groups. The NRDC was not a party.

Most of the water is used to transport the coal. It is ground up, mixed with pumped groundwater and then sent from northeast Arizona to the plant.

The Navajo Nation wants the water use stopped too, and has told the mine that repeatedly. But it also has worked with Peabody on studies on another supply, said George Hardeen, a tribal spokesman.

"The preliminary hydrology reports show there is plenty of water for that use," Hardeen said of the alternative supply. "So when the plant goes back on line, there is a very good chance that the water supply will be a different one."

Beckman said there are no assurances of that.

On the Net:

Natural Resources Defense Council: http://www.nrdc.org/

Peabody Energy: http://www.peabodyenergy.com

Southern California Edison: http://www.sce.com

Navajo Nation: http://www.navajo.org