The lawsuit alleges that valley fills, which are used to dispose of waste rock and earth from mountaintop removal mines, violate West Virginia water-quality standards.

Hobet Mining and two other Arch Coal subsidiaries have filed a motion to intervene in the lawsuit. The companies also filed a response which claims valley fills do not violate the Clean Water Act and state water-quality rules.

"This court previously authorized the procedures currently used by the WVDEP, the United States Environmental Protection Agency, and the Corps of Engineers for granting authority to place valley fills into waters of the United States pursuant to the Clean Water Act," wrote Roger Wolfe, a Jackson & Kelly lawyer representing the coal companies.

In its report, the Fish and Wildlife Service noted that the proposed Hobet mine expansion would affect not only Pigeonroost Branch, but two neighboring streams, Oldhouse Branch and White Oak Branch.

The report states that Hobet's consultants told regulators the flow of water in the streams was too small to measure or sample. Fish and Wildlife scientists, however, found the streams were large enough to measure and sample. They also found bugs, fish and crayfish in all three streams.

"Eliminating streams which support healthy aquatic communities and provide fresh water, nutrients, and food organisms to downstream aquatic ecosystems clearly violates state and federal anti-degradation policies," the report said.

"Based on the results of our field investigations, which have documented that the streams proposed to be filled for this project support aquatic life and wildlife uses, the Service concludes that the proposed valley fills will in fact violate the West Virginia Water Quality Standards and the Clean Water Act," the report states.

The report also notes that the DEP's "cumulative hydrologic impact assessment" for the Hobet mine expansion concludes, "Though stream water chemistry remains in compliance downstream of the majority of these impacts, no study has been done on what impacts this has on the overall biologic production of Spruce Fork. Such a study is beyond the scope of this report and is not addressed directly by state mining regulations."

Fish and Wildlife scientists responded, "In other words, West Virginia is proposing to issue this permit without knowing whether or not it will degrade downstream areas."

Hobet Mining Inc. wants to fill more than a mile of the creek with millions of tons of rock and earth from what would be the largest strip mine in state history.

The U.S. Department of the Interior has concluded the proposal would violate federal and state water-quality rules, according to a new report issued in late July.

In its first official action in the growing controversy over mountaintop removal, Interior's Fish and Wildlife Service urged regulators to conduct further studies of the proposed mine's potential effects.

"We do not believe that the state has adequately assessed the effects of this project on waters of the United States," wrote David Densmore, supervisor of the Fish and Wildlife Service field office in State College, Pa.

Hobet, an Arch Coal Inc. subsidiary, wants a permit from the state Division of Environmental Protection to expand its Dal-Tex complex near Blair.

The mine expansion would cover roughly five square miles along Pigeonroost Branch. The operation would produce 80 million tons of coal - about $2 billion worth - over a 15-year period.

The U.S. Environmental Protection Agency has temporarily blocked DEP from issuing a water pollution permit for the mine. EPA wants more information about the mine's potential environmental impacts.

EPA's objection to the permit was based in part on an analysis conducted by the Fish and Wildlife Service.

That report was made public last week when it was attached to motions filed by environmental groups in a federal court lawsuit which challenges mountaintop removal permitting.

The lawsuit alleges that valley fills, which are used to dispose of waste rock and earth from mountaintop removal mines, violate West Virginia water-quality standards.

Hobet Mining and two other Arch Coal subsidiaries have filed a motion to intervene in the lawsuit. The companies also filed a response which claims valley fills do not violate the Clean Water Act and state water-quality rules.

"This court previously authorized the procedures currently used by the WVDEP, the United States Environmental Protection Agency, and the Corps of Engineers for granting authority to place valley fills into waters of the United States pursuant to the Clean Water Act," wrote Roger Wolfe, a Jackson & Kelly lawyer representing the coal companies.

In its report, the Fish and Wildlife Service noted that the proposed Hobet mine expansion would affect not only Pigeonroost Branch, but two neighboring streams, Oldhouse Branch and White Oak Branch.

The report states that Hobet's consultants told regulators the flow of water in the streams was too small to measure or sample. Fish and Wildlife scientists, however, found the streams were large enough to measure and sample. They also found bugs, fish and crayfish in all three streams.

"Eliminating streams which support healthy aquatic communities and provide fresh water, nutrients, and food organisms to downstream aquatic ecosystems clearly violates state and federal anti-degradation policies," the report said.

"Based on the results of our field investigations, which have documented that the streams proposed to be filled for this project support aquatic life and wildlife uses, the Service concludes that the proposed valley fills will in fact violate the West Virginia Water Quality Standards and the Clean Water Act," the report states.

The report also notes that the DEP's "cumulative hydrologic impact assessment" for the Hobet mine expansion concludes, "Though stream water chemistry remains in compliance downstream of the majority of these impacts, no study has been done on what impacts this has on the overall biologic production of Spruce Fork. Such a study is beyond the scope of this report and is not addressed directly by state mining regulations."

Fish and Wildlife scientists responded, "In other words, West Virginia is proposing to issue this permit without knowing whether or not it will degrade downstream areas."