Two conservation groups have filed a lawsuit against the U.S. Forest Service to stop a logging project northwest of Big Timber that they say would harm bird habitat and violate water quality laws.

The suit, filed Tuesday in federal court in Helena, seeks to halt the Gallatin National Forest's Big Timber Canyon timber sale, which authorizes logging on 180 acres of old growth forest on the eastern slopes of the Crazy Mountains. It also names as defendants regional forester Tom Tidwell and district ranger William Avey.

The Alliance for the Wild Rockies and the Native Ecosystems Council contend the project would violate the Clean Water Act and Montana water quality laws by putting sediment into Big Timber Creek, which already is polluted and on the state's list of impaired water bodies.

The groups also claim the project would destroy critical northern goshawk habitat and violate the National Environmental Policy Act by not allowing the p-ublic to have a say in how the Gallatin National Forest is managed.

Marna Daley, spokeswoman for the Gallatin National Forest, said officials hope the project will minimize the impact of bark beetles in the area. She described the project as "minimal in scale and intensity."

"We feel very confident in the analysis we did and that it will stand up to a rigorous court test," she told The Billings Gazette.

The project would remove Douglas fir trees killed by a bark beetle infestation, and would require a half-mile of new temporary road. The Forest Service was preparing to advertise the timber sale when the lawsuit was filed.

"We're attempting to get ahead of the bark beetle infestation so we're not looking at a much larger mortality rate," Daley said.

Among the claims in the lawsuit are that the Forest Service failed to fully evaluate the effects of the project on the northern goshawk, and that it didn't use the best available science when designing mitigation measures.

Dr. Sara Johnson, director of the Three Forks-based Native Ecosystems Council and a former Gallatin Forest wildlife biologist, said the best available science calls for a 600-acre buffer around goshawk nests, but the proposed Big Timber Canyon logging project leaves only a 40-acre buffer.

Daley said the project was postponed in May to allow the agency more time to consider the effects on goshawks. She said the review found that effects on the birds of prey would be minimal and could be easily mitigated.

Regarding the groups' water concerns, Robert Ray, watershed protection section manager for the Montana Department of Environmental Quality, said the project could proceed without affecting Big Timber Creek if the Forest Service does something to reduce sediment loads in the creek, such as installing new culverts.

"The goal is to achieve water-quality standards in a reasonable amount of time," he said. "Best management practices can make a bad situation better."

Daley said that would be the case.

"We're confident we're following best management practices with water quality and in compliance with state law," she said.