A Colville National Forest tree-thinning project to prevent insects, diseases and wildfire from spreading onto an adjacent Indian reservation in northeast Washington has been challenged by an environmental group.

The Kettle Range Conservation Group claims the U.S. Forest Service should do a more detailed environmental study before logging, according to a suit filed in U.S. District Court for Eastern Washington.

The group’s director, Tim Coleman, said he doesn’t disagree with the project’s goals, but wants more assurances the timber harvests won’t harm the environment.

“In essence, the lawsuit boils down to, the Forest Service is saying, ‘Trust us.’ And I’m concerned we don’t know what they’re going to do,” Coleman said.

The Forest Service declined to comment on the lawsuit.

The Sanpoil project, named for a Columbia River tributary, includes commercially logging about 5,100 acres. Other acres would be thinned, but the trees would have marginal or no value, according to the Forest Service.

Other land would be cleared by fire or by hand. The logging, controlled burns and brush clearing would free up water, nutrients and sunshine for other trees, making the forest healthier and able to survive bugs, diseases and fires, according to the Forest Service.

Republic District Ranger Travis Fletcher approved the Sanpoil project after an environmental assessment concluded it would not cause significant environmental harm.

Fletcher stated his decision was heavily influenced by the project’s location, just north of the Confederation Tribes of the Colville Reservation.

The tribe-supported project was proposed under the Tribal Forest Protection Act, intended to keep insects, diseases and fires from spreading to tribal lands.

The Kettle Range lawsuit seeks a more-detailed environmental impact statement. It alleges logging and road building would turn forests into “clear-cut wastelands” and despoil pristine wildernesses and recreation areas.

According to the Forest Service, loggers would cut “smaller less vigorous trees and those infested by pathogens” and would stay away from old-growth areas.

If the logging produced 50 million board-feet over a decade, 90 private-sector and 10 public-sector jobs would be created, the Forest Service estimates. The non-commercial thinning would create 20 to 40 private-sector and 10 federal seasonal jobs.

The area has one grazing allotment authorized for 328 cow-calf pairs. The Forest Service figures that thinning the forest will open up about 10,000 more acres suitable for foraging cattle.

The agency has no plans to permit more cattle on the allotment, but each cow-calf pair would have 33 more acres to graze, reducing the intensity of grazing, especially along water, according to the Forest Service.

The suit alleges that expanding grazing acreage could be a problem because wolf-livestock conflicts lead to the state-sanctioned killing of wolves.

The suit also alleges that the Sanpoil project combined with other forest projects will have a cumulative effect on the environment.

“This is not an indictment of (grazing), an indictment of the timber industry or an indictment of treaty rights or anything like that. It has everything to do with the way the Forest Service is doing the project,” Coleman said.