A pair of Oregon-based conservation groups have told the Umpqua National Forest they intend to file a lawsuit to stop planned logging near Diamond Lake.

Oregon Wild and Cascadia Wildlands are challenging the D-Bug project, which U.S. Forest Service officials say would lower wildfire danger brought on by a mountain pine beetle outbreak around the lake and nearby Lemolo Lake.

“The forest service is using this old excuse to do heavy logging,” said Francis Eatherington, conservation director at Cascadia Wildlands.

The D-Bug project includes logging 3,629 acres, producing close to 16.2 million board-feet of timber, according to the April 2011 Forest Service report approving the planned logging. The logging would also be near Crater Lake National Park.

A mountain pine beetle outbreak has been under way in the forest around Diamond Lake since 2004, according to the Forest Service.

Tunneling underneath bark, the beetles impede the movement of nutrients within a tree. One prediction says as much as 90 percent of the trees in the infested lodgepole pine stands will likely die, increasing the chance of wildfire.

That prediction, made by researchers in 2007, simply isn’t coming true, contends Nick Cady, legal director for Cascadia Wildlands. He said the Forest Service is using the mountain pine beetle as an excuse to log forest that is home to the federally protected spotted owl.

“Their presence is no reason to go in and start logging mature forest that is providing spotted owl habitat,” he said.

The project focuses on woods around Diamond Lake and Lemolo Lake, according to the Forest Service. Between the two lakes, there are two resorts, eight developed campgrounds, 102 recreation residences and about 20 other developed sites. The lakes, on opposite sides of state Highway 138, bring in about 700,000 visitors each year.

“A large fire in this area could have catastrophic consequences, both in terms of damage to infrastructures and to people who are in the area at the time of the fire,” according to the Forest Service report.

Wildfire poses a particular danger to recreational residences on the west shore of Diamond Lake, according to the Forest Service.

While she declined to comment on the threat of a lawsuit by Oregon Wild and Cascadia Wildlands, Cheryl Caplan, spokeswoman for the Umpqua National Forest, was willing to discuss the D-Bug project. She said the purpose of the project is “to give people time to get out” in case of a wildfire.

“If there is a fire that hits that area, we wanted to slow it down enough to allow for safe evacuations,” Caplan said.

Cascadia Wildlands isn’t opposed to projects focused on lowering fire risk by thinning around homes, other buildings and evacuation routes, Eatherington said. But the D-Bug project extends deep into the forest, away from developments.

“We really think the Forest Service should reconsider selling this project,” she said.