YAKIMA – A federal judge has barred the U.S. Forest Service from building a bridge and relocating trails in a section of the Wenatchee National Forest, ruling that the federal agency must first review the environmental impacts of increased off-road vehicle use.

The ruling marks the second time in recent years that a federal court has ordered the Forest Service to complete an environmental impact statement, specifically looking at motorized vehicles, for a project in that area of central Washington’s Cascade Range.

The plan involves building a bridge, improving a campground, building a helicopter landing spot and relocating sections of trail east of Lake Wenatchee. The project is one of several either proposed, under way or recently completed that could expand off-road vehicle use in the Wenatchee National Forest through a series of connected trails.

The area, stretching between Lake Wenatchee and Lake Chelan on the east slope of the Cascades, includes 200 miles of motorized-use trails. An estimated 4,000 visitors use the trails each season, with 60 percent riding motorcycles.

Under the current project, off-road vehicles would gain access to an area of the Lower Mad River Trail near Maverick Saddle in the first week of June, when it is usually inaccessible because of high water.

Four conservation and recreation groups sued to block the project, arguing that the Forest Service must first complete an environmental impact statement. They also contend the project violates a similar federal court ruling in 1999, which halted construction of the adjacent Goose-Maverick project.

In that case, a judge ruled that the government had failed to examine the project’s cumulative environmental impacts to the entire trail system.

U.S. District Judge Ricardo Martinez of Seattle agreed with the plaintiffs in a ruling Tuesday.

While it appears the government made a significant effort to correct the failures cited in the previous court ruling, it also “failed to heed the warning” that any environmental review of the cumulative impacts of the project must review the impact to the entire off-road trail system, Martinez wrote.

“We’ve long asked the Forest Service to study the cumulative impacts of the entire network of motorcycle routes in the Mad River country, before deciding that a single component piece has insignificant impacts. It’s gratifying that the judge agrees,” Harry Romberg of The Mountaineers said in a statement.

Brian Kipnis, assistant U.S. attorney in Seattle who represented the Forest Service, said the government would review the ruling before deciding whether to appeal.

A coalition of conservation and recreation groups has been working for years to add the Mad River area to the Glacier Peak Wilderness Area, just south of North Cascades National Park.

The Forest Service is revising the 1990 Wenatchee Forest Plan, the management plan for the forest. As part of that process, the agency will review proposals for adding or subtracting wilderness areas, spokeswoman Robin DeMario said Thursday. Agency officials hope to complete that process by September 2007.

Congress must ultimately approve any changes or additions to wilderness areas, she said.

The organizations that filed suit in the latest case are The Mountaineers, North Cascades Conservation Council, Sierra Club and Washington Wilderness Coalition.