By MATEUSZ PERKOWSKI

Capital Press

A federal judge has stopped an herbicide spraying project aimed at discouraging invasive weeds in an Eastern Oregon national forest.

The U.S. Forest Service violated environmental law by approving the 23,000-acre project in the Wallowa-Whitman National Forest, according to the ruling.

U.S. District Judge Michael Simon has found that the agency didn't sufficiently study the cumulative environmental impacts of herbicide use in conjunction with grazing, logging and other activities that may spread weeds.

The Forest Service's analysis of the project "does not consider how the presence of herbicides in streams, even if fleeting and localized, might nonetheless exacerbate stream quality already impaired by other activities like logging, grazing, road maintenance, fire management or recreation," the ruling said.

Continued introduction of invasive weeds from these activities would prompt further herbicide spraying, but the agency didn't consider how this cycle would affect the forest, Simon said.

The Forest Service acknowledged that nontarget plants would be harmed by herbicides but assumed that the impact would be minimal, he said.

The agency didn't analyze the broader consequences of spraying nontarget plants, contrary to the requirements of environmental law, Simon said. "The very point of a cumulative impacts analysis is to draw attention to combined impacts that might otherwise be overlooked when considered separately."

The judge has blocked the Forest Service from continuing the spray program and ordered the agency to revise its analysis of the project.

Although the agency was found to have violated the National Environmental Policy Act, the judge rejected arguments that it also violated forest management law.

The Forest Service adopted the herbicide spraying project in 2010 but the plan was opposed by an environmental group, the League of Wilderness Defenders-Blue Mountains Biodiversity Project.

The group filed a lawsuit to stop the project, arguing that grazing is the top vector of weeds in the forest because cattle spread seeds through manure.

The agency should have analyzed other alternatives, like reduced grazing, rather than resorting to aerial spraying of herbicides that can harm fish, the group argued.

The Forest Service countered that the environmentalists wanted to ensure that the project had zero impact, which is an impossible standard to meet.

The environmental group doesn't oppose all herbicide usage to combat invasive weeds, but doesn't think they should be the first resort, said Tom Buchele, attorney for the plaintiff.

Buchele said he hopes the Forest Service will seek a "middle ground" and change its plans rather than just revise its analysis and go forward with the project as previously proposed.

"Sometimes they decide to rethink what they're doing," he said.

Capital Press was unable to reach an attorney for the federal government for comment.