By MATEUSZ PERKOWSKI

Capital Press

An herbicide spraying project in an Oregon national forest has been vacated by a federal judge, though some chemical treatments will be allowed to continue.

Earlier this year, U.S. District Judge Michael Simon ruled that the U.S. Forest Service authorized the herbicide program in the Wallowa-Whitman National Forest in violation of environmental law.

The agency was ordered to reevaluate the cumulative environmental impacts of the project, which an environmental group feared would harm fish and streams.

Initially, Simon completely barred the weed control project to the alarm of ranchers and weed control officials, who said the injunction would block even hand-pulling of weeds.

Surrounding landowners worried that a total lack of weed suppression would allow the national forest to become a refuge for invasive species that would spread onto private property.

The judge later lifted the injunction and heard arguments from the environmental plaintiffs and the Forest Service about how to proceed until the cumulative impact analysis is finished.

Due to regulatory procedures and a limited workforce, the additional study may require another year or two to complete, according to the agency.

Simon has now decided to partially vacate the portion of the project that amplified herbicide treatments, but carved out specific exemptions that will allow chemicals to be used in some areas.

The order details which herbicides can be applied to what weeds on about 870 sites across nearly 6,000 acres of the national forest. The full project would have allowed spraying on roughly 20,000 acres.

Prior to the Forest Service's approval of the herbicide project, the agency only used such chemicals as a last resort, after mechanical and manual treatment methods failed.

The agency said this approach was ineffective and permitted weeds to greatly expand in the national forest, requiring a more aggressive suppression regime.

The League of Wilderness Defenders-Blue Mountains Biodiversity Project, an environmental group, challenged the new herbicide program in federal court. According to the group, herbicides will denude stream banks of vegetation, raising water temperatures and harming fish.

The Forest Service should examine other options of arresting weed infestations, such as curtailing livestock grazing to prevent seeds from spreading, the group said.