A federal appeals court has rejected a petition for rehearing an appeal by four environmental groups who seek to block improvements to a stretch of southern Utah's scenic Burr Trail.

The decision by the U.S. 10th Circuit Court of Appeals Wednesday clears yet another hurdle in the quest by Garfield County, Utah, to widen, grade and make irrigation improvements to a 27-mile section of the 66-mile dirt road, which meanders from Boulder to Capitol Reef National Park.The original appeal and petition for rehearing were filed by the Sierra Club, the National Parks and Conservation Association, the Southern Utah Wilderness Alliance and the Wilderness Society against the Interior Department, Bureau of Land Management, Garfield County and Interior Secretary Donald Hodel.

The appeal had challenged the decision of U.S. District Judge Aldon Anderson, who ruled last Nov. 30 that Garfield County had a legal right of way to the trail and could proceed with improvements.

Anderson's decision, which followed a six-week trial and two months of deliberations, was upheld by the appeals court in July with one exception: The county and Bureau of Land Management were ordered to complete an environmental assessment of the work's impact on 12 miles of the road that abut wilderness study areas.

The petition for rehearing asked that the environmental assessment be expanded to include all areas bordering the proposed road work.

In rejecting that request, the three-judge appellate court noted such petitions are designed to correct errors of fact or law on issues already presented.

"They are not meant to permit parties to assert new grounds for relief," the court said.

After upholding Anderson's decision, the case was returned to U.S. District Court in Salt Lake City so that the judge could define the specific wilderness areas and determine their boundaries.

Garfield County Commissioner Tom Hatch said Wednesday that those areas have been mapped out and the environmental assessment is under way. The study is expected to be completed by Dec. 1.

If the assessment finds there would be no significant impact from the road work, the county will then ask Anderson to lift an injunction against the road work.

"I'm quite optimistic," Hatch said. "I feel confident that we'll actually start construction this winter. We have our funding in place, contracts are ready to go. We're just waiting to get through the final hoops."

The county could have asked Anderson earlier to lift the injunction. "But once we start, we don't want to piecemeal the project together," Hatch said. "We want to go through with it. We want to complete the environmental assessment and then get the injunction lifted."

Garfield County hopes to draw more tourists to the area by grading and widening the section from Boulder to the park's boundaries. skirting

Environmentalists want to preserve the solitude and wilderness experience provided by the current level of use.