Opponents of an asphalt plant just outside Petaluma city limits have lost another legal battle and are mulling whether to pursue one final appeal, a review by the state Supreme Court.

The 1st District Court of Appeal in San Francisco this week denied a request by the Petaluma River Council, city of Petaluma and other plaintiffs for a rehearing before the same three-judge panel that unanimously rejected their appeal last month.

The groups had appealed a 2011 ruling of Sonoma County Superior Court Judge Rene Chouteau, who determined that the county's environmental analysis of the proposed Dutra Materials plant was adequate and that open meeting laws were followed when the issue came before the Board of Supervisors.

Petaluma River Council attorney Richard Drury of Oakland said Friday denial of the recent petition wasn't a surprise.

"We knew it was highly unlikely," he said. "But we thought we had some good reasons to ask."

San Rafael-based Dutra in 2004 proposed a plant on 38 acres just east of Highway 101 and south of the Petaluma River. Environmental groups and others, including the city of Petaluma, protested, creating one of the county's most high profile land-use battles in the past decade.

After rejecting one version of the plant, the Sonoma County Board of Supervisors ultimately approved the environmental analysis, rezoning and construction of the facility in 2010.

Plaintiffs asked the panel to revisit its February decision on whether public meetings laws were followed in a Dec. 2010 hearing in which public comment wasn't accepted. A previous public hearing had been closed, but new documents were released afterward by the county.

They also asked the court to take additional testimony about worker health protections and to reconsider air-quality data submitted by Dutra, contending that the calculations the county relied upon were erroneous.

Deputy Sonoma County Counsel Jeff Brax said the court sought no further information from either side before issuing a one-sentence ruling.

"I assume now they'll petition for a review before the Supreme Court," he said. He predicted that such a review would be unlikely because the original appeals court decision was unpublished, meaning it can't be used as a legal precedent, and doesn't have broad issues the high court generally seeks to settle.

Drury said the Brown Act issues and the potential worker-safety and air quality issues could be argued as statewide issues the court may want to weigh in on, but acknowledged that's unlikely.

"They tend to like things that have big constitutional issues, issues of statewide importance," he said. "It would be unusual for them to take an asphalt-plant case."

The plant initially was proposed a decade ago as a replacement for a former Dutra plant less than a mile away. Dutra officials said the new plant, with an annual production capacity of 570,425 tons of asphalt and rock material, will have safeguards for environmental and public health.

Opponents argued the plant would harm air quality, scenic views and damage the sensitive wetlands of nearby Shollenberger Park, a popular walking and birding area.

The plaintiffs have until April 9 to appeal to the state high court.

(You can reach Staff Writer Lori A. Carter at 762-7297 or lori.carter@pressdemocrat.com.)