David Keller, founder of the Petaluma River Council, said studies for the 38-acre project by San Rafael-based Dutra Materials fail to adequately address environmental concerns such as the plant's effects on nesting birds and air quality, especially at nearby Shollenberger Park.
If the board follows Tuesday's straw vote approval with a formal endorsement on March 24, Keller said his group likely would file suit claiming violations of the California Environmental Quality Act and land use regulations.
Keller, a former Petaluma city councilman, called supervisors "intentionally deaf" to the outpouring of criticism of the project, including dozens who spoke against it at the 5?-hour public hearing.
Asphalt plant hearing
But supervisors by a 4-1 vote favored the proposal. Only newcomer Shirlee Zane of Santa Rosa was opposed.
Dutra's plans call for producing as much as 650,000 tons of road construction material a year, using river barges to reduce truck traffic, recycling materials and setting aside 19 acres as wetlands.
Supervisor Mike Kerns, who represents the south county, said the Petaluma River has always been home to industrial uses such as gravel operations and two previous Dutra sites farther upriver.
He defended his support for the latest project, saying there was no evidence that it would cause pollution or disrupt wildlife, and it would save taxpayers money on road repairs.
He said the county's lawyers determined environmental studies for the asphalt plant were done properly.
"The facts show they meet all the requirements," Kerns said. "You have to be fair to people. You can't base your decision on what a bunch of people who show up at a board meeting say."
Company spokeswoman Aimi Dutra did not return a call Thursday seeking comment.