The water was flat and calm at Shollenberger Park on a recent afternoon as ducks floated by visitors jogging and walking dogs on the park's popular trails. Given the peaceful scene, a newcomer might not guess that the park is at the heart of a long-simmering battle over an asphalt plant that Dutra Materials plans to build directly across the river.

The 37-acre facility at Haystack Landing was first proposed more than seven years ago, sparking a long, controversial approval process that continues today.

Opponents of the plant are holding their annual fundraiser this Saturday, which they say will pay for the ongoing legal battle to stop the asphalt plant. Dutra officials, meanwhile, are continuing to seek additional approvals from state and federal agencies that are needed to break ground, but appear to be waiting to begin construction until the outcome of legal fight is decided.

The issue has been in the courts since early 2011, shortly after the Sonoma County Board of Supervisors approved Dutra's application to develop the asphalt plant.

Local environmentalists and fans of the wetlands at Shollenberger Park expressed concerns early on that the plant and resulting truck traffic would create excessive noise and pollute the air and water quality at nearby residences and at the park, which is only separated from the proposed project by the Petaluma River.

The Petaluma City Council also opposed the project which, because it is just outside city limits, falls under the county's jursidiction.

Shortly after the supervisors approved the plant, a coalition made up of the City of Petaluma, non-profit groups and individuals filed a lawsuit against the county and Dutra to stop the plant, arguing that the environmental impacts hadn't been adquately considered.

In December of 2012, a Sonoma County judge dismissed the suit, and opponents quickly filed an appeal.

Dutra officials have long contended that the plant has been thoroughly vetted.

"Dutra is awaiting the ruling from the apellate court," said Dutra spokeswoman Aimi Dutra in an email. "In the interim we have been working with the appropriate agencies to secure all necessary approvals/permits so if a favorable ruling is received we will be able to move forward in an expeditious manner."

Opponents of the project, meanwhile, are hoping to raise money to fund the ongoing appeal costs through the upcoming event at Tara Firm Farms, called the Shollenberger Shindig, said Joan Cooper of Friends of Shollenberger, the group organizing the event.

Some of those funds will go to the City of Petaluma to offset the cash-strapped city's legal costs, which have been a factor in whether or not Petaluma should legally fight the plant. Some have argued that the city, whose general fund dwindled during recession, cannot afford the expensive legal battle. Dutra has also contended that the city would save money by having a local asphalt source — currently, the closest asphalt plant is in Santa Rosa, requiring city street crews to make multiple, hour-long trips a day when they are paving.

Opponents of the plant counter that the city is only paying a fraction of the appeal costs, and that Petaluma stands to get back the money it has already invested in the legal process if it wins the appeal. As of October 2012, it had spent about $80,000 in legal fees since opponents first filed suit in 2011, about $10,000 of that on the appeal. They also contend that Petaluma has already sunk millions into restoring the wetlands in and around Shollenberger Park, which draw tourists to town, and that the city should protect its investment.

"The park is part of the common good," said Cooper. "The taxpayers have invested $4 million in the park and restoring the surrounding wetlands. This plant would damage that ecosystem."

To offset the city's costs to join the appeal, Friends of Shollenberger and Moms for Clean Air volunteered to contribute $5,000 each to offset the city's costs, which they estimated would be around $10,000.

To date, Moms for Clean Air has paid the city the full $5,000 it promised and Friends of Shollenberger has paid $2,500.

Funds raised at the Shollenberger Shindig will help Friends make its second $2,500 payment. It will also raise money for the nonprofits, which are shouldering the bulk of the legal costs.

The appeal was filed with the California Court of Appeals in early February 2012. Judges have been appointed to the case, and it is expected that it could come to a hearing by the end of the year, according to Cooper.

(Contact Jamie Hansen at jamie.hansen@arguscourier.com.)