Neighbors of Sonoma County’s central landfill who threatened two months ago to file a lawsuit over wastewater from compost piles polluting Stemple Creek have made good on their promise.

The group Renewed Efforts of Neighbors Against Landfill Expansion, or RENALE, filed a federal Clean Water Act suit recently against three entities involved in the 25-acre composting operation atop the landfill.

The goal of the suit is to convince a judge to do what other government agencies are either unwilling or unable to do — shut down the compost operation to protect the creek, said Roger Larsen, a resident of the Happy Acres subdivision on Mecham Road west of Cotati.

“Despite the fact they know they are polluting Stemple Creek, they decided to continue to do so,” Larsen said. “Hopefully, this suit with stop them from polluting Stemple Creek anymore.”

The suit names Sonoma County, which owns the landfill; the Sonoma Waste Management Agency, which manages the county’s green waste program under a joint powers agreement; and Sonoma Compost, the private business that runs the compost operation.

David Rabbitt, chairman of the Board of Supervisors, said although he had not read the lawsuit and was not yet familiar with the details, the county has a stake in the outcome of the landfill and its composting facility.

“This has been a headache we’ve been dealing with for a long time,” Rabbitt said. “As the landlord, we want to do the right thing and be a part of fixing the problem. We’ll have to sit down with the other parties to figure out how to satisfy regulatory requirements.”

The 10-member waste agency board decided last week to keep the compost operation open this winter instead of shutting it down and hauling tons of green waste to other area compost facilities. The decision came after water regulators expressed support for a plan to reduce the pollution risks in the short term while accelerating efforts to find a long-term solution to the problem.

But regulators acknowledged that, depending on the amount of rainfall received this winter, water discharges from the compost site would likely continue into Stemple Creek. Regulators supported efforts by the county and waste agency to limit such discharges, including the expansion of a holding pond and trucking the runoff to another site.

The neighbors’ suit, brought by the Oakland-based law firm Lozeau Drury, asks a judge to block the importation of additional green waste to the site, require the removal of existing material, levy fines of $37,500 per day for every violation of the Clean Water Act, and grant attorney fees.

In their original notice to the county, the neighbors cited 180 separate rain events since 2009 that resulted in at least 0.10 inch of rainfall in the area. The 2009 date was selected because there is a five-year statute of limitations on Clean Water Act lawsuits. Each violation carries a maximum penalty of $37,500, for a total possible penalty of $6.75 million, though the full penalties are rarely imposed in such cases.

Henry Mikus, executive director of the waste management agency, said he didn’t know how the suit could impact operations. The agency’s attorney, Janet Coleson, did not return a call for comment.

Staff Writer Angela Hart contributed to this report. You can reach Staff Writer Kevin McCallum at 521-5207 or kevin.mccallum@pressdemocrat.com.