Three Texas environmental groups notified Valero Energy Corp. on May 22 of plans to file a lawsuit under the U.S. Clean Air Act for pollution at the company’s Port Arthur, Texas, refinery, the organizations said.

Environment Texas, the Sierra Club and the Port Arthur Community Action Network allege over 600 violations of pollution limits by the release of hazardous chemicals like sulfur dioxide, hydrogen sulfide and particulates from the refinery since 2014.

A Valero spokeswoman did not reply to a request for comment.

The lawsuit would be filed under a provision of the Clean Air Act that allows citizens to sue in federal court when government agencies have failed to halt pollution. Plaintiffs must first provide a 60-day notice to the companies and agencies of the planned lawsuit.

The organizations said Valero has released over 850,000 pounds of sulfur dioxide during emission events reported by the company to the Texas Commission of Environmental Quality.

“Valero’s Port Arthur refinery has a poor compliance record even when compared to other Texas oil refineries, spewing out millions of pounds of dangerous pollution into surrounding neighborhoods,” Luke Metzger, executive director of Environment Texas, said.

A storage tank fire at the Port Arthur refinery in 2017 released over 250,000 pounds (113,398 kilograms) of particulate matter, more than any other facility in the entire state released from emission events over that entire year, the groups said.

In similar lawsuits, Environment Texas and the Sierra Club Lone Star chapter reached settlements with Royal Dutch Shell Plc and Petrobras over pollution at Houston-area refineries.

In 2017, Exxon Mobil Corp. was ordered to pay $20 million for over 16,000 Clean Air Act violations at its Baytown, Texas, refinery following a lawsuit by Environment Texas and the Sierra Club Lone Star chapter.

The Clean Air Act provides penalties up to nearly $100,000 per each violation of the act.