In the end, it came down to the workers.

One by one, they took the witness stand and testified about benzene emissions and toxic sludge and how Tonawanda Coke seemed nervous about government inspectors.

A federal jury, after listening to those workers, found the Town of Tonawanda company and one of its executives guilty Thursday of polluting the air and ground at its River Road plant.

The panel of 12 men and women deliberated much of the day before returning guilty verdicts on 14 of the 19 criminal charges against the company and 15 of the 19 charges against Mark L. Kamholz, its environmental controls manager. The company and Kamholz face possible fines of more than $200 million, and Kamholz could be sentenced to up to 75 years in prison.

“Justice was served,” said Jackie James Creedon, founder of the Tonawanda Community Fund, a local citizens group. “It was a message to all industrial polluters.”

The verdict followed four weeks of testimony by more than 30 witnesses, many of them former and current Tonawanda Coke employees who testified about clean air violations and the improper handling of hazardous waste.

“I think the testimony from workers was very compelling,” said Erin Heaney, executive director of the Clean Air Coalition of Western New York. “I want to thank those workers for coming forward.”

Defense lawyers and company executives declined to comment after the verdict, which came after several hours of jury deliberation and just a day after lawyers on both sides gave their summations.

The case, believed to be the biggest local environmental trial in years and only the second criminal prosecution nationally involving the Clean Air Act, centered around a wide range of allegations.

Six of the 19 charges dealt with a little-known bleeder valve that spewed coke oven gas with benzene into the air.

The company also stood accused of using “quenching” or cooling towers that lacked necessary anti-pollution equipment and of illegally disposing of coal-tar sludge, one of the byproducts of its coking operation.

The jury found the company and Kamholz guilty of all three allegations but not guilty of similar charges related to one of its two quenching towers.

Kamholz, a 30-year employee of the company, also was found guilty of obstructing justice.

“This was an historic case on many levels,” said U.S. Attorney William J. Hochul Jr. “In the end, this was all about Tonawanda Coke and Mark Kamholz putting profits ahead of people.”

Hochul doesn’t think the trial hinged on any one piece of evidence or any single day of testimony. “I think it was the accumulation of evidence," he said.

Even the defense, in its closing arguments, acknowledged the importance of the workers who testified on behalf of the prosecution.

Of those witnesses, none seemed as influential as plant manager Patrick Cahill. It was Cahill, among others, who testified about the frequency and duration of the bleeder valve’s openings and Tonawanda Coke’s nervousness about inspectors learning about its emissions.

“We can’t have that going off when they’re here,” Kamholz is alleged to have told Cahill in the days leading up to an April 2009 inspection.

Cahill also claims he overheard Kamholz tell state and federal inspectors that it was steam, not coke oven gas, coming out of the valve. “I was mad,” he said at the trial when asked about Kamholz’s comments. “Mark should have known it was coke oven gas.”

Cahill admitted that he felt put on the spot by Kamholz’s comments but conceded he had already taken steps to prevent the valve from opening during the 2009 inspection. He acknowledged adjusting the back pressure on the coke oven gas line each day the inspectors were on site so that the bleeder valve would not open as frequently.

He never told anyone about the adjustments but later testified that he had assumed that’s what Kamholz and the company wanted him to do while the six-day inspection was under way.

“I didn’t want anyone to find out why I was making the adjustments,” Cahill told the jury and Chief U.S. District Judge William M. Skretny.

From the first day of the trial, prosecutors Aaron J. Mango and Rocky Piaggione portrayed Tonawanda Coke as a company eager to avoid spending money on environmental compliance.

The company tried to counter that by suggesting it had complied with state and federal regulations for 30 years and that its problems started when inspectors changed how Tonawanda Coke was regulated during the 2009 visit.

To make its point, the company called a former state inspector who testified that he had repeatedly found Tonawanda Coke in compliance with state and federal regulations.

“There was a tsunami change,” Rodney O. Personius, Kamholz’s defense lawyer, said of the change in attitude among regulators. “Our position is that it just wasn’t fair.”

The verdict drew praise from federal officials in Washington D.C.

“The Tonawanda Coke Corp. and Mr. Kamholz intentionally deceived federal regulators,” Ignacia S. Moreno, assistant attorney general for the Environment and Natural Resources Division of the Justice Department, said. “The conviction of the corporate and individual defendants on almost all of the counts charged is a just and fair result that will benefit the people of Buffalo.”

The trial was the result of an investigation by the Criminal Investigation Division of the U.S. Environmental Protection Agency and the New York State Department of Environmental Conservation Police.

Skretny will sentence the company and Kamholz on July 15.

News Staff Reporter Matt Gryta contributed to this report. email: