A federal judge has found Tonawanda Coke guilty of violating the terms of its probation.
U.S. District Judge William Skretny handed down that verdict Monday afternoon, saying the opacity of the emissions was darker than legally allowed.
Sentencing will take place on Friday to determine what penalty the plant will face.
Federal prosecutors are pushing to have the Town of Tonawanda plant shut down for the safety of the surrounding community. During the hearing, they presented data, photographs and witness testimony showing the company broke the law on multiple occasion by having smoke stack emissions exceeding a 20% opacity requirement.
A former employee testified that workers "cut corners" when inspectors were not around.
NYSDEC inspectors testified that Tonawanda Coke had a "low" commitment when it came to making repairs and following the law - with an air pollution control engineer telling the court that the condition of the coke ovens are deteriorating.
The inspector also told the court that he felt Tonawanda Coke was taking steps to deceive government inspectors when it came to testing emissions.
Prosecutors presented evidence and testimony that showed high levels of benzene - a carcinogen - were found in battery/oven areas where employees worked.
A NYSDEC inspector said air monitoring stations near the company reported twice the normal amount of benzene being released during the company's opacity problems.
Under cross examination, Tonawanda Coke attorneys pointed out the benzene emissions were below acceptable levels, but that was challenged later in the day by the government which said the neighborhood levels were higher than levels set by OSHA for workers wearing full protective gear.
Tonawanda Coke argued it would be a "death sentence" if it was forced to close down because it would cause millions in damage to the coke ovens.
A consultant for the company gave detailed testimony about cracks and leaks found in the ovens that was made worst by a waste heat tunnel collapse in spring.
The consultant said Tonawanda Coke had embarked on a program to fix its opacity problems, with a completion date of possibly mid-October 2018.
Federal prosecutors have argued that Tonawanda Coke failed to maintain the operation to make sure it complied with environmental law.