Even now, years later, Ronald Snyder remembers the black water that flowed off the coal piles at Tonawanda Coke after a heavy rain.

He also remembers seeing petroleum deposits and a “rainbow” like spectrum of colors in the water as it flowed into ditches around the coal piles.

“From there, I have no idea where it went,” the former plant superintendent told a federal court jury Friday.

Snyder, who left Tonawanda Coke in 2005, was the latest witness to testify about the company’s environmental record as part of an ongoing criminal trial before Chief U.S. District Judge William M. Skretny.

The trial, now in its third week, is the result of a 19-count federal indictment charging the Town of Tonawanda manufacturer with polluting the air and ground and then trying to hide its actions from federal officials.

Daniel Heukrath, a current employee, also testified about run-off from the coal piles and, at one point, offered an opinion on where it went after leaving the two ditches around the piles.

“It would basically head down to the river,” he told Assistant U.S. Attorney Aaron J. Mango.

“The Niagara River?” Mango asked him.

“Yes,” said Heukrath.

Earlier in the day, Snyder, one of several current and former employees to appear before the jury, also testified about a malfunctioning piece of equipment designed to carry coal tar sludge.

To hear Snyder talk, one of the problems with the equipment was sludge that often fell to the ground. Federal officials already have testified that hazardous levels of benzene were found in some of the sludge produced at the plant.

“There was leakage through the conveyor belts,” he told the jury. “There was always spillage.”

On cross-examination, Snyder acknowledged telling Thomas Thurston, a private investigator for the company, that he believed the state Department of Environmental Conservation had been negligent in its inspections of Tonawanda Coke.

At the core of the company’s legal defense is the argument that state inspectors gave it a clean bill of health for decades before suddenly changing the rules during a 2009 inspection by state and federal officials.

“Do you recall telling Mr. Thurston that you believed the DEC dropped the ball?” asked Gregory F. Linsin, a lawyer for the company.

“Yes,” said Snyder, “I think that’s true.”

The trial resumes Monday.