A former DuPont chemical plant operator testified Monday that plant workers used black plastic drain pipes held together with duct tape to try to stem the flow of toxic leaks from the company’s acid plant in Ascension Parish and avoid costly shutdowns.

Jeffrey M. Simoneaux, the plaintiff in a federal whistleblower lawsuit against DuPont over the leaks, claimed the piping routinely and unpredictably corroded, releasing toxic gases. He also said the piping would not collect all the leaking gas even when it worked as designed and would cease to be effective whenever the plant lost power.

Simoneaux, who lives in Prairieville, testified at the first day of a civil jury trial at the U.S. District Court in Baton Rouge that operators originally came up with the homemade piping system, which relied on the plant’s internal vacuum pressures, as a stop-gap measure to suck up leaks of sulfur dioxide and sulfur trioxide until cracked and leaking equipment could be permanently fixed by contract welders.

But the practice changed while he was on vacation in December 2011, which he testified he later learned about when returned to work in January 2012.

“It became more of a way to continue running the plant and never shut down” and continue running with the leaks, Simoneaux said. Simoneaux, who worked at the plant nearly 22 years, was chairman of its safety, health and environment committee for 14 years.

Before Simoneaux’s roughly hour of testimony Monday, DuPont defense attorney Monique Weiner reminded the nine-person jury that Simoneaux has the burden to prove the claims made against DuPont.

She said they would not hear any evidence of air, water or soil samples or other measurements indicating the leaks posed a danger to workers and residents or harmed the environment.

She added that jurors also would not hear about fines brought by the U.S. Environmental Protection Agency, the U.S. Occupational Health and Safety Administration or the state Department of Environmental Quality over the allegations that Simoneaux is making.

Weiner said Dupont is heavily regulated and submits to regular, unannounced inspections.

In his lawsuit, Simoneaux alleges that DuPont hid years worth of continuous leaks from the plant along the Mississippi River in Ascension Parish in an effort to avoid fines from the EPA. He also alleges he was retaliated against for trying to report the leaks and eventually left the company in August 2012.

He has sued under the False Claims Act and, if he prevails, would recover a sizable share of daily fines of $37,500 against DuPont for allegedly not reporting the leaks, as well as for damages over the alleged retaliation.

Simoneaux said the leaks were toxic sulfur dioxide, sulfur trioxide and a sulfuric acid mist that formed when the chemicals hit Louisiana’s humid air and went off-site. Sulfur trioxide is carcinogenic, Simoneaux testified, as he read DuPont’s own internal chemical safety information.

Simoneaux also testified how workers had trouble keeping rain and humidity out of the plastic pipes to prevent moisture from reacting with the leaking gases and forming sulfuric acid that would eat through the pipe.

“They’re taped together with duct tape so, you know, I don’t now how much moisture you can keep out with that,” Simoneaux said about the piping.

He was the first witness in a trial scheduled for two weeks and expected to include internal videos of the leaks, a recorded warning from plant manager Tom Miller in May 2012 not to report the leaks and testimony from former Louisiana Department of Environmental Quality Secretary Paul Templet, who is a plaintiff’s expert.

While Weiner in her opening statements acknowledged the leaks and the use of the piping system, which she claimed was developed by engineers, Weiner cautioned jurors to pay attention to how much of the chemicals was being released and whether, at those levels, DuPont had an obligation under the law to report the leaks.

She noted that when someone cuts an onion, enzymes in the onion react with moisture in the eye to form sulfuric acid that causes the eyes to burn but that doesn’t stop people from cutting onions for their gumbo.

“What makes the difference is the dose,” Weiner said.

She also revealed that DuPont is planning a $10 million replacement of the leaking equipment.

Weiner said the stories-high heat exchanger and related equipment, which were installed a few years ago to improve air emissions, have cracked and not worked as expected. They had to be replaced, requiring engineering work and construction of the equipment in China.

The piping system has been used while the replacement was being developed. She said the replacement equipment is already in the Port of New Orleans and work is expected to begin in February or March.

Earlier on Monday, plaintiffs’ attorney J. Arthur Smith III told jurors that DuPont has had “substantial information” about the leaking chemicals for three years and did not report it to the EPA.

He promised the jurors they would see plenty of evidence to that end.

Follow David J. Mitchell on Twitter @NewsieDave.