CertainTeed’s vinyl siding plant in Westlake, Louisiana, will pay civil penalties of $365,500 for violating the Safe Drinking Water Act and failing to provide employees with a safe source of drinking water.

The U.S. Environmental Protection Agency’s regional office in Dallas said the settlement is the largest civil penalty of its kind in state history.

The EPA charged that the company failed to correct “significant deficiencies” uncovered in an inspection by the Louisiana Department of Health (LDH) of CertainTeed’s public water system at the Westlake plant. The EPA charged in a Pennsylvania federal district court that the company took years to correct the problem, according to an EPA news release.

“Despite numerous enforcement efforts by both EPA and the state of Louisiana, including letters from LDH a joint inspection by LDH and EPA, and an EPA administrative order, CertainTeed took over four years to address the significant deficiencies identified in the survey,” the agency said.

Plastic News reported that the problems involved the supply of drinking water for the plant’s 43 employees. Three wells served the site, but the one earmarked as the source of potable water for five buildings and emergency wash stations was damaged by Hurricane Rita in 2005. The other two wells were not considered potable and were used instead to fill fire suppression tanks and cooling towers.

After the hurricane, the plant took water from the fire suppression system and disinfected it with chlorine for use by employees. But the water system had no filtration and no means or preventing the flow of water back to the fire suppression system.

The EPA said that violations included failure to provide approved drinking water and failure to monitor and test the water for contaminants that could cause health problems.

In a statement, CertainTeed said it had drilled a new well for drinking water and taken steps to ensure compliance with the Safe Water Drinking Act, Plastic News said. “The safety of its employees, the environment and the communities it serves is a top priority for CertainTeed,” the statement said.

The Valley Forge, Pennsylvania, company produces a variety of building products. It is a subsidiary of Saint-Gobain, a French conglomerate.

CertainTeed announced in 2011 that the plant had earned the International Organization for Standardization (ISO) 14001 certification recognizing its “ongoing commitment to environmental responsibility.” The plant was diverting material from waste streams by recycling cardboard, metal, electronic scrap, oil and other products, while reporting a 70% reduction in water use.

In order to win certification, CertainTeed developed an environmental management system that “underwent rigorous evaluations through a third party review,” the company said at the time.