An environmentalist is accusing the chemicals giant Huntman Chemical of poisoning the groundwater at its North Carolina refinery.

In a lawsuit filed Thursday, the American Civil Liberties Union said it is seeking $20 million in damages from the company, which it says has been using chemical waste as fertilizer for decades.

Huntman is a major consumer of the North Carolina-based refinery, where it has been dumping toxic waste and toxic metals for years.

In 2013, the company sued the state of North Carolina over a law that made it a crime to dump toxic waste into groundwater.

The company’s chemical waste is used in fertilizer, as well as pesticides and chemicals used in agriculture.

The suit alleges that Huntman has been repeatedly failing to disclose problems at its chemical processing facility at the time of the spill, the largest chemical spill in the U.S. Since 2008, the U-Haul plant has dumped nearly 8 million gallons of hazardous waste into the Owens River, according to a recent report by the state Department of Environment and Natural Resources.

Hunt, which has more than 1,200 employees and more than $30 billion in annual revenue, has also failed to disclose toxic waste that was spilled from a ruptured storage tank in 2013 that polluted Owens Creek, according the lawsuit.

Huntmen was also accused in the lawsuit of violating a law in 2008 that allowed the company to use chemical waste from other facilities to feed its chemical plant, according an email obtained by The Associated Press.

Hunt’s toxic waste spill is a prime example of the problems that come with an expanding industry that has been plagued by problems from pollution to worker safety.

The EPA said the spill is the biggest chemical spill the agency has ever investigated.