Wal-Mart Stores Inc. pleaded guilty in federal court Tuesday to criminal charges for improperly disposing of hazardous waste from stores in California and Missouri, a crime for which the retail giant will have to pay $81.6 million.

"This tough financial penalty holds Wal-Mart accountable for its reckless and illegal business practices that threatened both the public and the environment," said Tammy Dickinson, U.S. Attorney for the Western District of Missouri.

The U.S. Department of Justice said that Wal-Mart violated the Clean Water Act by illegally handling and disposing of hazardous materials in stores across the United States. The retailer also violated the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) by failing to properly handle pesticides that had been returned by customers at its stores across the country.

Wal-Mart entered the guilty plea in California for six counts of violating the federal Clean Water Act and in Missouri for violating the FIFRA. The Clean Water Act controls direct discharges from sources like pipes and sewers into navigable waters. The FIFRA mandates that the Environmental Protection Agency (EPA) regulate the use and sale of pesticides to protect human health and the environment. The EPA requires that wastes identified as hazardous be stored, treated, and disposed of according to very specific stipulations.

Documents filed in the U.S. District Court in San Francisco said that Wal-Mart failed to train employees on how to properly manage and dispose of hazardous waste. Consequently, the wastes were placed improperly into municipal trash bins or poured into local sewer systems, placing the general public at risk of contact with the potentially dangerous materials.

According to a plea agreement filed in Kansas City, Mo., Wal-Mart began sending marred household products, including damaged solid and liquid pesticides, from its return center to a recycling facility in Missouri where the products were processed for reuse and resale. Inadequate oversight at that facility led to regulated pesticides being mixed and offered to customers without the required registrations under the FIFRA.

"By improperly handling hazardous waste, pesticides and other materials in violation of federal laws, Wal-Mart put the public and the environment at risk and gained an unfair economic advantage over other companies," said Ignacia S. Moreno, Assistant Attorney General for the Justice Department's Environment and Natural Resources Division. "Today, Wal-Mart acknowledged responsibility for violations of federal laws and will pay significant fines and penalties, which will, in part, fund important environmental projects in the communities impacted by the violations and help prevent future harm to the environment."

Combined with previous actions by the states of California and Missouri, Wal-Mart will pay more than $110 million to resolve cases alleging violations of federal and state environmental laws.