Wal-Mart Stores Inc. will pay $81.6 million after pleading guilty on Tuesday to criminal charges of improperly disposing of fertilizer, pesticides and other hazardous products that were pulled from stores in California and Missouri because of damaged packaging and other problems.

The retail giant entered the plea in federal court in San Francisco to misdemeanor counts of violating the Clean Water Act and another environmental law regulating pesticides. The fine also settled Environmental Protection Agency allegations.

In Kansas City, Mo., the company pleaded guilty to improperly handling pesticides.

The plea agreements ended a nearly decade-old investigation involving more than 20 prosecutors and 32 environmental groups that has cost Wal-Mart a total of $110 million.

Court documents show illegal dumping occurred in 16 California counties from Del Norte to Orange between 2003 and 2005. Federal prosecutors said the company didn't train its employees on how to handle and dispose hazardous materials at its stores.

The result, prosecutors say, was that waste was tossed into trash bins or poured into sewer systems. The waste also was improperly taken to one of several product return centers throughout the U.S. without proper safety documentation, authorities said.