A California company that produces Crystal Geyser bottled water pleaded guilty Thursday to illegally storing and transporting hazardous waste and agreed to a $5 million fine, federal prosecutors said.

The waste was produced by filtering arsenic out of Sierra Nevada spring water at CG Roxane LLC’s facility in Owens Valley, authorities said.

The company entered the pleas to one count of unlawful storage of hazardous waste and one count of unlawful transportation of hazardous material, the U.S. Attorney’s Office in Los Angeles said.

The office said the $5 million fine was included in a recently filed plea agreement.

The U.S. Attorney’s Office statement noted that the investigation focused on handling, storage and transportation of CG Roxane’s wastewater, “not the safety or quality of CG Roxane’s bottled water.”

U.S. District Judge S. James Otero scheduled a sentencing hearing for Feb. 24. A call to a telephone listing for the company facility was not answered Thursday.

Prosecutors say the company used sand filters to reduce the concentration of naturally occurring arsenic in the spring water to meet federal drinking water standards.

“To maintain the effectiveness of the sand filters, CG Roxane back-flushed the filters with a sodium hydroxide solution, which generated thousands of gallons of arsenic-contaminated wastewater,” the office said.

The company had been discharging the wastewater into a manmade body known as “the Arsenic Pond” for about 15 years, prosecutors said.

Pond sampling by local water quality officials in 2013 found arsenic concentrations above the hazardous waste limit, as did subsequent sampling by state authorities and the company, prosecutors said.

State officials instructed the company to remove the pond but that was done by two hired companies without identifying the wastewater as hazardous material, resulting in 23,000 gallons being discharged into a Southern California sewer without proper treatment, prosecutors said.