DENVER (AP) — The owner of a Colorado aircraft painting company pleaded guilty to illegally treating hazardous waste by ordering employees to drain and clean an underground tank without using protective gear, authorities said Wednesday.

Norman Teltow, owner of Gold Metal Paint Co., could face a maximum sentence of five years in prison, a $250,000 fine, and three years of supervised probation when he is sentenced in June, the U.S. Justice Department said.

Federal public defender Robert Pepin, who represents Teltow, said it is too early to comment on the case because of the pending sentencing.

Teltow operated the company that paints small aircraft from of a hangar near the Front Range Airport in Watkins.

The company stored hazardous chemicals in an underground tank instead of sending the material to an authorized waste disposal site, authorities said.

The Colorado Department of Public Health and Environment said it had ordered Teltow to hire a licensed waste management company to pump the waste from the tank and dispose of it properly.

The department also ordered the company to clean the tank, seal a trench drain leading to the tank, and use a licensed waste management company to transport all hazardous waste.

Instead, Teltow ordered his employees to clean out the tank without any protective equipment, exposing them to hazardous waste containing methylene chloride, authorities said. Some suffered from headaches, dizziness and nausea.

The government said Teltow then ordered his employees to pour the hazardous waste onto the floor of the hangar and leave the doors open to let it evaporate.

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