A subsidiary of CH2M Hill Companies Ltd. has agreed to pay $1.5 million to resolve allegations that it submitted false claims and paid kickbacks relating to a federal contract to manage mixed radioactive waste at the Hanford nuclear site in south-central Washington state.

The Justice Department alleges two former employees of the Englewood, Colo.-based firm improperly made more than 200 purchases between 2003 and 2005 from companies owned by their spouses and charged it to the federal government. Prosecutors say in some cases, they charged double what goods were worth.

CH2M Hill spokesman John Corsi said Thursday the company fired the employees and alerted the government after the company detected their activities.

Federal prosecutors filed criminal charges against four people in the case, including the two former employees. Three pleaded guilty. A fourth awaits trial.