A Calvert County man pleaded guilty Monday in U.S. District Court to filing false tax returns and embezzling more than $630,000 from the Navy, authorities said.

Prosecutors said Christopher M. Hill, 46, of Lusby, a civilian Navy employee, received about $631,000 from a company that had previously been under contract to the Navy’s recycling program. Hill also chose not to disclose in tax filings that he received about $220,000 in income from the company, prosecutors said.

“Mr. Hill attempted to maneuver around the government contracting process to line his own pockets rather than play within the rules,” said Robert Craig, a Defense Criminal Investigative Service special agent involved in the case.

Authorities say that from 1998 to 2003, Hill managed the recycling program at Patuxent River Naval Air Station as the Navy contracted with companies to collect recyclable materials, sell them and give a portion of the sales proceeds to the military.

Although the contracts ended in 2003, one of the companies that had been under contract continued to retrieve scrap metal and gave part of the proceeds to Hill, according to court documents. In 2008, when Hill started working at the Washington Naval Yard, the company continued to send checks to Hill’s personal post office box in Calvert, the documents say.

Meanwhile, Hill did not file a tax return from 2005 to 2007, authorities say. He signed fake tax returns in 2008 and 2009, leaving out the $220,000 that he got from the company, according to the authorities.

According to court documents, Hill will pay the Navy $631,000 and the IRS more than $134,000. He will also give up a laptop computer.

Hill faces up to 13 years in prison and $500,000 in fines, according to court documents. He is expected to be sentenced Feb. 6.