A Woodbridge man was sentenced Thursday to six years in federal prison for his role in what authorities have called one of the largest bribery scams in the history of federal contracting.

Michael Alexander, 56, a former Army Corps of Engineers program manager, pleaded guilty in February to bribery and conspiring to commit money laundering. He is the first person to be sentenced in a scheme that involved more than $30 million in bribe and kickback payments.

Alexander admitted that starting in 2006 he and a co-worker conspired to give contracts to companies that rewarded them with bribes. In total, Alexander admitted receiving $1.25 million in bribes over a four-year period that began in 2007; he was promised another $320,000 just before he and several others were arrested in October.

Under federal guidelines, Alexander faced between nine and just over 11 years in prison. Prosecutors recommended six because he cooperated extensively with authorities.

Still, Assistant U.S. Attorney Michael Atkinson said a stiff sentence was needed to deter others from skimming from government contracts.

Alexander’s lawyer, Christopher M. Davis, sought three years, citing his client’s guilty plea and lifetime of public service.

Fighting back tears, Alexander told U.S. District Judge Emmet G. Sullivan that he apologized to the Army Corps, his family and his wife. “ “I hope that one day I can redeem myself,” he said.

Sullivan said the magnitude of the scheme was “shocking” and warranted at least six years in prison.

Twelve people have been charged in the investigation. Eleven have pleaded guilty, including Kerry Khan, 54, another former Army Corps program manager. No sentencing date has yet been set for Khan, whom U.S. Attorney Ronald C. Machen has called the conspiracy’s ringleader.