A leader of a large drug-trafficking operation was sentenced to more than four decades in prison Tuesday for his role in shipping cocaine from California to the Washington area and preparing it for sale.

William M. Bowman, 34, was one of three men found guilty in the District’s federal court in November after a five-week trial. In addition to a conspiracy charge, Bowman was found guilty of possessing a firearm during the commission of a narcotics offense.

U.S. District Judge Colleen Kollar-Kotelly said she had no choice but to sentence Bowman to the mandatory minimum of 45 years behind bars. She ordered him to forfeit $3 million, to be paid jointly by Bowman and 13 other associates implicated in the case.

“It’s a violent and risky business to be involved in. There’s absolutely no excuse for it,” Kollar-Kotelly said, while adding that Bowman’s sentence is a “high price to pay for easy money.”

At trial, prosecutors portrayed Bowman as an upper-level manager responsible for arranging shipments from California and processing the cocaine once it arrived. During a 15-month investigation, law enforcement officials monitored a storage locker in Hyattsville that Bowman and his associates used by obtaining a court order that allowed them to use closed-circuit video cameras.

Henry B. Williams of Glenn Dale was sentenced to a 51-month prison term in February, and the government is seeking a life sentence for Gezo G. Edwards of Silver Spring.

In April 2011, law enforcement officials seized about 30 kilograms (66 pounds) of cocaine with a street value of $3 million and several firearms from the locker, according to the government’s sentencing memo. A search of Bowman’s Acura, according to court papers, turned up chemical splash suits, goggles, spray bottles and other equipment used to process large quantities of cocaine.