SAN FRANCISCO (CBS SF/AP) — A San Francisco man has been sentenced to prison after admitting to mailing more than a quarter ton of marijuana to an associate in Virginia five pounds at a time, according to federal prosecutors.

Nathan Driver had pleaded guilty in U.S. District Court earlier this year to conspiracy to distribute marijuana charges. In doing so, the 26-year-old admitted that he shipped 530 pounds of marijuana in 136 parcels — about five a month — to Jonathan Hall of the Richmond area from March 31, 2016 to September 2018.

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Hall admitted depositing roughly $400,000 of proceeds into a bank account in 62 deposits of less than $10,000 each to avoid triggering a bank reporting requirement.

The money was mailed to Driver’s San Francisco home divided up into 33 packages.

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U.S. District Judge Henry E. Hudson, who will also hand a sentence to Hall in July, called the operation “a sophisticated criminal enterprise.”

“He’s (Driver) a well-educated young man … who got involved in serious drug trafficking,” the judge said.

Driver was sentenced on Wednesday to to 35 months in prison.

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According to the Richmond Times-HeraldDriver’s lawyer, Edward J. Ungvarsky, said, “What we have here is a crime that’s extremely stupid done by someone who should have known better… Perhaps he was using too much of his own product.”