PORTLAND — The only person arrested in connection with an elaborate marijuana grow on a private farm along the Willamette River in Yamhill County was sentenced Tuesday to two years and three months in federal prison.

Assistant U.S. Attorney Thomas Ratcliffe described 44-year-old Manuel Madrigal as playing a limited role tending to the marijuana crop, compared to others who were never caught but set up and cultivated about 6,400 plants found on the property.

Federal prosecutors pursued the case because of the size of the grow operation, and public safety and environmental concerns, as the plants were adjacent to a public recreational area, the Willamette River.

According to the Yamhill County Sheriff’s’ Office, the operation was located in Dayton in June 2016 on wetlands near the Willamette River and was run by a Mexican drug trafficking organization.

The Yamhill County Interagency Narcotics Team, along with state police, seized over 6,500 plants worth more than $9 million. Oregon State Police SWAT was called on to provide protection for the agencies during the raid.

Authorities arrested Madrigal after officers found him camping out in the gardens in a makeshift living area – “complete with a kitchen” – hidden underneath a tarp, according to the sheriff’s office.

Madrigal pleaded guilty in June to possession with intent to distribute 50 or more marijuana plants.

Officers had placed hidden cameras in the fields, capturing men tending to the plants and squatting at the site. The private landowners were unaware of the marijuana growing but cooperated with the two-month investigation.

Madrigal told authorities he arrived at the operation two weeks before his arrest.

The prosecutor sought a 2 1/2 -year sentence for Madrigal, while defense lawyer Fidel Cassino-DuCloux asked for two years.

Cassino-DuCloux cited Madrigal’s tough childhood, having watched his mother nearly die at the hands of his father, and being whisked away to Mexico by his father without his mother’s consent. The defense lawyer also referenced state law in Oregon, where recreational use of marijuana is legal, in his argument for a lesser sentence.

On July 1, 2015, Oregon became one of a handful of states where anyone 21 and older can possess pot and grow it in their backyard.

“There is a chasm between the state and the federal government,” Cassino-DuCloux argued. “The fight between the state and the federal law is an idiosyncrasy that’s lost on citizens.”

U.S. District Judge Anna J. Brown didn’t buy that.

“He’s not being charged with a state crime,” Brown said, noting that Madrigal pleaded guilty to a federal offense. The differences between state and federal law don’t warrant leniency, the judge said.

Brown also pointed out that Madrigal had previously been convicted under state law in Illinois of manufacturing and delivery of marijuana, and served 2 1/2- years in prison for that offense. Madrigal’s lawyer countered that the conviction was more than a decade old.

“I apologize I wasn’t more careful to observe the law,” Madrigal told the judge. “I can’t say how sorry I am your honor.”

Madrigal said he’s had a rough time turning 44 behind bars and promised to be an upstanding citizen when he’s released from prison.

Brown fashioned what she called a compromise sentence of two years and three months in prison. She said she believes Madrigal, a college graduate who has taught English and Spanish and is now learning French while in custody, is repentant.

She told him he must not associate with marijuana. “It’s a violent crime to even possess marijuana,” Brown said. “You have to stay miles away from that kind of conduct.”

The judge assured Madrigal that he would hear if the U.S. Congress ever changed the federal law on marijuana, but added, “I don’t see it coming.”

“You simply have to change your approach, or you’re going to end up in your 50s in a federal prison,” the judge said.

Brown recommended Madrigal serve his sentence at a federal prison near San Antonio, Texas, where his family lives.