Once the inmates return to the renovated prison, the new, more efficient design would save $2 million per year in worker pay, rising to $4.4 million per year after 30 years, the study said.

He died at that North Carolina prison in June – just five days after his fellow Supermax compatriot, Hanssen, was found dead in his cell in Florence at age 79.

The Supermax is home to the prison system’s most violent inmates as well as convicted terrorists. “They’ve been in jail. They’ve been in prison. They’ve killed staff.