Several sheriffs tell The (Myrtle Beach) Sun News that the plan would remove the inmates from overcrowded county jails, where they take up valuable space as they await officials to transfer them to the closest federal immigration court in Atlanta.
"It's easier to do it on a regional level than for each individual county to do it," said Horry County Sheriff Phillip Thompson.
The current plan calls for the three prisons to hold up to 400 inmates each.
State prison officials will run the facilities, which will be paid for through a program with the federal Department of Homeland Security, said Jeff Moore, executive director of the state Sheriff's Association, whose organization drafted the plan with help from the governor's office and federal officials.
But the proposal is a work in progress awaiting approval from Homeland Security and could be changed considerably, officials said.
Officials also have to figure out who will pay to build the prison. If state money is involved, the plan will need to be approved by legislators.
Families of illegal immigrants could be angry their relatives are housed several counties away, but the state has the right to house inmates where it sees fit, said Tammy Besherse, an attorney for the South Carolina Appleseed Legal Justice Center, an advocacy group for the poor.
The group is also worried that concentrating illegal immigrants in a few jails might lead to substandard care in those facilities, Ms. Besherse said.
"There would be a lot of potential for the undocumented immigrants to receive substandard treatment, food, etc.," Ms. Besherse wrote in an e-mail to the newspaper. "These guards will now know for a fact the inmates aren't here legally. That could lead to abusive situations."