Sen. Jim Hargrove, D-Hoquiam, said today that the Senate is weighing the closure of the country's last island prison that can only be accessed by boat.

McNeil Island Corrections Center, in Steilacoom, Pierce County, is one of the most expensive prisons in the state to operate because its age and location, Hargrove said. Lawmakers are searching for ways to close the $8.5 billion state budget shortfall.

McNeil Island also is home to the Special Commitment Center, the state's mental health treatment program for civilly committed sex offenders who have completed their prison sentences. The Special Commitment Center would not be affected by any closure because it is managed by the Department of Social and Health Services, not the Department of Corrections.

The medium security prison costs about $49 million a year to operate.

McNeil island had been a federal penitentiary from 1875 until 1976, according to the Department of Corrections (DOC). The state of Washington started leasing the facility in 1981. In 1984, the island was officially deeded to the state, DOC said.

DOC spokesman Chad Lewis said the prison has about 1,300 inmates, making it the sixth largest of the state's 15 prisons. He said it costs an average of $37,000 per year to house inmates at McNeil Island. Citing a 2007, statistic, Lewis said the state spends an average of about $31,000 to house inmates.

Hargrove emphasized that the possible prison closure is one of many options being weighed by the Senate. He said they are also talking about keeping inmates transferred to out-of-state prisons for overcrowding and cost savings reasons in those other states longer.

Hargrove said the final decisions will be contained in the Senate budget. Senate Democrat staffers said the budget is expected to be released on Tuesday.

UPDATE: DSHS spokesman Steve Williams called this afternoon to say that closure of McNeil Island would dramatically impact his agency.

"They [DOC} are the lifeline to get us from the island and the main land," Williams said. "We rely on DOC for transportation, they operate the boats. They operate the fire department and they have an emergency response team, kind of like a SWAT team, that we can call on if we have an emergency."

Williams said there are more than 280 sex offenders at the Special Commitment Center and more than 400 DSHS employees who work on the island.