Lawmakers expressed shock Friday over the exponentially rising cost of a program to keep some sex offenders locked up after they complete their criminal sentences.

The annual operating cost of Virginia’s Sexually Violent Predator Program is projected to hit $32 million next year – more than a tenfold increase in eight years.

The General Assembly created the program in 1998 to keep sex offenders deemed likely to re-offend off the streets after they finish their criminal sentences. The process is known as civil commitment.

The 300-bed Virginia Center for Behavioral Rehabilitation in Nottoway County, built just two years ago for $62 million, will be filled by this fall, the House Appropriations Committee was told Friday.

Gov. Bob McDonnell has proposed spending an additional $68.5 million this year to accommodate the growing number of offenders coming into the program, including $43.5 million in borrowed money to convert a closed prison in Brunswick County into a second 300-bed treatment center.

The numbers generated bipartisan alarm on the budget-writing panel.

“This has just exploded,” said Del. Chris Jones, R-Suffolk.

“I worry about where we’re heading,” said Del. James Scott, D-Fairfax County.

Del. Johnny Joannou, D-Portsmouth, likened the program’s mushrooming cost to the repeal of the local car tax a decade ago, which also blew a bigger-than-expected hole in the budget.

The committee took no action Friday, but several members expressed reservations about McDonnell’s proposal.

The panel grilled Olivia Garland, deputy commissioner of the state Department of Behavioral Health and Developmental Services, about how and why the program has grown so dramatically.

Initially the pool of offenders was limited to four crimes: rape, forcible sodomy, object sexual penetration and aggravated sexual battery. In 2006, however, the Assembly expanded the list of crimes to 28.

In addition, the state switched to a different screening test, which lowered the threshold for commitment.

As a result, Garland said, the number of offenders coming into the program, initially about one a month, now averages six to eight a month.

There are 252 offenders in the program. So far, 11 have been released.

The average annual operating cost is $91,000 per resident. That’s low compared to the cost in some of the other 19 states with similar programs, Garland said. In New York, for instance, the per-resident cost is $175,000.

A big factor in the cost is the high staffing ratio required for such a program, she said: roughly two staffers for every resident.

Garland cited several reasons why Virginia’s program is growing faster than those in many other states.

Unlike most states, Virginia commits mentally ill offenders and those who have been judged “unrestorably incompetent to stand trial.”

Also, most states require that an offender show a history or pattern of sexually dangerous behavior before becoming eligible for commitment. In Virginia, it takes only one offense.

The department is exploring ways to curb the program’s growth, Garland said.

For some lawmakers, that can’t come too soon.

Del. Rosalyn Dance, D-Petersburg, said the state needs to examine why so few offenders are being released.

“We have an elaborate get-you-in system,” she said. “I think we also need an elaborate get-you-out system.”