It was supposed to be open by now:

The second-largest construction project in Pennsylvania state history is State Correctional Institutions Phoenix, rising on former farmland next to the 87-year-old SCI Graterford prison in Montgomery County.

Only the $800 million Convention Center in Philadelphia cost taxpayers more.

Phoenix is a million-square-foot complex, about as big as the Comcast Center, the state's tallest office tower. It is designed to house 3,872 inmates, a few hundred more than now live at Graterford, the main state prison for the Philadelphia area. Graterford's 1,000 staff members will transfer to Phoenix, said state corrections spokeswoman Janet Kelley.

The Phoenix facilities, under general contractor Walsh-Heery Joint Venture, were supposed to be done last June 25. That got postponed to last Nov. 25. It's now "expected to be completed in fall of 2016," says Troy Thompson, spokesman for the Department of General Services.

The state agreed to pay $320 million in 2013, and boosted that to $350 million last summer after a string of change orders. Separate from those payments, $21 million has been paid to Philadelphia-based Hill International as project manager.

Plans for Phoenix date at least to the late 2000s, under Gov. Ed Rendell. The state scaled back an early proposal for a $400 million, 4,100-bed prison, citing a lack of sewer capacity. Gov. Tom Corbett added plans for a 100-bed "capital cases" unit - or death row - plus a women's unit.

More death-row beds are needed because Pennsylvania continues sentencing killers to death, even though, as my colleague Michaelle Bond wrote last week, the state hasn't executed anyone since 1999.

Indeed, Pennsylvania's prison population, which rose from 12,000 in 1983 to a peak of 51,000 in 2010, has fallen slightly to 49,000, after crime rates dropped.

With fewer prisoners, is Phoenix needed? The Pennsylvania Prison Society, which backs "community-based solutions" instead of prison for some offenders, mostly "doesn't want more prisons being built," executive director Ann Schwartzman told me.

Yet advocates do see advantages in replacing "crumbling" older buildings and adding program space, she added.

In 2013, state Corrections Secretary John Wetzel - hired by Republican Corbett and kept on by Gov. Wolf, his Democratic successor - told me he hadn't expected to build more prisons.

But Graterford, built in the 1920s, had become so expensive to run - $100 per prisoner each day - that Wetzel said he approved Phoenix after reviewing figures claiming savings of $30 a day per inmate, or $42 million a year.

Will the latest delay cost extra? "Per contract agreements and terms, the contractor will not receive any additional compensation for the extended period it is taking to complete the project beyond Nov. 20, 2015," Thompson told me.

Is that freeze getting the job done quicker? Officials at general-contracting partners Walsh Group, based in Chicago, and Heery International Inc., in Atlanta, didn't return calls seeking comment.