Gov. David Ige has taken an important step, capitalizing on an opportune moment to make progress in the relocation and redevelopment of Oahu Community Correctional Center.

The governor has released $5 million, set aside but unspent under the administration of former Gov. Neil Abercrombie, to start the planning on a long-needed expansion of jail capacity and the improvement of its deplorable conditions.

That funding will enable the state to solicit proposals to replace the Dillingham Boulevard facility that is infamous for its overcrowding. The official bed count at OCCC stands at 989, but in reality it houses as many as 1,300 inmates.

Nolan Espinda, director of the state Department of Public Safety, favors a replacement facility designed to accommodate 1,500. As much as this state needs to reduce overall incarceration, this sounds like a reasonable adjustment to make for current and anticipated future needs.

As it is, people being held at OCCC now are compelled to sleep on the floor amid the mold and other aspects of the jail’s decline. It’s inhumane to house people awaiting trial that way.

What makes the timing fortuitous, of course, is that there are now opportunities to leverage the value of the 16-acre Kalihi site into a redevelopment that can produce a better use for the urban parcel without an excessive cost to taxpayers.

The rail project’s alignment follows Dillingham, boosting the potential of transit-oriented development on the OCCC site to yield more affordable housing units for rent and purchase.

And that attraction means there could be significant benefits to a land swap involving this parcel and 15,000 acres of agricultural and conservation lands in Central Oahu. In exchange, a private partner could underwrite the construction of a new Halawa facility, thus saving the state money.

This notion is still alive at the state Capitol, with Senate Bill 284 still moving. That bill, principally about finalizing a deal preserving part of Turtle Bay, includes a call for the state Office of Planning to study the acquisition of agricultural acreage through a land swap.

Although planners must explore all the options, the new jail location adjacent to the existing medium- and high-security prisons in Halawa makes the most sense, providing that concerns about the water and sewer capacity of the site can be overcome.

As Espinda rightly noted, having the jail share a site with its largest prison would be efficient, allowing for economies of scale in managing the costs of laundry, kitchen and other operations.

The issue of keeping the jail population itself in check, meanwhile, must not be ignored. Kat Brady, who coordinates the Community Alliance on Prisons, makes a solid point that creating a more commodious facility must not reverse policy trends that now favor diverting people to treatment and other programs. Many of them — the homeless, the mentally ill — don’t belong in jail.

But the plain fact of Oahu’s critical need for a new correctional facility has been evident for years. State officials must not pass up this chance to advance a plan to fill that need at long last.