More than 15 years ago, planning began for an Intermodal Transportation Center that would, among other things, allow Amtrak to leave its outmoded station in North Charleston.

Now the push is to upgrade the old train station site for that purpose, despite having spent $10 million on the ITC property on Montague Avenue.

Apparently, there’s no way the 36-acre site can be developed as intended because of a fundamental conflict with Amtrak and CSX rail that would cost a staggering $25 million to fix.

The dilemma has local officials asking the Federal Transit Authority, which put up the money for the project, for permission to abandon the Montague Avenue site in favor of the old train station. Charleston County Councilman Elliott Summey tells us that ongoing conversations with the FTA are encouraging, and he expects a decision soon. Mr. Summey also is chairman of CARTA’s board.

In the interim, there needs to be an inquiry into how this multimillion error occurred.

The goal of the ITC was to serve as a central location for passenger trains, interstate buses and mass transit, with close access to the Charleston International Airport. It also could serve light rail or commuter rail.

It was a good idea, and maybe it can be replicated at the site of the Amtrak station on Gaynor Avenue in North Charleston’s Liberty Hill neighborhood.

The sticking point for the Montague Avenue site is a logistical problem with CSX railroad over access by Amtrak. It is difficult to imagine how the problem escaped the attention of CARTA officials or their consultants.

Mr. Summey says he “absolutely will get to the bottom of this” and will seek the assistance of CHATS, the transportation arm of the local Council of Governments. Meanwhile, Mr. Summey is convinced that the Amtrak site will serve the purpose for which the Montague Avenue location was designed. It would require no costly rail relocation. It is close to the center of mass transit operations. CARTA’s busiest route runs down nearby Rivers Avenue. And it could be completed without additional funding — if federal transit officials allow proceeds from the sale of the Montague property to be used.

Mr. Summey makes the point that the Intermodal Center was to have contributed to the redevelopment of the Montague Avenue area, which currently is doing fine on its own. Liberty Hill can benefit from the change in plans, he says.

Meanwhile, potential buyers for the Montague Avenue property already are lining up, pending action by the FTA. The city of North Charleston wants to use a portion of the site to handle overflow parking for the nearby Coliseum and Performing Arts Center. Charleston County wants a new site for a recycling center — a proposal that would require County Council’s approval. And the Lowcountry Graduate Center, a consortium of local public universities, reportedly is looking at the possibility of relocating to the site.

So maybe the feds will get on board with CARTA, the county and the city of North Charleston. But will everyone be happy with the project, even then?

As North Charleston City Councilman Bob King said, failure of the Montague Avenue project damages the credibility of CARTA and North Charleston, both of which have touted the project for years.

“This should be have been checked out,” he said. Certainly, it shouldn’t have taken 15 years to find out that the site wasn’t usable.

North Charleston City Council has been briefed on the project, but has yet to sign off on it.

They should ask: Will the old Amtrak site be adequate for the job? They should also find out what the residents of Liberty Hill think about it.

And those nagging questions about how this long-planned project went wrong need to be answered.

Determining how that happened is a matter of credibility. Getting answers should be a priority before the next big transit project gets under way.