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An aerial view of where Interstate 526 ends near Citadel Mall in West Ashley. File/Staff

Charleston County is ready to spend more money than they've ever spent on any single project to make the Interstate 526 extension a reality. 

To recap: On Tuesday, after years of disputes, the S.C. Transportation Infrastructure Bank and the county finally reached enough of a consensus on how the road project would be funded to start negotiating a new agreement.

The major selling point, for the bank at least, was that Charleston County agreed to cover anything beyond what the bank had already agreed to — $420 million — when the project was originally envisioned. The latest estimate by the DOT in 2015 put the cost at about $725 million, so, by that projection, the county would have to come up with $305 million. 

Formal agreements haven't been signed, so it's not a done deal. And there are many unanswered questions about what it could mean for county taxpayers. Here's an overview of the knowns and unknowns: 

What, exactly, is the I-526 project?

Currently, I-526, also called the Mark Clark Expressway, connects Mount Pleasant to North Charleston and terminates in West Ashley near Citadel Mall. The 7-mile extension would create a continuous path from West Ashley, across the Stono River to Johns Island and James Island, where it would tie into the James Island connector at Folly Road. The road would have speed limits between 35 and 45 mph, and most sections would have a planted median. The plan includes two 65-foot-tall bridges over the Stono River. 

The idea is to connect it with other major roads and ultimately the existing parts of 526, completing a traffic loop around the center of the region. In a 2007 joint agreement with the county and DOT, the state bank agreed to pay for its construction. 

Why has the state infrastructure bank tried to kill the project?

By 2012, at least five years after the project was set in motion, its price tag was pegged at $558 million. When the cost  rose to $725 million in 2015, the bank board wanted to just scrap the project, arguing there was no money to close the gap.

Charleston County and other local leaders, including Charleston Mayor John Tecklenburg, who took office in 2016, pitched various strategies to cover the costs with local funds, but the SIB rejected them. The county had made noise about challenging the bank in court, until the SIB decided Tuesday to reconsider.

Can the county afford to spend $305 million on it?

Most County Council members say yes. But the public can't be certain until a funding plan is put together. A different plan presented to the SIB earlier this year included a combination of funds from the 2004 half-cent sales tax, federal “guide share” dollars made available through the Berkeley-Charleston-Dorchester Council of Governments, and general obligation bonds. The county has the capacity to borrow about $129 million. BCDCOG spokesman Daniel Brock said it's unclear at this point if the federal dollars would still be used. There's no talk right now of raising taxes to pay for the project, beyond the sales tax voters have approved for transportation projects. 

Is $725 million still a good number?

The $725 million estimate is three years old, but prices haven't jumped significantly in the past three years, according to the National Highway Construction Cost Index.

Charleston County Councilman Elliott Summey said that DOT isn't required to update the cost estimate before another deal is worked out with the SIB. But an update will be presented before any work starts.

According to the outline of the bank's proposed deal with the county, the county would be on the hook for building — and covering all additional costs from inflation and possible legal fights.

Will it all get built?

One way to lower the cost would be to build the project in phases, perhaps beginning with a segment from Johns Island to West Ashley.

While there was little public discussion of this Tuesday, the "term sheet" agreed to by the bank and County Council opened the door for the possibility.

It says the DOT, county and the bank "will have the right to participate in any decisions at any time that would materially reduce the scope of the project." That possibility is expected to be clarified further in a new agreement next month.

Summey said the county intends to complete the whole project in one phase.

Robert Behre contributed to this report.

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Reach Abigail Darlington at 843-937-5906 and follow her on Twitter @A_Big_Gail.

Abigail Darlington is a local government reporter focusing primarily on the City of Charleston. She previously covered local arts & entertainment, technology, innovation, tourism and retail for the Post and Courier.

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