If you are a South Carolina resident and use the I-526 you’ve likely heard of the large upgrades being done to the Mark Clark Expressway. 

DOT officials explain that the project will increase the capacity of the regional transportation system, improve safety, and enhance mobility for the nearby areas.

The proposed extension would transform I-526 from its end at Savannah Highway in West Ashley through Johns Island and to James Island Connector. This makes up a 9 miles stretch. The highway currently connects Mount Pleasant, Daniel Island, and North Charleston.

Secretary of Transportation Christy Hall has said that the estimated project cost would be approximately $2.35 billion. 

The DOT’s latest cost estimate is more than three times the $725 million estimate from 2015, but because the state’s share of the cost was restricted to $420 million in a 2019 agreement with the county, the entire increase would be borne by Charleston County. One of the contributing factors to the overall rise in cost is the increasing level of inflation, for example growing asphalt costs linked to global oil prices.  

A SCDOT internal investigation led to this new estimate, and it has taken into consideration the base material and the last cost, estimated contracted labor, and certain potential risks.

So far, the county and the state have invested only around $12.5 million each into the project.

The growing price of real estate in Charleston County, according to Hall, is another reason the cost has increased so dramatically. The cost of acquiring the property required for the route is $261 million.

According to the DOT’s assessment, construction may begin in 2028, with two or three years of litigation in the interim.

“I think that in five years it’s going to be 4 billion and in 10 years it’s going to be 10 billion. So the prudent thing is to move this thing forward and get it shovel ready. The need has never changed, the need is only getting worse,” District seven councilman Brantley Moody said.

But the humongous cost of the project is deterring some. 

“That is astronomical 287 million dollars a mile. I don’t understand that, I really don’t, so my vote is not going to be speculative, my vote is going to be no.” said councilman Henry Darby.

The Coastal Conservation League has strongly opposed the I-526 extension, calling it in 2021 “a last-century highway project that benefits few and impacts many.” 

SCDOT has requested that the council consider authorizing 150 million from the county and the state Transportation Infrastructure Bank Board, split equally, for the balance of the preliminary work. Phase one development is expected to cost $1.35 billion, with phase two construction expected to cost $702 million.

A breakdown of the cost increase from the presentation is as follows:

• Base material costs/quantities and labor increases: + $700 million
• Mobilization increases: + $59 million
• Bridge structure/complexity increases: + $63 million
• Additional sound barrier walls: + $8 million
• Traffic control/lighting cost increase: + $11 million
• Misc. unit price and quantity increase: + $57 million
• Additional contingencies: + $76 million
• Project delay costs: + $112 million

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