The big, rugged tires that Michelin makes in South Carolina cover plenty of ground on land.

But they walk on water, too, via the Port of Charleston.

The manufacturer announced Tuesday it will fork out $750 million to build a new plant in Anderson County and add on to an existing factory in Lexington. The strategy is to expand now to meet growing global demand for heavy-duty earth-moving tires used in the construction and mining trades.

The two investments are expected to generate 500 direct jobs. When combined with several other sizable deals by other companies, they will likely vault South Carolina to the top of the heap among the nation's tire-making states by next year.

“How the heck could that have happened?” asked Pete Selleck, chairman and president of Michelin North America.

Port ties Charleston can take some credit and a bow, alongside the Upstate and Midlands, he said.

Selleck noted that the business ties between French-owned Michelin and South Carolina go back decades, 40 years, in fact. Over that period, the company has invested about $5 billion in the Palmetto State, including its latest manufacturing expansions far from the coast.

Selleck offered some historical perspective.

“One reason we came here was access to Charleston Harbor, to the Port of Charleston,” he said Tuesday. “In making tires, we use a lot of materials, including natural rubber. Natural rubber is grown predominantly in China, Malaysia and Indonesia. It's put on container vessels and shipped around the world.”

But times have changed, and Charleston is no longer just a convenient point of entry for raw materials. Michelin expects to ship to buyers overseas about half the earth-moving tires it will be making at its future inland plants.

“The port has become very important for us on the export side,” he said.

The mammoth earth- moving tires now made in Lexington run in the “tens of thousands of dollars” and demand is so high that each one is sold before it leaves the factory floor, Selleck said.

They're hard to miss in transit. Some of the rubber behemoths are lashed down on the flatbed of a truck and require special weight permits. Others are moved from the plant to the port in roofless 40-foot-long shipping containers, and “they actually stick out the top,” Selleck said.

“It's pretty impressive,” he added.

Depth charge Many of the tires will be heading for fast-growing markets such as China, India and Brazil.

“That growth is fueling increased demand for all sorts of things. Infrastructure. Mining. That demand clearly is going to be going up,” Selleck said.

He mentioned infrastructure, a clunky engineering term that encompasses roads, bridges, rail lines, runways, sewer systems and, last but not least, ports. Michelin took the opportunity at Tuesday's announcement to reinforce its support of efforts to deepen Charleston's shipping channel to 50 feet so the harbor can able to handle the longer, heavier container ships of the future.

“We're making some assumptions in making this investment,” Selleck said, referring specifically to the unresolved dredging plan.

State Ports Authority Chief Executive Jim Newsome described Michelin as a major longtime customer as well as a consistently “ardent supporter” on the harbor depth issue.

“This announcement today solidifies the company's relationship with our port and our state,” Newsome said in a statement Tuesday.

Contact John P. McDermott at 937-5572.