A French company that builds high-voltage cables in Goose Creek for the power industry is adding underwater cables to the site's product mix as part of an $80 million expansion.

Nexans, which opened its 350,000-square-foot plant in 2014 at the Charleston International Manufacturing Center, plans to add 125,000 square feet of space and double its workforce to roughly 135 employees over the next two years.

It also plans to build a shipping terminal at its site along the Cooper River, where the company's cable-laying vessels can load up before heading to offshore projects. The underwater, or submarine, cable expansion is prompting Nexans to build a second ship 

"Nexans is investing here because the submarine market is exploding — both in North America and globally," said Brian Boan, director of transformation projects for Nexans' plant in the Bushy Park area of Berkeley County.

The underwater power cable market is expected to grow from about $8 billion this year to more than $16 billion by 2023, according to industry researcher Markets-to-Markets.

"The overall market is set to witness significant growth because of increasing offshore wind installations, growing demand for inter-country and island connections, and demand from the offshore oil & gas sectors," the researcher said.

The Goose Creek site will be Nexans' only underwater cable manufacturing site in North America. Currently, the company builds underwater power cables at its Calais, France, headquarters and at a plant in Halden, Norway. Nexans has other North American facilities that make fiber-optic cables, wiring for the construction industry, low-voltage cables and other products.

Production of underwater cable won't be too different from the land-based power cables the company already makes at the Goose Creek plant. The process typically involves a copper conductor capable of handling up to 525 kilovolts being lowered into a 426-foot-tall tower where it is encased in melted plastic and then cured and cooled with nitrogen.

The land-based cables, which are used in underground power installations, are built in lengths that can stretch more than one mile. They are placed into drums and transported by trucks from the Nexans site to roughly 20 large customers that serve utilities nationwide. The Goose Creek plant builds about 60 miles of such cable each year, with 80 percent going to markets in North America.

The site plans to build up to 155 miles of underwater cable each year when manufacturing begins in 2020, serving markets around the globe as production ramps up to 24 hours a day.

"It's a very slow manufacturing process — we're not a widget environment," Boan said, adding the tower process takes about one minute for every 3.3 feet of cable. "Every cable that comes out of this factory is a very specific design to a very specific customer and need. We never produce the same cable twice here."

The expansion in Goose Creek comes at a difficult time for Nexans, which said last week that its full-year earnings would be weaker than expected because of an "abrupt deterioration of the high-voltage project activities forecast for the second half of 2018." That includes postponements of some underwater cable projects and a weak backlog of land-based cable deals.

Nexans' shares have lost nearly 30 percent of their value this year and Arnaud Poupart-Lafarge, the company's CEO, unexpectedly announced he would leave the company by Sept. 30 for personal reasons. The high-voltage cable industry also is being challenged by growing competition from Chinese manufacturers.

The Goose Creek expansion is part of a long-range plan to diversify production of the underwater cables that Nexans sees as a future profit driver for the company.

"It's a big commitment for Nexans, and it shows a lot of confidence in our facility, the Charleston area and our workforce," Boan said. "We take pride in the fact that we're using local resources as far as people and other businesses supporting us. It's exciting to be a part of this community, and now to be stepping into the maritime and port industry that's growing so fast here."

Reach David Wren at 843-937-5550 or on Twitter at @David_Wren_