US broadband provider SDN Communications is doubling its data center in Sioux Falls, South Dakota.

The construction will add another 25,000 square foot (2,320 sqm) pod to the original structure. The company said construction crews broke ground in the Fall of 2021 and the company is looking for tenants.

“All of the real estate suites have been leased since our 2012 opening,” said SDN CEO Ryan Punt. “We still have capacity in SDN’s colocation space for carriers doing data delivery services, but there’s no square footage for other business ventures until we complete our expansion.”

SDN built it as an emergency backup facility in 2012, the data center features 12-inch-thick concrete walls able to withstand an F4 tornado (200+ mph winds). The company says the facility is known as ‘the bunker.’

“Two unique organizations reached out to us, not for data center needs, but for the hardened construction of the building,” added SDN Vice President of Marketing Vernon Brown. “They handle either critical functions that can’t be interrupted by weather or hold priceless elements that must be protected from weather events.”

Established in 1989 by a number of local operators and based in Sioux Falls, SDN operates more than 50,000 miles of fiber in eight states, including South Dakota, North Dakota, Nebraska, Minnesota, Iowa, Montana, Wyoming, and Colorado.

SDN owns 66 acres of land at the location and there’s room for another two pods of future construction of 50,000 sq ft (4,645 sqm). The area can’t be fully developed until the city sewer reaches the area. However, SDN has already created a preliminary master design in case city growth outpaces its planned infrastructure build-out.