Reaching Cape Hatteras National Seashore on the Outer Banks of North Carolina just got a lot tougher. The state Transportation Department has closed the Herbert C. Bonner Bridge over the Oregon Inlet on N.C. 12 along the Outer Banks due to safety concerns.

There are just two ways to reach Hatteras and Ocracoke islands -- either via the Bonner Bridge, or via ferry.

"We have no idea how long it will be before it reopens," Cyndy Holda, the national seashore's public affairs officer, said Tuesday afternoon of the bridge closure. "They are talking ferry service will start up again tomorrow from Stumpy Point. So the trip is worth it, but may take a lot longer."

According to the Transportation Department, "(R)outine sonar scanning of the bridge identified scouring concerns, or areas where too much sand has eroded from the support structure of the bridge. As NCDOT crews continued to monitor these conditions, inspections revealed additional areas of concern, which led department officials to decide to close the bridge immediately for the safety of all residents and visitors of the area."

Department officials issued a release Tuesday stating that the bridge would remain closed at least as long as it takes for additional safety inspections to be conducted and to "make necessary repairs to fortify the structure."

"NCDOT has declared a state of emergency as a way of expediting the process and steps are already underway to begin repair work as soon as possible," the department said.

Since 1989 there has been talk about replacing the Bonner Bridge, which dates to 1963 and is the only evacuation route for the two islands, short of ferries. NCDOT awarded a contract to a design-build team to replace the bridge in August 2011. Design work began immediately and construction of the replacement bridge was originally set to begin in early 2013. All work is currently on hold following a series of legal challenges by the Southern Environmental law center on behalf of the Defenders of Wildlife and National Wildlife Refuge Association.

On Sept. 16, NCDOT received a favorable ruling in the federal lawsuit filed by the SELC when Judge Louise Flanagan issued a 42-page order denying all claims that NCDOT violated federal law when the department studied and selected the parallel bridge.

“Closing the Bonner Bridge is necessary to keep all travelers safe, but we know it will have a devastating effect on the people who live along and visit the Outer Banks,” said NCDOT Secretary Tony Tata in a prepared statement. “We will work to safely reopen this vital lifeline quickly, and hope to be able to begin construction on a new bridge as soon as possible.”

The Bonner Bridge is the only highway access for vehicles between Hatteras Island and the mainland. Until it is safe to reopen, the NCDOT Ferry Division will provide emergency support to move people and cars across the Pamlico Sound.

Ferry Division workers have already tested the emergency ferry ramps at Stumpy Point and Rodanthe, and the division is currently sending four 180-foot River Class vessels to begin operating the emergency Hatteras Island route. All tolls currently in place on the Ocracoke-Swan Quarter and Ocracoke-Cedar Island ferry routes will be waived for residents, emergency personnel and vendors while the bridge is closed and the emergency ferry route is in operation. The U.S. Coast Guard is also currently on standby.

“We expect the emergency ferry route to be up and running Wednesday morning,” said Ferry Division Deputy Director Jed Dixon. “We know the residents of Hatteras Island are depending on us to be their lifeline, and we take that responsibility very seriously.”

At full capacity on a full schedule, the route can ferry 760 single cars a day, 380 from each side. A detailed emergency ferry route schedule will be available on the Ferry division website.