MIDDLEBURY — Vermont Agency of Transportation Secretary David Dill has declared an emergency over the sudden closing of a key bridge across Lake Champlain.

Dill said the declaration is different from a disaster declaration that can be made in the aftermath of a natural disaster.

But Dill said the emergency declaration could help get federal aid and reprioritize state money to help repair or replace the bridge between Addison and Crown Point, N.Y.

The New York State Department of Transportation closed the bridge on Friday because it's unsafe.

Dill said it will be at least two weeks before authorities know the extent of the problem.

The bridge closure is hurting commuters and people who rely on the bridge for their businesses.

Additional ferry service may be able to ease the problems that commuters and emergency services face due to the closing of the Champlain Bridge, Dill said at a press conference Tuesday.

Talks are under way with the Lake Champlain Transportation Co., which operates eight ferry boats at three crossings, Charlotte-Essex, N.Y.; Burlington-Port Kent; and Grand Isle-Plattsburgh. The Burlington crossing takes an hour and is closed for the season. Dill said they are also in touch with the Coast Guard to see if they could help to keep ferries going into the winter.

Plans are already being drawn up for an additional ferry landing closer to the bridge site than Charlotte or Ticonderoga, where there is a small, cable-drawn ferry, in case the Federal Highway Administration approves the concept, Dill said.

At a public hearing in Addison on Oct. 8, residents had ridiculed the idea of substituting ferry service for the ailing bridge. Dill made no suggestion that ferries would be anything but a short-term alternative to people driving 100 miles to work in another state.

The initial estimate was that a new ferry would require a round-trip ticket price of $131, Dill said. But it might be possible to get a federal subsidy for the additional ferry route, thus reducing that price, he said — but not compensating affected individuals or companies directly for their expenses during the declared transportation emergency, he said.

State officials are also talking with Addison County Transit Resources, the public transit bus company, about how they might reduce the distances that people who rely on the bridge have to drive, Dill said.

At the Oct. 8 meeting, New York transportation officials said repairs to the steel structure had made it safe for one lane of traffic. Asked why the bridge was shut down so soon after those statements and why problems were not detected by crews working on the bridge all summer, Dill said the problem had been hidden until this fall.

Dan Landry, a project manager with the Vermont Agency of Transportation structures division, said high water from the wet summer had kept bridge inspectors from examining the place where damage is most likely to occur for any bridge piling: the place where it meets regular water levels, water-borne objects and ice.

As soon as the lake subsided, inspectors went to the two weakest pilings of the 12 pairs that support the 11 spans of the bridge (nos. five and eight), where spalling (cracking that can result in pieces falling off) had been measured a few months ago to have penetrated five inches, he said.

When core sampling found that the cracks now penetrated 18 inches, New York and Vermont transportation officials agreed to close the bridge immediately, Landry said. They did so at 1:30 p.m. on Friday, although they realized travelers would be stranded, thinking it would be worse to have a catastrophe like the bridge collapse in Minneapolis, he said.

Some pilings have yet to be tested by engineers, Landry said. At their deepest, they go down about 100 feet to the lake bottom, he said.

The Oct. 8 meeting was part of the "scoping" process, an investigation of possible alternatives mandated by federal law, since federal money would pay 80 percent of the bridge overhaul or a new bridge. Dill reiterated that with the two states only paying 10 percent apiece, there was no avoiding a lengthy federal process with all its draft plans and public meetings.

The schedule unveiled on Oct. 8 gave 2013 as the expected date of actual work to remedy the Champlain Bridge situation.

Herald correspondent Ed Barna contributed to this report.