As Hurricane Sandy draws closer, the state’s two electricity companies are already citing unprecedented levels of flooding that could necessitate shutting down substations in some of the largest cities.

At a press briefing at the state Emergency Operations Center, executives from both United Illuminating and Connecticut Light and Power expressed concerns over the water levels surrounding several of their substations.

Anthony Marone, a senior vice president at UI, said just before the briefing the utility came “very close” to deenergizing a substation at Congress Street in Bridgeport because of high tide flooding. He said the company is keeping a close eye on 10 of its substations, which together serve about a third of their customers.

The Congress Street substation serves between 35,000 and 40,000 customers in downtown Bridgeport.

“We were prepared to shut that station down in order to protect it and be able to then bring it back in a shorter time period. It’s very, very critical that if we believe a substation is going to flood, then we must de-energize it before the water reaches critical components,” Marone said.

While a shift in the wind helped keep the flooding to less than originally projected, he said it’s probable the station will need to be de-energized when high tide comes around again near midnight.

Marone said the company also is watching two stations in New Haven. One of them is a switching station that does not directly serve customers but contains important equipment. New Haven’s Mill River substation, which feeds the downtown New Haven area and about 14,000 customers, is also being monitored. During the most recent high tide neither got wet, Marone said.

“They weren’t nearly as close as the issue down in Bridgeport. I hope we say the same thing later tonight,” he said.

CL&P Senior Vice President of Emergency Operations William Quinlan said his company is also monitoring two stations. One serves the south end and downtown district of Stamford. The other serves most of Branford and part of Guilford.

Quinlan said a project to build a dike around the Stamford station to keep water out was going well. But he was grilled as to why the company waited until Monday to start the project. He said the company didn’t experience flooding like this last year. 

“The thing that makes this storm unique, I do believe, is the flooding risk. That is not something that we’ve experienced at Connecticut Light and Power in recent history. That does distinguish this event,” he said.

Quinlan said there were about 13,500 customers without power before the briefing but he expects that number to rise as the storm approaches. As of Sunday night, he said the company has brought in 1,060 extra linemen to help with the recovery efforts. He said the goal is to get a total of 2,000 linemen in addition to the 400 linemen the utility has on staff. Quinlan offered no guarantees the utility will get that many.

“In many instances, as we’ve been talking about for the last couple of days, those resources are deployed around the country also for storm response. In the mid-Atlantic there’s a huge demand for lineworkers right now,” he said.

Gov. Dannel P. Malloy continued to urge residents in evacuation zones to leave while they could and urge everyone else to stay home. At 11 a.m., Malloy ordered the state’s highways closed to non-emergency trucks. At 1 p.m. he closed the highways to all non-emergency vehicles. Having said that, the governor added that police would be making safety a priority rather than fining people using the highways anyway.

“What I’m hoping for is that people stay off the roads, that’s what we’re trying to get to… Given the nature of the danger that our residents face, we will prioritize our efforts on life safety concerns, not writing tickets,” Malloy said, adding that being on the roads represents an unnecessary danger.

The governor also advised residents to stay away from flood water, which he said easily becomes contaminated and poses health risks.

Malloy said people should prepare for the worst of the storm.

“We’re about to enter the most difficult and damaging time of the storm. The next 24 hours will be tough — very tough,” he said.