A year after superstorm Sandy tore through New York City, the full extent of its damage to the subway system is still being assessed by the MTA, with work to safeguard the system from future storms potentially lasting beyond 2016, officials said.

"This is a multiyear, multiphase process in order to really start preparing for these types of storms moving forward," said Veronica Vanterpool, executive director of the Tri-State Transportation Campaign.

The damage Sandy wrought knocked the A train out of service in the Rockaways, washed out 1,500 feet of tracks and littered them with debris including personal watercraft and boats. It flooded a new South Ferry station two years after it opened and flooded nine underwater train tunnels, causing a shutdown of the R train Montague tunnel in August until next October. The G train Greenpoint tunnel was shutdown for 10 weekends starting in July and will be closed for two more in December, according to the MTA.

The MTA continues to assess damage to the system, making fixes on equipment that was brought back in operation soon after the storm with temporary band-aids, and restoring underwater tunnels that took in corrosive salt water.

The subway system suffered $4.8 billion of damage during Sandy and the MTA figures $5 billion will be needed to gird it against future storms by waterproofing stations and tunnels, and moving sensitive equipment out of harm's way.

"When it's men and women versus Mother Nature, Mother Nature wins," Gov. Andrew M. Cuomo told reporters last week. "But we are in better shape than we were last time and we'll be in even better shape."

Cuomo on Tuesday will join MTA officials to unveil designs for waterproofing the stations and tunnels as part of a $3.5 billion package of federal Sandy aid.

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Fred Smith, the MTA's chief engineer and a capital program executive, said there are more than 600 points in lower Manhattan where water can seep into the system.

"Number one thing we've learned is locations of our vulnerable entry points," Smith said. "A half inch or one-inch gap in an emergency exit can bring in a million gallons in less than an hour. The numbers are staggering."

During the storm, sandbags and wood barriers used in some lower Manhattan stations were no match for floodwaters that shattered them into debris.

Smith said the MTA is looking at barriers for station entrances where at least three sides can withstand 11-feet of water. "Then, we would look for something that could be quickly deployed over the front of the entrance," Smith said.

The MTA is also considering using logs as barriers that would fit into grooves at a station entrance, according to Smith.

"We're looking at ways that we can build into the entrance . . . the ability to close them quickly," he said.

There are nine fan plants -- facilities that house fans that pull out smoke or push fresh air into the subway -- that would be redesigned and fitted with reinforced concrete walls to withstand the pressure of flood water, Smith said.

While contractors are designing a storm-resistant transit system, crews are making permanent repairs on signals, cables and the electromechanical equipment housed deep in stations, away from riders' eyes.

"People don't see where we're doing all the repairs," Smith said. "They're in rooms at track level, they're in between stations."