Construction workers carry boards of wood to cover air vents that could cause the New York subway system to flood in preperation for Hurricane Sandy.
From the trains underground to the skyscrapers overhead, New York City has a slate of features that threaten to make hurricanes a unique urban disaster:
SUBWAY: The system that carries 5 million riders on an average weekday sits anywhere from one story to 180 feet underground. While pumps clear 13 million to 15 million gallons of water out of the subway on an average day, they would likely be overwhelmed if a storm surge sent water pouring down subway entrances and sidewalk grates. For example, a 1992 winter storm that packed an 8-foot storm surge knocked out a commuter train line for 10 days.
To help protect the subway system, Gov. Andrew Cuomo ordered it shut down at 7 p.m. Sunday; the Metropolitan Transportation Authority's buses and commuter rails also will be halted. The MTA was shut down 14 months ago during Hurricane Irene, for the first time for weather-related reasons.
UNDERGROUND POWER: Manhattan alone has some 21,000 miles of power lines beneath its streets. Con Edison has said most of the belowground equipment is sealed to protect it from flooding, but the utility said Sunday it was considering cutting power to 17,000 customers in Lower Manhattan if the surge is severe enough to threaten underground lines there, as saltwater is more damaging to equipment if power is on.
STEAM, WATER AND GAS: Those lines are nestled in the 30 feet of ground below the power and telecommunications lines. Because cool water and hot steam pipes is a bad combination, Con Ed is considering shutting down the service _ used for hot water, heat and air conditioning.
SEWERS: Unlike more modern wastewater systems, New York's carries sewage and storm runoff in the same pipes to treatment plants. Even moderate storms often overwhelm the system and force officials to release untreated sewage into the city's waterways.
TALL BUILDINGS: Gusts from the superstorm are expected to hit 70 to 80 mph in New York City and could be 10 to 15 mph higher on the high floors of tall buildings. Most New York buildings are designed to handle the winds forecast from the coming storm, but there's always the possibility of loose debris breaking windows, Mayor Michael Bloomberg said. High-rise residents can also face the loss of elevator service and water if power goes out.