City transit officials have prepared for an “unprecedented” storm surge that threatens to flood the subway tunnels between boroughs for the first time in 20 years and knock out service for days.
“Service will be restored only when it is safe to do so, and after careful inspections of all equipment, tracks and other sub-systems,” an MTA advisory said. “Even with minimal damage this is expected to be a lengthy process.”
In anticipation of the storm surge that could top 11 feet and flood the tunnels that cross the Harlem and East rivers, the MTA has used plywood and sandbags to board up station entrances and sidewalk vent grating in low-lying areas of the city. The S and G trains are the only subway lines that do not cross either river.
Below ground, where subway service has been halted for nearly 24 hours, patrol trains are traveling the length of the subway system and looking for signs of water infiltration. Transit workers are preparing to remove power from the signal system should any water—especially salt water, which conducts electricity particularly well—enter the tunnels. Stop motors, which help trains slow to a halt, are also being removed to protect them from damage.
While these efforts could slow any flooding and make for a speedier clean-up, several scenarios could complicate matters and delay the reopening of the subway system.
If power fails, electric water pumps that “remove millions of gallons of water” from the system on a dry day, would become useless. Salt water poses another problem. Once water is pumped out of the system, deposits left behind would have to be cleaned to prevent corrosion and further damage.
The MTA has three pump trains on hand to deal with flooding in under-river tunnels, but the complete clean-up, which includes pumping out water, getting signals up and running and cleaning up residue left by the flooding, could take anywhere from 14 hours to four full days.
The last time the subway tunnels under rivers flooded was in Dec. 11 1992 when a “nor’easter” battered New York and New Jersey. Three tunnels filled with water and it took crews several days to restore service to all subway lines.
The worst of Hurricane Sandy, which was packing 90 mph winds and barreling in toward the Jersey shore at 5 p.m., is expected to arrive in the New York area Monday evening, and continue to cause extreme coastal flooding and widespread power outages through Tuesday morning.