Investigations found that the structure's foundation was weakened by the piling of excavated soil on one side and the digging of an underground garage by an unqualified contractor, China Daily reported.
The MTA took extensive measures before the storm to limit the amount of water flooding into tunnels, including by boarding up ventilation grates in low-lying stations, piling sandbags at station entrances, inflating a rubber dam in the Long Island Rail Road's West Side yards in Manhattan and hastily erecting a floodwall across the mouth of the No. 3 train tunnel near East 148th Street in Harlem.