NY1 VIDEO: The MTA says thousands of workers are on the job securing the transit system.
NY1 has learned that one of the subway rail yards the MTA is most concerned about already flooded during Monday morning's high tide.
The MTA confirmed that the Harlem River flowed over a dyke that the MTA set up to prevent flooding at the rail yard at 148th Street and Lenox Avenue.
Crews were setting up additional pumps at the nearby 145th Street subway station Monday afternoon to minimize track damage. They also installed a dam of sand bags on the tracks.
Further down, NY1 is told there was a sand bag wall several feet high.
Workers were setting up portable pumps in case there was any more flooding.
The MTA is concerned about flooding at several other stations, particularly in Lower Manhattan and the Coney Island and 148th Street yards.
The MTA says it expects the worst flooding after midnight Tuesday. They expect to have to pump out the water and then access the damage before they know when service can be restored.