After Hurricane Irene, officials at NYU Langone Medical Center spent several million dollars protecting its backup power system from flooding, according to Richard Cohen, vice president of facilities operations.

The hospital removed a fuel tank and a set of emergency generators at street level and chose to depend on what Cohen termed an “extremely modern, extremely reliable” system of rooftop generators.

The hospital also built a new, flood-resistant house for pumps that draw fuel from the hospital’s sealed underground tank and feed it to the generators that make electricity when New York City’s power fails.

One vulnerability remained, and it proved to be the system’s Achilles Heel. A portion of the hospital’s power distribution circuits, which direct the generated electricity out into various areas of the hospital, were located in the hospital’s basement.

“It’s like what happens when you have a flood in your basement and the electrical panel is in your basement,” Cohen said.

The predicted storm surge heights feet from Sandy did not worry NYU officials. “We had Hurricane Irene last year,” Cohen said. “We did not have any compromised or flooded areas in the hospital, so frankly we had no reason to think this would be any specific risk.”

However, the National Weather Service upgraded its predicted storm surge heights for lower Manhattan to as high as 11 feet as early as Sunday morning. That day, dozens of EMS units could be seen idling in front of NYU Langone Medical Center. EMTs said they were standing by to transfer patients. But the hospital leadership decided to keep the patients in place.

NYU’s Cohen stressed that the hospital’s system complied with building codes at the time it was constructed. Hospitals are generally not required to upgrade their systems to current code.

Even newly built hospitals in low-lying coastal zones are not necessary required to flood-proof their systems, according to George Mills, director of the engineering department at the Joint Commission, the organization that accredits most American hospitals.

Mills said his organization and the U.S. Centers for Medicare and Medicaid Services require hospitals to adhere to the 2000 edition of National Fire Protection Association life safety code. It calls for “careful consideration” to be given to protecting electrical components from “natural forces common to the area” such as storms, floods and earthquakes.

The 2012 version of the code upgrades that language, saying the systems “shall be designed” to protect against these hazards. However, CMS and the hospital accreditation agency have not yet adopted this edition.

“All of these systems are only as reliable as the weakest link,” Mills said.

During the storm, according to Cohen, the hospital also experienced a temporary loss of the system that pumps fuel to the generators. That occurred when a rapid, forceful rise in water breached the underground vault that holds the fuel tank. Sensors within the vault automatically shut off the fuel pumps.

“As soon as the staff was able to access that pump house, able to reset the pumps, they were able to feed fuel to those generators and those generators are running now.” Cohen estimated the loss lasted about an hour. During that period, he said, hospital leaders decided to evacuate.

After the pumps came back online, he said, areas of the hospital where backup power is distributed through a circuit panel located on a higher floor of the hospital regained electricity, including the intensive care units and labor and delivery.

Cohen said the hospital’s elevators were also powered through the upper level circuits and had safety features to keep them from running into the floodwater that had poured into their shafts.  The hospital decided not to use the elevators out of concern for safety. “There would have been a very good chance the elevators would have failed,” Cohen said. “We then would have had an elevator extraction in the middle of patient evacuation and that was a prospect that really nobody wanted to face.”

Cohen said the hospital is in the midst of constructing its own power cogeneration facility. When that is completed, the basement-level distribution circuits that proved the system’s downfall during Sandy will be relocated to an upper level. “We’ve purchased all the equipment,” Cohen said. “We currently expect to have it completed sometime around 2014.”