New York subway’s boss said last week that he would support the construction of a flood barrier around the city to protect the transit system.
Subway operator Metropolitan Transportation Authority (MTA) president Tom Prendergast said greater protection is needed in areas such as Lower Manhattan which was devastated during last week’s tidal surge.
“We need to look at whether sea walls need to be constructed,” Prendergast told NCE.
Seven of the MTA’s 14 tunnels were flooded during Hurricane Sandy. Engineers have been working 24 hours a day to clear them.
But Prendergast added that discussion about the need for a new flood barrier would be at a “higher level”, outside MTA’s mandate.
“We are facing a paradigm shift - sea levels are rising,” he added. Prendergast said Hurricane Sandy inflicted the worst damage recorded on the subway system. He estimated that repairs would cost hundreds of millions of dollars.
“It is a surge we have never seen before,” he said.
Prendergast said New York’s underground subway system makes it vulnerable to any sort of flooding. The tunnels are cut and cover construction with trackbeds 7m below street level.
Ventilation is provided by grills at street level and these were inundated during the tidal surge sending water into the running tunnels.
Prendergast said investments in reactionary measures - such as the three high volume pump trains MTA purchased several years ago - are now no longer sufficient to protect the system against flooding.
“It is just not enough to have pump trains,” said Prendergast. “We need to look at hardening the system.”
He said this would include covering the entrances into the subway system, and covering the ventilation ducts during a major storm.
“We cannot close the ventilation system; we have to design a system that we can close up in the course of two or three days beforehand,” he added.
“We tried to do it with this storm,” he said. “We had sandbags and plywood but it got breached.” Prendergast also explained the methodology behind deciding which tunnels MTA chose to clear first.
“It was a combination of which lines gave us highest [passenger] volume and lowest amount of water to extract,” said Prendergast.
He said the Joralemon Street tunnel had only a small amount of water but was the busiest tunnel in the country, so MTA focused its efforts there.
“Some tunnels were severely flooded but had relatively low usage,” he added.
Prendergast said there has been no discussion about how the repairs will be paid for, but added it is generally met by federal and state emergency funds.
Subway operator admits more flood protection is needed