There's A Huge Problem Threatening New York's Subway System, And No One's Talking About It

It carries nearly 8.5 million people across America's densest city each day. If its tracks were laid out in a single line, it would stretch all the way from Manhattan to Chicago. Its 500 stations and 6,000 trains are together worth more than $32 billion.

It's the New York City subway, North America's biggest public transit network. And it is at risk of total failure.

A massive report issued back in 2011 accurately predicted which of the city's subway stations would fail when Sandy hit. In the future, these kinds of intense storms are expected to make landfall every 1 to 4 years rather than hitting us every 100 years.

But storms aren't the only issue highlighted in the report, based on climate models it shows the potential damage of rising seas, warmer summers, and colder winters.

And it looks more and more like a doomsday scenario.

Flooding

Global warming is making dangerous storms like Hurricane Sandy, which threaten to overwhelm the subway system with flooding, more intense and more frequent.

Many existing subway tunnels in lower Manhattan, the report says, can flood completely in just 40 minutes if waters rise to the levels seen during Sandy. Pumping that water out takes at least a week per station and it's only the first step to recovering our transit system.

The MTA was able to rescue the subway from the brunt of Sandy's damage. In just a few weeks of intense pumping, drying, and reconstruction, several flooded stations were up and running again. Years later, only a few stations carry the scars of the storm's devastation. We're pretty much back to business-as-usual.

But not quite.

Flood waters from the next storm will certainly overwhelm the subway stations flooded during Sandy (all five tunnels between lower Manhattan and Brooklyn and the Steinway Tube between Midtown and Queens flooded), but a total of 14 more stations near the Harlem and East Rivers are also at risk.

Draining those corridors will take time - about a week per tunnel, according to the report. Aside from draining the tunnels, though, there's another problem: all that salty water doesn't play well with 20th-century steel and cast iron.

Storms And Salt

Storms like Sandy stir up the salty water in oceans and estuaries and carry it to shore. There, the sea salt mixes with the salt already on the ground - about a million tons are used each year to de-ice snowy New York streets - and begins eating away at the metal and iron underground. Bigger winter storms and plunging temperatures form a disturbed polar vortex could make this problem worse.

"Our subway system and salt water do not mix," MTA chairman Joseph Lhota recently told the Wall Street Journal.

Salt is a relentless foe - it degrades motors and metal fasteners, eats away at the relays that run the subway's signal system, and conducts electricity, potentially barring train conductors from communicating - something they need to do to prevent smashing into one another.

Worse still, salt's chemical composition makes it react with iron, steel, and concrete - all of the components of the subway system. When it does that, it also changes their chemical makeup, reducing solid black iron into crumbly brown rust, for example.

Many of these damaged parts will need to be replaced. But since the city's first subway lines opened back in 1904, many of those parts no longer exist. As a result, construction crews will have to completely redesign entire portions of the subway system, a task that will likely be as costly as it is daunting.

Extreme Heat

As temperatures rise, summers will heat up. July in Brooklyn will feel like August in Miami. All that heat won't just hurt people - it could cripple the metal and iron equipment that keeps the trains running.

Summers already turn New York's subway platforms into sweltering, foul-smelling caverns of misery. As these months get hotter as a result of climate change, though, this temporary discomfort could become dangerous.

Hotter subway platforms could harm older people who are already at risk for heat stroke, which often strikes suddenly and can be deadly. Older people can't control their body temperature as well as they once could, anyone over age 65 should limit their exposure to extreme heat, according to the CDC. Only one subway platform in the entire New York City network is air-conditioned: the 4, 5, 6 platform in Grand Central Station. And it barely functions.

Trains suffer from the heat too. A recent panel convened by New York's governor Andrew Cuomo found that higher temperatures can put extra stress on rail tracks, increasing the chances that they'll buckle. Buckling causes bends in the tracks which can slow trains.

Rescuing New York's Transit System

Fixing the massive problems that climate change presents to the subway system will be a challenge.

But we have some great models to learn from.

In the Netherlands, engineers have designed a flood protection system that combines a series of giant flood gates and several low-lying drainage canals to hold back the sea from the city's densest communities, while letting some of the rising water spillover into certain areas designated for that purpose.

The Japanese have a massive, $3 billion water discharge system that diverts floodwaters from Tokyo to a special facility, ensuring that heavy rains and high storm waters don't destroy the city's public transit network.

And in New York, a group of engineers has designed a plan to surround all of lower Manhattan with 10 miles of artificial embankments, gardens and sloping green hills to protect the island from surging seas. The strategy would do little for the tunnels linking Manhattan to Brooklyn and the Bronx, however. Other potential rescue plans for the city include combinations of flood barriers and sea walls and attempts to use waterways for transit.

As far as heat goes, Cuomo's transit experts say lighter trains could help cool the system, because they produce less heat. Other options include adding screen doors to platforms to lock in air-conditioned air, and improving ventilation throughout the tunnels.