3. Toxic Train Wreck

Icon: Bryan Christie Design; Background: Brian Staufffer

On the evening of 4 July 2007, a man sits on a bench at a railway crossing near the Mall, in Washington, D.C., where hundreds of thousands of people have gathered for the Independence Day fireworks. He thinks of the execution that morning of his distant cousin, Ali Hassan al-Majid, aka Chemical Ali, the Iraqi general who ordered the poison gas attack that killed thousands of Kurds in Halabja, in 1988. “Atrocity,” he mutters. “I’ll give them atrocity!” For the third time in 15 minutes, he looks at a pocket compass and checks that the breeze is still blowing from the southeast.

At last a locomotive pulls into view, and he spots the cylindrical tank car, 12 cars from the front, just where his confederate had told him it would be. Clambering up the car’s ladder, he attaches a backpack to the valve at the top, then bolts away to his coconspirator’s car, parked nearby with its engine running. The car screams away down the nearby freeway, and 40 seconds later, the pack explodes, blowing a hole in the side of the tank car. A jet of chlorine gas erupts, emptying the car’s 90 000 kilograms of chlorine in a couple of minutes. The resulting plume floats on the wind toward the Mall. Within a few minutes, the assembled crowds begin to choke, and though some think to cover their mouths with dampened clothing, few know which way to run, and thousands die from inhaling the toxic gas or from being trampled by the fleeing crowd.

A scenario like this one—assuming a chlorine release, but not necessarily an intentional one—was presented in 2003 to the Council of the District of Columbia, which was considering what to do about the toxic railway cargoes that pass through the capital. The model, by Jay Boris, a fluid dynamics expert at the Naval Research Laboratory, in Washington, D.C., assumed that on Independence Day, half a million people would be present in the Mall, that the chlorine would be released about 1 kilometer from them, and that the gas would be carried there by a wind moving at 16 kilometers per hour.

Within half an hour, the advancing plume would cover much of the gathered crowd, and as many as a fifth of them—100 000 people—would die, Boris estimated. (Should you ever be caught in such a plume, or if you learn that you are directly downwind from one, get out of its way by moving crosswind to the plume, away from the projected centerline. A plume’s shape depends on wind and terrain; in Boris’s model, it spreads only about 1 meter for every 5 meters that it advances.)

Fred Millar, a toxic-hazards specialist with Friends of the Earth, also in Washington, D.C., says that terrorists wouldn’t need a great deal of planning to catch a laden tank car. “About 11 000 dangerous railway cargoes come through D.C. every year—explosives, poison gas, and highly inflammable chemicals,” he says. “Rent an apartment near the tracks and wait a day, or maybe just a couple of hours, and you’ll get one.”

Poison-gas cargoes are held under high pressure, so a large hole in the tank will empty it quickly; a smaller one will also do the job, but very slowly. That was pretty much what happened, by accident, in Graniteville, S.C, in January 2005, when a train collision ruptured a tank car containing chlorine, which leaked for hours. Ten people died, hundreds were hurt, and thousands were forced temporarily from their homes—this in a sparsely populated area.

What kinds of countermeasures are most effective against such a scenario? “Rerouting is the no-brainer way to reduce risk,” Millar says. “You could switch cargoes from one railroad company to another [to bypass populated areas]. But railroads oppose it on principle—they hate the government telling them to do it.” Jacksonville, Fla.–based CSX, the freight railroad that travels across the U.S. capital, has said that it is rerouting some of its toxic cargoes that were running near the U.S. Capitol building; the railcars now take a westerly route that passes through Ohio and the New York City metropolitan area. CSX did not respond to requests for an interview.

Not all such hazards can be solved with rerouting. Take a city like Miami, a dominant economic hub sitting at the bottom of a peninsula. There are no alternative routes, and so the only way to keep out hazardous cargoes is to ban their transit altogether. Miami-Dade County officials are now looking at the feasibility of switching their sewage facility from chlorine gas to a safer alternative.

Another countermeasure that’s been considered by the Department of Homeland Security’s Transportation Security Administration, which shares responsibility for railroad security with the Department of Transportation’s Federal Railroad Administration, is to adapt a method used on the armored Humvees in Iraq so that it can protect tank cars. The technique involves spraying on a plastic coating that can help heal a puncture.

Millar notes that the United States is far from the only country whose dangerous cargoes could be exploited by terrorists. The regulatory body Transport Canada, in Ottawa, rejected the armoring of railroad tank cars and rerouting, and it has decided instead to “expedite” the most dangerous cargoes through major cities. In the United Kingdom, meanwhile, cargo rerouting is not even being seriously discussed.

—Philip E. Ross