Engineering Ethics Blog: Atlanta Burns a Bridge


For several years—possibly
since 2006, according to one report—construction crews working near an elevated
section of Interstate 85 near Piedmont Road in northeast Atlanta had stored
large quantities of bright-orange high-density-polyethylene (HDPE) pipe.  It’s used for a variety of things in
public works, such as conduits for streetlight and traffic-signal cables, and
comes in large reels two or three feet high each, that were stacked two high
under a bridge span.  It’s not the
kind of thing one could just shove in a backpack and walk off with, so
authorities thought that just surrounding the stash of pipe with a chain-link
fence was enough security.

Last Thursday, March 30, a
fire was reported under the span, and despite desperate attempts by
firefighters to combat the fierce heat for over an hour, several emergency
responders barely escaped with their lives when the span over the pipes
collapsed, damaging both northbound and southbound parts of the interstate to
the extent that it will be closed for several months for repairs.  Eyewitnesses reportedly saw Basil
Eleby, an apparently homeless man, standing on a chair in a shopping cart near
the fence shortly before the blaze, and Eleby is now in jail, unable to post
$200,000 bond and awaiting trial for arson.

Fortunately, no one was
killed or injured in the fire or collapse, but Atlanta commuters are going to
have to deal with serious disruptions, as that part of I-85 is the main
transportation corridor between downtown and the northeastern suburbs, normally
carrying over 100,000 cars a day. 
It was how I would get downtown from the suburb of Chamblee during my two
years working as an engineer at Scientific-Atlanta, and I can only imagine the
traffic snarls that this will cause.

Clearly, nobody expected
this to happen, and for over a decade it didn’t happen.  Those pipes have been sitting there at
least that long, and as far as accident-prevention policies are concerned, it
didn’t look much like an accident waiting to happen.  Of course, arson isn’t an accident, but it’s unlikely that
Mr. Eleby had any idea what would happen if he tried to set those pipes on
fire.  It’s too early to know what
his motives might have been, but even if it turns out that he was hoping to
cause major damage, I doubt that he really expected to bring down a bridge span
single-handed.

One good thing that could
result from this fire is that construction organizations everywhere will now
view large accumulations of HDPE pipe with a different attitude.  It’s not as dangerous as big piles of
ammonium nitrate, which is known to be a powerful explosive under the wrong
conditions.  But HDPE is a little
bit like solid gasoline, in that it’s just concentrated carbon and hydrogen
with convenient air holes in it to aid combustion, and it’s not surprising that
a large stack of such pipes burned so hot for so long. 

It’s far from criminally
negligent to store that much flammable pipe under a vital transportation
artery, but it wasn’t the smartest thing to do, either, especially in an area
where homeless people tend to hang out. 
For complex sociological and economic reasons, many highway overpasses
in major cities across the U. S. have been informally colonized over the past
few decades by people who don’t have, or don’t wish to have, any other place to
stay that will keep the rain and sun off. 
Most of the time, the worst things these folks do is deal drugs, harass
passersby, and leave messes, but now and then they can turn to more
consequential criminal activity, such as the apparent arson that brought down
the I-85 span.

I’ll leave it to the civil
engineers who will no doubt be combing through the wreckage to figure out
exactly how hot a bridge has to get before it collapses.  But if steel was a significant
component of the bridge—and it had to be, either as the main support or as
rebar in concrete—well, steel melts at a certain temperature, and well before
that it gets soft enough to lose most of its tensile strength, and there goes
your bridge. 

Like many isolated mishaps
that don’t fit the usual patterns, a number of individually common events and
conditions had to come together to cause this fire.  Both homeless people and construction supervisors see
otherwise wasted public land under overpasses as a good place to take advantage
of, either for living space or for storage.  And in secure warehouses, HDPE pipe is no more hazardous
than furniture or wooden forklift pallets, which are notorious for burning fast
because of the combination of flammable material and openings where
combustion-aiding air can get in. 
The chain-link fence around the pipes apparently kept intruders out for
the ten or more years the pipes had been stored there, and there was no obvious
reason to be concerned that some disgruntled or mentally deranged person would
come along and try to damage the pipes. 
But he did.

This fire, as bad as it
was, could have been much worse. 
It lasted long enough for first responders to isolate the area and stop
traffic along the highway, keeping commuters out of harm’s way.  And while fire-department personnel
were unable to put out the fire before the span collapsed, at least no one was
injured in the collapse.  Still, it
would have been nice if they could have extinguished it before it got so
widespread that it endangered the highway bridge overhead. 

Maybe it would be a good
idea to install remotely monitored fire alarms in every big pile of HDPE in a
public place, especially if it would cause serious damage if it caught
fire.  True, there might be an
issue with false alarms.  But I bet
Atlanta’s first responders would have been willing to put up with a few false
alarms in order to prevent something that’s now going to be a serious inconvenience
for millions of drivers, and a multimillion-dollar expense for the
taxpayers.  Next time you’re in
Atlanta, your best bet in getting around may be their MARTA trains, at least
until they fix I-85.



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