Dexter Filkins – BLDGBLOG

Voids and Vacuums

[Image: Google Maps view of Mosul Dam (bottom center) and the huge reservoir it creates].

Dexter Filkins—author of, among other things, The Forever War—has a long new piece in the first 2017 issue of The New Yorker about the impending collapse of Iraq’s Mosul Dam.

The scale of the potential disaster is mind-boggling.

If the dam ruptured, it would likely cause a catastrophe of Biblical proportions, loosing a wave as high as a hundred feet that would roll down the Tigris, swallowing everything in its path for more than a hundred miles. Large parts of Mosul would be submerged in less than three hours. Along the riverbanks, towns and cities containing the heart of Iraq’s population would be flooded; in four days, a wave as high as sixteen feet would crash into Baghdad, a city of six million people. “If there is a breach in the dam, there will be no warning,” Alwash said. “It’s a nuclear bomb with an unpredictable fuse.”

Indeed, “hundreds of thousands of people could be killed,” according to a UN report cited by Filkins.

What’s interesting from a technical perspective is why the dam is so likely to collapse. It’s a question of foundations. The dam was built, Filkins writes, on rock “interspersed with gypsum—which dissolves in contact with water. Dams built on this kind of rock are subject to a phenomenon called karstification, in which the foundation becomes shot through with voids and vacuums.”

Filling those voids with grout is now a constant job, requiring dam engineers to pump huge amounts of cementitious slurry down into the porous rock in order to replace the dissolved gypsum.

[Image: Mosul Dam spillway; photo by U.S. Army Staff Sgt. Brendan Stephens].

At one point, Filkins goes inside the dam where “engineers are engaged in what amounts to an endless struggle against nature. Using antiquated pumps as large as truck engines, they drive enormous quantities of liquid cement into the earth. Since the dam opened, in 1984, engineers working in the gallery have pumped close to a hundred thousand tons of grout—an average of ten tons a day—into the voids below.”

Finding and caulking these voids, Filkins writes, is “deeply inexact.” They are deep underground and remain unseen; they have to be inferred. The resulting process is both absurd and never-ending.

The engineers operating [the grout pumps] can’t see the voids they are filling and have no way of discerning their size or shape. A given void might be as big as a closet, or a car, or a house. It could be a single spacious cavity, requiring mounds of grout, or it could be an octopus-like tangle, with winding sub-caverns, or a hairline fracture. “We feel our way through,” [deputy director Hussein al-Jabouri] said, standing by the pump. Generally, smaller cavities require thinner grout, so Jabouri started with a milky solution and increased its thickness as the void took more. Finally, after several hours, he stopped; his intuition, aided by the pressure gauges, told him that the cavity was full. “It’s a crapshoot,” [civil engineer Azzam Alwash] told me. “There’s no X-ray vision. You stop grouting when you can’t put any more grout in a hole. It doesn’t mean the hole is gone.”

It’s hard not to think of a scene in Georges Perec’s novel Life: A User’s Manual, a scene I have written about before. There, a character named Emilio Grifalconi picks up an old, used table only to find that the support column at its center is “completely worm-eaten.” Slowly, painstakingly, operating by intuition, he fills the worm-eaten passages with a permanent adhesive, “injecting them with an almost liquid mixture of lead, alum and asbestos fiber.”

The table collapses anyway, alas, giving Grifalconi an idea: “dissolving what was left of the original wood” in order to “disclose the fabulous arborescence within, this exact record of the worms’ life inside the wooden mass: a static, mineral accumulation of all the movements that had constituted their blind existence, their undeviating single-mindedness, their obstinate itineraries; the faithful materialization of all they had eaten and digested as they forced from their dense surroundings the invisible elements needed for their survival, the explicit, visible, immeasurably disturbing image of the endless progressions that had reduced the hardest of woods to an impalpable network of crumbling galleries.”

Whether or not such a rhizomatic tangle of grout-filled chambers, linked “voids and vacuums” like subterranean grapes, could ever be uncovered and explored beneath the future ruins of a safely dismantled Mosul Dam is something I will leave for engineers.

[Image: Mosul Dam water release; photo by U.S. Army Staff Sgt. Brendan Stephens].

However, Filkins points out one possible solution that would sidestep all of this: this option, he writes, “which has lately gained currency, is to erect a ‘permanent’ seal of the existing dam wall—a mile-long concrete curtain dropped eight hundred feet into the earth.”

This would not be the only huge subterranean wall to be proposed recently: think of the “giant ice wall” under construction beneath the Fukushima nuclear power plant in Japan: “Japan is about to switch on a huge refrigeration system that will create a 1.5-km-long, underground frozen ‘wall,’ in hopes of containing the radioactive water that’s spilling out of the Fukushima nuclear power plant, which went into meltdown following the earthquake and tsunami of March 2011.”

Warsound

[Image: U.S. helicopter over Baghdad, via (scroll down)].

I’ve mentioned The Forever War by Dexter Filkins before, but I was struck again the other day by a passage in which Filkins catalogs the mechanically unprecedented sounds of the American siege of Falluja, a collection of noises so alien and overpowering that he describes it as “an entire ecosystem” with its own hidden predators and prey.

Filkins writes that “rocket-propelled grenades whizzed out of the darkness, striking the M-1s and exploding but doing no harm. Whoosh-bang, like a fireworks show. Whoosh-bang.” He quickly adds, however, that “the real weirdness was circling above.”

The night sky echoed with pops and pings, the invisible sounds of frantic action. Most were being made by the AC-130 gunships, whose propellers were putting out a reassuring hum. But over the droning came stranger sounds: the plane’s Gatling gun let out long, deep burps at volumes that were symphonic. Its 105mm cannon made a popping sound, the same as you would hear from a machine that served tennis balls. A pop! followed by a boom! Pop-boom. And then there was the insect buzz of the ScanEagle, the pilotless airplane that hovered above us and beamed images back to base. It was as if we were witnessing the violent struggles of an entire ecosystem, a clash of airborne nocturnal beasts we could not see.

Of course, the unnatural acoustic ecology of humans at war is surely something you could find throughout history, from the fibrous zing of crossbow strings and the thunderous lurch of the catapult to endlessly irritating scrapings of metal on metal as swords and shields collide. What ancient Roman warfare actually sounded like is something for the acoustic archaeologists.

But, while an acoustic history of war has yet to be written—though some have treated sound itself as war—it would be a fascinating study to pursue.

Sonic Warfare

The opening scene of The Forever War by Dexter Filkins presents us with the sight of U.S. soldiers preparing for their invasion of Falluja. Filkins is there to witness the attack; amidst the growl of tanks and Humvees, and “by the light of airstrikes and rockets,” he writes, there is suddenly something sonically unexpected.

[Image: “An Advanced Individual Training Soldier in the Psychological Operations Specialist Course attaches a loud speaker on top of a High Mobility Multi-Wheeled Vehicle, or HUMVEE, at Forward Operating Base Freedom, Camp MacKall, N.C.” Courtesy of the John F. Kennedy Special Warfare Center and School].

“And then, as if from the depths,” Filkins writes, “came a new sound: violent, menacing and dire.”

I looked back over my shoulder to where we had come from, into the vacant field at Falluja’s northern edge. A group of marines were standing at the foot of a gigantic loudspeaker, the kind used at rock concerts.

It was AC/DC, the Australian heavy metal band, pouring out its unbridled sounds. I recognized the song immediately: “Hells Bells,” the band’s celebration of satanic power, had come to us on the battlefield.

While by no means advocating the use of sonic warfare as a tool in U.S. military adventures or police operations, I nonetheless instantly thought of this scene—of armed soldiers holding aloft rock-blaring boom boxes, like some John Milius-directed remake of Say Anything—when I read, in a very different context, that bark beetles can be driven out of the pine forests they currently infest if you play digitally-altered sounds of their own chewing back at them through loud speakers. The high-volume sound of themselves drives them away.

A research assistant suggested using sounds to aggravate the beetles, much as police sometimes blare music in hostage situations. The researchers tried Queen and Guns N’ Roses and played snippets of radio talker Rush Limbaugh backward. None produced the desired results.

Then, the beetles were exposed to digitally altered recordings of their own calls, the sounds they make to attract or repel other beetles. The response was immediate. The beetles stopped mating or burrowing. Some fled, helter-skelter. Some violently attacked each other.

Most important, they stopped chewing away at the pine tree, suggesting that the scientists may have discovered a sort of sonic bullet that could help slow the beetles’ destructive march.

Again, I do not mean to imply that infestation metaphors are the most appropriate to use when discussing Operation Phantom Fury, or that military action in that city was analogous to clearing a forest of bark beetles; but the audio possibilities here, and the specifics of the set-up, seem amazing.

[Image: A ponderosa pine forest; within those trunks might be beetles].

More about the actual experiment, run at Northern Arizona University’s Forestry Lab:

They collected tree trunks infested with bark beetles… Working in the lab, [research assistant Reagan McGuire] piped in the music through tiny speakers, the sort you might find in a singing greeting card. He watched the reaction of the beetles using a microscope. The rock music didn’t seem to annoy the bugs, nor did Rush in reverse.

McGuire and [Northern Arizona University forest entomologist Richard Hofstetter] decided to try something different. They recorded the sounds of the beetles and played them back, manipulating them to test the response.

Suddenly, every little thing they did seemed to provoke the beetles.

“We could use a particular aggression call that would make the beetles move away from the sound as if they were avoiding another beetle,” Hofstetter said.

When they made the beetle sounds louder and stronger than a typical male mating call, he said, the female beetle rejected the male and moved toward the electronic sound.

These audio simulations, in other words, had demonstrable physical effects on another species; their own warped sonic portrait drove them crazy.

So could you reprogram your Marsona 1288A (“create a personalized sound environment“) with the digitally-altered ambient sounds of termites and thus clear your house of insectile pests? The USDA, after all, has published a paper—download the PDF—explaining how a “portable, low-frequency acoustic system was used to detect termite infestations in urban trees.” Indeed, “termite sounds could be detected easily underneath infested trees, despite the presence of high urban background noise.” So why not reverse this—drive them out of the city using weird MP3s specially produced for boom cars?

Perhaps we should petition Clear Channel or Sirius XM to premiere a new, insect-only broadcast hour, killing ants and roaches in every city where it’s played (or perhaps just driving them all out, streaming from the floorboards, in a moment of utter horror).

I’m reminded here of the famous example of Sgt. Pepper’s Lonely Hearts Club Band by The Beatles, with its “dog whistle—which humans can’t hear—buried on the album’s second side.” Only, in our case, it would be a different kind of beetle-whistle, and one with anti-infestational effects.

(Bark beetle story found via @treestrategist).