Chapter 8
The Human Cost of Tragedy
Mario Pancini had successfully designed one of the strongest, safest concrete-arch dams in the world: the Vajont Dam, completed in 1959. Rising more than one hundred feet higher than the famed Hoover Dam, the dam formed a sharp V high above the village of Longarone, Italy, in the steep walls of Vajont Canyon. It was a remarkable accomplishment of modern engineering, proved by a catastrophe of unprecedented proportions that left the dam intact in 1963. More than 2,500 people had perished in a fully predictable disaster. Pancini had tried to avoid putting people in such danger, but it had been forced upon him by powerful political interests. After it happened, he was wracked with guilt and overwhelmed by depression, feeling that he had no right to live when so many others had perished. Of the hundreds of people responsible, he was the only one to express public remorse and offer an apology. All the others called it an “act of God” when, in fact, it was anything but. Pancini was tormented as he struggled to make sense of how his greatest accomplishment had led to such tragedy.
A modern view of the Vajont Dam.
Overview
As one of the Axis powers in World War II, Italy was the scene of some of the most intense fighting of the war. Like much of the rest of Europe, its economy was devastated by the destruction of combat. As a result, in the years following World War II, the Italian government was always on the lookout for public works projects to put people to work. In the late 1950s, they found the ideal prestige project: building the tallest concrete-arch dam in the world. The new dam was to be sited in the narrow Vajont Gorge at the southern end of the Dolomites. Located sixty miles north of Venice, this project was expected to produce electricity, irrigation, and tourism. With so much public money to be spent, there was ample opportunity for political graft and corruption to enrich the politicians and contractors who sponsored the project.
Fateful Choices
Initial site assessments showed a variety of geological defects where the dam was to be built, specifically that it would rest exclusively on ancient limestone beds, which are subject to fracturing under pressure. The height of the dam was specified at 860 feet from base to crest (130 feet taller than Hoover Dam in the United States). A concrete structure of that size and weight would require a stable foundation. A second problem was that the extremely steep slopes of Monte Toc (Mount Toc), which formed one side of the canyon, were subject to landslides. The limestone layers were intermixed with thin clay layers that became slippery when saturated with rainwater. Additionally, these ancient layers of sediment were tilted on a downward-sloping incline toward the base of the valley floor, which increased the likelihood of slippage if the area was inundated by a reservoir.
Despite these hazards, the opportunity to efficiently generate electric power based on the high head of water behind an 860-foot-tall dam was just too tempting. The electricity monopoly for northeastern Italy, “SADE,”1 pushed for the authority to build the dam. Under intense political pressure, site engineers concluded that the chances of large-scale landslides were extremely rare, given that “areas of weakness were not identified in the three test borings; it was assumed that any shear plane would have a ‘chair-like’ form that would exert a ‘braking effect’; [and] seismic analyses had suggested that the banks consisted of very firm in-situ rock with a high modulus of elasticity.”2
With these conclusions in writing, SADE secured the necessary permits to continue and with great fanfare started construction of the dam in 1956.
To compensate for the deficiencies in the limestone at the base of the foundation, the dam’s designer, Carlo Semanza, and construction engineer Mario Pancini injected a 500-foot grout curtain to stabilize the base and abutments. This effort was successful and allowed construction to proceed. But a large-scale movement of the canyon wall in late 1958 caused a temporary halt in construction. Three new engineering studies again warned that the base of Monte Toc was extremely unstable and would likely collapse if the dam was completed. All three recommended suspension of the project. But SADE ignored these studies and pushed ahead. Instead of responding to the warnings, Semanza and the government agencies that oversaw construction of the project filed lawsuits against journalists for bringing any attention to perceived deficiencies. The charge: “Their reports acted against the common interests of the people.” With powerful political protection, construction of the dam continued. The concrete arch structure was completed in October 1959.
It was a remarkable sight to behold. Comparable in height to an eighty-story building, the new dam stood as high as the main structure of the Chrysler Building in New York City. To demonstrate the steepness of the slopes of the canyon walls, consider that the dam is 627 feet wide at the top, but just eighty-nine feet wide at the base. It towers like a very sharp V in the majestic Vajont Canyon, high above the villages below. The dam was designed to impound 316,000 acre-feet of water, approximately ten times greater than the water held by the St. Francis Dam in Los Angeles.
SADE was granted permission to start filling the reservoir early in 1960, and full pool was achieved in 1961. At this point, it was considered likely that all electrical generation in Italy would be nationalized. Semanza was determined to put the dam into full operation, to achieve the highest possible price if the government decided to buy out his company.
But there was a problem—the predicted landslides had started. For example, on November 4, 1961, a small promontory on the eastern shore of the reservoir shuddered and then collapsed into the lake. This produced a large wave that rippled towards the western shore. At the same time, a large fissure appeared on the face of Mount Toc, above the lake. The fissure was three feet wide and 9,000 feet long. This demonstrated the instability of the material on the eastern shore.
In response to this, SADE decided that the best way to stabilize the mountain was to expose it to changing water levels and pressure. It was hoped that in doing so, the rock and clay would adjust through moderate movements until the material reached a new point of equilibrium in the environment of the reservoir. Thus, the lake was raised and held steady for a time, then lowered, then raised slightly, then lowered again. Each of these adjustments caused movement in the eastern abutment, but none so dramatic as to raise serious alarm.
Still, engineers were so concerned that SADE decided to excavate a large bypass tunnel in Mount Salta on the western shore of the lake. This would allow a second way for water to exit the reservoir if the lake was ever divided into two parts by a landslide. It was a very dramatic cure for a problem that didn’t yet exist.
By November 1962, the water level was raised again to nearly full pool in anticipation of the nationalization of SADE. From Semanza’s point of view, it was critical that the dam be labeled operational to get the maximum selling price. If it was labeled “under test” or “non-operational,” the government could purchase the dam at a fraction of its operational value. Even though there were extremely disturbing signs of instability on the Monte Toc side of the reservoir, SADE pressed for operational status. It was granted, despite the appearance of cracks (from ground movement) in the homes on the slope of Mount Toc, above the waterline. Paint splintered on the walls, doors warped, and a brand-new school that SADE had built was so damaged by earth movement that it was deemed unfit for use. Even a brand-new road built by SADE around the shore of the new lake shifted out of its original alignment, making travel difficult.
Danger near the Shoreline
What is remarkable, in retrospect, is that few people seemed to have concerns about the integrity of the dam in the event of a large landslide, even those living below the dam. The most concerned group were those whose villages were near the shores of the new lake above the dam, particularly in the towns of Erto and Casso. Their primary fear was that people living on the eastern shore could be hurt if the land underneath them started sliding, particularly since landslides saturated with water move at incredible speeds. Their second concern was that a large landslide into the reservoir could create a tsunami wave that would wash up and over their towns. The small slides already experienced prior to the fall of 1962 had created waves that came worryingly close to the footings of buildings on the shore of the lake. These concerns became so great that in early September 1963, the mayor of Erto sent a letter to SADE, urging them to lower the level of the lake. He pleaded that his fellow citizens felt as if they were living in a nightmare because of constant concern that a wave could destroy their lives and their property. SADE did not respond to his letter.
By this point, crews at the dam were near panic. The rocky slope on Monte Toc was sliding down towards the lake, sometimes as much as seventy feet per day. It was obvious that if nothing was done, the ramifications would be deadly. The problem was trying to figure out how to manipulate the level of the reservoir to minimize the chance of a landslide. The thinking was that if the water level dropped too quickly, it would be a shock to the slide-prone area and precipitate a rapid collapse. If the water level was lowered too slowly, and an earthquake occurred, the inevitable tsunami wave was far more likely to cause serious damage. There was even the risk of some water overtopping the dam. So SADE began lowering the level of the lake gradually, but at exactly the rate that maximized electrical power generation—a very convenient event for SADE.
Tuesday, October 8, 1963, was a day of increasing anxiety. Movement of the eastern abutment was so severe that trees were falling over. The road built around the lake was completely unusable. By late morning, SADE sent out a warning that all people living on the eastern shore should evacuate the area immediately. They also suggested that residents of Casso at the upper end of the lake move to higher ground since “landslides can create frightening waves in the whole lake.” They were thoughtful enough to suggest that swimmers would be particularly vulnerable to such waves.
Unintended Consequences
Wednesday, October 9, 1963—Catastrophe!
At 10:39 p.m., the entire slope of Monte Toc collapsed into the reservoir in a mighty explosion. 800 million cubic feet of clay and limestone displaced an equal amount of water in the reservoir. This gigantic slide moved at a rate of sixty miles per hour, sliding into the lake in just forty-five seconds.
The effect was completely unexpected—the water in the lake rose more than 600 feet above the top of the dam, and then fell over the front. This crushing waterfall created a shock wave at the base of the dam more powerful than that of the atomic bomb exploded at Hiroshima, Japan. Landing in such a narrow canyon, the displaced air blasted down the canyon, obliterating everything in its path—buildings, trees, rock, and people. Nearly all the bodies of the victims of the shock wave were found naked, their clothes blown off by the force. Of course, the water itself quickly followed, in a mighty wave that scoured away all remnants of human habitation in the narrow gorge. Once the water reached the mouth of the canyon, it flattened out into a wider wave, but that was little comfort to the 2,500 people who were killed by the flood.
The community of Longarone and its satellite villages were hardest hit, with more than 80 percent casualties. Above the dam, the tsunami wave created by the landslide destroyed the town of Casso as well as the lower buildings in Erto. Survivors who witnessed the landslide said it was as if the entire side of the mountain disappeared into a giant white cloud. At first, they thought the cloud was dust, but it was the water of the lake rising 600 feet into the air. It was an epic disaster, but it had been both foreseeable and preventable.
The aftermath of the landslide, with the still-intact Vajont Dam visible in the center bottom of the photograph.
The Dam Survives!
Perhaps the most remarkable part of the story is that the Vajont Dam survived the catastrophe. It was so well-engineered that it resisted the incredible increase in force and held firm as the water overtopped it. The highway across the top of the dam was destroyed, ripped away by the force of the water passing over the concrete. But the dam itself held. In fact, it is still there today. It appears as a huge white V when seen from below. It is an odd structure, sitting high above the now almost completely earth-filled canyon behind the dam where the reservoir once was. So massive was the amount of material sloughed by the landslide that it is impossible to excavate. Now a large plain shelters behind the dam, 600 feet above the valley below. Two small lakes have formed upstream from the slide above the dam. As rain falls and the level in these lakes rises, water is released through the original outlet tunnel as well as through the second tunnel built on the other side, high up on the canyon wall. Looking at the dam from below, one is struck by the beautiful waterfalls rushing from both sides of the mountain, below the crest of the dam.
Victims and
First-Responder Heroes
In 2013, BBC News correspondent Mark Duff interviewed several survivors of the catastrophe for the fiftieth anniversary of the collapse of the dam in 1963. Here is the story shared by Micaela Colletti, one of just thirty children who survived from the town of Longarone and the only survivor in her family. Her father, mother, sister, and grandmother all perished in the flood. She was just twelve years old on the night of October 9, 1963:
“‘I heard what I thought was a thunderclap. It was incredibly loud. My granny came into my room and said she was going to close all the shutters because a storm was coming.
“‘At exactly the same moment all the lights went out and I heard a sound, impossible to describe properly. The closest thing I’ve ever heard to it is the sound of metal shop shutters rolling down, crashing shut, but this was a million, a billion times worse.
“‘I felt my bed collapsing, as if there was a hole opening beneath me and an irresistible force dragging me out. I couldn’t do anything. I had no idea what was happening.’
“[Micaela] was hurled more than [1,000 feet] through the air and buried.
“‘When they pulled me out there was a popping sound, like when you open a bottle, and someone said ‘We’ve found another old one.’ I was just 12 but I was covered in mud and completely black and must have looked like an old woman.
“‘I remember I was on the shoulders of the only fireman from the town to survive and he kept stumbling over these bright, incredibly white, translucent rocks and I kept asking him to put me down, but he wouldn’t.
“‘. . . There was this huge moon so close and so bright it scared me. I felt if I stretched out my hand, I could touch it. I’ve never seen a moon like it, so close and so huge.
“‘Then they put me in a car, and I heard someone crying and I suddenly realized it was me.’”3
Micaela laments the fact that the bodies of her mother, sister, and grandmother were never found. Her father’s remains were identified, and he was buried, but the site is unknown. Markers commemorate the deaths of her family members, but their experience in death is unknown.
A resident of Casso who lived above the reservoir reported that he was awakened at 10:15 p.m. by “a very loud and continuous sound of rolling rocks.” But this did not disturb him since there had been lots of slide activity in the area. It was raining hard. “About 10:40 p.m. a very strong wind struck the house, breaking the window panes. Then the house shook violently; there was a very loud rumbling noise. Soon afterward the roof of the house was lifted so that the rain and rocks came hurtling into the room on the second floor in what seemed like half a minute. He had jumped up and out of bed to open the door and leave when the roof collapsed onto the bed. The wind suddenly died down and everything in the valley was quiet.”4 He had experienced the shock wave that was created by the tsunami wave, which was created by the crashing of the landslide into the reservoir.
The 600-foot wall of water that overtopped the canyon crashed onto the valley floor at approximately 10:40 p.m. Three minutes later, the shock wave blasted the canyon below the dam at supersonic speed, smashing out windows and shaking the earth with tremors. The destruction caused by the blast of air, followed by the jet of water, was incredible. For example, the massive steel I-beams in the underground powerhouse were “twisted like a corkscrew and sheared.”5 The shock wave was quickly followed by a 230-foot-high flood that tore down the valley. It destroyed nearly everything in the village of Longarone in the mouth of the canyon, except for a church bell tower, which was only partially damaged. Then the flood wave broadened out before turning into the Piave Valley, where it wrecked the villages of Cadissago, Pirago, and Villanova. Unlike the St. Francis flood that took many hours to play out as it worked its way to the ocean, the destruction of the Vajont flood ended quickly, mostly because the area affected was remote and lightly populated.
So fierce was the force of the landslide, shock wave, and crashing of water over the face of the dam that seismic tremors were recorded at earthquake stations over a wide area of Europe, even as far north as Brussels, Belgium. These stations established that the recorded seismic waves were the result of the landslide, not its cause. That was an important distinction in ruling out an earthquake as the primary cause of the disaster.
The disruption in power that caused a blackout just moments after the water and shock wave destroyed the powerhouse was the first indication to the rest of Italy that something was wrong.
As reports flooded in, rescue workers started making their way to the devastated area. Local Italian resources were supplemented by US Army helicopters and paratroopers on assignment in Italy who aided in rescue efforts and brought supplies into the devastated areas. Taking more than 300 flights, they ferried out more than 4,000 survivors. It was because of the earnest and heroic efforts of Italians and Americans working side by side that the surviving victims were saved from further suffering. Through the help of those who rushed to the scene, the survivors were soon given medical attention, food, and temporary shelter. Their villages had been destroyed, but they were still alive.
Professional Heroes: Acting to Prevent Future Tragedy
The owners of the dam quickly declared that the flood was an “act of God,” completely unpredictable and not a result of human error or faulty design. This was a hard case to make to the people living in the area. They had warned the government about Monte Toc’s instability and had watched as the electric company had manipulated the lake level to try to create a controlled slide. But before an independent investigation could establish cause and responsibility, the disaster was politicized by the Communists, who had opposed the dam from the beginning. They declared the disaster to be the result of greed and mismanagement. Italy’s prime minister quickly reacted to this by accusing the Communists of “political profiteering” at the expense of the victims, and then moved to silence the debate. A trial was held, in which a handful of engineers were found negligent. The government never sued the electric company for damages.
The only person to fully accept responsibility was the construction engineer, Mario Pancini, who fell into such despair that he committed suicide. He had tried mightily to prevent tragedy but was unable to resist the political pressure to construct a dam in an area he knew to be unsuitable. For this he paid with his life.
Many of the survivors were relocated to a new village, Vajont, southeast of the mouth of the canyon. Longarone and other villages were rebuilt, offering new housing for those who chose to return. The government also offered loans and subsidies to survivors who wished to start new businesses to revitalize the area. But the corruption continued: most of these subsidies were granted to large industrial concerns that built factories and plants elsewhere in Italy using the credits intended for the flood victims.
Within a few years, almost no one talked about the tragedy—it was an embarrassment to be avoided. It was many decades later that survivors started sharing their stories to keep the memory of that awful night alive. A memorial church designed by the noted architect Giovanni Michelucci was built in Longarone to honor both the victims and the survivors of the tragedy.
A modern view of the Vajont Dam from the valley below.
Yet, all was not in vain. The Vajont Reservoir tragedy drew international attention to the dangers of building reservoirs in canyons that had steep slopes faced with slide-prone material. It became an additional consideration in properly siting dams to reduce the risk of a tragedy like Vajont.
The Vajont Dam Today
A pumping station was built on the upside of the dam to draw water from the two small lakes into the outlet tunnels. In 2002, a visitors’ center was built at the crest of the dam so tourists could visit the site and see the irony of a huge dam impounding a dry basin that is now covered in vegetation. In 2006, a track and field event entitled “Paths of Remembrance” was inaugurated, allowing runners to go inside some of the tunnels used in construction and originally intended to aid in power generation.
Notes
1. SADE is the acronym for the Società Adriatica di Elettricità (Adriatic Electricity Company).
2. David Pettley, “The Vajont (Vaiont) Landslide”; paragraphing altered.
3. Mark Duff, “Italy Vajont anniversary: Night of the ‘tsunami.’”
4. See George A. Kiersch, “The Worst Dam Disaster in the World (Vaiont),” in Mineral Information Service, Vol. 18, no. 7 (July 1965): 129–41.
5. See Kiersch, “The Worst Dam Disaster in the World (Vaiont),” 129–41.