The Heron Road Bridge Disaster

10 August 1966

Heron Road forms part of one of the busiest, east-west arteries in Ottawa. The four to six lane, divided thoroughfare runs from Walkley Road in the east, crosses the Rideau River and the Rideau Canal, where it becomes known as Baseline Road, and ends at Richmond Road in the west. Of the thousands of commuters that use the road each day, few are probably aware that the bridge over the river and canal was the location of the worst industrial accident in Ottawa’s history. On 10 August 1966, a span of the Heron Road Bridge, which was then under construction, collapsed while 60 workmen were pouring concrete on a segment of the southern, eastbound roadway. Seven men were killed on the scene, crushed under tons of falling concrete. Another man died later than day, while a ninth victim succumbed to his injuries a month after the horrendous accident. A further fifty-seven men were injured, many severely. Victims were trapped in a horrifying mess of solidifying concrete, tangled ironwork and splintered wood that made extracting them difficult.

Picnickers who had been listening to a rock n’ roll band in nearby Vincent Massey Park that hot, sultry afternoon, described the collapse of the bridge as sounding like a low-flying, jet airplane. So great was the impact that the seismograph at the Dominion Observatory three kilometres away on Carling Avenue registered the event at 3.27pm. Some eyewitnesses likened it to an exploding bomb. The loud roar of the collapse was accompanied by a large cloud of dust thrown up into the air.

Heron Bridge

Heron Road Bridge After The Collapse, 1966

Immediately, passersby, police, workmen from nearby work sites, and firemen descended on the disaster scene to help rescue the casualties, many digging in the wet concrete using only their bare hands. There was blood everywhere. Aiding the injured was perilous; a slab of semi-hard concrete overhung the disaster site. The Civic Hospital set up a triage station, with the injured ferried to hospital by ambulance, trucks, and police cars. Disaster relief continued after dark; in the early hours of the following morning, a heavy rain made rescue conditions even more treacherous. On the scene throughout the recovery operations was Ottawa’s Mayor Don Reid. Rev. Georges Larose, the Ottawa Fire Department’s chaplain, comforted survivors, and administered the last rights to victims as they were recovered. The Salvation Army distributed sandwiches, coffee, and cold drinks.

One survivor, Jorge Veiga, was stuck in wet concrete up to his neck. Rescuers carefully washed the hardening mess that threatened to suffocate him from his nose and mouth with water, while welders cut through the iron reinforcing rods that trapped his body. A bucket brigade was organized to keep the metalwork cool enough that the heated metal from the blow torches didn’t burn him. Thankfully he was successfully extracted without his rescuers having to resort to amputation as earlier feared. Another worker, Thomas Daly, was impaled, and was transported to hospital with an iron rod protruding from his arm. Fate was capricious. A nineteen-year old man amazingly survived the sixty foot fall from the bridge with only a slightly injured arm; his glasses landed beside him intact.

Work on the Heron Road Bridge had commenced early the privious year. In February 1965, the City of Ottawa signed a contract with Beaver Construction (Ontario) for the construction of footings for the reinforced concrete piers on which the Heron Street Bridge would rest. This work was successfully completed without mishap by June 1965. The contract for building the two three-lane bridges, (the northern bridge for west-bound traffic and the southern bridge for east-bound traffic), each 877.5 feet long made of pre-stressed concrete, was awarded to O.J. Gaffney Ltd in August 1965. The City of Ottawa also hired the firm M.M. Dillon & Company Ltd as consulting engineers to help design and supervise the Heron Bridge Project.

Work began in the fall of 1965 starting at the western end of the twin bridges. Each bridge was divided into four spans—PT1N (meaning post-tensioned, 1st span, north bridge), PT2N, PT3N, PT4N, and PT1S, PT2S, PT3S, PT4S for the south bridge. The concrete used to construct each span of the bridge decks was poured in two layers.  By August 1966, the western half of the twin bridges (PT1N, PT2N and PT1S and PT2S) was essentially complete. The contractor had also constructed the wooden falsework (the temporary supporting structure or scaffolding) to support the eastern spans (PT3N, PT4N, PT3S, and PT4S) as they were built. A month prior to the accident, the first layer of concrete, 217 feet long by 50 feet wide, had been poured over spans PT3N and PT3S. Disaster struck while the second layer of concrete was being poured on span PT3S. According to the Ottawa manager of M.M. Dillion, the consulting engineers, as workers poured the concrete starting from the centre of the span moving east, the single-layer section of the span that overhung the western end of the span flipped into the air, pancaking onto the rest of the bridge, bringing it down.

Immediately, the Ontario Government launched an inquiry into the disaster. Ontario’s supervising coroner Dr H.B. Cotnam hired the engineering firm H.G. Acres Ltd to assist him in his investigation of the causes of the collapse. The focus of the inquest was the factors that led to the death of Clarence Beattie, a foreman who died in the collapse, though the inquiry’s findings were applicable to all nine fatalities. A five-member Coroner’s jury met in late November 1966 to hear the conclusions of the investigating engineers, and to listen to the testimony of witnesses. Jury members quickly focused on the strength and stability of the wooden falsework used to support the bridge while the concrete spans were being poured. Of particular interest was whether the falsework, which lacked diagonal, longitudinal bracing, was able to support the bridge while under construction. The overwhelming consensus of professional opinion was to the contrary. To help demonstrate the weakness of such a design, Prof. Carson Morrison, head of the department of civil engineering at the University of Toronto, demonstrated the relative strength of braced and unbranced falsework using two wooden models.

After seven days of testimony from H.G. Acres Ltd and other witnesses, the jury reached its verdict. It concluded that Clarence Beattie died from being crushed, his injuries due to the failure of the falsework, and his subsequent entanglement in steel bars and cement. The jury also concluded that the failure of the falsework was due to the absence of diagonal, longitudinal bracing. Indeed, the jury contended that the falsework had been technically inadequate to even support the first layer of concrete that had been poured a month prior to the disaster. The jury also pointed to secondary factors, including the use of poor quality lumber in the construction of the falsework, as well as the differential settling of footings, and a temporary overloading of certain posts. However, the jury concluded that these secondary factors would not likely have caused the falsework structure to fail. The jury blamed both O.J. Gaffney, the construction firm, and M.M. Dillion, the firm of consulting engineers, for the bridge’s collapse.

As with all disasters, the Heron Road Bridge failure reflected a number of things that had gone wrong, any one of which if caught earlier might have averted the bridge’s collapse. Most importantly, there was confusion over the design of the falsework. There had been three different sets of plans owing to changes demanded by the consulting engineers. Although the second draft plans of the falsework had contained diagonal longitudinal bracing, the third set did not. Testimony at the inquiry indicated that the consulting engineers viewed the third design plan as supplementary to the second design plan, whereas the construction team viewed the third design plan as complete.

There was also conflicting testimony about the falsework itself. Robert McTavish, the chief engineer of the construction firm, testified that the bracing had been dropped from the third design plan following discussions with Victor J. Bromley, the project engineer from M.M. Dillion, since a different “system” had been included as a substitute. This system was not, however, included in the final plans which McTavish approved, nor was it built.  Bromley, on the other hand, denied that he ever agreed to the removal of the diagonal, longitudinal bracing.

Regardless of who was right, neither McTavish nor Bromley had an adequate explanation for why they both failed to notice that the falsework was inadequately braced. McTavish said “he was interested in something else.” Bromley held himself “guilty” for not noticing the absence of the bracing despite regular visits to the work site. He testified “I didn’t notice it. I can’t explain it. My mind must have been confused at the time.”

Heron Bridge today

Heron Road Bridge, Looking West, cirica 2012

While city and provincial safety inspectors had noted the absence of diagonal longitudinal bracing in the falsework structure when they had been taken on a tour of the worksite by an engineering student who had been recently hired by the construction company, they had been satisfied with the student’s response that the falsework design had been approved by qualified engineers. “If it’s good enough for them (the consulting engineers), it’s good enough for us,” the inspectors were reported to have said. They did not to raise their reservations with their superiors, or with qualified engineers from either the construction firm or the consulting engineering firm. Later, it came out that neither inspector was a trained engineer. Moreover, they had been instructed not to question decisions made by professional engineers.

Despite the jury’s findings of human error, it may not have discovered the root cause of the disaster. Behind most cases of human error lies a design error says Don Norman, Professor of Applied Psychology at the University of California, San Diego. Several issues may not have been sufficiently probed. Why, for example, did the many professional engineers employed by the construction firm and the consulting engineering firm fail to spot the design flaw in the plans for the falsework? Why did they subsequently fail to spot the absence of adequate falsework bracing despite on-site supervision and frequent inspections? With so many engineers involved, was it a problem of “if everybody is responsible, nobody is responsible?” Was it difficult for one professional engineer to question the work of another? Why did the city and provincial safety inspectors fail to report their concerns about the absence of diagonal, longitudinal bracing to their superiors? Did they see themselves as being inferior to professional engineers, and hence unqualified to raise concerns? Were the safety systems put in place to avert disaster themselves flawed?

The jury made a number of recommendations to reduce the possibility of future disasters. It recommended that there be a clear definition of the responsibilities of the building contractor and those of the consulting engineers. In addition, it advised that approved design and construction drawings for falsework be stamped by a qualified civil engineer, and that safety inspectors be better trained, and be required to make written reports regarding any area of the falsework which in their personal opinion was inadequate. The jury also urged that graded lumber be used in building falsework, and that a mandatory building code be developed by the province of Ontario for the construction of bridges and falsework.

The collapse of the Heron Street Bridge led to major improvements to Ontario’s building code. Robert McTavish, the chief engineer of O.J. Gaffney, the building contractor, and Victor J. Bromley, the project manager from M.M. Dillion, the consulting engineering firm, were both suspended from practicing as engineers in Ontario by the Association of Professional Engineers of Ontario for a period of one year. Bernard Houston, the chief estimator for Gaffney, who took responsibility for the majority of the design calculations for the bridge, was reprimanded. O.J. Gaffney was found guilty on two charges levelled under the Construction Safety Act, and was fined $5,000, the maximum penalty under the law at that time. The widows of the nine men who died in the Heron Bridge collapse received lump-sum compensation of $300 each (a little over $2,000 in today’s money), and a widow’s allowance of $75 per month, and an additional $40 per month for each child.

In 1987, the Canadian Labour Congress dedicated a memorial to those who lost their lives in the collapse of the Heron Street Bridge. The memorial, which lists the names of the nine workers who died in the disaster, can be found in Vincent Massey Park, close to where the fatal accident occurred.

 

Sources:

Kardos, G. 1969. Heron Road Bridge, Engineering Case Library, Leland Stanford Junior University, California, https://archive.org/details/ECL-133.

Globe and Mail (The), 1966. $250,000 estimated as compensation cost,” 20 August.

————————–, 1967. “Bridge builder charged in Heron road collapse”14 Janaury.

————————–, 1968. “Two suspended in fatal collapse of new bridge.” 27 January.

Ottawa Citizen (The), 1966. “Engineer Takes Blame,” 24 November.

————————–, 1966. “Bridge mock-up is sent crashing at inquest,” 25 November.

————————–, 1966. “Inquest jury pins blame on two firms,” 30 November.

————————–, 2006. “The day the bridge came tumbling down.” 5 August.

Montreal Gazette (The), 1966. “Nine Dead in Ottawa Disaster, 11 August.

Norman Don, 2013. The Design of Everyday Things,” New York: Basic Books.

Winnipeg Free Press, 1966. “Span that collapsed at western end of the eastbound lane between two 60’ abutments that remained intact,” 11 August.

Images:

Heron Road Bridge after the collapse, 1966, Workers’s Heritage Centre, http://whc-cpo.ca/albums/heron.html.

Heron Road Bridge, Looking West, circa 2012, Pomerleau,  http://www.pomerleau.ca/construction-contractor/Projects/555/49/Heron-Road-Bridge-Reconstruction.aspx.

 

The Arrival of the R-100

10 August 1930

When we think  of airships what typically comes to mind are German Zeppelins, and the tragic crash of the Hindenburg. That disaster, which occurred in Lakeport, New Jersey in May 1937 and claimed the lives of 36 people, was seared into our collective consciousness by the dramatic newsreel footage of the crash, as well as the heart-rending radio broadcast of Herbert Morrison who reported on the accident as it happened. The tragedy put an end to the pre-war dream of a lighter-than-air, transatlantic, passenger service that could rival the fastest ocean liners.

Much less well-known is the British airship scheme. It was the brainchild of Sir Dennis (Dennistoun) Burney who dreamed of building an imperial airship service that would link the far-flung British Empire. Winning the support of the Labour Government of Ramsay MacDonald, Burney’s plan was put into action in 1924. The government decided to fund two competing teams, one from the private sector and the other from the public sector. Each would build an airship to the same specifications. The R-100, referred to as the “capitalist” ship, was designed and constructed under a fixed contract by the Airship Guarantee Company, a subsidiary of Vickers Ltd, a large British armaments firm. Burney became the managing director of the airship subsidiary. The R-100’s chief designer was Barnes Wallis. The R-101, the “socialist” ship, was built by the Royal Airship Works owned by the Air Ministry. The two teams were extremely hostile to each other. There was virtually no communication between the two groups while the two airships were under development.

It took five years to design and built the airships. Without electronic calculators or computers, all the calculations to determine the forces and stresses on each airship part had to be done by hand, or by slide rule, a process that took months to complete, check and double check. The novelist Nevil Shute, who was the Chief Calculator on the R-100 design team, and later the Deputy Chief Engineer, said that he filled “perhaps fifty foolscap sheets of closely pencilled figures.”

At 706 feet in length with a diameter of 130 feet, and a volume of more than 5 million cubic feet, the R-100 was as big as an ocean liner. But when its fourteen gas bags were filled, it was as light as a feather. The slightest breeze could move it. The easily-torn, fabric gas bags were made of linen lined with “gold-beater’s skin,” a thin, transparent membrane with a high tensile strength. Hydrogen was used for lift since it was far cheaper to manufacture than helium. People were aware of the fire danger of using hydrogen, but it was expected that any escaping gas, being lighter than air, would simply float upward out of harm’s way. The “tare” weight of the airship was roughly 102 tons. With a “gross” weight of 156 tons, it had a lifting capacity of about 54 tons. Powered by six Condor, petrol airplane engines, the R-100 had a top speed of 81 miles per hour, and cruised at 70 miles per hour.

The contract for the R-100 called for a demonstration flight to India. However, with the decision to use petrol engines, the destination was changed to Canada on the erroneous belief that the use of petrol engines in the tropics would be unsafe. Instead, the Air Ministry decided to send the R-101, which was powered by diesel engines, to Karachi, then part of British India, on its demonstration flight.

After seven short testing flights during early 1930, the R-100 left RAF Cardington airfield in Bedfordshire north of London at 3.50am on 29 July 1930 bound for Montreal. There was a lot riding on a successful trip. The Great Depression was underway. It was evident to all that the government would be unable to indefinitely fund two separate airship teams. A choice would have to be made that would send the losing team to the dole line.

His Majesty's Airship R-100 at its mooring pier, St Hubert, Quebec

His Majesty’s Airship R-100, St Hubert, Quebec, August 1930

According to Nevil Shute, the R-100’s flight across the Atlantic was very comfortable though there were a number of minor problems. Some large tears in the gas bags had to be repaired en route. While the riggers were equipped with safety belts, “which they could sometimes hitch [] to a wire,” they had to tight-walk their way out to the holes with nothing beneath them but the St Lawrence River, 1,000 feet below. The R-100 arrived at its mooring at the St Hubert airfield east of Montreal on 1 August after a flight of 78 hours, having journeyed 3,300 miles at an average ground speed of 42 miles per hour.

The airship received a rapturous welcome. During its stay in Montreal, hundreds of thousands of people visited the airfield to get a close-up look at the great air vessel. Posters of its picture were plastered across the city. Even a song was written about it. On 10 August, the R-100 took a 24-hour local flight over Ottawa, Toronto, and Niagara Falls, before returning to Montreal. On board were a number of prominent Canadian military figures. It was hoped that if the Canadian government was impressed, it would contribute funds that would help make Burney’s dream of a trans-Empire airship service a reality.

The R-100 was scheduled to arrive over Ottawa from St Hubert at about 8pm on Sunday, 10 August. But the airship was delayed by roughly two hours due to a late departure owing to rain squalls. Bulletins giving its position and estimated time of arrival were released by the long-range wireless station of the Royal Canadian Signals Corps that maintained communications with the airship. If anything, the delay magnified the excitement of the crowds that occupied every open field, roof top, and driveway. It was estimated that 35,000 waited on Parliament Hill and Nepean Point for the arrival of the airship.

The R-100’s two vertical nose lights were first spotted coming from the southeast at about 9.35pm. Several minutes later, searchlights began to pick out the huge dark bulk in the night sky that blotted out the stars. Finally, with its engines roaring, it flew at an altitude of about 1,500 feet northward above O’Connor Street to hover over Parliament Hill. Illuminated by the city’s lights, one could easily read its name “R-100” on its side, and its smaller registration markings “G-FAAV.” The Ottawa Evening Journal found the experience both moving and disturbing, saying that sight of the airship “combined the creepy thrills of war-time air raids by stealthy Zeppelins with the delicious illusion of dreamland phantasy.” With the airship over Parliament Hill, the parliamentary carillon played “Rule Britannia” and other patriotic songs. The R-100 then dipped its nose up and down towards the Peace Tower in salute of the soldiers who died in the Great War while the carillon played “God Save The King.”

The silver airship made three great circles over the Ottawa-Hull area before heading towards Carleton Place and onward to Kingston, Toronto, and Niagara Falls. During its time above the national capital, two-way telephone communication was established connecting Commander Booth of the R-100 with Prime Minister R.B. Bennett and Ottawa Mayor Frank Plant. The telephone conversations were carried live over Ottawa’s CBC radio station CNRO. The prime minister and the mayor welcomed the R-100 to Ottawa and congratulated its officers, crew and the airship’s design team. Mayor Plant, described the R-100 as a “worthy successor to the stout ships of British oak which ruled the waves.”

After its tour over southern Ontario, the R-100 returned to the St Hubert airfield to ready itself for its return trip to Britain. It left Montreal on 13 August, 1930, arriving back at RAF Cardington 57 1/2 hours later. On board were eleven Canadians, mostly journalists. It was the last flight of His Majesty’s Airship R-100.

Six weeks later, on 4 October 1930, its sister ship, the R-101, left for India on its long-distance demonstration flight. On board was Lord Thomson of Cardington, the Secretary of State for Air who had overall responsibility within government for the airship programme. Roughly seven hours after its launch, the airship crashed in bad weather near Beauvais, France, north of Paris. Of the 54 persons on board, only 6 survived. Lord Thomson was among the fatalities.

According to Nevil Shute, the successful return flight of the R-100 between Britain and Canada was in part responsible for the crash as it put undue pressure on the R-101 team to match the R-100’s success even though the R-101 was unready. He pointed the finger at a number of serious known problems, which included weaknesses in the outer cover, chafing gas bags, and leaking gas valves, all of which he claimed were minimized in order to get the ship aloft. Bad weather, including high winds over France, were also ignored despite the fact that one of the airship’s engines wasn’t working. The source of the pressure was apparently Lord Thomson who was eager to demonstrate the capabilities of the R-101 before the 1930 Imperial Conference convened in London on 20 October. At the conference, the Imperial Airship programme was scheduled to be discussed. The responsible engineers, faced with the choice of scrubbing the flight and earning Lord Thomson’s wrath, or taking a chance, decided to go ahead. They lost the gamble, and their lives.

With the crash of the R-101, the British airship scheme also died. Despite its successful trans-Atlantic flight, the R-100 was deflated by the Air Ministry, and was sold for scrap in 1931 for £600.

Today, more than eighty years after the R-101 disaster, there is renewed interest in lighter-than-air vessels. At the Cardington airfield, the same airfield from which the R-100 and the R-101 set off on their fateful long-distance trips, work is progressing on a twenty-first century version of the airship—the Airlander 10. Much smaller than the old R-100 and R-101, it has a high-tech. polymer outer covering, and is filled with non-flammable helium. Investors in the Airlander, which include the British government, hope that there is a market for a greener alternative to trucks or airplanes, especially for deliveries of goods and people to places that are off the beaten track.

Sources:

Ars Technica, 2015. “Airlander 10: World’s largest aircraft slowly drifts toward commercial use,” 8 April, http://arstechnica.com/cars/2015/04/airlander-10-worlds-largest-aircraft-slowly-drifts-towards-commercial-use/.

Shute, Nevil. 2009. Slide Rule, Vintage Books: London.

The Evening Citizen. 1930. “Ottawa Thrilled As Great Air Liner Appears,” 11 August.

The Ottawa Evening Journal, 1930. “R-100 Expected Over Ottawa After 8pm Sunday,” 9 August.

———————————–, 1930, “R-100 Thrills May Thousand Over Ontario, 11 August.

———————————–, 1930. “Thousands See R-100 In Flight Over The Capital, 11 August.

———————————–, 1930. “Bennett and Plant Talk Over Radio to R-100 Officers,” 11 August.

Image: R.100, 9 August 1930, http://en.wikipedia.org/wiki/R100.