De la Concorde overpass collapse


De la Concorde overpass collapse

On September 30, 2006, part of an overpass (65-foot / 19.8 m section of a three-lane overpass) (The Associated Press 2006a) collapsed in Laval, a suburb of Montreal, on Boulevard de la Concorde running over Autoroute 19. The collapse crushed two vehicles under it, killing five people and seriously injuring six others who went over the edge while travelling on the overpass (Marotte & Magder 2006). The autoroute was closed for almost 4 weeks (CanWest News Service 2006), "disabling an important north-south link between Montreal and its northern suburbs as well as the Laurentian region" (The Associated Press 2006a).

Contents

Immediately before

A number of people had noticed that the overpass wasn't in good shape:

  1. "People living near de la Concorde and Highway 19 told The Gazette they had noticed the overpass had begun to crumble in recent months" (Lunau, Coates & Banerjee Branswell)
  2. Carole Hackenbeck, less than a month before the collapse, noticed that there were "unusually large gaps and misaligned spacing in the deck-support structure underneath" (The Associated Press 2006a).
  3. "One witness told TVA television network that he noticed the road had sunk an inch or two when he travelled over the overpass minutes before the collapse, and he called emergency dispatchers" (The Associated Press 2006a).
  4. Also, "several motorists told LCN they had called police up to an hour before the collapse to report seeing fissures appearing in the overpass roadbed and chunks of concrete falling to the road below" (Reuters 2006a).

Responses to calls

When the Quebec Ministry of Transport was contacted regarding blocks of concrete falling onto Autoroute 19 from the Concorde Boulevard overpass above, a patroller was sent to do a sight and sound test (Lunau 2006) to gauge whether the road should be closed and to clear away to concrete hazards; this was 30 minutes before the collapse (Marotte & Magder 2006). Neither roads were closed (Lunau 2006) as the official concluded that the bridge presented no immediate danger (Marotte & Magder 2006). The patroller however did demand that an inspection be carried out as soon as possible, but was told "that an inspector would show up only on Monday, two days later" (Charron 2006).

The Ministry also sent out messages to journalists and traffic reporters warning of the concrete debris; this was confirmed by Josee Seguin, a spokeswoman for the Ministry (The Associated Press 2006b) (Lunau 2006).

Bridge history and design problems

The overpass on the Boulevard de la Concorde (Concorde Boulevard) was built in 1970 and was expected to have a life span of 70 years, of which it only lasted 36 (Arseniuk 2006). David Lau, as part of an article for the Ottawa Citizen, suggests that this estimation of 70 years was inaccurate. They underestimated traffic volumes; they also did not take into account that "the amount and weight of trucks [on] today's roadways are significantly higher" (Arseniuk 2006). "30 or 40 years ago, engineers could not anticipate the traffic some of their bridges would be forced to accommodate in the coming decades" (Arseniuk 2006).

The design of the overpass was considered innovative at the time; however, this design made it nearly impossible to inspect thoroughly, as the entire deck would have had to be removed for such an inspection.[1]

Michel Despres (Transport Minister of Quebec) stated that it was inspected once a year, and got a more in-depth inspection once every three years, as per the usual inspection requirements in Quebec (Lanau 2006), last being May 2005 (Marotte & Magder 2006). Ken Bontius, a civil/structural engineer at Hatch Mott MacDonald adds that the bridge was examined bi-annually by structural engineers (Arseniuk 2006).

The aftermath

After the collapse of the overpass, the government moved quickly to rescue survivors, remove the dead, and clear away the debris. The Ministère du Transport du Québec (MTQ) immediately requested that any overpasses of similar design in Quebec be identified. Of several such overpasses, only the de Blois overpass adjacent to the collapsed overpass was confirmed as similar. Indeed, this overpass was built in the same construction project as the de la Concorde overpass and was later found to have had the same flaws. It was closed to traffic less than three hours after the collapse and subsequently demolished.[1]

Behavioural effects

The Monday (October 2) following the collapse, as everyone was trying to get to work, three major expressways into Montreal from Laval were gridlocked with vehicle line-ups stretching for kilometres (Marotte & Magder 2006)(CTV News 2006). "Traffic was backed up as early as 6:00am on Autoroute 25 and Autoroute 15" (CBC News 2006a).

Normal traffic flows along Autoroute 19 amount to 57,000 vehicles per day in both directions (CBC News 2006a). The collapse caused some changes to these figures with motorists choosing different routes (mainly official detour routes), changing the time they left for work (earlier or later) or change in mode (to bus, metro, etc.) being the main responses.

Agency responses

In response to the incident, the Quebec government instigated several strategies to speed the recovery effort and to minimise the inconvenience of commuters. The Quebec government made it a priority to rescue survivors, remove the dead and the debris from Autoroute 19. The demolition work (of the Concorde Boulevard) closed Autoroute 19 for a little under four weeks (CanWest News Service 2006) and caused "motorists [to] get up earlier and use special buses to commute into the city" (Canadian Press 2006). These buses were shuttles provided to ferry commuters between new park and ride sites and subway stations.

The government also put detour routes in place, urged commuters to take public transport and to carpool (CBC News 2006a) (CTV News 2006). CAA-Quebec, a non-profit organisation also has urged commuters to consider carpooling as an alternative to driving, suggesting their free carpool ride-sharing program which allows drivers and passengers to network to organise carpools (Canada NewsWire 2006). Transit authorities in Laval and Montreal also increased services on some routes to accommodate more commuters (CBC News 2006a) (Marotte & Magder 2006) (CTV News 2006):

  • An extra commuter train (donated by Ontario's GO Train commuter rail to assist with higher rider numbers)
  • Extra park-and-ride parking lots including a free bus shuttle to subway stations - to encourage commuters to not use the already overtaxed detour routes
  • Reserved bus lanes extended
  • Adding 6 km to two high-frequency bus routes (Riga 2006)
  • More buses

Riga (2006) interviewed Marc LaForge from the Societe de transport de Laval about the transport department suing Transport Quebec to pay for all these extra services:

"Laval's transit authority - the Societe de transport de Laval - is asking for $312,500, for now. That's $12,000 for each of the 25 weekdays from October 2nd to November 3rd on which it provided extra services for commuters whose routes were affected by the collapse" (Riga 2006).

Costs also included paying overtime to drivers (Riga 2006).

Detour routes

The official detour routes were as follows:

Donations from other provinces

To aid Laval commuters, and to help the province cope with traffic problems (Artuso 2006), Ontario donated a "GO Train" to increase ridership in the wake of the weekend collapse. Ontario's premier Dalton McGuinty - "[Quebec officials] tell me there has been an increase, [a] fairly dramatic increase, in demand for the rail." Also "There's a rail line that runs along the site of the tragedy, and more and more people want to use that rail line" (CBC News 2006b).

Official inquiry

On October 3, 2006, the Government of Quebec called an inquiry to determine the cause of the collapse. Just over a year later, on October 15, 2007, the Inquiry Commission released a report of its findings.[1] This report recounts the events just before, during, and after the collapse, discusses the overpass design and history, identifies the cause of the collapse as well as other contributing factors, suggests who is directly responsible for the collapse, and makes recommendations to prevent such an event from recurring.

Determined causes

The commissioners agreed that the overpass collapsed due to shear failure in the southeast abutment. This was due to a horizontal plane fracture that had slowly grown over the years. The fracture allowed the part of the abutment below it to break away from the part above, causing the collapse.

The three main causes of the fracture and subsequent collapse[2] were:

  • During design, the steel reinforcement was concentrated in one layer, causing a weak plane. This did not contravene the code provisions of the time.
  • During construction, the reinforcement was not put into the proper locations, as defined in the design, exacerbating the design weakness. The contractors and inspecting engineers were blamed by the commission for this cause.
  • A low quality concrete was used in the abutments, causing poor freeze-thaw behavior. This was blamed on poor communication at all levels, including that of the government-defined requirements at the time

Three other contributing causes were identified by the committee, but not agreed to by all the experts.

  • All thick reinforced concrete slabs should have shear reinforcing, and this is a deficiency in the existing bridge design code.
  • Proper waterproofing was never installed, even during the bridge repairs done in 1992.
  • Extensive concrete removal and rebar exposure caused during the 1992 repairs caused weakening of the structure.

The final report names four individuals who were responsible for unprofessional work on the overpass:

  • Marcel Dubois, engineer with Desjardins Sauriol et Associés (DSA), for improper supervision during construction
  • Claude Robert, president of Acier d'Armature de Montreal (AAM), for poor quality control caused by passing off responsibilities
  • Tiona Sanogo, engineer, for the damage caused during the 1992 repairs
  • Christian Mercier, engineer, for an incomplete inspection of the overpass in 2004

Policy changes

This event, and another similar overpass collapse in 2000, have increased scrutiny of Quebec's infrastructure and has led to increased efforts to detect signs of wear in aged structures. Accused of consistently putting off repairs to pass balanced budgets, the Quebec government has since increased spending on highways and projects and has increased infrastructure spending for future budgets.

This is welcome news to the Canadian Council of Professional Engineers (CCPE) as they have been campaigning for infrastructure renewal and maintenance. "Hopefully this tragic event did not happen in vain and we, as a society, will learn from it and make the conscious decision to re-invest in infrastructure using a long-term, holistic approach as well as life-cycle management guidelines" (Evans 2006), Marie Lemay the CEO of CCPE says. "long-term adequate financial resources are needed from all levels of government in order to support a sustainable and planned approach over the full life cycle of any infrastructure project" (Evans 2006).

In July 2007, incidentally just weeks before the I-35W Mississippi River bridge collapse, the Quebec department of transports issued a list of 135 overpasses that were considered potentially unsafe. These overpasses were put under close scrutiny and closed to all overweight trucks (in excess of 20 tonnes). Also, the City of Montreal issued a list of a few overpasses under its own responsibility, citing that those were also under close scrutiny and closed to overweight traffic. The day after the I-35W Mississippi River bridge collapse, the City of Montreal revised its policies for one of those, the Henri-Bourassa overpass above Pie IX Boulevard, closing it completely to all trucks. This overpass has since been under surveillance by authorities and have plans to demolish it.

As of April 2008, 28 bridges in Quebec are slated to be demolished due to structural deficiencies, and 25 are to receive major repairs.[3]

Footnotes

References

External links

Coordinates: 45°35′0.6″N 73°40′30.94″W / 45.5835°N 73.6752611°W / 45.5835; -73.6752611


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