A "chain of causes" spanning 35 years caused the deadly Laval overpass collapse last year, but no single person or group can be held responsible for the disaster, the Johnson commission has concluded.

But the commission blames several players including Quebec's Transport Ministry for ignoring long-standing problems with the overpass, neglecting its maintenance, and tolerating violations of the province's standardized inspection protocols for road structures.

Workers clean up debris after the Highway 19 overpass collapse in Laval in September 2006.
(Paul Chiasson/Canadian Press)

Engineers and companies that worked on the overpass through the years share the blame as well, commission head Pierre Marc Johnson said. 

The former premier appointed to head the overpass commission released his long-awaited report Thursday detailing several factors that contributed to the Highway 19 overpass collapse on Sept. 30, 2006, which killed five people, including a pregnant woman, and injured six.

"The collapse comes from a series of shortcomings," in design, material use and maintenance, Johnson said at a press conference in Montreal Thursday. "But no one person or one organization can be assigned responsibility for what happened on Sept. 30, 2006."

In his report, however, he wrote that transport workers and organizations "failed to assume their responsibilities during construction [and] during the bridge's service life."

Johnson told the news conference that a transport road patroller called to the Concorde overpass the day it collapsed isn't responsible for what happened that Saturday, because he did what his job required.

The commission found three major causes contributed to the overpass failure:

• Improper rebar support for the design, which caused a "plane of weakness" where cracks eventually occurred.
• Improper rebar installation at the time of the overpass's construction in 1970.
• Use of low-quality concrete to build the overpass.

The commission's report also outlined several other contributing causes – which experts testifying at the enquiry did not all agree on –  for the overpass collapse:

• Shear vulnerability: The thick concrete overpass was vulnerable to shear failure because it was not reinforced to withstand cracking and deterioration.
• Lack of adequate waterproofing: A major repair job in 1992 called for a waterproof membrane. The engineer leading the project decided the concrete had deteriorated too much and did not install the protective membrane.
• Weakening of the structure in 1992: The routine replacement of expansion joints was a bigger repair job than expected, and engineers had to remove more concrete than originally anticipated to make the fix, weakening the structure.

Recommendations include sustained funding, change in transport culture

The Johnson report makes 17 recommendations in light of its findings, which include spending $500 million a year for 10 years on bridge and overpass repair and construction.

Johnson reproached the government for ignoring roads and highways for decades, but said it was a choice Quebec society made at the time as it focused on building its education and health services in the 1960s and 1970s. "They didn't go far in the transport division," he said in French.

Johnson urged the government to make bridge and overpass inspections a priority, and to set up stable long-term financing for road infrastructure that could include user fees, tolls or partnerships with the private sector where "there is investment capital" for long-term projects, he said.

Other recommendations include revising Transport Quebec codes, norms and inspection manuals, and reviewing the legal framework for bridge design construction supervision and construction work.

The commission reiterated its limited mandate, which stops short of establishing criminal and civil responsibility. Given Quebec's no-fault automobile insurance laws, victims have very little recourse to sue the government for damages.

The commission's 200-page report is available online.

Since the inquiry began its hearings, more than 100 bridges and overpasses in Quebec have been inspected, with many of them repaired or closed.

The Quebec government pledged this fall, before the Johnson report, to spend $30 billion as part of a five-year plan to refurbish or replace bridges and overpasses, as well as schools, jails and other provincial buildings.