Dismantling the Champlain Bridge: Protecting the St. Lawrence at All Costs

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Dismantling of the Champlain Bridge: protect the St. Lawrence at all costs

Since the summer of 2020, workers have been deconstructing the old bridge Champlain. A complex operation that requires pushing the limits of engineering to protect the St. Lawrence.

A large pier has been built on the side of Nuns' Island. The river was not deep enough to allow the circulation of the barges.

The disappearance of the Champlain Bridge, once an icon of the Montreal landscape, has brought its share of challenges. For months, engineers worked to dismantle the imposing structure, taking care to salvage the concrete and steel and to protect the river, a place of refuge for dozens of species.

Severely tested by Quebec winters, the bridge built in the late 1950s had to be reinforced over the years before its access was closed for good on June 28, 2019.< /p>

3.4 kilometers long, the structure that linked Montreal to Brossard, via Île des Soeurs, was made of 200,000 tons of concrete and 25,000 tons of steel. Materials that workers salvaged rather than letting them sink to the depths of the St. Lawrence.

Unlike other doomed bridges, the Champlain Bridge does not; was not intended to be destroyed with explosives. The engineers bet on dismantling the structure, avoiding any maneuver likely to cause it to collapse into the river.

Time-lapse video of the descent of the main span of the old Champlain Bridge.

Antoine Audoynaud , project director of the Nouvel Horizon St-Laurent (NHSL) consortium, which brings together the engineering companies responsible for the work, prefers to speak of deconstruction, not [of] demolition.

The teams coordinating the destruction of the bridge also wanted to prevent the operations from disturbing the fragile ecosystem of the river inhabited by fish and birds, including species with precarious status. In particular, it was necessary to ensure that the parts of the bridge would not end up in the water, since the greases, paints and lead in them could have put these populations at risk.

  • 3.4 kilometers long
  • 200,000 tons of concrete
  • 25,000 tons of steel
  • 42 spans removed
  • 48 piers and 45 footings deconstructed
  • 92 modular trusses dismantled

To carry out this delicate operation , each ton moved was calculated beforehand. And each step, thought out with a view to not upsetting the species that inhabit the St. Lawrence.

The St. Lawrence River has been very disturbed in the past, explains Philippe Larouche, environmental project manager for The Jacques Cartier and Champlain Bridges Incorporated (PJCCI), the federal Crown corporation that is leading the dismantling.

“It is important that we change our ways of doing things, that we put in place the most innovative measures , the most environmentally friendly. »

— Philippe Larouche, environmental project manager at PJCCI

The deconstruction work, which was launched in August 2020, required the installation of a huge temporary pier in the Île des Soeurs sector. Nearly 120,000 tonnes of rock were dumped into the river to allow crews to dismantle the bridge deck on dry land rather than in the water.

The stones of the pier were chosen to prevent erosion or suspended matter from descending into the river, underlines Philippe Larouche.

The report by Dominique Forget and Hélène Morin will be broadcast on the show Découverte Sunday at 6:30 p.m. on ICI RADIO-CANADA TÉLÉ.

As the jetty was on the migratory route of several species of fish – such as bass and lake sturgeon, likely to be designated a vulnerable species – corridors were built to allow water to flow throughout the work.

Oceanographer Stéphane Lorrain, who supervised the installation of these passages, recalls that the fish usually go upstream in the spring to find substrates. Some species can ascend to the Lachine Rapids, he notes.

Underwater cameras and electrodes made it possible to follow the movements of the fish. A sign of the success of the installations, according to Stéphane Lorrain, the runs reached hundreds of fish per day in May 2021.

Catherine Julien and Timothée Ostiguy, environmental consultants, observe cliff swallows that have made their nest in the structure of the bridge.

Other teams have been looking instead for cliff swallows, whose populations have been declining across the country.

These birds that tend to their nest in the rock walls had taken up residence in the structure of the Champlain Bridge. Although netting was installed under the bridge decks to discourage swallows from dwelling there, some nests were still found on the edges of the bridge.

But there was no question of dismantling the structure as long as the chicks were there, for fear of disturbing the nesting period. Each discovery of an active nest led to a stoppage of operations and forced the teams to review the phasing of the work, according to Philippe Larouche.

It's only' x27; once on the floating barges or on the banks of the river, various elements of the bridge could be deconstructed or destroyed to recycle the materials.

Crews first tackled trellises that had been installed to reinforce concrete beams damaged by de-icing salts. In the summer of 2021, workers installed on floating platforms gently lowered these huge 50-ton pieces.

Brought to the docks, these trellises were dismantled before being take the path to the foundries. They are transformed there either into steel beams or into vehicle parts, cites Antoine Audoynaud as an example.

Route 132, a key link for mobility around Montreal, was closed to traffic while demolishing four spans of the bridge.

Of the approximately 40 approach spans that made up the bridge, 30 were deconstructed from the water, between the jetty of the x27; Île des Soeurs and the St. Lawrence Seaway.

This difficult task was carried out thanks to an imposing barge-catamaran. Its surface area, which covers the equivalent of two NHL rinks, and its lifting system, which can reach nine stories and lift up to 4,800 tons, have earned it the nickname “Giant of the River”.

As the barge-catamaran reached almost 5,500 tons once the span was dislodged, the engineers limited the movements of the platform on the river and chose to destroy its cargo using cranes directly on the water.

The impressive barge-catamaran that dismantled the spans of the bridge has been dubbed the “giant of the river .

The concrete was then transported by smaller barges to the wharf before being sent to a recycling center, where it was crushed to be reused in pavements.

Unhooked in the middle of winter 2022, the main span was brought to the banks before being dismantled in the spring. While some pieces were destined for research, the vast majority of them were recycled.

We recycled all the steel materials within a radius of 150 kilometers, explains Philippe Larouche. This is a measure that prevents steel from being put in containers and sent abroad to be recycled and then sold to us.

Other elements of the structure, however, lay at the bottom of the river, such as the concrete footings poured every 50 meters to support the bridge pillars (piers). Girded with barges, steel trays and a rubber membrane, the piles were demolished in a sealed area, where the concrete was recovered.

A sealed area has been set up to allow cranes to demolish the 10 meter wide footings which are were at the bottom of the river.

The soles were also destroyed directly in the water, using sonar and GPS, in an area partitioned off by steel walls.

In the large holes left by the footings, the teams dumped large rocks in order to replenish the natural habitat of the fish.

Of this major operation, which spanned more than three years, only a few pillars will remain, preserved to bear witness to the presence of the Champlain Bridge, which was one era one of the most borrowed in Canada.

PJCCI estimates that the deconstruction work will be completed in the winter of 2024.

June 2019 : Closure of the bridge to traffic.

August 2020 : Beginning of deconstruction in the Île des Soeurs sector.

January 2022 : Dismantling of the main span.

April 2022 : Demolition of cantilevered steel structures in Brossard.

May 2022 : Destruction of piles and footings, at the bottom of the river.

November 2022 : Destruction of spans over Route 132.

January 2024 : Estimated end of work.

Based on a report by Dominique Forget and Hélène Morin, from Discovery

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