Champlain Bridge Deconstruction

Montreal, QC

JCCBI

CLIENT NAME

July 2020 – December 2023

PROJECT DATE

Civil

PROJECT CATEGORY

Abatement, Asset Recovery, Demolition, Recycling

PROJECT SERVICES

The bridge is 3,441 m in length from abutment to abutment and consists of three sections, which are numbered from west to east as 5, 6 and 7. The west and east sections, which have lengths of 2150 m and 528 m respectively, were built using prestressed concrete I-beams spanning between concrete piers and supporting post-tensioned concrete decking paved with asphalt. Section 6, which is the central portion over the St. Lawrence Seaway, consists of steel trusses that also bear on reinforced concrete piers, which support a steel deck with an overall length of 763 m including a cantilevered span of 215 m.

Due to the structural deterioration of the bridge over time from de-icing salts coupled with a poor drainage system, various reinforcement measures and rehabilitation programs were undertaken since the 1990s culminating in the installation of 94 modular steel trusses and 6 shoring systems to stabilize the condition of the bridge girders in the mid-2010s.

The Jacques Cartier and Champlain Bridges Incorporated (JCCBI) – a Canadian Government Crown Corporation – which is responsible for the management, maintenance, and monitoring of the bridge – decided to construct a replacement bridge just downstream from the original construction. The new bridge opened on the 1st of July 2019 and the old one closed to traffic after only 57 years in service.

The project

The Champlain Bridge, which was constructed between 1957 and 1962, spans the St. Lawrence River and Seaway, in Montreal, Quebec, Canada. The bridge provided a critical link for commuters between the city, which is located on an island between two rivers, and the expanding suburbs, while also spurring the economic growth of the region by facilitating transportation to and from the northeastern United States. The bridge, which became one of the busiest in Canada with about 50 million crossings per year, consisted of a six-lane expressway that carried traffic from three different highways (Autoroutes 10, 15, and 20).

Following a tendering process, JCCBI contracted “Nouvel Horizon Saint-Laurent (NHSL)” – which is a joint venture that includes Delsan-A.I.M. Environmental Services Inc. (Delsan-A.I.M.) as a main partner – to undertake the planning, engineering, and deconstruction of the original Champlain Bridge. The overall project started in July 2020 and is scheduled to be completed over a 3-year period by December 2023.

Of particular note was the demolition of thirty (30) spans of the western portion of the bridge, which began in July 2021 and was completed in May 2022. The work entailed a very challenging level of planning and engineering to ensure the safe and successful execution of this part of the overall project.

Each span – having a length of 53.7 m and a width of 24.1 m – was supported on concrete piers that varied in height from 10 to 28 m. The structure, which carried a paved, post-tensioned concrete deck, consisted of seven (7) precast, prestressed concrete girders that were tied laterally using post-tensioned, lightly reinforced concrete, transversal diaphragms. Due to the deterioration of the post-tensioning, modular trusses had previously been installed to maintain the stability of the spans and prolong the life of the bridge.

The design of the demolition methodology needed to take into consideration several constraints including the type of construction, which prevented the spans from being demolished using "traditional" approaches due to not only the lack of reinforcing steel in the girders but also the poor condition of the post-tensioning cables. The St. Lawrence River, which is a protected environment for wildlife and a source of drinking water for millions of people, was also central to the design process since no debris was allowed to fall into the water and explosives were not permitted.

Although the river is more than 3 km wide from one bank to the other, its depth varies widely from only 1.5 m in some places to more than 8 m in others. This factor along with the high current speed of the river near the bridge, which can reach more than 5 knots, and the extremely cold weather conditions that can occur in winter were other important design constraints that affected the choice of maritime equipment, access to the structure, and the overall execution of the work.

Despite these challenges and constraints, Delsan-A.I.M. and its partners put their expertise and professionalism to the test since no "typical" methods could be used. In addition to the many factors that played a role in selecting the method, the safety of the workers, the structural integrity of the bridge, and the protection of the environment were the deciding factors considered in the final choice.

The final methodology that was designed and engineered by our team involved removing the whole span (which weighed almost 2000 tonnes) in one lifting operation using hydraulic jacking towers that were mounted on an assembly of barges and positioned below the span to be removed. The specially engineered system consisted of two (2) rows of three (3) lifting towers having a capacity of 800 tonnes each, which were controlled from a computerized control room located directly on the barge.

Three (3) steel box girders, approximately 47 metres in length, were used to join the two (2) sets of towers. On top of the box girders, a steel platform was then erected to provide bridging for the towers; a supporting structure for the span to be lifted; as well as a work area for demolition and material handling once it was lowered. The entire weight of the temporary support structures and platforms was 4800 tonnes, which was well within the barge’s maximum load capacity of 7000 tonnes.

The barges were used to transport the lifted span upstream to clear the piers. The span was subsequently lowered and demolished directly on the lifting platform by conventional means using two (2), 40-tonne excavators, which were positioned on an adjacent temporary work platform. The work platform consisted of a podium constructed on the barge using sea containers. The debris generated during the demolition was transferred to secondary barges for material handling that shuttled between the demolition barge and a temporary wharf that was set up on the shore.

Steel chutes, which were hydraulically operated, were erected on either side of the platform to make it easier to convey the demolition debris directly into the secondary barges.

Another important engineering challenge was the in-house design of a sophisticated ballasting system to enable the lifting and displacement of the 2000-tonne spans, while ensuring the stability of the system when it was deployed to its maximum height of more than 28 metres. Like the hydraulic jacking system, the ballast system was fully automated and managed by a computer.

According to our jacking system provider, the raising and displacement of a span on a barge of 2000 tonnes at a height greater than 28 m had never been done before and was completed for the first time in history.

Apart from all the above, our greatest achievement was to complete these complex operations under trying conditions without any incidents, material failures, delays, or environmental damage. It should be noted that almost half of the work was completed in the middle of the winter in subfreezing temperatures on a partially frozen river. Delsan-A.I.M. and its partners executed the work in accordance with strict health and safety protocols, which included established maritime rescue procedures to address the risks associated with working on the water in the event of a vessel sinking or a person falling into the water.

Several environmental monitoring systems were set up to ensure compliance with the project specifications and regulatory requirements with respect to air, water, and noise quality. The results demonstrated that the demolition operations had no negative environmental effects. In terms of waste management and material recovery, all the concrete and steel produced by the demolition of the spans was recycled at licensed facilities and/or reused in the regional construction industry.