Champlain Bridge Deconstruction

Controlled Demolition of the Spans
Each span, measuring 53.7 m in length and 24.1 m in width, was supported by concrete piers ranging from 10 to 28 m in height. The structure, carrying a post-tensioned concrete deck, consisted of seven (7) precast, prestressed concrete girders, laterally tied by lightly reinforced, post-tensioned concrete diaphragms. Due to deteriorating post-tensioning, modular trusses were previously installed to stabilize the spans and extend the bridge's life.

The demolition methodology had to account for several constraints, including the bridge's construction type, which made traditional demolition methods unsuitable due to the lack of reinforcing steel in the girders and the poor condition of the post-tensioning cables. The St. Lawrence River, a protected wildlife area and a drinking water source for millions, played a central role in the design process, as no debris was allowed to fall into the water, and explosives were prohibited.

Despite the river being more than 3 km wide, its depth varies from only 1.5 m to more than 8 m, and the current speed near the bridge can exceed 5 knots. The cold winter temperatures also posed challenges for maritime equipment selection, access to the structure, and overall work execution.

Innovative Demolition Methodology
In response to these challenges, Delsan-A.I.M. and its partners applied their expertise and professionalism, as no “typical” methods could be used. The final methodology involved removing the entire span, weighing nearly 2,000 tonnes, in a single lift using hydraulic jacking towers mounted on barges positioned beneath the span. The specially engineered system consisted of two (2) rows of three (3) lifting towers, each with an 800-tonne capacity, controlled from a computerized control room on the barge.

The barges transported the lifted span upstream to clear the piers. The span was then lowered and demolished using conventional means with two (2) 40-tonne excavators positioned on an adjacent temporary work platform. The work platform was built on the barge using sea containers. Debris from the demolition was transferred to secondary barges for material handling, shuttling between the demolition barge and a temporary wharf on the shore.

Engineering Challenges and Safety
A significant engineering challenge was the in-house design of a ballast system to enable the lifting and displacement of the 2,000-tonne spans while ensuring stability when deployed at heights greater than 28 meters. Like the hydraulic jacking system, the ballast system was fully automated and controlled by a computer.

According to the jacking system provider, the lifting and displacement of a 2,000-tonne span at over 28 meters in height on a barge had never been done before and was a historic achievement.

Accomplishments and Environmental Management
Despite the complex operations and challenging conditions, the work was completed without incidents, material failures, delays, or environmental damage. Notably, nearly half of the work was done in the winter under subfreezing temperatures on a partially frozen river. Delsan-A.I.M. and its partners adhered to strict health and safety protocols, including established maritime rescue procedures to address risks associated with working on the water.

Environmental monitoring systems were implemented to ensure compliance with project specifications and regulatory requirements concerning air, water, and noise quality. The results confirmed that the demolition operations had no negative environmental effects. In terms of waste management and material recovery, all concrete and steel produced from the demolition were recycled at licensed facilities and/or reused in the regional construction industry.