Demolition of Fairview Overpass
Location: Halifax, NS, Canada
Client: Dexter Construction
Duration: 2009
Approximate Value: $1.0 M
Key Staff: Robbie Fraser
Project Description
In 2009, the Fairview overpass was slated for demolition. The bridge was set to be redesigned and replaced due to the age and condition of the existing structure. This was coupled with the fact that the structure was similar in construction to that of the highway overpass in Laval Quebec that collapsed in 2006. The critical detail of concern was the bearing support corbel for the middle drop in span that was lightly reinforced and inaccessible for proper condition surveys.
Harbourside’s Role
Hired by Dexter Construction, Harbourside developed the full demolition design and phasing for the existing south structure of the Fairview Overpass. HEC developed a demolition method that involved removing the deck and interior diaphragms from the top of the structure while avoiding a potential overload in the corbel areas. To do so, cranes were positioned beneath the structure and the concrete girder segments were lifted onto a flatbed truck. The interior drop-in span girders were removed first, followed by the exterior spans.
In addition to ensuring the stability of the girders throughout the demolition operation, Harbourside also developed crane positions for each phase, ensuring that the lifts were within the limits of the available crane sizes. The detailed plan ensured that all demolition operations were completed within the allowable closures for both Joseph Howe Drive and the adjacent rail line.
Unique Challenges
At the onset of the project there were significant concerns from citizens as to the delays that would result on both the Bedford Highway (above) and Joseph Howe Drive (below), both of which are major arteries for vehicles travelling onto or off the Halifax peninsula. The detailed demolition plan limited closures and delays on both roads to the point where public sentiment throughout the actual demolition was overwhelmingly positive.
Social Impact
The necessary demolition, and subsequent replacement, of the Fairview overpass was an important endeavour in ensuring the continued safety of Haligonians. Age of the structure aside, its design led to an increased risk that could not be ignored. Its removal prevents a similar tragedy as to what occurred in Laval, Quebec in 2006.