The Knight Street Bridge, owned by TransLink, consists of a 4-lane, 1200m South Bridge; a 6-lane, 250m North Bridge; and a 6-lane, 65m Marine Drive Overpass. With 110,000+ vehicles per day, the bridge is the 2nd busiest crossing in B.C. and carries the highest volume of heavy trucks in the Major Road Network. In 2017, Mott MacDonald was retained by TransLink as prime consultant for design engineering and construction support for the bridge. We developed a comprehensive and systematic rehabilitation plan, identifying a long-term asset preservation strategy to maximize the service life of the bridge, and led a multi-disciplinary team of structural, materials, and environmental experts to complete the project.

To prolong the remaining service life of the bridge deck from 25 to 45 years, we proposed a Polyester Polymer Concrete (PPC) overlay deck replacement instead of a conventional concrete mill-and-fill method, which uses polyester resin as a binder, replacing cement and water in traditional concrete. This durable overlay seals and protects the deck and superstructure below from further chloride ingress that would enable corrosion and delamination, resulting in reduced long-term capital efforts for TransLink. It is a cost-effective and schedule-efficient option, making it a more sustainably conscious choice. The scope included PPC deck overlay replacement with shallow/deep delamination repairs, substructure concrete repairs and bearing replacement, and sidewalk safety improvements with new railing installation and parapet repairs.
The overlay replacement covered nearly 28,000 m2 of deck area and is the largest PPC application on a bridge deck in Western Canada to our understanding.

The project was done in collaboration with TransLink, City of Vancouver, City of Richmond, British Columbia Rapid Transit Company, as well as provincial and federal governments. The Bridge is now a safer, reliable, and resilient main transportation link between Vancouver and Richmond.

TransLink’s priorities for the project were: state of good repair, customer experience/public support, and business efficiency. We met these objectives by addressing the following key challenges:
Asset preservation: Research and cost-benefit analysis over time supported the decision to replace 25mm of the existing overlay with PPC to preserve and extend the service life of the deck below. A thin overlay made efficient use of materials, reduced milling disposals, solved geometric complications associated with the existing elevations of expansion joints and catch basins.

Traffic disruption: With PPC’s quick application and short curing time, deck replacement was completed at night and allowed the bridge to fully reopen to daytime traffic, facilitating a rapid construction timeline and reducing user impacts.

Nature: Ausenco, our environmental consultant, reviewed spill, containment, and erosion control measures and monitor laydown areas and working zones. When peregrine falcon nests were observed underneath the South Bridge, we implemented proactive mitigation measures, which included no-work zones, atmospheric noise monitoring, and a live stream motion detector camera to minimize potential distress.
Future planning: The existing concrete traffic barrier for the sidewalks was upgraded with a railing attachment, improving user safety, encouraging use, setting the stage for an active transportation improvement to the sidewalks, which would involve widening of the structures.

Mott MacDonald provided design engineering and construction support for the Knight Street Bridge Deck Rehabilitation, using PPC for deck overlay replacement. Our technical expertise supported TransLink to strategically preserve the critical bridge structures while balancing capital funding constraints, limiting traffic disruptions on one of the busiest bridges in BC, and minimizing environmental impacts. The PPC overlay will preserve the good condition of the bridge deck for the next 20 years.