Montréal's Darwin Bridges

Provencher_Roy’s reconstruction of the Montréal's Darwin Bridges on Nuns’ Island makes noteworthy use of locally sourced recycled glass, a world premiere (ground glass pozzolan or GGP).

Nearly 60 years old, the Darwin Bridges on Nuns’ Island had endured the ravages of time and erosion. In fact, the tightening of the sidewalks was beginning to cause discomfort for pedestrians, bicycles, and strollers alike; and the passage underneath the bridges was starting to accumulate puddles of water amidst limited visibility. Ville de Montréal therefore called upon Provencher_Roy to reconstruct this emblematic infrastructure, and simultaneously bring the design up to code. The great novelty of this bridge construction lies in the unprecedented materials choice. The bridges were built with cast-in-place concrete, composed of 10% finely ground recycled glass. In fact, this ground-breaking project builds upon 17 years of research on the integration of ground glass into civic infrastructures, in collaboration with the Université de Sherbrooke and Ville de Montréal. A world premiere, this 100% Québécois patented GGP invention was added as a ternary binder, enabling the project to make a direct environmental impact by reducing greenhouse gas emissions by 40 tonnes, the equivalent of driving 200,000 kilometres in a vehicle. The GGP used replaced the cement typically used, constituting 40,000 kilograms of locally recycled glass and representing 70,000 wine bottles. The architectural team developed the whitest GGP possible for the bridges, characterized by a less raw colour than traditional aggregates. It is also much more solid, due to the addition of stainless steel bars to reinforce the lifespan of the bridges, estimated at over 125 years, compared to 75 years for a typical concrete structure. The design is currently a candidate for ENVISION environmental certification, the urban infrastructure equivalent of LEED. The Darwin Bridges act as the meeting place of an ordered circulation, at the crossroads of a Nuns’ Island urban boulevard and pedestrian and cycling path. Our intention therefore reconciles these two rudimentary propositions in the development of a solution that at once enhances the architectural language and fulfills safety regulations. Between the two bridges, the central median strip was opened up and dug out. Starting from the highway, two circular arches descend the slope towards the cycling path, delineating the pedestrian crossing enclave and revealing a landscape design opportunity manifested in strategically placed retaining walls between the bridges to create vegetated terrace levels, a nod to the nearby Parc de West-Vancouver. The exterior-facing sides of the bridges are adorned with hollowed-out half-circles and flower stems, creating the illusion of a low-relief of stylized flowers, while at nightfall, the pathway becomes illuminated with warm tones, thanks to sustainable LED lighting. This pleasant opening up of the space, along with the integration of safety lighting fixtures under the bridges, inspire safety amongst users and prevent tunnel sensations.