The Vancouver Convention Centre Expansion Project is an excellent example of collaboration between design and engineering disciplines to create an outstanding project that excels at providing both public amenity and environmental benefits. Careful design by the project landscape architects, engineers, and architects produced the largest non-industrial living roof in North America. This living roof, which helped the overall project attain LEED Gold status, improved the building's energy efficiency, contributes long-absent habitat to the downtown area, and features recycled-blackwater irrigation.
This distinctive project completes the chain of public open spaces that link Stanley Park, the Coal Harbour waterfront, and the existing Convention Centre. The landscape architects completed a seamless extension of Vancouver's iconic seawall and married the disparate architectural forms of the existing and new Convention Centre structures through the use of hardscape materials. Paving materials and patterns act as wayfinding devices, while benches and handrails offer visual unity to this large project. Because the entire structure is on marine deck, the landscape architects worked with the project engineers to devise innovative solutions for the inclusion of tree trenches and planters at the street level.
In the spring of 2009, a fascinating transformation took place in downtown Vancouver. Flushes of grasses and wildflowers began to appear 12 storeys above Coal Harbour and were soon visited by insects, songbirds, and butterflies. This new habitat, absent from the downtown area for over 150 years, is a self-maintaining, self-regenerating living roof; along with the 5800 m2 plaza and seawall promenade extension, the living roof demonstrates the diverse contributions made by the landscape architecture team to the Vancouver Convention Centre Expansion Project.
The 2.4 hectare extensive living roof is a key component to the overall project's achievement of LEED Gold certification. The roof moderates heat gain and loss in the building, improves urban air quality, cleanses and reduces rainwater runoff, and creates valuable habitat. It includes a roof deck, fluid-applied rubber reinforced build-up with root barrier and leak detection grid, and the living roof overlay. The overlay is comprised of a filter cloth layer, 15cm of growing medium, drainage runnels, and a drip irrigation system. The thriving plantings, first tested in a three-year test plot program, include sedges, perennial herbs, and grasses, modeled after British Columbia coastal grasslands for their ability to thrive in climatic extremes and restricted growing depth.
The landscape architects contributed solutions to two major design challenges in the overall project. First, for a structure entirely on marine deck and 40% over water, conventional planting approaches were not possible. The plaza, designed to hold up to 8000 people, did not offer the depth or structural support for tree plantings. Instead, smaller peripheral spaces defined by planters moderate the scale of the plaza and create intimate, comfortable, and flexible areas. The landscape architects also worked with the structural engineers to modify the viaduct truss structure to facilitate tree planting. With these modifications, the trusses now contain enough growing medium to provide continuous trenches for street trees along the south edge of the project.
The second design challenge was to mediate disparate architectural forms. The original Convention Centre and the new expansion feature strikingly different architecture and a 12 meter grade change at the west end. The landscape architects used paving patterns and furnishings as wayfinding devices and unifying elements. Working with the architects, the landscape architects created a grand staircase, complete with fully accessible ramps, between the existing Harbour Green Park and the plaza 12 meters above.
The vocabulary of regional and sustainable materials includes locally sourced growing medium, plants, railings, concrete and basalt pavers, and permeable pavers. Rainwater runnels run throughout the plaza and articulate the district markers at the street ends, celebrating this defining West Coast characteristic. Treated blackwater from the building irrigates both the living roof and the plaza plantings.
PWL's landscape design for the Vancouver Convention Centre Expansion Project features the largest non-industrial living roof in North America and Vancouver's first large plaza for public gatherings and events. The simplicity of the design is an amazing contrast to the complex building and engineering systems, and a model for compatible, progressive, and sustainable urban design.
