Using light rail transit to integrate a diverse and growing regional population with its city centre

The Valley Line Southeast travels along a wide variety of environments on its 13-kilometre route, requiring an array of structures, stations, facilities, tunnels and reinforcements. The line includes 11 at-grade stops, a transfer connection downtown to Edmonton’s existing high-floor LRT lines, an elevated station with a park-and-ride facility and a full transit centre, an operations and maintenance facility, a 400-metre double bore tunnel (total of 800 metres) and two kilometres of elevated guideways and bridges, including the signature Tawatinâ Bridge spanning the North Saskatchewan River. 

The city opted for a low-floor LRT system to enhance accessibility, connectivity and environmental and community integration. Low-floor trains open at street level for step-free boarding. Relative to traditional LRT systems, low-floor transit also requires relatively minimal infrastructure and allows for smaller, more frequent stops.

As a shared-use system, the line operates in alignment with traffic signaling and responds to changing contexts as it travels through densely populated areas. The route design safely integrates with various traffic modes, speeds and flow, interfacing roadways, sidewalks and bicycle lanes, creating pedestrian-friendly zones around stops and stations. Depending on the needs of the location, Arup integrated cues, such as visual and audible signals at intersections, mid-block crossings, and landscaping, that indicate the relative transit opportunities for drivers, pedestrians and cyclists.

Expressing local and cultural input

The new route’s structures also reflect the feel and character of the city’s variety of distinctive neighbourhoods with culturally relevant designs guided by public input—part of the city’s extensive and ongoing public engagement throughout the course of the project. Station design themes reflect the collective decisions of their respective area residents in five distinct zones along the LRT. For the tunnel portal adjoining Chinatown, the design incorporates a Chinese pagoda style in celebration of the neighbourhood, for example. During the detailed design phase, Arup ensured these community-driven design features adhered to safety features and structural requirements. Additionally, Arup devised opportunities for integrating public art into the new line’s structures. 

As the Valley Line Southeast travels from downtown to the north bank of the North Saskatchewan River, the route preserves the landscape of Edmonton’s prized River Valley Park system by tunneling beneath it and being elevated above it. Construction of the tunnel required measures to substantially stabilize the south portal of the tunnel, which is located on a hill with a history of major landslides. We designed a geotechnical solution of reinforced drilled shafts and soil nails to secure the tunnel infrastructure in case of future slides. 

Arup used state of the art 3D geo-structural modeling tools to develop integrated designs for landslide stabilization and tunnel excavation in this challenging geology. Our resulting tunnel design includes a double-shell lining system to seal it from groundwater and ground gas. Arup also conducted advanced 2D and 3D numerical modeling to ensure constructability and limit surface movement while tunneling beneath busy roadways. 

A distinctive structure that reduces construction costs

The Valley Line Southeast LRT emerges from the south tunnel portal by an elevated guideway leading to the Arup-designed Tawatinâ Bridge, which crosses the North Saskatchewan River. The 260-metre extradosed bridge balances the natural aesthetics of the river valley with a distinctive structure. In this unique design, a concrete box girder supports the rail, and a lightweight steel bridge for pedestrians and cyclists is suspended from below, connecting them to river valley trails on both sides of the river, eliminating the need for unsightly ramp structures. Arup also designed the innovative U-shape trough girders that enable the train to ride at a lower profile, which also creates less demand on the substructure, reducing construction costs. 

Low-impact strategies for the environment

To reinforce the city’s efforts to improve environmental sustainability of transit projects, low-impact development approaches were incorporated along the LRT corridor, including dry and wet ponds, rain gardens, enhanced grass swales and a multitude of structural soil cells integrated within the landscaped boulevard to promote infiltration. Arup relied on its extensive worldwide expertise in urban water management to deliver and amplify this aspect of the project scope.