Abstract Manager

A transit maintenance yard has been designed to facilitate the expansion of the public transportation system in Metro Vancouver. The project involves several key yard structures, including a single-span road overpass, retaining walls, and a guideway embankment that have been designed to address and resolve numerous site constraints. The paper will discuss these constraints and their successful resolution, including design rationale and criteria adopted in the detailed design which was completed in March of 2024.  The yard is bounded by both existing heavy rail tracks and an underground pipeline to the north, a river to the east and south, and a major road to the west. This necessitates careful planning and design to accommodate the proposed maintenance buildings, utilities, and transit tracks within the limited space. Proximity of the pipeline and river also involved constructability considerations in the design. The road overpass is a 30-meter long single-span prestressed concrete box girder bridge gaining access to the interior of the storage tracks. It features a clear deck width of 7.150 meters, accommodating one lane of oversized traffic in each direction for the delivery of transit cars to/from the site, with a raised sidewalk on the south side. The superstructure is supported on MSE wall perched abutments with concrete spread footings founded on granular pads. Box girders were chosen for their benefits in minimizing formwork and field adjustments, particularly in seismic design.  Three Retaining Walls (RWs) serve various functions, including retaining access roads and parking lots, providing grade separation for the yard access, future tracks and sidewalk. RW1 is a cast-in-place concrete cantilever wall, selected for its ability to accommodate buried utilities. RW2 is a reversed cantilever wall, designed to maximize site usage while maintaining grade separation from an existing adjacent roadway. RW3 utilizes top-down excavation and permanent soil anchors to minimize excavation costs.  The guideway embankment employs standard precast MSE retaining wall structures to address geometric constraints and mitigate settlements. Miscellaneous other walls, including Lock Block walls, are designed to meet specific site requirements and maintain grade differences.  The design adheres to the Canadian Highway Bridge Design Code CSA S6:19 and the BC Ministry of Transportation and Infrastructure standards. Seismic design considerations are based on site-specific geotechnical reports, with the site classified primarily as Soil Site Class C. The road overpass is assigned to Seismic Performance Category 3, ensuring compliance with performance criteria for single-span bridges.