brought in Dr. Sauer and Partners, a tunnelling consulting group based out of Salzburg, Austria, to provide the temporary mining support design underneath the subway box that provided structural underpinning support installation. The initial excavation below the subway line took place in six galleries perpendicular to the existing subway boxes. The galleries were designed with shotcrete facing and temporarily supported the subway box above with vertical props. When a gallery was completed, needle beams were installed through the galleries and connected to the plate girders on either side of the subway line. The props were then removed. Mining gallery construction was completed by HC Matcon. During the design phase, it was decided to use the shoring system to support the suspended subway box during the underpinning phase to reduce the number of support caissons required, which would impact the future excavation works and future train testing inside Cedarvale Station. This design change resulted in significant additional load 2,050 kN Live traffic over the job site (460 kips) being carried through the secant pile wall on each side of the existing subway box. The structural plate girders were supported by a recessed connection in the secant pile wall on the south side and structural columns on the north. Jacks were set up on each needle beam and the plate girders to allow adjustments to accommodate movement of the support system during excavation. The support of excavation under the subway adjacent to the underpinning mining galleries was particularly challenging because of very limited space for equipment due to the 2.4 m (8 ft) mining gallery height and 4 m (13 ft) gallery width, further congested Preloading of the walers 74 * DEEP FOUNDATIONS * JAN/FEB 2023