These large ducts are for the 230 kV transmission cables that were stored on the south side of the MX tracks for a while. They are replacing 3 old circuits that bring energy in from the Portlands Energy Centre and previously from the Hearn Generating Station to the Esplanade Transmission Station on Lower Sherbourne. There may be a duct per cable - 3 conductor cables, plus a neutral cable per circuit. The structures that supported the 2 overhead circuits have been removed to make room for the extra 2 tracks from the Don Yard to Union station and for the expanded Wilson Yard.
The location of the previous structures are shown below.
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