Historical pic of the Dunsmuir Tunnel portal at Portal Park before the area was covered over.
Page 12 of the Transit Museum Society SkyTrain Gallery.
https://transitmuseumsociety.org/wp/photo-albums-skytrain/
On Page 9 is an east facing view.
You can see some footings for the future Waterfront Centre complex already set between the tracks to avoid future disruption.
https://transitmuseumsociety.org/wp/photo-albums-skytrain/
On Page 2 is this pic showing the other end of the waterfront area with the Canada Gate to Expo 86's Canada Pavilion at Canada Place.
Note the footings between the tracks.
The current Howe St. entrance to Waterfront Station was within Expo grounds and fed people from the main Expo 86 site via SkyTrain. The platform at Waterfront was divided longitudinally (lengthwise) with a chain link fence with one side having revenue service (access from the CP Station) and the other side having Expo 86 shuttle service (access from the Expo Howe St. entrance) from the Stadium Station 3rd platform.
https://transitmuseumsociety.org/wp/photo-albums-skytrain/