Friday, October 23, 2009

DOTT plans affect west side residents (ix): downtown west station

The western most downtown station would be located deep under Albert Street * in the block between Kent and Bay. There will be two major entrances for the "base" station design. If developers wish to tie in, there could be more.

One entrance will be right where the CS CoOp building is now. The entire block housing the CoOp is to be purchased by the City for the new library project. If the library is under construction at the same time as the DOTT, then the station will be incorporated into the Library. If the Library is to be constructed at a later time, then a permanent elevator and escalator facilities will be built up from the underground station to the surface at the present CoOp location with a temporary building at the surface, which would later be incorporated into the new Library building.

The second entrance will be on the north side of Albert, in front of Place de Ville (PDV) right where the existing transitway bus stop is by the fountain and pyramid skylight into the PDV underground concourse. There will be a building at that location to weather-protect the entrances to the elevators and escalators going down. The surface facilities will intrude on the private property of PDV, in return for that, there will be a direct connection from the escalators and elevators into the PDV concourse. So this station at least will have some elements of the "underground city" some people want to see. It remains to be seen if the city can convince PDV to permit ongoing connections of their concourse to other buildings, such as the proposed ones immediately to the east or 240 Sparks (PDV has not connected to adjacent concourses over the last 25 years and I dont think they are likely to change that since their concourse - and buildings above - will have higher value being exclusively on the DOTT).

The DOTT planners also show a possible connection from an underground mezzanine in the escalator area across the street to Constitution Square complex. The City does not plan to build this connection (they provide two access elevators/escalators sets per station), the owners of Constitution would have to do this. Note that the connection would permit transit users to access Constitution Sq and thus weather-proof connections to Slater Street and Kent, but the link is from a mezzanine level below that of the PDV concourse. It is not a connection of the PDV concourse to another complex. Users could travel through PDV, enter the fare-paid zone of the transit station, travel down one or more floors, and then exit the station again towards Constitution Square. Do-able, but not convenient.

* Critics of the tunnel depth should note that the ground elevation of downtown Ottawa varies significantly, even though we generally view it as "flat". The tunnel will be deepest underground at the eastern downtown station, shallower at Rideau and Campus. The exact depth of the tunnel will be determined based on the results of bore holes to be drilled in the next planning phase. If the rock conditions are excellent, the tunnel might be shallower than if rock conditions are fractured. The planning to date assumes the worst, and keeps the tunnel deep.


  1. First, I am recent to gathering detail on this project beyond city releases and compliment you on your even handed and complete treatment of the issue. In Washington DC all transit is wheelchair accessible even the underground metro. Do we know if disabled access is planned?

  2. The reason for the depth of the tunnels is twofold:
    (1) to go beneath certain underground parkades, a requirement of the so-called "cross-country" routing
    (2) to be able to mine out the stations from below in a cavern-like fashion

    The 1988 bus tunnel study also called for bored tunnels (one each under Albert and Slater, but going counterflow - i.e. east under Albert, west under Slater) with stations built by cut-and-cover. The stations would have been 'H-shaped' with the connecting segment underneath a north-south street - which is why the tunnels were to be counterflow. At any rate, the depth requirement this time is only partly related to rock conditions in the sense that it is the rock cover above the top of the station caverns that is defining the bore depth rather than the cover above the bores themselves. Since the caverns will be bigger than the boreholes, even more rock cover is required.

    This study is quite a departure from all previous tunnel studies/ideas (going back to the Holt Report). All previous studies had assumed either full cut-and-cover of the entire tunnel OR bored tunnels with cut-and-cover stations, but here we have bored tunnels and mined stations.

    The upshot is that the tunnel could be made considerably shallower by sticking to an alignment under a street or at least by avoiding going beneath buildings with deep foundations (it's notable that no one has thought to tunnel into the lowest level of an underground parkade... especially at the Rideau Centre) and by using cut-and-cover for the stations.

  3. all facilities will be wheelchair and accessible. Indeed, there will be many long ramps since the ramp slope is to 20:1 !