Thursday, June 4, 2009

DOTT Station Depth, Tie-Ins to Buildings, Etc.

There has been a lot of concern lately about the deep depth of the downtown Ottawa transit tunnel(s).

I share that unease. But I also sense that critics of anyLRT/tunnel/initiative are also seizing on this one issue as it is a safe one to pile onto.

Recall that the shallower tunnel schemes mean that the tunnel has to fit between the existing buildings of the downtown. Neither Albert nor Slater are wide. Utilities are burried under the road and sidewalk surfaces. If the station is under the street, the access points will likely have to be up through existing buildings (for eg Albert between Bank and Elgin is 100% built out already). Following Albert or Slater means the LRT line will pass south of the Rideau Street rather than on Rideau/the Market, and will in any case be very deep under the MacKenzie King Bridge (I gather it is nigh impossible to bring it up from underground to use the bridge surface, due to NAC garage, utilities, etc).
It would also be difficult to put a spacious centre-platform station into the narrow Albert right of way - and few people liked the alternative of having one tunnel under Albert and the other way under Slater.

Going deep allows for spacious platforms and stations, and the 'cross country' route, which in my mind is the best route (although I don't like the depth we end up with...).

I expect some people want shallow stations that open directly into underground concourses such as Place de Ville. But in any scenario the stations would be much much deeper, and (multiple) escalators will be required. What happens once users exit into say, Place de Ville. Please do not dream of a connected underground city. Pl de Ville has for decades refused to connect its mall to 240 Sparks, Constitution Sq or other adjacent developments. I suspect other landlords also feel the highest and best capture of revenue and benefits is to be one of the very few buildings directly connected to the DOTT. In this scenario, a shallow station will only connect to the first adjacent building.

But if the stations are very deep, then a horizontal pedestrian tunnel can be run out north/south (or any other desirable direction) from the mezzanine level of the new station, underneath the nearest building and 'up access' can be built to several building complexes, sometimes a few blocks away.

But what are the probabilties of such connections? I personally think they are very low, for these reasons: First, the downtown office building market is not a open market, there is essentially only one tennant, the Feds. What landlord wants to increase his expenses to land a price-conscious tennant who probably won't pay extra to have a direct link to transit? In Toronto, or NYC, there is competition for tennants, and a transit link is a marketing advantage, that can be paid for by increased rents. Those rules don't work in Ottawa. I hope the (Delcan / Toronto / London )consultants realize that our market is different.

Second, Toronto, NYC, and other places are much larger than Ottawa, with larger (higher) downtown buildings. Thousands of people per hour access 70 storey buildings, enough to crowd the surface sidewalks and fill up the underground concourses. In Ottawa, buildings are not very big, and I dont think we can support two "streets" - one at sidewalk level, one underground. Minneapolis is my example for that. Also, those landlords that have built concourses like Pl de Ville, 240 Sparks, L'Esplanade Laurier, 90 Sparks, are busy shrinking these malls and converting them into office space or dentist offices.

Thirdly, Ottawa has a downtown ghosttown once the civil servants flee their cubicles. There are few apartments or street amenities/bistros, etc now. It will be even more barren if half the crowds are underground. I fear the underground concourses, if connected, will render the downtown more barren and sterile than it now is. Let's not go there.

One thing to keep in mind that is of benefit in having deep tunnels is the operating economy of the trains. As the trains cross LeBreton Flats and enter the tunnel at the LeBreton Station they will continue straight under the city, the track need not descend nor ascend, because the surface level conveniently rises up to let the train continue on the level. The deep tunnel means gentle turns on both sides of the Rideau Station, for a smoother ride and less wheel wear and tear. Of course, the possible savings in running flat, with gentle turns, is then lost by the extensive and expensive access required to the stations. At the other end of the tunnel, it exits the tunnel at Campus Station with only a gentle downhill glide towards the next station at Lees.

Keep in mind too that this tunnel is the first, but may not be the last, underground transit tunnel. ( I am looking VERY long term here). A deep tunnel can be linked to other future deep tunnels, which is not possible if the tunnel is sandwiched between building foundations. Image the circle route through downtown Ottawa to downtown Gatineau using the DOTT tunnel now, but if traffic grows (on either the ottawa or gatineau routes) , maybe someday it would need its own tunnel if volumes warranted. If peak oil is real, if cities spend the next 60 years getting much much denser ... we should leave the option open to expand the tunnel system.

The choice of a deep tunnel is not a whim of the consultants and staff. It was made during the evaluation of a bunch of other, related factors, like station configuration, location, routing, train operating costs, station costs. If critics kill the deep tunnel option, are they prepared to accept the consequences that follow, or will they then pile on to criticise the next feature they don't like, like the reduced routing options or the narrow platform stations that result? Nibbled to death by fishes ....


  1. Albert and Slater are 60' wide, or about 20 m. The two single bores would be 5-6 m each. That leaves 8-10 m, which is plenty wide enough for a spacious platform. It also ignores the fact that not the full width of the 5-6 m is actually needed at the stations, so there are a couple more metres available. The deep cross-country route was not premised on wide stations. It was premised on getting what is thought to be a better alignment but mainly, I think, so that the stations can be mined out from below rather than dug down from above, thereby reducing on-street disruption. That's the likely rationale.

    You should read the 1998 Bus Tunnel study. While I don't think much of creating a bus sewer, the principles of tunnels remain common with LRT. Most of the principles identified in that study have been thoroughly violated in this one.

    Where did you get the idea that the tunnel depth allows it to be run in horizontally from LeBreton Flats? It doesn't - LeBreton Flats is not 10 storeys below the streets of downtown Ottawa. It's maybe 3 storeys down. That tunnel will be descending a long way over its journey once it enters the portal. A shallow tunnel, by contrast, would be close to level.

  2. I don't always agree with you, but I'm behind you 100% on this issue. Yes, we should be scrutinizing this tunnel carefully, but I think critics have latched on to the tunnel depth unneccessarily. As you say, a deep tunnel will be more economical to run, have more room for stations and be much easier to build. I'd also much rather have the long, gentle curve between a Sussex\Rideau station and Campus than the tight turn that would be required for a station at Mackenzie King. With a modern subway, there'd be no excuse for building a rail curve with a tigh radius like that, which would likely be loud and uncomfortable—see the approach to the TTC's Union station for an example.

    Back to tunnel depth, I also think a lot of people forget how deep the Montreal Metro is. Many stations have platforms 20, even 30metres below the surface, and that doesn't seem to affect things there too terribly. It just means people have to spend an extra thirty seconds on an escalator. No big deal, in the grand scheme of things.

  3. The new LRT track along the transitway will be at least 2m below the current road surface, if I recall correctly. The elevation of the transitway at Booth is 56m according to google earth; the intersection of Bank and Albert is 72m. Lower the transitway at Booth by 2m to 54m, the difference in elevation between the LRT track at Booth and downtown is 18m or 54 feet. So it is probable that the LRT will slope down as it goes under the downtown.

    -Eric Darwin