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Exploring the CBD Rail Tunnel

The lengthy thread of comments in response to my post about the CBD Rail Tunnel on Tuesday have raised a number of questions about the details of that project that I think are worth exploring a bit further. One interesting point discussed was the issue of the grade of the tunnel, how problematic that might be, and what could potentially be done about it. As I said in the previous post, I really do think that even with only two additional CBD stations (Karangahape Station and Midtown Station) we’re pushing the limits of what is feasible in terms of the tunnel’s grade. Adding more stations could push the gradient over the acceptable limit – thereby potentially creating a rather unsolvable problem.

Previous studies into the CBD Rail Tunnel also recognised this potential problem. The URS/GHD study in 2004 provides us with the most detailed map yet of the potential alignment of the railway tunnel – although there is currently a study underway to provide us with a final design, put together a business case for the project and prepare the necessary documentation to lodge a notice of requirement. But anyway, in terms of the grade of the tunnel, the URS/GHD study suggested that this could be eased by effectively lowering the section of the western line (or at least the links between the CBD Rail Tunnel and the Western Line) around the Mt Eden station – thereby reducing the height the tunnel would need to climb to and reducing its overall grade.

This is shown in the URS/GHD map below – which also gives us a reasonable indication of where they thought the stations should be located:CBDloop-route One interesting aspect of this alignment is that the Mt Eden station would be shifted away from its current alignment on the Western Line and actually into the rail tunnel – basically underneath Exmouth Street. I think this is a pretty good idea, as it would make it possible for trains heading to the tunnel from the west or south (or vice versa) to access the station. While the odd train from the west to Britomart via Newmarket (probably the services using diesel trains from Huapai) wouldn’t stop at this station, I don’t think that’s a big problem. Furthermore, the current Mt Eden station is located fairly poorly in my opinion – hidden away behind a bunch of buildings – while the new one could have good access off New North Road and Newton Road. It would probably need its name changed to Eden Terrace station or Newton station – but I don’t think that’s a problem.

In the diagram below is my idea for how this end of the rail tunnel could work. The green lines show parts of the track that would effectively be a lowered trench (to reduce the tunnel’s grade), while red lines are the tunnel. The extent of the station is shown, while the blue crosses mark where I think there could be entrances and exits from the station:eden-terrace-station copy The next image looks at the Karangahape Road station. This station would be quite deep, at around 20 metres below ground level by my calculations. The depth is necessary because at a constant grade of 1 in 35 the tunnel will be around 40m above sea level by the time it reaches the Karangahape Road ridge – whereas the ridge itself (along which the road runs) is around 60m above sea level. 20 metre deep stations certainly are not unheard of around the world, so I don’t see this as a show-stopper. However, it will be an expensive station to construct.

Once again, the red line shows where I think the tracks might go (they generally follow road alignments to minimise the number of strata titles that would need to be purchased) and the blue crosses mark possible entry/exit points:k-road-station copy And finally, let’s have a look at the Midtown station. This station would basically be built underneath Albert Street within the block that stretches from Victoria Street to Wellesley Street. One very good thing about this station is that it could have excellent access to Queen Street via the Atrium on Elloitt shopping centre and Darby Street, which by good coincidence is going to be turned into a pedestrian mall in the near future. Midtown station is likely to rival Britomart as Auckland’s busiest station in the future – particularly as its location is right in the heart of the CBD and it is a relatively short walk from the university. The blue cross in the map below that is some distance from the station itself shows where the main entrance from the Queen Street side of the station would be – at the northern end of the Atrium on Elliott shopping centre as I stated above:midtown-station copy I must say it certainly will be interesting to see what the current study into this project comes up with – and whether there are any significantly altered alignments from what I have outlined above.

14 comments to Exploring the CBD Rail Tunnel

  • Jeremy Harris

    Yes what you outline is the most cost effective way the project can be built while still providing transformational benefits… All the stations would be very busy and patronage throughout Auckland would skyrocket…

  • It would certainly revolutionise the K Road area and probably encourage a lot of redevelopment, which is a good thing. Furthermore, if the Eden Terrace station was built I would encourage council to effectively reclassify the Newton area as part of the CBD in terms of its planning rules.

  • Nicholas O'Kane

    This will not only revolutionize public transport in Auckland, but possibly also the CBD.

    Regarding the timetable, the study should be complete in December 2010.

    I don’t know how much the study will cover, but I imagine:
    a) route determinination
    b) station locations (including depth and entrances)
    c) geological evaluations (rock types).
    d) cost/benefit ratio, economic assesment (including patronage increases)

    Once the first study is complete I hope that by 2012 we can have the design fuly complete and construction ready to start. This will allow it to be built by 2018, and set us up to have the airport link by 2025ish.

  • George D

    What about a third Myers Park entrance to the K Rd station? It would open the station up to a valuable part of the urban environment.

    I also think that Beresford St could be a great place for putting a main entrance into the station.

  • I think that’s a realistic timetable Nicholas. The only hitch is somehow getting the $1.5 billion to pay for it.

    George, yeah it’ll be interesting to see where entrances are put. Generally underground stations have a concourse immediately below ground level, with a number of entry points – and then have the escalators from there taking you down to the platforms.

  • Jeremy Harris

    The council could rezone CBD to end at the railway rather than the CMJ from the NW motorway across to Symonds –> Mt Eden Rd…

  • Yeah that area of Newton/Eden Terrace already has a Business Mixed Use zone, which allows for a range of activities at a reasonable density.

    However, unlike the CBD it still has minimum parking requirements, which means that an awfully large amount of land is still wasted on carparking for a part of the city that is within walking distance of the CBD and has superb public transport access (particularly once there’s a railway station in the middle of it).

    I suppose that the new Super City will have drawn up a whole new District Plan by the time this project is anywhere near completion – so perhaps the planning changes will come before the CBD Rail Tunnel. Which would further enhance the need for the project.

  • Tobias Barkley

    How does spaghetti junction affect the tunnel route? I would guess 20m below ground at K’rd would be somewhat close to the motorway altitude in Newton Gully. Has anyone addressed this?

  • I don’t think the motorway is that far below the K Road ridge. I suspect the rail tracks will pass about 10 metres below the motorway.

  • Nick R

    Jarbs, could you do us all a favour and post the long section out of the URS report, the one that shows the tunnel depth along it’s route.

    I think that the main Midtown station entrance should be in the new Elliot tower site, so that it leads directly onto the newly pedestrianised Darby st. Also, a concourse at the southern end that connects to Queen St near the civic and to Bledisloe lane (leading to Aotea Square) would be on my wish list.

    I would assume that the K Rd station ‘box’ will be entirely north of K Rd, as the Mercury Lane road reserve is very narrow while the Pitt St one is very wide. Beresford square would be an obvious entrance location, rather than the fairly narrow footpath on the corner of K Rd itself.

    I have always thought that St Kevins Arcade (and possibly the George Courts Building opposite) could make a fantastic main entrance, as these two buildings were designed to allow access of a large number of people through their grand entrances. They are both a fair way away from where the station box would be, however given the fair amount of depth to cover via long escalators it is unlikely the station concourse would be directly over the platforms anyway.

    I really hope they design the platforms according to the ‘spanish solution’ style. They need to go into this project with the possibiliy of 90 sec headways on the cards. There is a lot of capital to be sunk into this infrastructure that might still be serving the city 100 years later, so they do need to spend a little extra to make sure it can operate a worlds best practice in the future, rather than the 10 min headways that have been talked about in the past.

  • Nick I would love to post those long sections but unfortunately I don’t have the URS/GHD report – just that map from it. I do agree with you regarding the need to design the CBD Rail Tunnel for very high capacity – as I can’t see us winning the argument for it to be a four-track tunnel.

  • Nick R

    Oh, I thought you had it. I’ll fish it off my old hard drive and send it to you.

    Four tracks would be ideal in a perfect world but in the real world I think that is simply impossible, so yes it should be a case of getting the maximum out of the two track tunnel as possible.

    So the tunnel should be designed to eventually handle eight car sets at 90sec headways, including the stations/ platforms and the connecting junctions. I can’t see how it would cost that much more to do that rather than the base case.
    A basic tunnel for six car sets at three minute headways could handle around 24,000 pax per hour. That alone would be fantastic, but a tunnel that can handle eight car sets every 90 sec could carry more than double, but it certainly wouldn’t double the cost of the project to ensure flying junctions at either end and a platform design that can handle that many people.

    Any you already know my thoughts on avoiding Britomart terminal and building new tunnel platforms alongside.

  • It would be great if you could send that through – plus anything else you think I might be interested in.

  • Nick R

    Hmmm, if I get stuck into my old collection of Auckland transport reports and maps I would have to post you a DVD or two!

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