Metro Trains and flooded pedestrian subways

On Friday night winter finally hit Melbourne, with over 100 millimetres of rain falling in some areas, leading to flash flooding around the city, and flooded railway station subways around the suburbs.

Flooded subway at Ascot Vale: is it really that hard to maintain drains?

Blackburn is usually the first to go underwater, and on Friday night it didn’t fail to disappoint.

But three more stations were also closed for the same reason.

So why do so many railway station subways in Melbourne end up underwater? The Victorian Rail Industry Operators Group ‘Railway Station Design Standard and Guidelines‘ document has the following to say:

Water migration in Underpasses

The underpass shall be designed such that the ingress of moisture into the subway is kept to an absolute minimum and adequate measures to mitigate the risk of flooding shall be employed. Total area drainage shall be such that the water is removed from the underpass within X time for a 1 in 200 year flood event.

Where a pump or pumps is deemed to be necessary, a staged sump pumping system is to be designed and installed to prevent flooding. The design of the sump pumping system shall consider how maintenance access to the pumping system is to be achieved without disruptions to pedestrian traffic. Where the underpass is the only means of crossing the
track an alarm should be included to indicate flooding and/or operational issues with the sump pumping system.

a) Engineering Requirements:

Where there is a requirement for a pump to be installed to mitigate the risk of
flooding in underpasses the following engineering requirements shall be applied:

  • Pumps shall be an automatic duty/standby arrangement Flygt pump and controls or approved equivalent.
  • Pumps system health and operation shall be monitored by a telemetry system connected to the station alarm network.

So do any pedestrian subways in Melbourne actually have working pumps in them? From the flooding seen on Friday one would assume the answer is ‘zero’ – but last year I actually saw a maintenance crew removing an old sumo pump, and replacing it with a brand new unit.

Replacing the sump pump in the pedestrian subway at Ascot Vale station

Amazing! Metro spending money to replace the sump pump in a pedestrian underpass!

So what about the standards for drainage? Unfortunately the VRIOGS document above only gives us ‘X time’ so we can’t tell – but the frequent flooding suggests either the standards allow a few hours for water to drain away, or that nobody at Metro cares about them.

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9 Responses to “Metro Trains and flooded pedestrian subways”

  1. Daniel says:

    Apart from Friday night, there were problems on Saturday as well. Bayswater (appropriately named?) also went under, for instance. But maybe things are improving – Ormond used to be a regular, but apparently managed okay.

    • Marcus Wong says:

      I wonder if the lack of flooding at Ormond was due to drainage upgrades, or just the heavy rain missing the station. I’ve always associated Blackburn station with regular flooding.

  2. Chris says:

    Surrey Hills used to be first, but considerable effort made a few years ago when the car park was rebuilt as seen it manage well these days.

    Others like Oakleigh survived because of less rainfall in those areas, the heavy rains missed much of the South East.

    As for VRIOGS, all the subways predate the standard, not really fair to use that standard against those subways. Few have built in recent years, but look at Lynbrook and Cardina Road for modern examples.

    • Marcus Wong says:

      I forgot to take into account that only new infrastructure will follow the current standards – the pedestrian subways at Lynbrook and Cardina Road are a lot more ‘open’ than others around Melbourne.

      I’m guessing that any changes to existing infrastructure will require them to meet current standards. Just looking at the steep ramps that lead into most subways suggests that our current infrastructure also has no hope of meeting the Disability Discrimination Act!

  3. Andrew S says:

    As a civil engineer who has designed drainage for a living (and boarded the train at Sandown for many years) I can safely say that pumps there have failed several times before! On top of the surface runoff you get soil infiltration that passes through weep holes into the pumping system (you can see water poring out the subway weep holes for days afterwards. Oakleigh has the benefit of partly covered entrances and plenty of paved areas around leading to runoff entering the stormwater system directly rather than seeping into the subway.

    The pumping systems will be designed to various standards depending on how old they are – and I would guess some of them would be arbitrary!

    Best to avoid pumping if possible is the general rule but the new grade separations we do now involve lowering the rail line at great expense through a long cutting so you don’t see it and many these will require pumping unless the terrain allows a gravity feed out somewhere.

    • Marcus Wong says:

      Covering the entrances to the subways would go a long way to fixing the flooding issues: if the water doesn’t get in to start with, you don’t need to pump it back out again.

      Another way to keep the water out would be to have a small ‘hump’ at the start of the ramp, so that groundwater is directed away from the subway to somewhere else at ground level.

      • Andrew S says:

        I suspect the regular issue at Blackburn is not helped by the car parking/hardstand area on the northern side – runoff can just enter the subway directly but no one seems to have bothered to rectify this issue.

      • FightForRail says:

        The hump idea sounds interesting. Also, the simple act of having a drain grate across the path, the whole width of the path, just above the ramp, would collect and redirect a lot of that water.

  4. FightForRail says:

    Arh, perhaps the solution is always to ‘go over the top’ rather than down and under.

    Perhaps we need bypass access, for the times of such flooding even if you need to put in a level crossing at say the other end of the platform.

    Better design would include;

    + A drain at the top of the ramp to catch water before it will enter the subway

    + Roofing over the entrance area, to stop rain dropping in, and would be a comfort to passengers who do not want to get wet from the rain

    + Somewhere for water to just seep or leak into, such as a basin directly below the floor of the subway. Large enough to catch the dump of the worst known rain storm.

    Under this plan, the flood water would just leak through drain holes, and flood the basement basin. That way, it would not matter of the pump is defective, or if the rain is a little bit stronger than normal.

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