Why did the MRT tunnel flood?

By October 17, 2017Current

TL;DR – Three feet of snow does not form in a day.

A week after SMRT tunnels flooded, Mr Desmond Kuek, CEO of SMRT, has finally come out to apologise for the incident. Even SMRT Chairman Seah Moon Ming was also present at the press conference to face the media and to make an apology.


At the press conference, SMRT also explained what caused the incident.

We picked out three interesting points from the press conference.

1. Pump had a single point of failure, which failed

There is a huge storm water pit underneath the tracks where water can flow into. Water was supposed to flow into that pit instead of flooding the tracks. When the water level in the storm water pit reaches a certain level, there are pumps that pump out the water. This ensures that the storm pit never gets full.

Water pump at the Bishan storm water pit. (Photo: LTA)

Unfortunately, the pumps didn’t work, the storm pit was filled up. And when the rain came pouring down over the weekend, the water had no where to go, which resulted in the tunnel being flooded. The thing is, only one small part of the pump didn’t work – the stop switch didn’t close.

The whole system has a series of floats that triggers different things. At the lowest level, there is a stop switch. If the water level is below the float of the stop switch is open, all the pumps switch off. This is to prevent the pumps from running dry, which could cause overheating and damage the pump. When the water level rises above the float of the stop switch, the switch will close. If the switch doesn’t close, the pumps will not run.

If the stop switch is closed and the water level rises to the next float, then the first duty pump starts working to pump out the water. If the water level rises to the next float, then the second duty pump starts working. If the water still rises and hits the next float, the standby pump starts working. If the water still rises, then the last float will trigger a high level alarm.

Unfortunately, the stop switch couldn’t close, even though the storm water pit was full of water.

It was found that the bottom of the storm water pit was lined with debris and sludge. That was likely to be what prevented the lowest float from closing the stop switch, which consequently prevented the three pumps from working even when the water levels rose to fill the storm water pit.

The bottom of the Bishan storm water pit was functional but lined with sludge. (Photo: LTA)

2. Lapses in maintenance likely reason why stop switch failed

Apparently, that happened because of lapses in maintenance. The whole system was supposed to be inspected and maintained once a quarter. This quarter’s maintenance was supposed to have happened in September. However, the maintenance team apparently couldn’t get get a slot to access the track during engineering hours. As such, the missed the September date.


3. Future steps to prevent this from happening

Recognising that it’s not safe to have a single point of failure, SMRT will work with LTA to design backup flood prevention systems that work independently. These are known as redundancies. Which sounds like a waste of money, but redundant and independent measures are necessary to ensure that no single point of failure will cripple the entire system.

One of the redundancies that SMRT is looking to put in is to use radar sensors to activate pumps. Also, SMRT will increase the frequency of checks on water pumps and flood sensors from once a quarter to once a month.

Increased investments in maintenance

These measures will increase the expenditure in maintenance. And they come on top of a whole slew of other measures already put in place to improve the maintenance of the train systems. For example, the staff strength of Trains team has increased from 3,500 to 5,000.

Also, SMRT has set up a Technology Management Office in 2014 to develop condition monitoring tools for critical systems, and this year started a Future Systems Office to harness digital technology and data analytics for predictive maintenance so that rail excellence can be achieved and, more importantly, sustained in an affordable way into the future.

SMRT would never have incurred such expenses under the previous CEO, Saw Phaik Hwa. From what we understand, she was obsessed with increasing profit margins, and was completely against spending on engineering and maintenance. As a result, many pieces of equipment on the sprawling train network operated by SMRT are in a very bad state.

But it seems that the current CEO, Mr Kuek, sees expenditure in maintenance as an investment. Unfortunately for him, he has to undo many years of neglect and damage.

That’s not an easy task. He doesn’t have infinite resources at his disposal. He has a time constraint. He therefore has to prioritise. As a result, things will still be breaking down even as the SMRT team fixes different parts of the system.

It’s like trying to change a tyre when it’s still in motion.


Yes, we are all angry.

And yes, it’s tempting to ask him to leave.

But if he leaves now, who is going to take over him? And if someone else takes over, chances are, there will be a halt in all the work that is being done to improve the stability and reliability of the train systems. That would be disruptive and delay much needed maintenance work.

And, just as it took years before the neglect under the regime of the previous CEO to result in major disruptions (she was CEO for about 10 years), it could well take the same amount of time before the efforts of the current CEO to bear fruit (Mr Kuek took over as CEO in late 2012).

That said, let’s hope that the team can work a little bit harder, and we can see significant improvements in the system soon.

You can watch the full Q&A from yesterday here.


Don't be selfish... Click here to share this on Facebook!

If you like what you read, follow us on Facebook to get the latest updates.

Jake Koh

Author Jake Koh

Recovering sushi addict, I'm a man of mystery and power, whose power is exceeded only by his mystery.

More posts by Jake Koh

Leave a Reply