MRT disruption 'could have been avoided', says expert

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Call for more checks and back-up system after one of the worst delays to hit train network since 2011

Transport experts have called for more measures to be taken to prevent a repeat of a nearly 21-hour disruption of the North-South Line over the weekend, one of the worst here since 2011.

A malfunction in a water pumping system had caused flooding in the MRT tunnels.

Experts said more checks and having a back-up system could prevent a repeat of the incident.

Thousands of commuters on a 13-station stretch of the North-South Line from Ang Mo Kio to Marina South Pier were affected when services were halted for more than four hours on Saturday night.

More than 40 buses from SMRT and SBS Transit were deployed for bridging services and officers from the Singapore Civil Defence Force, PUB, Land Transport Authority and SMRT worked overnight to clear water from the tunnel and restore train services.

The disruption stretched further yesterday - services between Ang Mo Kio and Newton MRT station were restored only at 1.50pm.

Yesterday, LTA said preliminary investigations showed that water had entered the tunnels between Bishan and Braddell stations through the opening near Bishan station - where aboveground rail tracks transit underground - after Saturday afternoon's downpour.

MRT tunnels are equipped with pumps designed to kick in when water enters the tunnels.

Usually, rainwater run-off accumulated in the adjacent storm water sump pit - designed to collect water - would be siphoned off by pumps, said LTA.

But on Saturday, the water pumps failed, causing rainwater to overflow into the tunnel opening and accumulate at the lowest point of the Bishan and Braddell stretch of the tunnel.

SMRT deactivated the trackside power supply as a safety measure, and the pump system has been repaired. Investigations into the cause of the disruption are ongoing, added LTA.

The disruption was made worse by a trackside fire between Marina Bay and Raffles Place stations that died out by itself. LTA said that the fire was unrelated to the earlier incident and is investigating its cause.

National University of Singapore professor Lee Der Horng, who specialises in transportation systems, said the disruption "could have been avoided".

He said the malfunction could be due to insufficient maintenance or testing of the water pumping system.

"SMRT should identify critical systems and should have redundancy in place, so if the first-line equipment fails, the back-up system can kick in."

Singapore Institute of Technology assistant professor Zhou Yi suggested that SMRT install back-up pumping systems at transit areas between the underground and overground sections of the tunnel and increase checks on the pumping and underground drainage systems during the rainy season.

He added that the frequency of checks on the pumping and underground drainage systems may need to be stepped up during the rainy season.

"However, it is good to see that the buses were arranged effectively... It is also good to see the joint effort from various parties, including LTA, SMRT, PUB and the Singapore Civil Defence Force (SCDF)," he said.

Train operator SMRT, in an update on Facebook at 1.52pm yesterday, said the resumption of train services followed an "all-out, overnight effort" to clear water in the tunnels between Bishan and Braddell stations.

SMRT said it worked with teams from SCDF, national water agency PUB and LTA to pump out water from the tunnels, an operation that SCDF said was completed at around 11am yesterday.

Affected trackside equipment was inspected, cleaned, replaced and tested before passenger services resumed. Checks were also conducted on other tunnel portal pump systems located throughout the North-South and East-West lines, said the LTA.