SINGAPORE: A water pumping system malfunction led to the flooding of the MRT tunnel between Bishan and Braddell stations and the delay of train services on the North-South Line (NSL), according to a statement by the Land Transport Authority (LTA) on Sunday (Oct 8).
A torrential downpour caused a section of the tunnel between the two stations to be flooded on Saturday afternoon, halting service on half the NSL - from Ang Mo Kio to Marina South Pier - for more than 3 hours.
Train services in both directions were suspended between Ang Mo Kio and Newton MRT stations for almost 20 hours before they resumed at 1.50pm on Sunday.
Preliminary investigations have indicated that water entered the tunnels through a "portal opening" near Bishan MRT station where rail tracks that are above ground descend underground, LTA said.
"Under normal circumstances, rainwater runoff accumulated in the adjacent storm water sump pit would have been siphoned off by a system of pumps," said LTA.
However the water pumping system malfunctioned, causing rainwater to overflow from the collection pit into the tunnel and to collect at the tunnel's lowest point, between Bishan and Braddell stations.
As a safety measure, transport operator SMRT immediately deactivated the trackside power supply, said LTA.
It added that the pump system has since been repaired, and that investigations into the incident are ongoing. Checks have also been carried out on other portal pump systems located along the NSL and East-West Line.
Officers from the Singapore Civil Defence Force (SCDF) and national water agency PUB worked through the night along with LTA and SMRT staff members to clear water from the flooded tunnel. SBS Transit was also on standby to support their efforts.
"Affected trackside equipment was subsequently inspected, cleaned, replaced and tested before passenger services resumed," said LTA.
In a Facebook post, SCDF said that the water was cleared at 11am on Sunday.
In its statement, LTA said that it was also investigating the small trackside fire which happened between Marina Bay and Raffles Place MRT stations on Saturday evening.