Jermyn Chow Straits Times 23 Mar 13;
IT WAS excavation works for the Downtown Line 2 that caused last Saturday's massive sinkhole on Woodlands Road. The construction destabilised the soil, which ruptured an underground water pipe.
The soil movement and pipe's rupture then weakened the ground under the road, causing the sinkhole to open up.
That is according to the Land Transport Authority (LTA), which has concluded its investigation into the cause of the incident.
The sinkhole, which was as wide as one of the road's lanes, appeared near West View Primary School, next to where construction work for Downtown Line 2 is being carried out.
It is the second one that has been reported near a construction site for the new train line, which will run from Bugis to Bukit Panjang.
The first happened last July, when a section of Bukit Timah Road near the Newton flyover, in the direction of the Stevens Road intersection, sank.
Last weekend's cave-in was also the fourth sinkhole to be reported this year. On Jan 30, a sinkhole appeared on Keppel Road.
This was followed by a 2m- wide and 3m-deep hole that appeared on Clementi Road on March 8. Five days after it was filled, it caved in again.
The spate of sinkholes has put the spotlight on the construction projects undertaken by the LTA, as it continues to dig underground to build more rail lines, such as the 16.6km Downtown Line 2, in which 19 tunnel boring machines are being used.
To prevent the Woodlands stretch from sinking again, an LTA spokesman said it will continue to "actively monitor ground movement and carry out works to stabilise soil conditions".
More people will also be deployed to conduct daily inspection of the road, the spokesman added.
The Straits Times understands that LTA engineers already take two to three years to investigate the soil condition and foundation records of nearby buildings, before deciding on construction methods and how deep to dig tunnels for a rail line.
