Hard rocks, water seepage: LTA flags unexpected construction challenges along North-South Corridor

SINGAPORE — Construction of the North-South Corridor (NSC) has hit unexpected ground conditions at Novena and Thomson, complicating works as the project enters its most complex engineering phase, the Land Transport Authority said.In Novena, tunnelling crews encountered a mix of materials, including hard rocks, rather than the more uniform and softer clay material previously anticipated. This caused a change in construction method.In the Thomson area, the hard rock layer was closer to the surface than expected and large boulders were also found. This slowed progress because more work was needed.At a media briefing on Sept 8, LTA said that such conditions were fully detected only during excavation. Earlier investigations had been constrained by live traffic, utility networks and existing MRT infrastructure.