North-South Corridor will open 2 years later than expected due to significant construction challenges

North-South Corridor challenges include large boulders found along the tunnel alignment: LTA

The massive North-South Corridor (NSC) project, which has been under construction since 2018, will face a two-year delay in completion due to “significant construction challenges”.

Its first phase is now expected to open in 2029, instead of 2027, said the Land Transport Authority (LTA) in a news release on Thursday (17 Sept).

More time needed to complete works safely: LTA

The two-year increase in the overall completion timeline came after LTA determined that more time was needed to complete the remaining works safely, it said.

It explained that construction of each stage of the NSC is dependent on the one before.

Thus, delays at “critical work fronts” would cause a “knock-on impact” on subsequent activities.

But the full extent only became clearer as works progressed and actual ground conditions were established, it added.

The 8.8km-long viaduct from Admiralty Road West to Lentor Avenue — the longest road structure of its kind in Singapore — will now open in phases from 2029, instead of 2027.

Initially expected to open in 2029, the 12.3km-long tunnel from Lentor Avenue to the East Coast Parkway (ECP) should now open in phases from 2031.

Slower method of excavation in Novena due to MRT tunnels

The Novena area, which has been ravaged by construction work since at least 2020, is “one of the most technically demanding sections” of the NSC, LTA said.

This is because the NSC tunnel passes as close as 1m above and below the North-South Line MRT.

While direct tunnelling was originally planned, rock and groundwater inflows found underneath the MRT tunnel forced LTA to adopt a more precise and time-intensive mining method of excavating in smaller sections.

These ground conditions could not be fully identified in advance as they are located beneath MRT tunnels and only became apparent as excavation reached the lower crossing.

Unexpected rock levels & large boulders found in Thomson

Around the Thomson area, site investigations revealed stronger and higher rock levels, varying rock profiles and large boulders along parts of the tunnel alignment.

This meant that extensive controlled rock blasting, additional rock removal and ground stabilisation works were required.

The construction methodology and earth-retaining systems also had to be revised to suit the challenging ground conditions — again requiring more time.

Piling of viaduct at Gambas & Woodlands taking longer than expected

Along Gambas Avenue and Woodlands Avenue 8, foundation works for the viaduct have taken longer than anticipated due to utility diversions and adverse ground conditions encountered during piling and pilecap construction.

The cumulative effect of the challenges became apparent only as the works progressed, as they affected later construction activities.

When the foundation works are completed, the next phase will also be complex — the launching of large viaduct segments across existing roads, which requires careful planning and coordination to ensure the safety of workers and road users.

Over 90& of viaduct & tunnel foundation works completed

The good news is that more than 90% of the viaduct foundation works have been completed as of August, LTA said.

Similarly, more than 90% of the foundation works have also been completed for the tunnel section.

More construction activities will move underground from next year, it noted. This will ease disruption on surrounding roads as surface-level construction will be reduced.

From 2028, the public will be able to progressively use roads, footpaths and other areas occupied by construction.

LTA acknowledges inconvenience from North-South Corridor delay

This is the second time the NSC completion date has been delayed, after it was pushed back by two years in 2023 due to Covid-19 disruptions and challenging terrain conditions.

LTA acknowledged that the delay will prolong the inconvenience for residents and businesses, as well as the public travelling along the affected areas.

It appreciates the public’s “patience and support” and pledged to make up time where feasible by deploying additional manpower and equipment, optimising construction sequences and prioritising critical activities.

Residents, businesses and other stakeholders will be updated on upcoming works and traffic arrangements, it added.

Also read: North-South Corridor To Be Completed By 2029, Delay Due To Covid-19 & Tough Soil Conditions

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Featured image adapted from Land Transport Authority and Google Maps.