Nine days after a sinkhole formed on Tanjong Katong Road South, towards East Coast Parkway (ECP), road repairs and reinstatement works have been completed. 

Just before 5am on Monday (Aug 4), workers removed barricades facing Mountbatten Road and Tanjong Katong Road, allowing motorists to pass. 

Bus services 36 and 48 also resumed their west-bound routing. 

 

East-bound bus services and the bound of Tanjong Katong Road South, towards Mountbatten Road, resumed at noon last Saturday (Aug 2).  

Residents whom AsiaOne spoke to in the first week were concerned with inconvenience and safety. Many of them use the road frequently, some even within the hour before the sinkhole formed. 

Said Mr Ho, 70, who lives 500m away at a property along Amber Gardens Road: "Work has been ongoing at the PUB construction site for many months. Of course I am concerned to hear the news (of the sinkhole). Hopefully, PUB and the relevant agencies will check other worksites for safety before this repeats." 

Other residents told AsiaOne that both bounds of the road are heavily used by motorists and commuters in Marine Parade to get to and from ECP — connecting them to the airport, city, and western parts of Singapore (via the Marina Coastal Expressway). 

MP for Marine Parade-Braddell Heights GRC Goh Pei Ming, who made twice-daily visits to the site in the days following the incident, and authorities urged patience so that thorough assessment and tests could be carried out to certify the roads are safe for use. 

During a visit to the site on July 29, Sustainability and Environment Minister Grace Fu said that the incident was serious and should not have happened.

She apologised to the driver of the vehicle, members of public and residents in the vicinity and affected motorists and commuters.  

Rigorous tests to ensure safety: LTA

After the car was lifted out of the sinkhole on Sunday (July 27), national water agency PUB, which coordinated and led the recovery works, commenced backfilling the sinkhole with liquified stabilised soil (LSS).

LSS is made of cement, soil and water, and is used to fill cavities in the soil. It also provides the strength neededfor road construction.

The authorities then carried out "a series of rigorous tests" to assess the ground condition, to ensure that the road was safe for reinstatement and reopening. 

Both the Land Transport Authority (LTA) and national water agency PUB said that ground-penetrating radar (GPR), physical probes, and seismic sensors were deployed for checks and scans. 

Timeline, what's next? 

A two-lane wide sinkhole formed on Tanjong Katong Road South, just after the slip road from Mountbatten Road, on Saturday (July 26). 

Adjacent to the sinkhole is a PUB worksite where a 16m-deep shaft connecting three sewer lines was being constructed. 

PUB said that a concrete component in the shaft, known as a caisson ring, failed at around 5.50pm. 

It is not known yet what caused the caisson ring to fail.

A car, which had turned into Tanjong Katong Road South (from Mountbatten Road), fell into the sinkhole as the roads collapsed.

The female driver was able to escape from the car before water filled up, and she was rescued by quick-thinking migrant workers and taken to hospital. 

That night, BCA conducted preliminary checks on the nearby One Amber condominium and landed houses in the vicinity. It later said that the buildings were not affected by the incident.

On July 27,following overnight checks on the integrity of adjacent roadways, the sinkhole was drained and the stricken car hoisted out at around 2pm. 

 

That evening, PUB said it had called for a safety time-out to review and assess sewer construction works similar to the Tanjong Katong incident. 

Backfilling works, which commenced after the car was lifted out, was completed on Monday (July 28).

The same day, the Building and Construction Authority (BCA) saidit was commencing an independent investigation into the sinkhole incident. 

BCA said that the investigation will "examine the circumstances leading to the formation of the sinkhole, identify the root causes, and take the necessary actions against any non-compliance under the Building Control Act". 

During her site visit on Tuesday (July 29), Sustainability and Environment Minister Grace Fu also announced the formation of an internal investigation panel within the Ministry of Sustainability and Environment (MSE) to probe the cause of the incident, and how to prevent similar incidents.

Recovery work at Tanjong Katong Road South may have been completed, but investigation into the incident has just begun.

According to BCA and MSE it could take months due to the complexity and the need for geophysical tests.

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editor@asiaone.com