Sewage shaft failure linked to sinkhole; PUB calling safety time-out on similar works islandwide

Straits Times

5 days ago

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The sinkhole has been filled with liquefied stabilised soil to further stabilise the area, and works to reinstate the road will start after.
SINGAPORE - A concrete structure in a shaft being built at a PUB worksite along Tanjong Katong Road South failed at around 5.50pm on July 26, said PUB.
At around the same time, a sinkhole formed on the road next to the site,
swallowing a black car. The driver managed to get out of the vehicle on her own and was rescued by construction workers.
PUB said the works at the site next to the sinkhole that formed involved the construction of a 16m-deep shaft to connect three existing sewer lines. It is still not clear what contributed to the failure of the caisson ring, the national water agency added in a statement issued on the night of July 27.
As a precautionary measure, PUB will be calling a safety time-out to review and ensure the safety of similar sewer construction works across Singapore.
The shaft has been backfilled to stabilise the surrounding ground, PUB said.
A ground-penetrating radar (GPR) scan and analysis are still being carried out to assess the surrounding area, the agency said.
PUB said it is working closely with the Land Transport Authority and Building and Construction Authority on repair works and to investigate what caused the sinkhole incident.
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Workers began pumping water out of the sinkhole from 9.45am on July 27, and this was completed by 1.20pm, PUB said. The black car was hoisted out of the sinkhole at around 2pm.
The sinkhole has been filled with liquefied stabilised soil to further stabilise the area, and works to reinstate the road will start after, PUB added.
The stretch of Tanjong Katong Road South between Mountbatten Road and East Coast Parkway will remain closed to facilitate ongoing repair works.
'Motorists and commuters are advised to plan their routes in advance and expect possible delays during the weekday peak periods,' said PUB.
The agency apologised for the inconvenience caused, and said the authorities will provide further updates on the progress of works and when the affected road can be reopened.
Around 10 minutes after the sinkhole formed on July 26, 18 households had their water supply disrupted.
PUB said preliminary findings suggest that water mains may have been damaged as a result of ground movement linked to the sinkhole.
The affected pipes were isolated, and water supply was fully restored by 2.30am on July 27, PUB said.
It added that the damaged water pipes had led to water filling up the sinkhole. Videos of the incident showed water gushing into the cavity, completely submerging the car.
This stopped once the water mains were shut off, said PUB.
Correction note: An earlier version of this story said ground-penetrating radar scan was carried out, while the authorities are analysing its results. PUB has clarified that the scan is still being carried out to assess the surrounding area.