MRTA addresses road subsidence at Vajira Hospital, vows to restore traffic within 14 days

Gardphajon Udomdhammabhakdi, Governor of the Mass Rapid Transit Authority of Thailand (MRTA), together with representatives from the CKST-PL Joint Venture, on Thursday held a press conference following the road subsidence in front of Vajira Hospital on Samsen Road, Dusit District, Bangkok, which occurred on September 24, 2025. The subsidence is linked to the ongoing construction of the Purple Line metro in the Tao Poon - Rat Burana Section (Kanchanaphisek Ring Road).

Gardphajon expressed sincere apologies to the affected hospital patients, commuters, and residents, confirming that the MRTA and the construction team are making every effort to restore the road and services as quickly as possible. They are also addressing the impact on local residents.

The subsidence began around 5:00 am when citizens noticed the road surface began to shift, though traffic remained possible, albeit uneven. By 5:30 am, water began to flood the area, and by 7:00 am, the road collapsed, forming a 30x30 metre hole, 20 metres deep. Several vehicles and a power pole fell into the sinkhole.

The initial investigation suggested that the issue was caused by the soil conditions combined with water trapped in the soil. The instability led to a 3-metre-deep water pipe breaking and mixing with contaminated water, further destabilising the area. The resulting pressure caused the soil and water to flow into the construction site, damaging the underground station and tunnel areas.

“The MRTA has been building the metro system for ten years using standardised techniques, and we’ve always worked with reputable contractors. This is the first time such an event has occurred, and it’s an exceptional case. The Ministry of Transport, along with experts, will conduct further investigations to determine the exact cause. We are committed to ensuring that additional measures are put in place to prevent this from happening again,” Gardphajon concluded.

Gardphajon stated that to resolve the issue, the MRTA has discussed the matter with the contractor, and the repair work is divided into two phases:

• Phase 1 involves rapidly restoring the area. Initial surveys have already been conducted, and the current situation indicates that the ground is relatively stable, with only slight sliding remains. The team will begin sealing the gaps with around 50,000 sandbags between the tunnel and the station. Afterward, the area will be mixed with cement to restore the surface to its normal level, with a temporary road surface adjustment made to reopen traffic as quickly as possible.
• Phase 2 involves repairing the tunnel station to return it to normal functionality. This phase will require further detailed analysis and discussion between the MRTA and the contractor, particularly regarding the repair of buildings that have been affected, such as the Samsen Police Station, which will be addressed during Phase 2 to ensure structural integrity and return it to normal use.

Regarding the Samsen Police Station, Gardphajon explained that the soil supporting the foundation and piles beneath the station had disappeared due to the road subsidence. At present, it is not yet safe to begin repairs. The first step will be to stabilise the surrounding area as much as possible. The Ministry of Transport has instructed the MRTA to scan all construction sites and review all safety protocols for each phase of the construction to ensure public confidence.

“Yesterday (September 24), we confirmed that all construction methods and equipment used meet the required academic standards. Currently, we have not found any changes in soil and water conditions in other areas of construction that could indicate a similar cause to the Samsen Road subsidence. However, the MRTA will continue its investigations. The Ministry of Transport plans to set up a committee, consisting of experts from various engineering councils, to help with the investigation,” Gardphajon concluded.

Meanwhile, a representative from CKST-PL Joint Venture confirmed that they will work to restore the Samsen Road area within 2 weeks. Initially, the company will use sandbags to seal any gaps and pour concrete over the area this afternoon. However, the concrete will be poured step by step, allowing each layer to set before adding the next. The goal is to restore the road surface within 14 days to make it safe for traffic again.

The representative explained that in the section of the tunnel where the soil has moved in approximately 20 metres, pouring concrete is deemed safe, but any additional backfilling would be unsafe. Therefore, sandbags will be used to create a supporting system to ensure the stability of the concrete pouring process. Currently, sandbags are being placed to prevent further water and soil intrusion. He confirmed that the concrete pour will not affect the station, and any concrete laid will be removed during future construction.

As for the damage to the police vehicle, it will be retrieved later, though the recovery process may not restore it to its original condition, and it may need to be dismantled. This will be addressed in Phase 2 of the work, he added.

Kittikorn Tanpao, MRTA Deputy Governor of Engineering and Construction, added that in case of heavy rainfall, the team has already coordinated with the Drainage Bureau to borrow tools and machinery and to plan the route for draining water from the affected area. He mentioned that this is a standard procedure, but since the area has a deep hole, they need to urgently seal the hole to prevent water from leaking into the station and make plans to pump out the water.