Bangkok authorities are working around the clock to stop a water leak inside an unfinished MRT tunnel from causing further ground subsidence at the Wongwian Yai intersection in Thonburi, an emergency that began on July 9 and has already forced the evacuation of dozens of residents and the closure of a major road, according to several news sources. The Bangkok Metropolitan Administration, the Mass Rapid Transit Authority of Thailand and the project’s contractor are coordinating the response from a forward command center set up near the site.
The trouble started when water seeped into a drainage sump at the lowest point of the Purple Line South tunnel, a section of the project running between Saphan Phut and Dao Khanong. The leak let surrounding soil flow into the underground structure, causing the ground and road surface above to sink and raising concerns about the stability of nearby buildings.
Bangkok Governor Chadchart Sittipunt inspected the site on July 9 alongside Deputy Governor Wisanu Subsompon and Deputy Permanent Secretary Kanokwan Iamlim. Officials evacuated roughly 60 residents from three commercial buildings within 30 meters of the damaged road surface, moving them into temporary accommodation, including hotels, for about a week while engineers assess the buildings. The MRTA’s contractor is covering the cost of accommodation and other related expenses.
Authorities closed a roughly 200 meter stretch of Prachathipok Road between the Ban Khaek intersection and the King Taksin the Great Monument at Wongwian Yai to cut down on traffic vibration that could further destabilize the soil. Two lanes normally used for inbound traffic were converted for outbound vehicles, and motorists coming from Memorial Bridge or Phra Pok Klao Bridge were advised to detour through Itsaraphap, Lat Ya or Somdet Chao Phraya roads, or to use the elevated BTS rail line instead.
The Department of Disaster Prevention and Mitigation installed two Rescue Guardian sensor units on buildings near the site to track tilting and structural movement in real time, with an automatic warning triggered if abnormal movement is detected. Engineers from Thailand’s national Urban Search and Rescue team joined the inspection to evaluate the surrounding structures.
By Saturday, July 11, the operation had entered a more intensive phase. Overnight crews demolished a pedestrian overpass crossing Wongwian Yai to ease pressure on the unstable ground and clear space for heavier machinery, finishing the job by around 7 a.m. Engineers then began injecting cement and chemical grouting material beneath the road surface to reinforce weakened soil layers and block the paths water was taking into the tunnel. Officials said about 170 cubic meters of grouting material had been injected by Saturday, with cement grouting completed at one point 37 meters underground and work continuing at four additional seepage points.
Officials reported that the volume of water entering the tunnel had declined compared with Friday and that no further subsidence had been detected in nearby buildings, allowing crews to scale back pumping operations. Even so, the Bangkok Metropolitan Administration barred entry to buildings it considers at risk and expanded the cordoned zone around the site after cracks appeared in some structures.
The restrictions widened the pool of affected residents well beyond the initial group evacuated on July 9. A complaints and assistance center opened near the King Taksin Monument, and by Saturday afternoon 105 residents had sought help there, with some moving in with relatives or friends and others accepting contractor arranged accommodation. Officials said 32 residents who already had accommodation arranged for them had not yet been reached to confirm the details.
Officials had initially estimated the emergency operation could take about three days to resolve but were reassessing that timeline as of Saturday, with no revised completion date announced. Traffic restrictions on Prachathipok Road will remain in place until engineers confirm the road and surrounding buildings are stable, authorities said.
The affected tunnel section runs along the same broader Purple Line South alignment where an earlier road collapse occurred near Vajira Hospital, though a different contractor is handling construction at Wongwian Yai. City officials are also weighing measures for schools in the area, including Suankularb Wittayalai School and Suksanari School, and have suggested additional shuttle services, similar to those used after the Vajira Hospital incident, to reduce the number of parents’ vehicles entering the area during the closure.
