Bangkok Reopens Part of Key Road as Engineers Continue Repairs on Purple Line Tunnel Leak
Bangkok Line tunnel leakPublished: July 20, 2026
By TAD Editorial Team
Traffic has begun returning to one of Bangkok’s busiest corridors after authorities partially reopened Prajadhipok Road while engineers continued efforts to stabilize an underground leak linked to the city’s Purple Line railway extension.
The reopening marks the first sign of progress following weeks of disruption in the Wongwian Yai area, where water leaking into a tunnel under construction triggered ground subsidence, forced road closures and prompted safety inspections of nearby buildings.
From early Sunday, three inbound lanes heading from Wongwian Yai toward Ban Khaek Intersection were reopened to motorists, easing congestion that had affected commuters since the incident was first detected. Outbound traffic, however, remains closed as repair work continues beneath the surface, with officials advising drivers to use Lat Ya Road as an alternative route.
Deep below the road, engineers are working nearly 37 meters underground to seal the water leak using grouting techniques designed to strengthen the surrounding soil and prevent further movement. The affected tunnel forms part of the southern extension of Bangkok’s MRT Purple Line, one of the capital’s largest ongoing rail infrastructure projects.
According to the Mass Rapid Transit Authority (MRTA), continuous monitoring has found no signs of additional ground movement or structural instability in buildings located within a 30-meter radius of the repair site. Officials also reported that no new subsidence has been detected since emergency stabilization measures were introduced.
The incident began after water entered one of the twin railway tunnels under construction, causing part of Prajadhipok Road to sink by approximately 30 centimeters. Cracks later appeared in several nearby buildings, leading authorities to evacuate some residents and establish safety zones while engineers assessed the damage.
Although construction setbacks occasionally occur in large underground transport projects, the latest incident has renewed public attention on engineering safety as Bangkok continues expanding its mass transit network. The Purple Line extension stretches 23.6 kilometers from Tao Poon to Rat Burana and is expected to improve connections between several major districts once completed, linking with existing MRT routes to reduce travel times across the city.
The affected construction zone also recalls another high-profile infrastructure incident last year, when a large sinkhole developed near an MRT construction site on Samsen Road, highlighting the technical challenges involved in building underground transport systems beneath one of Southeast Asia’s busiest capitals.
Why It Matters
While traffic conditions are gradually improving, the incident serves as a reminder that major infrastructure projects require continuous engineering oversight, especially in densely populated urban areas. For thousands of commuters and local businesses, the partial reopening represents an important step toward restoring normal daily activity, even as repair work continues beneath the city.
TAD Perspective
Bangkok’s expanding rail network is essential to the city’s long-term transportation strategy, but projects of this scale inevitably face engineering risks. Transparent communication, rapid emergency response and ongoing structural monitoring will be critical to maintaining public confidence as construction progresses. The partial reopening of Prajadhipok Road signals positive progress, yet authorities are likely to keep the area under close observation until repairs are fully completed.
